refactor: remove repeating code etc

.clinerules

@@ -0,0 +1,48 @@
+# TimeTracker Project Rules (v2)
+0. GENERAL
+DONT OVERENGINEER.
+USE IN LINE REPLACEMENTS IF POSSIBLE.
+SOLVE TASKS AS FAST AS POSSIBLE. EACH REQUEST COSTS THE USER MONEY.
+1. ARCHITECTURE
+- Multi-tenancy enforced via company_id in all DB queries
+2. CODING PRACTICES
+- Type safety enforced (Go 1.21+ generics, TypeScript strict mode)
+- Domain types must match across backend (Go) and frontend (TypeScript)
+- All database access through repository interfaces
+- API handlers must use DTOs for input/output
+- Use tygo to generate TypeScript types after modifying Go types
+3. SECURITY
+- JWT authentication required for all API endpoints
+- RBAC implemented in middleware/auth.go
+- Input validation using github.com/go-playground/validator
+- No raw SQL - use GORM query builder
+4. DOCUMENTATION
+- Architecture decisions recorded in docu/ARCHITECTURE.md
+- Type relationships documented in docu/domain_types.md
+5. TESTING
+- 80%+ test coverage for domain logic
+- Integration tests for API endpoints
+- Model tests in backend/cmd/modeltest
+6. FRONTEND
+- Next.js App Router pattern required
+8. DEVELOPMENT WORKFLOW
+- Makefile commands are only available in the backend folder
+- Common make commands:
+  - make generate: Run code generation (tygo, swagger, etc.)
+  - make test: Run all tests
+  - make build: Build the application
+  - make run: Start the development server
+9. CUSTOM RULES
+- Add custom rules to .clinerules if:
+- Unexpected behavior is encountered
+- Specific conditions require warnings
+- New patterns emerge that need documentation
+- DO NOT FIX UNUSED IMPORTS - this is the job of the linter
+10.Implement a REST API update handling in Go using Gin that ensures the following behavior:
+- The update request is received as JSON.
+- If a field is present in the JSON and set to null, the corresponding value in the database should be removed.
+- If a field is missing in the JSON, it should not be modified.
+- If a field is present in the JSON and not null, it should be updated.
+- Use either a struct or a map to handle the JSON data.
+- Ensure the update logic is robust and does not unintentionally remove or overwrite fields.
+- Optional: Handle error cases like invalid JSON and return appropriate HTTP status codes.

backend/.env

@@ -0,0 +1,14 @@
+DB_HOST=localhost
+DB_PORT=5432
+DB_USER=timetracker
+DB_PASSWORD=password
+DB_NAME=timetracker
+DB_SSLMODE=disable
+API_KEY=
+
+# JWT Configuration
+#JWT_SECRET=test
+#JWT_KEY_DIR=keys
+#JWT_KEY_GENERATE=true
+JWT_TOKEN_DURATION=24h
+ENVIRONMENT=production

backend/.gitignore

@@ -0,0 +1 @@
+keys

backend/Makefile

@@ -0,0 +1,104 @@
+# Time Tracker Backend Makefile
+
+.PHONY: db-start db-stop db-test model-test run build clean migrate seed swagger help
+
+# Default target
+.DEFAULT_GOAL := help
+
+# Variables
+BINARY_NAME=timetracker
+DB_CONTAINER=timetracker_db
+
+# Help target
+help:
+	@echo "Time Tracker Backend Makefile"
+	@echo ""
+	@echo "Usage:"
+	@echo "  make db-start    - Start the PostgreSQL database container"
+	@echo "  make db-stop     - Stop the PostgreSQL database container"
+	@echo "  make db-test     - Test the database connection"
+	@echo "  make model-test  - Test the database models"
+	@echo "  make run         - Run the application"
+	@echo "  make build       - Build the application"
+	@echo "  make clean       - Remove build artifacts"
+	@echo "  make migrate     - Run database migrations"
+	@echo "  make seed        - Seed the database with initial data"
+	@echo "  make db-drop-users - Drop the users table"
+	@echo "  make db-reinit   - Re-initialize the database"
+	@echo "  make swagger     - Generate swagger documentation"
+	@echo "  make help        - Show this help message"
+	@echo "" make generate-ts - Generate TypeScript types
+
+# Start the database
+db-start:
+	@echo "Starting PostgreSQL database container..."
+	@cd .. && docker-compose up -d db
+	@echo "Database container started"
+
+# Stop the database
+db-stop:
+	@echo "Stopping PostgreSQL database container..."
+	@cd .. && docker-compose stop db
+	@echo "Database container stopped"
+
+# Test the database connection
+db-test:
+	@echo "Testing database connection..."
+	@go run cmd/dbtest/main.go
+
+# Test the database models
+model-test:
+	@echo "Testing database models..."
+	@go run cmd/modeltest/main.go
+
+# Run the application
+run:
+	@echo "Running the application..."
+	@go run cmd/api/main.go
+
+# Build the application
+build:
+	@echo "Building the application..."
+	@go build -o $(BINARY_NAME) cmd/api/main.go
+	@echo "Build complete: $(BINARY_NAME)"
+
+# Clean build artifacts
+clean:
+	@echo "Cleaning build artifacts..."
+	@rm -f $(BINARY_NAME)
+	@echo "Clean complete"
+
+# Run database migrations
+migrate:
+	@echo "Running database migrations..."
+	@go run -mod=mod cmd/migrate/main.go
+	@echo "Migrations complete"
+
+# Seed the database with initial data
+seed:
+	@echo "Seeding the database..."
+	@go run -mod=mod cmd/seed/main.go
+	@echo "Seeding complete"
+
+# Drop the users table
+db-drop-users:
+	@echo "Dropping the users table..."
+	@export PG_HOST=$(DB_HOST); export PG_PORT=$(DB_PORT); export PG_USER=$(DB_USER); export PG_PASSWORD=$(DB_PASSWORD); export PG_DBNAME=$(DB_NAME); go run cmd/dbtest/main.go -drop_table=users
+	@echo "Users table dropped"
+
+# Re-initialize the database
+db-reinit:
+	@echo "Re-initializing the database..."
+	@PG_HOST=$(DB_HOST) PG_PORT=$(DB_PORT) PG_USER=$(DB_USER) PG_PASSWORD=$(DB_PASSWORD) PG_DBNAME=$(DB_NAME) go run cmd/migrate/main.go -create_db -drop_db
+# Generate swagger documentation
+swagger:
+	@echo "Generating swagger documentation..."
+	@swag init -g cmd/api/main.go
+	@echo "Swagger documentation generated"
+
+# Generate TypeScript types
+generate-ts:
+	@echo "Generating TypeScript types..."
+	@go run scripts/fix_tygo.go
+	@echo "TypeScript types generated"
+

backend/README.md

@@ -0,0 +1,147 @@
+# Time Tracker Backend
+
+This is the backend service for the Time Tracker application, built with Go, Gin, and GORM.
+
+## Database Setup
+
+The application uses PostgreSQL as its database. The database connection is configured using GORM, a popular Go ORM library.
+
+### Configuration
+
+Database configuration is handled through the `models.DatabaseConfig` struct in `internal/models/db.go`. The application uses sensible defaults that can be overridden with environment variables:
+
+- `DB_HOST`: Database host (default: "localhost")
+- `DB_PORT`: Database port (default: 5432)
+- `DB_USER`: Database user (default: "timetracker")
+- `DB_PASSWORD`: Database password (default: "password")
+- `DB_NAME`: Database name (default: "timetracker")
+- `DB_SSLMODE`: SSL mode (default: "disable")
+
+### Running with Docker
+
+The easiest way to run the database is using Docker Compose:
+
+```bash
+# Start the database
+docker-compose up -d db
+
+# Check if the database is running
+docker-compose ps
+```
+
+### Database Migrations
+
+The application automatically migrates the database schema on startup using GORM's AutoMigrate feature. This creates all necessary tables based on the model definitions.
+
+### Initial Data Seeding
+
+The application seeds the database with initial data if it's empty. This includes:
+
+- A default company
+- An admin user with email "admin@example.com" and password "Admin@123456"
+
+## Running the Application
+
+### Using Make Commands
+
+The project includes a Makefile with common commands:
+
+```bash
+# Start the database
+make db-start
+
+# Test the database connection
+make db-test
+
+# Run database migrations
+make migrate
+
+# Seed the database with initial data
+make seed
+
+# Test the database models
+make model-test
+
+# Run the application
+make run
+
+# Build the application
+make build
+
+# Show all available commands
+make help
+```
+
+### Manual Commands
+
+If you prefer not to use Make, you can run the commands directly:
+
+```bash
+# Start the database
+cd /path/to/timetracker
+docker-compose up -d db
+
+# Test the database connection
+cd backend
+go run cmd/dbtest/main.go
+
+# Run database migrations
+cd backend
+go run cmd/migrate/main.go
+
+# Seed the database with initial data
+cd backend
+go run cmd/seed/main.go
+
+# Run the backend application
+cd backend
+go run cmd/api/main.go
+```
+
+The API will be available at http://localhost:8080/api and the Swagger documentation at http://localhost:8080/swagger/index.html.
+
+### Environment Variables
+
+You can configure the database connection using environment variables:
+
+```bash
+# Example: Connect to a different database
+DB_HOST=my-postgres-server DB_PORT=5432 DB_USER=myuser DB_PASSWORD=mypassword DB_NAME=mydb go run cmd/api/main.go
+```
+
+## Database Models
+
+The application uses the following models:
+
+- `User`: Represents a user in the system
+- `Company`: Represents a company
+- `Customer`: Represents a customer
+- `Project`: Represents a project
+- `Activity`: Represents an activity
+- `TimeEntry`: Represents a time entry
+
+Each model has corresponding CRUD operations and relationships defined in the `internal/models` directory.
+
+## GORM Best Practices
+
+The application follows these GORM best practices:
+
+1. **Connection Pooling**: Configured with sensible defaults for maximum idle connections, maximum open connections, and connection lifetime.
+
+2. **Migrations**: Uses GORM's AutoMigrate to automatically create and update database tables.
+
+3. **Transactions**: Uses transactions for operations that require multiple database changes to ensure data consistency.
+
+4. **Soft Deletes**: Uses GORM's soft delete feature to mark records as deleted without actually removing them from the database.
+
+5. **Relationships**: Properly defines relationships between models using GORM's relationship features.
+
+6. **Error Handling**: Properly handles database errors and returns appropriate error messages.
+
+7. **Context Support**: Uses context for database operations to support timeouts and cancellation.
+
+8. **Logging**: Configures GORM's logger for appropriate logging based on the environment.
+
+9. **Graceful Shutdown**: Properly closes database connections when the application shuts down.
+
+10. **Validation**: Implements validation for model fields before saving to the database.

backend/cmd/api/main.go

@@ -1,24 +1,34 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"log"
 	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
 
 	"github.com/gin-gonic/gin"
 	swaggerFiles "github.com/swaggo/files"
 	ginSwagger "github.com/swaggo/gin-swagger"
-	_ "github.com/timetracker/backend/docs" // This line is important for swag to work
+	_ "github.com/timetracker/backend/docs"
+	"github.com/timetracker/backend/internal/api/middleware"
+	"github.com/timetracker/backend/internal/api/routes"
+	"github.com/timetracker/backend/internal/config"
 	"github.com/timetracker/backend/internal/models"
 	_ "gorm.io/driver/postgres"
-	// GORM IMPORTS MARKER
 )
 
 //	@title						Time Tracker API
 //	@version					1.0
 //	@description				This is a simple time tracker API.
 //	@host						localhost:8080
-// @BasePath /
+//	@BasePath					/api
+//	@securityDefinitions.apikey	BearerAuth
+//	@in							header
+//	@name						Authorization
 
 // @Summary		Say hello
 // @Description	Get a hello message
@@ -31,25 +41,71 @@ func helloHandler(c *gin.Context) {
 }
 
 func main() {
-
-	dbConfig := models.DatabaseConfig{
-		Host:     "localhost",
-		Port:     5432,
-		User:     "postgres",
-		Password: "password",
-		DBName:   "mydatabase",
-		SSLMode:  "disable", // Für Entwicklungsumgebung
+	cfg, err := config.LoadConfig()
+	if err != nil {
+		log.Fatalf("Failed to load config: %v", err)
 	}
 
-	// Datenbank initialisieren
-	if err := models.InitDB(dbConfig); err != nil {
-		log.Fatalf("Fehler bei der DB-Initialisierung: %v", err)
+	// Initialize database
+	if err := models.InitDB(cfg.Database); err != nil {
+		log.Fatalf("Error initializing database: %v", err)
 	}
+	defer func() {
+		if err := models.CloseDB(); err != nil {
+			log.Printf("Error closing database connection: %v", err)
+		}
+	}()
+
+	// Migrate database schema
+	if err := models.MigrateDB(); err != nil {
+		log.Fatalf("Error migrating database: %v", err)
+	}
+
+	// Initialize JWT keys
+	if err := middleware.InitJWTKeys(); err != nil {
+		log.Fatalf("Error initializing JWT keys: %v", err)
+	}
+
+	// Create Gin router
 	r := gin.Default()
 
-	r.GET("/", helloHandler)
+	// Basic route for health check
+	r.GET("/api", helloHandler)
+
+	// Setup API routes
+	routes.SetupRouter(r, cfg)
+
+	// Swagger documentation
 	r.GET("/swagger/*any", ginSwagger.WrapHandler(swaggerFiles.Handler))
 
-	fmt.Println("Server listening on port 8080")
-	r.Run(":8080") // Use Gin's Run method
+	// Create a server with graceful shutdown
+	srv := &http.Server{
+		Addr:    ":8080",
+		Handler: r,
+	}
+
+	// Start server in a goroutine
+	go func() {
+		fmt.Println("Server listening on port 8080")
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatalf("Error starting server: %v", err)
+		}
+	}()
+
+	// Wait for interrupt signal to gracefully shut down the server
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
+	<-quit
+	log.Println("Shutting down server...")
+
+	// Create a deadline for server shutdown
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	// Shutdown the server
+	if err := srv.Shutdown(ctx); err != nil {
+		log.Fatalf("Server forced to shutdown: %v", err)
+	}
+
+	log.Println("Server exited properly")
 }

backend/cmd/dbtest/main.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/timetracker/backend/internal/models"
+)
+
+func main() {
+	dropTable := flag.String("drop_table", "", "Drop the specified table")
+	flag.Parse()
+
+	// Get database configuration with sensible defaults
+	dbConfig := models.DefaultDatabaseConfig()
+
+	// Initialize database
+	fmt.Println("Connecting to database...")
+	if err := models.InitDB(dbConfig); err != nil {
+		log.Fatalf("Error initializing database: %v", err)
+	}
+	defer func() {
+		if err := models.CloseDB(); err != nil {
+			log.Printf("Error closing database connection: %v", err)
+		}
+	}()
+	fmt.Println("✓ Database connection successful")
+
+	// Test a simple query
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	// Get the database engine
+	db := models.GetEngine(ctx)
+
+	// Test database connection with a simple query
+	var result int
+	var err error
+
+	if *dropTable != "" {
+		fmt.Printf("Dropping table %s...\n", *dropTable)
+		dropErr := db.Exec(fmt.Sprintf("DROP TABLE IF EXISTS %s", *dropTable)).Error
+		if dropErr != nil {
+			log.Fatalf("Error dropping table %s: %v", *dropTable, dropErr)
+		}
+		fmt.Printf("✓ Table %s dropped successfully\n", *dropTable)
+		return
+	}
+
+	err = db.Raw("SELECT 1").Scan(&result).Error
+	if err != nil {
+		log.Fatalf("Error executing test query: %v", err)
+	}
+	fmt.Println("✓ Test query executed successfully")
+
+	// Check if tables exist
+	fmt.Println("Checking database tables...")
+	var tables []string
+	err = db.Raw("SELECT table_name FROM information_schema.tables WHERE table_schema = 'public'").Scan(&tables).Error
+	if err != nil {
+		log.Fatalf("Error checking tables: %v", err)
+	}
+
+	if len(tables) == 0 {
+		fmt.Println("No tables found. You may need to run migrations.")
+		fmt.Println("Attempting to run migrations...")
+
+		// Run migrations
+		if err := models.MigrateDB(); err != nil {
+			log.Fatalf("Error migrating database: %v", err)
+		}
+		fmt.Println("✓ Migrations completed successfully")
+	} else {
+		fmt.Println("Found tables:")
+		for _, table := range tables {
+			fmt.Printf("  - %s\n", table)
+		}
+	}
+
+	// Count users
+	var userCount int64
+	err = db.Model(&models.User{}).Count(&userCount).Error
+	if err != nil {
+		log.Fatalf("Error counting users: %v", err)
+	}
+	fmt.Printf("✓ User count: %d\n", userCount)
+
+	// Count companies
+	var companyCount int64
+	err = db.Model(&models.Company{}).Count(&companyCount).Error
+	if err != nil {
+		log.Fatalf("Error counting companies: %v", err)
+	}
+	fmt.Printf("✓ Company count: %d\n", companyCount)
+
+	fmt.Println("\nDatabase test completed successfully!")
+}

backend/cmd/migrate/main.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/timetracker/backend/internal/models"
+	"gorm.io/gorm/logger"
+)
+
+func main() {
+	// Parse command line flags
+	verbose := false
+	dropDB := flag.Bool("drop_db", false, "Drop the database before migrating")
+	createDB := flag.Bool("create_db", false, "Create the database if it doesn't exist")
+
+	flag.Parse()
+
+	for _, arg := range os.Args[1:] {
+		if arg == "--verbose" || arg == "-v" {
+			verbose = true
+		}
+	}
+
+	if verbose {
+		fmt.Println("Running in verbose mode")
+	}
+
+	// Get database configuration with sensible defaults
+	dbConfig := models.DefaultDatabaseConfig()
+
+	// Override with environment variables if provided
+	if host := os.Getenv("DB_HOST"); host != "" {
+		dbConfig.Host = host
+	}
+	if port := os.Getenv("DB_PORT"); port != "" {
+		var portInt int
+		if _, err := fmt.Sscanf(port, "%d", &portInt); err == nil && portInt > 0 {
+			dbConfig.Port = portInt
+		}
+	}
+	if user := os.Getenv("DB_USER"); user != "" {
+		dbConfig.User = user
+	}
+	if password := os.Getenv("DB_PASSWORD"); password != "" {
+		dbConfig.Password = password
+	}
+	if dbName := os.Getenv("DB_NAME"); dbName != "" {
+		dbConfig.DBName = dbName
+	}
+	if sslMode := os.Getenv("DB_SSLMODE"); sslMode != "" {
+		dbConfig.SSLMode = sslMode
+	}
+
+	// Set log level
+	dbConfig.LogLevel = logger.Info
+
+	// Initialize database
+	fmt.Println("Connecting to database...")
+
+	var err error
+
+	gormDB, err := models.GetGormDB(dbConfig, "postgres")
+	if err != nil {
+		log.Fatalf("Error getting gorm DB: %v", err)
+	}
+	sqlDB, err := gormDB.DB()
+	if err != nil {
+		log.Fatalf("Error getting sql DB: %v", err)
+	}
+
+	if *dropDB {
+		fmt.Printf("Dropping database %s...\n", dbConfig.DBName)
+		_, err = sqlDB.Exec(fmt.Sprintf("DROP DATABASE IF EXISTS %s", dbConfig.DBName))
+		if err != nil {
+			log.Fatalf("Error dropping database %s: %v", dbConfig.DBName, err)
+		}
+		fmt.Printf("✓ Database %s dropped successfully\n", dbConfig.DBName)
+	}
+
+	if *createDB {
+		fmt.Printf("Creating database %s...\n", dbConfig.DBName)
+		_, err = sqlDB.Exec(fmt.Sprintf("CREATE DATABASE %s", dbConfig.DBName))
+		if err != nil {
+			log.Fatalf("Error creating database %s: %v", dbConfig.DBName, err)
+		}
+		fmt.Printf("✓ Database %s created successfully\n", dbConfig.DBName)
+	}
+
+	if err = models.InitDB(dbConfig); err != nil {
+		log.Fatalf("Error initializing database: %v", err)
+	}
+	defer func() {
+		if err := models.CloseDB(); err != nil {
+			log.Printf("Error closing database connection: %v", err)
+		}
+	}()
+	fmt.Println("✓ Database connection successful")
+
+	// Run migrations
+	fmt.Println("Running database migrations...")
+	if err = models.MigrateDB(); err != nil {
+		log.Fatalf("Error migrating database: %v", err)
+	}
+	fmt.Println("✓ Database migrations completed successfully")
+}

backend/cmd/modeltest/main.go

@@ -0,0 +1,208 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/models"
+	"github.com/timetracker/backend/internal/types"
+)
+
+func main() {
+	// Get database configuration with sensible defaults
+	dbConfig := models.DefaultDatabaseConfig()
+
+	// Initialize database
+	fmt.Println("Connecting to database...")
+	if err := models.InitDB(dbConfig); err != nil {
+		log.Fatalf("Error initializing database: %v", err)
+	}
+	defer func() {
+		if err := models.CloseDB(); err != nil {
+			log.Printf("Error closing database connection: %v", err)
+		}
+	}()
+	fmt.Println("✓ Database connection successful")
+
+	// Create context with timeout
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	// Test Company model
+	fmt.Println("\n=== Testing Company Model ===")
+	testCompanyModel(ctx)
+
+	// Test User model
+	fmt.Println("\n=== Testing User Model ===")
+	testUserModel(ctx)
+
+	// Test relationships
+	fmt.Println("\n=== Testing Relationships ===")
+	testRelationships(ctx)
+
+	fmt.Println("\nModel tests completed successfully!")
+}
+
+func testCompanyModel(ctx context.Context) {
+	// Create a new company
+	companyCreate := models.CompanyCreate{
+		Name: "Test Company",
+	}
+
+	company, err := models.CreateCompany(ctx, companyCreate)
+	if err != nil {
+		log.Fatalf("Error creating company: %v", err)
+	}
+	fmt.Printf("✓ Created company: %s (ID: %s)\n", company.Name, company.ID)
+
+	// Get the company by ID
+	retrievedCompany, err := models.GetCompanyByID(ctx, company.ID)
+	if err != nil {
+		log.Fatalf("Error getting company: %v", err)
+	}
+	if retrievedCompany == nil {
+		log.Fatalf("Company not found")
+	}
+	fmt.Printf("✓ Retrieved company: %s\n", retrievedCompany.Name)
+
+	// Update the company
+	newName := "Updated Test Company"
+	companyUpdate := models.CompanyUpdate{
+		ID:   company.ID,
+		Name: &newName,
+	}
+
+	updatedCompany, err := models.UpdateCompany(ctx, companyUpdate)
+	if err != nil {
+		log.Fatalf("Error updating company: %v", err)
+	}
+	fmt.Printf("✓ Updated company name to: %s\n", updatedCompany.Name)
+
+	// Get all companies
+	companies, err := models.GetAllCompanies(ctx)
+	if err != nil {
+		log.Fatalf("Error getting all companies: %v", err)
+	}
+	fmt.Printf("✓ Retrieved %d companies\n", len(companies))
+}
+
+func testUserModel(ctx context.Context) {
+	// Get a company to associate with the user
+	companies, err := models.GetAllCompanies(ctx)
+	if err != nil || len(companies) == 0 {
+		log.Fatalf("Error getting companies or no companies found: %v", err)
+	}
+	companyID := companies[0].ID
+
+	// Create a new user
+	userCreate := models.UserCreate{
+		Email:      "test@example.com",
+		Password:   "Test@123456",
+		Role:       models.RoleUser,
+		CompanyID:  &companyID,
+		HourlyRate: 50.0,
+	}
+
+	user, err := models.CreateUser(ctx, userCreate)
+	if err != nil {
+		log.Fatalf("Error creating user: %v", err)
+	}
+	fmt.Printf("✓ Created user: %s (ID: %s)\n", user.Email, user.ID)
+
+	// Get the user by ID
+	retrievedUser, err := models.GetUserByID(ctx, user.ID)
+	if err != nil {
+		log.Fatalf("Error getting user: %v", err)
+	}
+	if retrievedUser == nil {
+		log.Fatalf("User not found")
+	}
+	fmt.Printf("✓ Retrieved user: %s\n", retrievedUser.Email)
+
+	// Get the user by email
+	emailUser, err := models.GetUserByEmail(ctx, user.Email)
+	if err != nil {
+		log.Fatalf("Error getting user by email: %v", err)
+	}
+	if emailUser == nil {
+		log.Fatalf("User not found by email")
+	}
+	fmt.Printf("✓ Retrieved user by email: %s\n", emailUser.Email)
+
+	// Update the user
+	newEmail := "updated@example.com"
+	newRole := models.RoleAdmin
+	newHourlyRate := 75.0
+	userUpdate := models.UserUpdate{
+		ID:         user.ID,
+		Email:      &newEmail,
+		Role:       &newRole,
+		HourlyRate: &newHourlyRate,
+	}
+
+	updatedUser, err := models.UpdateUser(ctx, userUpdate)
+	if err != nil {
+		log.Fatalf("Error updating user: %v", err)
+	}
+	fmt.Printf("✓ Updated user email to: %s, role to: %s\n", updatedUser.Email, updatedUser.Role)
+
+	// Test authentication
+	authUser, err := models.AuthenticateUser(ctx, updatedUser.Email, "Test@123456")
+	if err != nil {
+		log.Fatalf("Error authenticating user: %v", err)
+	}
+	if authUser == nil {
+		log.Fatalf("Authentication failed")
+	}
+	fmt.Printf("✓ User authentication successful\n")
+
+	// Get all users
+	users, err := models.GetAllUsers(ctx)
+	if err != nil {
+		log.Fatalf("Error getting all users: %v", err)
+	}
+	fmt.Printf("✓ Retrieved %d users\n", len(users))
+
+	// Get users by company ID
+	companyUsers, err := models.GetUsersByCompanyID(ctx, companyID)
+	if err != nil {
+		log.Fatalf("Error getting users by company ID: %v", err)
+	}
+	fmt.Printf("✓ Retrieved %d users for company ID: %s\n", len(companyUsers), companyID)
+}
+
+func testRelationships(ctx context.Context) {
+	// Get a user with company
+	users, err := models.GetAllUsers(ctx)
+	if err != nil || len(users) == 0 {
+		log.Fatalf("Error getting users or no users found: %v", err)
+	}
+	userID := users[0].ID
+
+	// Get user with company
+	user, err := models.GetUserWithCompany(ctx, userID)
+	if err != nil {
+		log.Fatalf("Error getting user with company: %v", err)
+	}
+	if user == nil {
+		log.Fatalf("User not found")
+	}
+	if user.Company == nil {
+		log.Fatalf("User's company not loaded")
+	}
+	fmt.Printf("✓ Retrieved user %s with company %s\n", user.Email, user.Company.Name)
+
+	// Test invalid ID
+	invalidID := ulid.MustNew(ulid.Timestamp(time.Now()), ulid.DefaultEntropy())
+	invalidUser, err := models.GetUserByID(ctx, types.FromULID(invalidID))
+	if err != nil {
+		log.Fatalf("Error getting user with invalid ID: %v", err)
+	}
+	if invalidUser != nil {
+		log.Fatalf("User found with invalid ID")
+	}
+	fmt.Printf("✓ Correctly handled invalid user ID\n")
+}

backend/cmd/seed/main.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+
+	"github.com/timetracker/backend/internal/config"
+	"github.com/timetracker/backend/internal/models"
+	"gorm.io/gorm"
+)
+
+func main() {
+	// Parse CLI flags
+	_ = flag.String("config", "", "Path to .env config file")
+	flag.Parse()
+
+	// Load configuration
+	cfg, err := config.LoadConfig()
+	if err != nil {
+		log.Fatalf("Failed to load config: %v", err)
+	}
+
+	// Initialize database
+	if err := models.InitDB(cfg.Database); err != nil {
+		log.Fatalf("Error initializing database: %v", err)
+	}
+	defer func() {
+		if err := models.CloseDB(); err != nil {
+			log.Printf("Error closing database connection: %v", err)
+		}
+	}()
+
+	// Execute seed operation
+	if err := seedDatabase(context.Background()); err != nil {
+		log.Fatalf("Error seeding database: %v", err)
+	}
+
+	log.Println("Database seeding completed successfully")
+}
+
+// seedDatabase performs the database seeding operation
+func seedDatabase(ctx context.Context) error {
+	// Check if seeding is needed
+	var count int64
+	if err := models.GetEngine(ctx).Model(&models.Company{}).Count(&count).Error; err != nil {
+		return fmt.Errorf("error checking if seeding is needed: %w", err)
+	}
+
+	// If data exists, skip seeding
+	if count > 0 {
+		log.Println("Database already contains data, skipping seeding")
+		return nil
+	}
+
+	log.Println("Seeding database with initial data...")
+
+	// Start transaction
+	return models.GetEngine(ctx).Transaction(func(tx *gorm.DB) error {
+		// Create default company
+		defaultCompany := models.Company{
+			Name: "Default Company",
+		}
+		if err := tx.Create(&defaultCompany).Error; err != nil {
+			return fmt.Errorf("error creating default company: %w", err)
+		}
+
+		// Create admin user
+		adminUser := models.User{
+			Email:      "admin@example.com",
+			Role:       models.RoleAdmin,
+			CompanyID:  &defaultCompany.ID,
+			HourlyRate: 100.0,
+		}
+
+		// Hash password
+		pwData, err := models.HashPassword("Admin@123456")
+		if err != nil {
+			return fmt.Errorf("error hashing password: %w", err)
+		}
+
+		adminUser.Salt = pwData.Salt
+		adminUser.Hash = pwData.Hash
+
+		if err := tx.Create(&adminUser).Error; err != nil {
+			return fmt.Errorf("error creating admin user: %w", err)
+		}
+
+		return nil
+	})
+}

backend/go.mod

@@ -4,6 +4,7 @@ go 1.23.6
 
 require (
 	github.com/gin-gonic/gin v1.10.0
+	github.com/joho/godotenv v1.5.1
 	github.com/oklog/ulid/v2 v2.1.0
 	github.com/swaggo/files v1.0.1
 	github.com/swaggo/gin-swagger v1.6.0
@@ -12,6 +13,7 @@ require (
 )
 
 require (
+	github.com/golang-jwt/jwt/v5 v5.2.1
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
 	github.com/jackc/pgx/v5 v5.5.5 // indirect

backend/go.sum

@@ -37,6 +37,8 @@ github.com/go-playground/validator/v10 v10.25.0 h1:5Dh7cjvzR7BRZadnsVOzPhWsrwUr0
 github.com/go-playground/validator/v10 v10.25.0/go.mod h1:GGzBIJMuE98Ic/kJsBXbz1x/7cByt++cQ+YOuDM5wus=
 github.com/goccy/go-json v0.10.5 h1:Fq85nIqj+gXn/S5ahsiTlK3TmC85qgirsdTP/+DeaC4=
 github.com/goccy/go-json v0.10.5/go.mod h1:oq7eo15ShAhp70Anwd5lgX2pLfOS3QCiwU/PULtXL6M=
+github.com/golang-jwt/jwt/v5 v5.2.1 h1:OuVbFODueb089Lh128TAcimifWaLhJwVflnrgM17wHk=
+github.com/golang-jwt/jwt/v5 v5.2.1/go.mod h1:pqrtFR0X4osieyHYxtmOUWsAWrfe1Q5UVIyoH402zdk=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
@@ -52,6 +54,8 @@ github.com/jinzhu/inflection v1.0.0 h1:K317FqzuhWc8YvSVlFMCCUb36O/S9MCKRDI7QkRKD
 github.com/jinzhu/inflection v1.0.0/go.mod h1:h+uFLlag+Qp1Va5pdKtLDYj+kHp5pxUVkryuEj+Srlc=
 github.com/jinzhu/now v1.1.5 h1:/o9tlHleP7gOFmsnYNz3RGnqzefHA47wQpKrrdTIwXQ=
 github.com/jinzhu/now v1.1.5/go.mod h1:d3SSVoowX0Lcu0IBviAWJpolVfI5UJVZZ7cO71lE/z8=
+github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
+github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
 github.com/josharian/intern v1.0.0 h1:vlS4z54oSdjm0bgjRigI+G1HpF+tI+9rE5LLzOg8HmY=
 github.com/josharian/intern v1.0.0/go.mod h1:5DoeVV0s6jJacbCEi61lwdGj/aVlrQvzHFFd8Hwg//Y=
 github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=

backend/internal/api/dto/activity_dto.go

@@ -0,0 +1,28 @@
+package dto
+
+import (
+	"time"
+)
+
+type ActivityDto struct {
+	ID           string    `json:"id" example:"a1b2c3d4e5f6"`
+	CreatedAt    time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID string    `json:"lastEditorID" example:"u1v2w3x4y5z6"`
+	Name         string    `json:"name" example:"Development"`
+	BillingRate  float64   `json:"billingRate" example:"100.00"`
+}
+
+type ActivityCreateDto struct {
+	Name        string  `json:"name" example:"Development"`
+	BillingRate float64 `json:"billingRate" example:"100.00"`
+}
+
+type ActivityUpdateDto struct {
+	ID           string     `json:"id" example:"a1b2c3d4e5f6"`
+	CreatedAt    *time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    *time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID *string    `json:"lastEditorID" example:"u1v2w3x4y5z6"`
+	Name         *string    `json:"name" example:"Development"`
+	BillingRate  *float64   `json:"billingRate" example:"100.00"`
+}

backend/internal/api/dto/auth_dto.go

@@ -0,0 +1,13 @@
+package dto
+
+// LoginDto represents the login request
+type LoginDto struct {
+	Email    string `json:"email" example:"admin@example.com"`
+	Password string `json:"password" example:"Admin@123456"`
+}
+
+// TokenDto represents the response after successful authentication
+type TokenDto struct {
+	Token string  `json:"token" example:"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"`
+	User  UserDto `json:"user"`
+}

backend/internal/api/dto/company_dto.go

@@ -0,0 +1,23 @@
+package dto
+
+import (
+	"time"
+)
+
+type CompanyDto struct {
+	ID           string    `json:"id" example:"01HGW2BBG0000000000000000"`
+	CreatedAt    time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID string    `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
+	Name         string    `json:"name" example:"Acme Corp"`
+}
+
+type CompanyCreateDto struct {
+	Name string `json:"name" example:"Acme Corp"`
+}
+
+type CompanyUpdateDto struct {
+	CreatedAt *time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt *time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	Name      *string    `json:"name" example:"Acme Corp"`
+}

backend/internal/api/dto/customer_dto.go

@@ -0,0 +1,32 @@
+package dto
+
+import (
+	"time"
+
+	"github.com/timetracker/backend/internal/types"
+)
+
+type CustomerDto struct {
+	ID           string    `json:"id" example:"01HGW2BBG0000000000000000"`
+	CreatedAt    time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID string    `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
+	Name         string    `json:"name" example:"John Doe"`
+	CompanyID    *string   `json:"companyId" example:"01HGW2BBG0000000000000000"`
+	OwnerUserID  *string   `json:"owningUserID" example:"01HGW2BBG0000000000000000"`
+}
+
+type CustomerCreateDto struct {
+	Name      string  `json:"name" example:"John Doe"`
+	CompanyID *string `json:"companyId" example:"01HGW2BBG0000000000000000"`
+}
+
+type CustomerUpdateDto struct {
+	ID           string                 `json:"id" example:"01HGW2BBG0000000000000000"`
+	CreatedAt    *time.Time             `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    *time.Time             `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID *string                `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
+	Name         *string                `json:"name" example:"John Doe"`
+	CompanyID    types.Nullable[string] `json:"companyId" example:"01HGW2BBG0000000000000000"`
+	OwnerUserID  types.Nullable[string] `json:"owningUserID" example:"01HGW2BBG0000000000000000"`
+}

backend/internal/api/dto/project_dto.go

@@ -0,0 +1,28 @@
+package dto
+
+import (
+	"time"
+
+	"github.com/timetracker/backend/internal/types"
+)
+
+type ProjectDto struct {
+	ID           string    `json:"id" example:"01HGW2BBG0000000000000000"`
+	CreatedAt    time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID string    `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
+	Name         string    `json:"name" example:"Time Tracking App"`
+	CustomerID   *string   `json:"customerId" example:"01HGW2BBG0000000000000000"`
+}
+
+type ProjectCreateDto struct {
+	Name       string  `json:"name" example:"Time Tracking App"`
+	CustomerID *string `json:"customerId" example:"01HGW2BBG0000000000000000"`
+}
+
+type ProjectUpdateDto struct {
+	CreatedAt  *time.Time             `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt  *time.Time             `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	Name       *string                `json:"name" example:"Time Tracking App"`
+	CustomerID types.Nullable[string] `json:"customerId" example:"01HGW2BBG0000000000000000"`
+}

backend/internal/api/dto/timeentry_dto.go

@@ -0,0 +1,41 @@
+package dto
+
+import (
+	"time"
+)
+
+type TimeEntryDto struct {
+	ID           string    `json:"id" example:"01HGW2BBG0000000000000000"`
+	CreatedAt    time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID string    `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
+	UserID       string    `json:"userId" example:"01HGW2BBG0000000000000000"`
+	ProjectID    string    `json:"projectId" example:"01HGW2BBG0000000000000000"`
+	ActivityID   string    `json:"activityId" example:"01HGW2BBG0000000000000000"`
+	Start        time.Time `json:"start" example:"2024-01-01T08:00:00Z"`
+	End          time.Time `json:"end" example:"2024-01-01T17:00:00Z"`
+	Description  string    `json:"description" example:"Working on the Time Tracking App"`
+	Billable     int       `json:"billable" example:"100"` // Percentage (0-100)
+}
+
+type TimeEntryCreateDto struct {
+	UserID      string    `json:"userId" example:"01HGW2BBG0000000000000000"`
+	ProjectID   string    `json:"projectId" example:"01HGW2BBG0000000000000000"`
+	ActivityID  string    `json:"activityId" example:"01HGW2BBG0000000000000000"`
+	Start       time.Time `json:"start" example:"2024-01-01T08:00:00Z"`
+	End         time.Time `json:"end" example:"2024-01-01T17:00:00Z"`
+	Description string    `json:"description" example:"Working on the Time Tracking App"`
+	Billable    int       `json:"billable" example:"100"` // Percentage (0-100)
+}
+
+type TimeEntryUpdateDto struct {
+	CreatedAt   *time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt   *time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	UserID      *string    `json:"userId" example:"01HGW2BBG0000000000000000"`
+	ProjectID   *string    `json:"projectId" example:"01HGW2BBG0000000000000000"`
+	ActivityID  *string    `json:"activityId" example:"01HGW2BBG0000000000000000"`
+	Start       *time.Time `json:"start" example:"2024-01-01T08:00:00Z"`
+	End         *time.Time `json:"end" example:"2024-01-01T17:00:00Z"`
+	Description *string    `json:"description" example:"Working on the Time Tracking App"`
+	Billable    *int       `json:"billable" example:"100"` // Percentage (0-100)
+}

backend/internal/api/dto/user_dto.go

@@ -0,0 +1,37 @@
+package dto
+
+import (
+	"time"
+
+	"github.com/timetracker/backend/internal/types"
+)
+
+type UserDto struct {
+	ID           string    `json:"id" example:"01HGW2BBG0000000000000000"`
+	CreatedAt    time.Time `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    time.Time `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID string    `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
+	Email        string    `json:"email" example:"test@example.com"`
+	Role         string    `json:"role" example:"admin"`
+	CompanyID    *string   `json:"companyId,omitempty" example:"01HGW2BBG0000000000000000"`
+	HourlyRate   float64   `json:"hourlyRate" example:"50.00"`
+}
+
+type UserCreateDto struct {
+	Email      string  `json:"email" example:"test@example.com"`
+	Password   string  `json:"password" example:"password123"`
+	Role       string  `json:"role" example:"admin"`
+	CompanyID  *string `json:"companyId" example:"01HGW2BBG0000000000000000"`
+	HourlyRate float64 `json:"hourlyRate" example:"50.00"`
+}
+
+type UserUpdateDto struct {
+	CreatedAt    *time.Time             `json:"createdAt" example:"2024-01-01T00:00:00Z"`
+	UpdatedAt    *time.Time             `json:"updatedAt" example:"2024-01-01T00:00:00Z"`
+	LastEditorID *string                `json:"lastEditorID" example:"01HGW2BBG0000000000000000"`
+	Email        *string                `json:"email" example:"test@example.com"`
+	Password     *string                `json:"password" example:"password123"`
+	Role         *string                `json:"role" example:"admin"`
+	CompanyID    types.Nullable[string] `json:"companyId" example:"01HGW2BBG0000000000000000"`
+	HourlyRate   *float64               `json:"hourlyRate" example:"50.00"`
+}

backend/internal/api/handlers/activity_handler.go

@@ -0,0 +1,180 @@
+package handlers
+
+import (
+	"context"
+
+	"github.com/gin-gonic/gin"
+	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/api/dto"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/api/utils"
+	"github.com/timetracker/backend/internal/models"
+	"github.com/timetracker/backend/internal/types"
+)
+
+// ActivityHandler handles activity-related API endpoints
+type ActivityHandler struct{}
+
+// NewActivityHandler creates a new ActivityHandler
+func NewActivityHandler() *ActivityHandler {
+	return &ActivityHandler{}
+}
+
+// GetActivities handles GET /activities
+//
+//	@Summary		Get all activities
+//	@Description	Get a list of all activities
+//	@Tags			activities
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.ActivityDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/activities [get]
+func (h *ActivityHandler) GetActivities(c *gin.Context) {
+	utils.HandleGetAll(c, models.GetAllActivities, convertActivityToDTO, "activities")
+}
+
+// GetActivityByID handles GET /activities/:id
+//
+//	@Summary		Get activity by ID
+//	@Description	Get an activity by its ID
+//	@Tags			activities
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Activity ID"
+//	@Success		200	{object}	utils.Response{data=dto.ActivityDto}
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/activities/{id} [get]
+func (h *ActivityHandler) GetActivityByID(c *gin.Context) {
+	utils.HandleGetByID(c, models.GetActivityByID, convertActivityToDTO, "activity")
+}
+
+// CreateActivity handles POST /activities
+//
+//	@Summary		Create a new activity
+//	@Description	Create a new activity
+//	@Tags			activities
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			activity	body		dto.ActivityCreateDto	true	"Activity data"
+//	@Success		201			{object}	utils.Response{data=dto.ActivityDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/activities [post]
+func (h *ActivityHandler) CreateActivity(c *gin.Context) {
+	utils.HandleCreate(c, createActivityWrapper, convertActivityToDTO, "activity")
+}
+
+// UpdateActivity handles PUT /activities/:id
+//
+//	@Summary		Update an activity
+//	@Description	Update an existing activity
+//	@Tags			activities
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id			path		string					true	"Activity ID"
+//	@Param			activity	body		dto.ActivityUpdateDto	true	"Activity data"
+//	@Success		200			{object}	utils.Response{data=dto.ActivityDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/activities/{id} [put]
+func (h *ActivityHandler) UpdateActivity(c *gin.Context) {
+	utils.HandleUpdate(c, models.UpdateActivity, convertActivityToDTO, prepareActivityUpdate, "activity")
+}
+
+// DeleteActivity handles DELETE /activities/:id
+//
+//	@Summary		Delete an activity
+//	@Description	Delete an activity by its ID
+//	@Tags			activities
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Activity ID"
+//	@Success		204	{object}	utils.Response
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/activities/{id} [delete]
+func (h *ActivityHandler) DeleteActivity(c *gin.Context) {
+	utils.HandleDelete(c, models.DeleteActivity, "activity")
+}
+
+// Helper functions for DTO conversion
+
+func convertActivityToDTO(activity *models.Activity) dto.ActivityDto {
+	return dto.ActivityDto{
+		ID:          activity.ID.String(),
+		CreatedAt:   activity.CreatedAt,
+		UpdatedAt:   activity.UpdatedAt,
+		Name:        activity.Name,
+		BillingRate: activity.BillingRate,
+	}
+}
+
+func convertCreateActivityDTOToModel(dto dto.ActivityCreateDto) models.ActivityCreate {
+	return models.ActivityCreate{
+		Name:        dto.Name,
+		BillingRate: dto.BillingRate,
+	}
+}
+
+func convertUpdateActivityDTOToModel(dto dto.ActivityUpdateDto) models.ActivityUpdate {
+	id, _ := ulid.Parse(dto.ID)
+	update := models.ActivityUpdate{
+		ID: types.FromULID(id),
+	}
+
+	if dto.Name != nil {
+		update.Name = dto.Name
+	}
+
+	if dto.BillingRate != nil {
+		update.BillingRate = dto.BillingRate
+	}
+
+	return update
+}
+
+// prepareActivityUpdate prepares the activity update object by parsing the ID, binding the JSON, and converting the DTO to a model
+func prepareActivityUpdate(c *gin.Context) (models.ActivityUpdate, error) {
+	// Parse ID from URL
+	id, err := utils.ParseID(c, "id")
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid activity ID format")
+		return models.ActivityUpdate{}, err
+	}
+
+	// Parse request body
+	var activityUpdateDTO dto.ActivityUpdateDto
+	if err := utils.BindJSON(c, &activityUpdateDTO); err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return models.ActivityUpdate{}, err
+	}
+
+	// Set ID from URL
+	activityUpdateDTO.ID = id.String()
+
+	// Convert DTO to model
+	return convertUpdateActivityDTOToModel(activityUpdateDTO), nil
+}
+
+// createActivityWrapper is a wrapper function for models.CreateActivity that takes a DTO as input
+func createActivityWrapper(ctx context.Context, createDTO dto.ActivityCreateDto) (*models.Activity, error) {
+	// Convert DTO to model
+	activityCreate := convertCreateActivityDTOToModel(createDTO)
+
+	// Call the original function
+	return models.CreateActivity(ctx, activityCreate)
+}

backend/internal/api/handlers/company_handler.go

@@ -0,0 +1,169 @@
+package handlers
+
+import (
+	"context"
+
+	"github.com/gin-gonic/gin"
+	"github.com/timetracker/backend/internal/api/dto"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/api/utils"
+	"github.com/timetracker/backend/internal/models"
+	"github.com/timetracker/backend/internal/types"
+)
+
+// CompanyHandler handles company-related API endpoints
+type CompanyHandler struct{}
+
+// NewCompanyHandler creates a new CompanyHandler
+func NewCompanyHandler() *CompanyHandler {
+	return &CompanyHandler{}
+}
+
+// GetCompanies handles GET /companies
+//
+//	@Summary		Get all companies
+//	@Description	Get a list of all companies
+//	@Tags			companies
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.CompanyDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/companies [get]
+func (h *CompanyHandler) GetCompanies(c *gin.Context) {
+	utils.HandleGetAll(c, models.GetAllCompanies, convertCompanyToDTO, "companies")
+}
+
+// GetCompanyByID handles GET /companies/:id
+//
+//	@Summary		Get company by ID
+//	@Description	Get a company by its ID
+//	@Tags			companies
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Company ID"
+//	@Success		200	{object}	utils.Response{data=dto.CompanyDto}
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/companies/{id} [get]
+func (h *CompanyHandler) GetCompanyByID(c *gin.Context) {
+	utils.HandleGetByID(c, models.GetCompanyByID, convertCompanyToDTO, "company")
+}
+
+// CreateCompany handles POST /companies
+//
+//	@Summary		Create a new company
+//	@Description	Create a new company
+//	@Tags			companies
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			company	body		dto.CompanyCreateDto	true	"Company data"
+//	@Success		201		{object}	utils.Response{data=dto.CompanyDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/companies [post]
+func (h *CompanyHandler) CreateCompany(c *gin.Context) {
+	utils.HandleCreate(c, createCompanyWrapper, convertCompanyToDTO, "company")
+}
+
+// UpdateCompany handles PUT /companies/:id
+//
+//	@Summary		Update a company
+//	@Description	Update an existing company
+//	@Tags			companies
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id		path		string				true	"Company ID"
+//	@Param			company	body		dto.CompanyUpdateDto	true	"Company data"
+//	@Success		200		{object}	utils.Response{data=dto.CompanyDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/companies/{id} [put]
+func (h *CompanyHandler) UpdateCompany(c *gin.Context) {
+	utils.HandleUpdate(c, models.UpdateCompany, convertCompanyToDTO, prepareCompanyUpdate, "company")
+}
+
+// DeleteCompany handles DELETE /companies/:id
+//
+//	@Summary		Delete a company
+//	@Description	Delete a company by its ID
+//	@Tags			companies
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Company ID"
+//	@Success		204	{object}	utils.Response
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/companies/{id} [delete]
+func (h *CompanyHandler) DeleteCompany(c *gin.Context) {
+	utils.HandleDelete(c, models.DeleteCompany, "company")
+}
+
+// Helper functions for DTO conversion
+
+func convertCompanyToDTO(company *models.Company) dto.CompanyDto {
+	return dto.CompanyDto{
+		ID:        company.ID.String(),
+		CreatedAt: company.CreatedAt,
+		UpdatedAt: company.UpdatedAt,
+		Name:      company.Name,
+	}
+}
+
+func convertCreateCompanyDTOToModel(dto dto.CompanyCreateDto) models.CompanyCreate {
+	return models.CompanyCreate{
+		Name: dto.Name,
+	}
+}
+
+func convertUpdateCompanyDTOToModel(dto dto.CompanyUpdateDto, id types.ULID) models.CompanyUpdate {
+	update := models.CompanyUpdate{
+		ID: id,
+	}
+
+	if dto.Name != nil {
+		update.Name = dto.Name
+	}
+
+	return update
+}
+
+// prepareCompanyUpdate prepares the company update object by parsing the ID, binding the JSON, and converting the DTO to a model
+func prepareCompanyUpdate(c *gin.Context) (models.CompanyUpdate, error) {
+	// Parse ID from URL
+	id, err := utils.ParseID(c, "id")
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid company ID format")
+		return models.CompanyUpdate{}, err
+	}
+
+	// Parse request body
+	var companyUpdateDTO dto.CompanyUpdateDto
+	if err := utils.BindJSON(c, &companyUpdateDTO); err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return models.CompanyUpdate{}, err
+	}
+
+	// Convert DTO to model
+	return convertUpdateCompanyDTOToModel(companyUpdateDTO, id), nil
+}
+
+// createCompanyWrapper is a wrapper function for models.CreateCompany that takes a DTO as input
+func createCompanyWrapper(ctx context.Context, createDTO dto.CompanyCreateDto) (*models.Company, error) {
+	// Convert DTO to model
+	companyCreate := convertCreateCompanyDTOToModel(createDTO)
+
+	// Call the original function
+	return models.CreateCompany(ctx, companyCreate)
+}

backend/internal/api/handlers/customer_handler.go

@@ -0,0 +1,278 @@
+package handlers
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/timetracker/backend/internal/api/dto"
+	"github.com/timetracker/backend/internal/api/middleware"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/api/utils"
+	"github.com/timetracker/backend/internal/models"
+	"github.com/timetracker/backend/internal/types"
+)
+
+// CustomerHandler handles customer-related API endpoints
+type CustomerHandler struct{}
+
+// NewCustomerHandler creates a new CustomerHandler
+func NewCustomerHandler() *CustomerHandler {
+	return &CustomerHandler{}
+}
+
+// GetCustomers handles GET /customers
+//
+//	@Summary		Get all customers
+//	@Description	Get a list of all customers
+//	@Tags			customers
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.CustomerDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/customers [get]
+func (h *CustomerHandler) GetCustomers(c *gin.Context) {
+	utils.HandleGetAll(c, models.GetAllCustomers, convertCustomerToDTO, "customers")
+}
+
+// GetCustomerByID handles GET /customers/:id
+//
+//	@Summary		Get customer by ID
+//	@Description	Get a customer by its ID
+//	@Tags			customers
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Customer ID"
+//	@Success		200	{object}	utils.Response{data=dto.CustomerDto}
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/customers/{id} [get]
+func (h *CustomerHandler) GetCustomerByID(c *gin.Context) {
+	utils.HandleGetByID(c, models.GetCustomerByID, convertCustomerToDTO, "customer")
+}
+
+// GetCustomersByCompanyID handles GET /customers/company/:companyId
+//
+//	@Summary		Get customers by company ID
+//	@Description	Get a list of customers for a specific company
+//	@Tags			customers
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			companyId	path		int	true	"Company ID"
+//	@Success		200			{object}	utils.Response{data=[]dto.CustomerDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/customers/company/{companyId} [get]
+func (h *CustomerHandler) GetCustomersByCompanyID(c *gin.Context) {
+	// Parse company ID from URL
+	companyIDStr := c.Param("companyId")
+	companyID, err := parseCompanyID(companyIDStr)
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid company ID format")
+		return
+	}
+
+	// Create a wrapper function that takes a ULID but calls the original function with an int
+	getByCompanyIDFn := func(ctx context.Context, _ types.ULID) ([]models.Customer, error) {
+		return models.GetCustomersByCompanyID(ctx, companyID)
+	}
+
+	// Get customers from the database and convert to DTOs
+	customers, err := getByCompanyIDFn(c.Request.Context(), types.ULID{})
+	if err != nil {
+		responses.InternalErrorResponse(c, "Error retrieving customers: "+err.Error())
+		return
+	}
+
+	// Convert to DTOs
+	customerDTOs := utils.ConvertToDTO(customers, convertCustomerToDTO)
+
+	responses.SuccessResponse(c, http.StatusOK, customerDTOs)
+}
+
+// CreateCustomer handles POST /customers
+//
+//	@Summary		Create a new customer
+//	@Description	Create a new customer
+//	@Tags			customers
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			customer	body		dto.CustomerCreateDto	true	"Customer data"
+//	@Success		201			{object}	utils.Response{data=dto.CustomerDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/customers [post]
+func (h *CustomerHandler) CreateCustomer(c *gin.Context) {
+	// We need to use a custom wrapper for CreateCustomer because we need to get the user ID from the context
+	userID, err := middleware.GetUserIDFromContext(c)
+	if err != nil {
+		responses.UnauthorizedResponse(c, "User not authenticated")
+		return
+	}
+
+	// Use a closure to capture the userID
+	createFn := func(ctx context.Context, createDTO dto.CustomerCreateDto) (*models.Customer, error) {
+		return createCustomerWrapper(ctx, createDTO, userID)
+	}
+
+	utils.HandleCreate(c, createFn, convertCustomerToDTO, "customer")
+}
+
+// UpdateCustomer handles PUT /customers/:id
+//
+//	@Summary		Update a customer
+//	@Description	Update an existing customer
+//	@Tags			customers
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id			path		string					true	"Customer ID"
+//	@Param			customer	body		dto.CustomerUpdateDto	true	"Customer data"
+//	@Success		200			{object}	utils.Response{data=dto.CustomerDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/customers/{id} [put]
+func (h *CustomerHandler) UpdateCustomer(c *gin.Context) {
+	utils.HandleUpdate(c, models.UpdateCustomer, convertCustomerToDTO, prepareCustomerUpdate, "customer")
+}
+
+// DeleteCustomer handles DELETE /customers/:id
+//
+//	@Summary		Delete a customer
+//	@Description	Delete a customer by its ID
+//	@Tags			customers
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Customer ID"
+//	@Success		204	{object}	utils.Response
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/customers/{id} [delete]
+func (h *CustomerHandler) DeleteCustomer(c *gin.Context) {
+	utils.HandleDelete(c, models.DeleteCustomer, "customer")
+}
+
+// Helper functions for DTO conversion
+
+func convertCustomerToDTO(customer *models.Customer) dto.CustomerDto {
+	var companyID *string
+	if customer.CompanyID != nil {
+		s := customer.CompanyID.String()
+		companyID = &s
+	}
+	return dto.CustomerDto{
+		ID:        customer.ID.String(),
+		CreatedAt: customer.CreatedAt,
+		UpdatedAt: customer.UpdatedAt,
+		Name:      customer.Name,
+		CompanyID: companyID,
+	}
+}
+
+func convertCreateCustomerDTOToModel(dto dto.CustomerCreateDto) (models.CustomerCreate, error) {
+	var companyID *types.ULID
+	if dto.CompanyID != nil {
+		wrapper, err := types.ULIDFromString(*dto.CompanyID) // Ignoring error, validation happens in the model
+		if err != nil {
+			return models.CustomerCreate{}, fmt.Errorf("invalid company ID: %w", err)
+		}
+		companyID = &wrapper
+	}
+	create := models.CustomerCreate{
+		Name:      dto.Name,
+		CompanyID: companyID,
+	}
+	return create, nil
+}
+
+func convertUpdateCustomerDTOToModel(dto dto.CustomerUpdateDto) (models.CustomerUpdate, error) {
+	id, err := types.ULIDFromString(dto.ID)
+	if err != nil {
+		return models.CustomerUpdate{}, fmt.Errorf("invalid customer ID: %w", err)
+	}
+
+	update := models.CustomerUpdate{
+		ID: id,
+	}
+
+	if dto.Name != nil {
+		update.Name = dto.Name
+	}
+
+	if dto.CompanyID.Valid {
+		companyID, err := types.ULIDFromString(*dto.CompanyID.Value)
+		if err != nil {
+			return models.CustomerUpdate{}, fmt.Errorf("invalid company ID: %w", err)
+		}
+		update.CompanyID = &companyID
+	} else {
+		update.CompanyID = nil
+	}
+
+	return update, nil
+}
+
+// Helper function to parse company ID from string
+func parseCompanyID(idStr string) (int, error) {
+	var id int
+	_, err := fmt.Sscanf(idStr, "%d", &id)
+	return id, err
+}
+
+// prepareCustomerUpdate prepares the customer update object by parsing the ID, binding the JSON, and converting the DTO to a model
+func prepareCustomerUpdate(c *gin.Context) (models.CustomerUpdate, error) {
+	// Parse ID from URL
+	id, err := utils.ParseID(c, "id")
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid customer ID format")
+		return models.CustomerUpdate{}, err
+	}
+
+	// Parse request body
+	var customerUpdateDTO dto.CustomerUpdateDto
+	if err := utils.BindJSON(c, &customerUpdateDTO); err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return models.CustomerUpdate{}, err
+	}
+
+	// Set ID from URL
+	customerUpdateDTO.ID = id.String()
+
+	// Convert DTO to model
+	customerUpdate, err := convertUpdateCustomerDTOToModel(customerUpdateDTO)
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid request body: "+err.Error())
+		return models.CustomerUpdate{}, err
+	}
+
+	return customerUpdate, nil
+}
+
+// createCustomerWrapper is a wrapper function for models.CreateCustomer that takes a DTO as input
+func createCustomerWrapper(ctx context.Context, createDTO dto.CustomerCreateDto, userID types.ULID) (*models.Customer, error) {
+	// Convert DTO to model
+	customerCreate, err := convertCreateCustomerDTOToModel(createDTO)
+	if err != nil {
+		return nil, err
+	}
+
+	// Set the owner user ID
+	customerCreate.OwnerUserID = &userID
+
+	// Call the original function
+	return models.CreateCustomer(ctx, customerCreate)
+}

backend/internal/api/handlers/project_handler.go

@@ -0,0 +1,234 @@
+package handlers
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/gin-gonic/gin"
+	"github.com/timetracker/backend/internal/api/dto"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/api/utils"
+	"github.com/timetracker/backend/internal/models"
+	"github.com/timetracker/backend/internal/types"
+)
+
+// ProjectHandler handles project-related API endpoints
+type ProjectHandler struct{}
+
+// NewProjectHandler creates a new ProjectHandler
+func NewProjectHandler() *ProjectHandler {
+	return &ProjectHandler{}
+}
+
+// GetProjects handles GET /projects
+//
+//	@Summary		Get all projects
+//	@Description	Get a list of all projects
+//	@Tags			projects
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.ProjectDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/projects [get]
+func (h *ProjectHandler) GetProjects(c *gin.Context) {
+	utils.HandleGetAll(c, models.GetAllProjects, convertProjectToDTO, "projects")
+}
+
+// GetProjectsWithCustomers handles GET /projects/with-customers
+//
+//	@Summary		Get all projects with customer information
+//	@Description	Get a list of all projects with their associated customer information
+//	@Tags			projects
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.ProjectDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/projects/with-customers [get]
+func (h *ProjectHandler) GetProjectsWithCustomers(c *gin.Context) {
+	utils.HandleGetAll(c, models.GetAllProjectsWithCustomers, convertProjectToDTO, "projects with customers")
+}
+
+// GetProjectByID handles GET /projects/:id
+//
+//	@Summary		Get project by ID
+//	@Description	Get a project by its ID
+//	@Tags			projects
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Project ID"
+//	@Success		200	{object}	utils.Response{data=dto.ProjectDto}
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/projects/{id} [get]
+func (h *ProjectHandler) GetProjectByID(c *gin.Context) {
+	utils.HandleGetByID(c, models.GetProjectByID, convertProjectToDTO, "project")
+}
+
+// GetProjectsByCustomerID handles GET /projects/customer/:customerId
+//
+//	@Summary		Get projects by customer ID
+//	@Description	Get a list of projects for a specific customer
+//	@Tags			projects
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			customerId	path		string	true	"Customer ID"
+//	@Success		200			{object}	utils.Response{data=[]dto.ProjectDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/projects/customer/{customerId} [get]
+func (h *ProjectHandler) GetProjectsByCustomerID(c *gin.Context) {
+	utils.HandleGetByFilter(c, models.GetProjectsByCustomerID, convertProjectToDTO, "projects", "customerId")
+}
+
+// CreateProject handles POST /projects
+//
+//	@Summary		Create a new project
+//	@Description	Create a new project
+//	@Tags			projects
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			project	body		dto.ProjectCreateDto	true	"Project data"
+//	@Success		201		{object}	utils.Response{data=dto.ProjectDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/projects [post]
+func (h *ProjectHandler) CreateProject(c *gin.Context) {
+	utils.HandleCreate(c, createProjectWrapper, convertProjectToDTO, "project")
+}
+
+// UpdateProject handles PUT /projects/:id
+//
+//	@Summary		Update a project
+//	@Description	Update an existing project
+//	@Tags			projects
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id		path		string				true	"Project ID"
+//	@Param			project	body		dto.ProjectUpdateDto	true	"Project data"
+//	@Success		200		{object}	utils.Response{data=dto.ProjectDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/projects/{id} [put]
+func (h *ProjectHandler) UpdateProject(c *gin.Context) {
+	utils.HandleUpdate(c, models.UpdateProject, convertProjectToDTO, prepareProjectUpdate, "project")
+}
+
+// DeleteProject handles DELETE /projects/:id
+//
+//	@Summary		Delete a project
+//	@Description	Delete a project by its ID
+//	@Tags			projects
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Project ID"
+//	@Success		204	{object}	utils.Response
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/projects/{id} [delete]
+func (h *ProjectHandler) DeleteProject(c *gin.Context) {
+	utils.HandleDelete(c, models.DeleteProject, "project")
+}
+
+// Helper functions for DTO conversion
+
+func convertProjectToDTO(project *models.Project) dto.ProjectDto {
+	customerId := project.CustomerID.String()
+	return dto.ProjectDto{
+		ID:         project.ID.String(),
+		CreatedAt:  project.CreatedAt,
+		UpdatedAt:  project.UpdatedAt,
+		Name:       project.Name,
+		CustomerID: &customerId,
+	}
+}
+
+func convertCreateProjectDTOToModel(dto dto.ProjectCreateDto) (models.ProjectCreate, error) {
+	create := models.ProjectCreate{Name: dto.Name}
+	// Convert CustomerID from int to ULID (this is a simplification, adjust as needed)
+	if dto.CustomerID != nil {
+		customerID, err := types.ULIDFromString(*dto.CustomerID)
+		if err != nil {
+			return models.ProjectCreate{}, fmt.Errorf("invalid customer ID: %w", err)
+		}
+		create.CustomerID = &customerID
+	}
+	return create, nil
+}
+
+func convertUpdateProjectDTOToModel(dto dto.ProjectUpdateDto, id types.ULID) (models.ProjectUpdate, error) {
+	update := models.ProjectUpdate{
+		ID: id,
+	}
+
+	if dto.Name != nil {
+		update.Name = dto.Name
+	}
+
+	if dto.CustomerID.Valid {
+		if dto.CustomerID.Value == nil {
+			update.CustomerID = nil
+		} else {
+			customerID, err := types.ULIDFromString(*dto.CustomerID.Value)
+			if err != nil {
+				return models.ProjectUpdate{}, fmt.Errorf("invalid customer ID: %w", err)
+			}
+			update.CustomerID = &customerID
+		}
+	}
+
+	return update, nil
+}
+
+// prepareProjectUpdate prepares the project update object by parsing the ID, binding the JSON, and converting the DTO to a model
+func prepareProjectUpdate(c *gin.Context) (models.ProjectUpdate, error) {
+	// Parse ID from URL
+	id, err := utils.ParseID(c, "id")
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid project ID format")
+		return models.ProjectUpdate{}, err
+	}
+
+	// Parse request body
+	var projectUpdateDTO dto.ProjectUpdateDto
+	if err := utils.BindJSON(c, &projectUpdateDTO); err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return models.ProjectUpdate{}, err
+	}
+
+	// Convert DTO to model
+	projectUpdate, err := convertUpdateProjectDTOToModel(projectUpdateDTO, id)
+	if err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return models.ProjectUpdate{}, err
+	}
+
+	return projectUpdate, nil
+}
+
+// createProjectWrapper is a wrapper function for models.CreateProject that takes a DTO as input
+func createProjectWrapper(ctx context.Context, createDTO dto.ProjectCreateDto) (*models.Project, error) {
+	// Convert DTO to model
+	projectCreate, err := convertCreateProjectDTOToModel(createDTO)
+	if err != nil {
+		return nil, err
+	}
+
+	// Call the original function
+	return models.CreateProject(ctx, projectCreate)
+}

backend/internal/api/handlers/timeentry_handler.go

@@ -0,0 +1,316 @@
+package handlers
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/gin-gonic/gin"
+	"github.com/timetracker/backend/internal/api/dto"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/api/utils"
+	"github.com/timetracker/backend/internal/models"
+	"github.com/timetracker/backend/internal/types"
+)
+
+// TimeEntryHandler handles time entry-related API endpoints
+type TimeEntryHandler struct{}
+
+// NewTimeEntryHandler creates a new TimeEntryHandler
+func NewTimeEntryHandler() *TimeEntryHandler {
+	return &TimeEntryHandler{}
+}
+
+// GetTimeEntries handles GET /time-entries
+//
+//	@Summary		Get all time entries
+//	@Description	Get a list of all time entries
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.TimeEntryDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries [get]
+func (h *TimeEntryHandler) GetTimeEntries(c *gin.Context) {
+	utils.HandleGetAll(c, models.GetAllTimeEntries, convertTimeEntryToDTO, "time entries")
+}
+
+// GetTimeEntryByID handles GET /time-entries/:id
+//
+//	@Summary		Get time entry by ID
+//	@Description	Get a time entry by its ID
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Time Entry ID"
+//	@Success		200	{object}	utils.Response{data=dto.TimeEntryDto}
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries/{id} [get]
+func (h *TimeEntryHandler) GetTimeEntryByID(c *gin.Context) {
+	utils.HandleGetByID(c, models.GetTimeEntryByID, convertTimeEntryToDTO, "time entry")
+}
+
+// GetTimeEntriesByUserID handles GET /time-entries/user/:userId
+//
+//	@Summary		Get time entries by user ID
+//	@Description	Get a list of time entries for a specific user
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			userId	path		string	true	"User ID"
+//	@Success		200		{object}	utils.Response{data=[]dto.TimeEntryDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries/user/{userId} [get]
+func (h *TimeEntryHandler) GetTimeEntriesByUserID(c *gin.Context) {
+	utils.HandleGetByFilter(c, models.GetTimeEntriesByUserID, convertTimeEntryToDTO, "time entries", "userId")
+}
+
+// GetMyTimeEntries handles GET /time-entries/me
+//
+//	@Summary		Get current user's time entries
+//	@Description	Get a list of time entries for the currently authenticated user
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.TimeEntryDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries/me [get]
+func (h *TimeEntryHandler) GetMyTimeEntries(c *gin.Context) {
+	utils.HandleGetByUserID(c, models.GetTimeEntriesByUserID, convertTimeEntryToDTO, "time entries")
+}
+
+// GetTimeEntriesByProjectID handles GET /time-entries/project/:projectId
+//
+//	@Summary		Get time entries by project ID
+//	@Description	Get a list of time entries for a specific project
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			projectId	path		string	true	"Project ID"
+//	@Success		200			{object}	utils.Response{data=[]dto.TimeEntryDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries/project/{projectId} [get]
+func (h *TimeEntryHandler) GetTimeEntriesByProjectID(c *gin.Context) {
+	utils.HandleGetByFilter(c, models.GetTimeEntriesByProjectID, convertTimeEntryToDTO, "time entries", "projectId")
+}
+
+// GetTimeEntriesByDateRange handles GET /time-entries/range
+//
+//	@Summary		Get time entries by date range
+//	@Description	Get a list of time entries within a specific date range
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			start	query		string	true	"Start date (ISO 8601 format)"
+//	@Param			end		query		string	true	"End date (ISO 8601 format)"
+//	@Success		200		{object}	utils.Response{data=[]dto.TimeEntryDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries/range [get]
+func (h *TimeEntryHandler) GetTimeEntriesByDateRange(c *gin.Context) {
+	utils.HandleGetByDateRange(c, models.GetTimeEntriesByDateRange, convertTimeEntryToDTO, "time entries")
+}
+
+// CreateTimeEntry handles POST /time-entries
+//
+//	@Summary		Create a new time entry
+//	@Description	Create a new time entry
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			timeEntry	body		dto.TimeEntryCreateDto	true	"Time Entry data"
+//	@Success		201			{object}	utils.Response{data=dto.TimeEntryDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries [post]
+func (h *TimeEntryHandler) CreateTimeEntry(c *gin.Context) {
+	utils.HandleCreate(c, createTimeEntryWrapper, convertTimeEntryToDTO, "time entry")
+}
+
+// UpdateTimeEntry handles PUT /time-entries/:id
+//
+//	@Summary		Update a time entry
+//	@Description	Update an existing time entry
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id			path		string					true	"Time Entry ID"
+//	@Param			timeEntry	body		dto.TimeEntryUpdateDto	true	"Time Entry data"
+//	@Success		200			{object}	utils.Response{data=dto.TimeEntryDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries/{id} [put]
+func (h *TimeEntryHandler) UpdateTimeEntry(c *gin.Context) {
+	utils.HandleUpdate(c, models.UpdateTimeEntry, convertTimeEntryToDTO, prepareTimeEntryUpdate, "time entry")
+}
+
+// DeleteTimeEntry handles DELETE /time-entries/:id
+//
+//	@Summary		Delete a time entry
+//	@Description	Delete a time entry by its ID
+//	@Tags			time-entries
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"Time Entry ID"
+//	@Success		204	{object}	utils.Response
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/time-entries/{id} [delete]
+func (h *TimeEntryHandler) DeleteTimeEntry(c *gin.Context) {
+	utils.HandleDelete(c, models.DeleteTimeEntry, "time entry")
+}
+
+// Helper functions for DTO conversion
+
+func convertTimeEntryToDTO(timeEntry *models.TimeEntry) dto.TimeEntryDto {
+	return dto.TimeEntryDto{
+		ID:          timeEntry.ID.String(),
+		CreatedAt:   timeEntry.CreatedAt,
+		UpdatedAt:   timeEntry.UpdatedAt,
+		UserID:      timeEntry.UserID.String(),     // Simplified conversion
+		ProjectID:   timeEntry.ProjectID.String(),  // Simplified conversion
+		ActivityID:  timeEntry.ActivityID.String(), // Simplified conversion
+		Start:       timeEntry.Start,
+		End:         timeEntry.End,
+		Description: timeEntry.Description,
+		Billable:    timeEntry.Billable,
+	}
+}
+
+func convertCreateTimeEntryDTOToModel(dto dto.TimeEntryCreateDto) (models.TimeEntryCreate, error) {
+	// Convert IDs from int to ULID (this is a simplification, adjust as needed)
+	userID, err := types.ULIDFromString(dto.UserID)
+	if err != nil {
+		return models.TimeEntryCreate{}, fmt.Errorf("invalid user ID: %w", err)
+	}
+
+	projectID, err := types.ULIDFromString(dto.ProjectID)
+	if err != nil {
+		return models.TimeEntryCreate{}, fmt.Errorf("invalid project ID: %w", err)
+	}
+
+	activityID, err := types.ULIDFromString(dto.ActivityID)
+	if err != nil {
+		return models.TimeEntryCreate{}, fmt.Errorf("invalid activity ID: %w", err)
+	}
+
+	return models.TimeEntryCreate{
+		UserID:      userID,
+		ProjectID:   projectID,
+		ActivityID:  activityID,
+		Start:       dto.Start,
+		End:         dto.End,
+		Description: dto.Description,
+		Billable:    dto.Billable,
+	}, nil
+}
+
+func convertUpdateTimeEntryDTOToModel(dto dto.TimeEntryUpdateDto, id types.ULID) (models.TimeEntryUpdate, error) {
+
+	update := models.TimeEntryUpdate{
+		ID: id,
+	}
+
+	if dto.UserID != nil {
+		userID, err := types.ULIDFromString(*dto.UserID)
+		if err != nil {
+			return models.TimeEntryUpdate{}, fmt.Errorf("invalid user ID: %w", err)
+		}
+		update.UserID = &userID
+	}
+
+	if dto.ProjectID != nil {
+		projectID, err := types.ULIDFromString(*dto.ProjectID)
+		if err != nil {
+			return models.TimeEntryUpdate{}, fmt.Errorf("invalid project ID: %w", err)
+		}
+		update.ProjectID = &projectID
+	}
+
+	if dto.ActivityID != nil {
+		activityID, err := types.ULIDFromString(*dto.ActivityID)
+		if err != nil {
+			return models.TimeEntryUpdate{}, fmt.Errorf("invalid activity ID: %w", err)
+		}
+		update.ActivityID = &activityID
+	}
+
+	if dto.Start != nil {
+		update.Start = dto.Start
+	}
+
+	if dto.End != nil {
+		update.End = dto.End
+	}
+
+	if dto.Description != nil {
+		update.Description = dto.Description
+	}
+
+	if dto.Billable != nil {
+		update.Billable = dto.Billable
+	}
+
+	return update, nil
+}
+
+// prepareTimeEntryUpdate prepares the time entry update object by parsing the ID, binding the JSON, and converting the DTO to a model
+func prepareTimeEntryUpdate(c *gin.Context) (models.TimeEntryUpdate, error) {
+	// Parse ID from URL
+	idStr := c.Param("id")
+	id, err := types.ULIDFromString(idStr)
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid time entry ID format")
+		return models.TimeEntryUpdate{}, err
+	}
+
+	// Parse request body
+	var timeEntryUpdateDTO dto.TimeEntryUpdateDto
+	if err := utils.BindJSON(c, &timeEntryUpdateDTO); err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return models.TimeEntryUpdate{}, err
+	}
+
+	// Convert DTO to model
+	timeEntryUpdate, err := convertUpdateTimeEntryDTOToModel(timeEntryUpdateDTO, id)
+	if err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return models.TimeEntryUpdate{}, err
+	}
+
+	return timeEntryUpdate, nil
+}
+
+// createTimeEntryWrapper is a wrapper function for models.CreateTimeEntry that takes a DTO as input
+func createTimeEntryWrapper(ctx context.Context, createDTO dto.TimeEntryCreateDto) (*models.TimeEntry, error) {
+	// Convert DTO to model
+	timeEntryCreate, err := convertCreateTimeEntryDTOToModel(createDTO)
+	if err != nil {
+		return nil, err
+	}
+
+	// Call the original function
+	return models.CreateTimeEntry(ctx, timeEntryCreate)
+}

backend/internal/api/handlers/user_handler.go

@@ -0,0 +1,359 @@
+package handlers
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/timetracker/backend/internal/api/dto"
+	"github.com/timetracker/backend/internal/api/middleware"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/api/utils"
+	"github.com/timetracker/backend/internal/models"
+	"github.com/timetracker/backend/internal/types"
+)
+
+// UserHandler handles user-related API endpoints
+type UserHandler struct{}
+
+// NewUserHandler creates a new UserHandler
+func NewUserHandler() *UserHandler {
+	return &UserHandler{}
+}
+
+// GetUsers handles GET /users
+//
+//	@Summary		Get all users
+//	@Description	Get a list of all users
+//	@Tags			users
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.UserDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/users [get]
+func (h *UserHandler) GetUsers(c *gin.Context) {
+	utils.HandleGetAll(c, models.GetAllUsers, convertUserToDTO, "users")
+}
+
+// GetUserByID handles GET /users/:id
+//
+//	@Summary		Get user by ID
+//	@Description	Get a user by their ID
+//	@Tags			users
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"User ID"
+//	@Success		200	{object}	utils.Response{data=dto.UserDto}
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/users/{id} [get]
+func (h *UserHandler) GetUserByID(c *gin.Context) {
+	// We need a custom wrapper for GetUserByID because the ID parameter is parsed differently
+	id, err := utils.ParseID(c, "id")
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid user ID format")
+		return
+	}
+
+	// Get user from the database
+	user, err := models.GetUserByID(c.Request.Context(), id)
+	if err != nil {
+		responses.InternalErrorResponse(c, "Error retrieving user: "+err.Error())
+		return
+	}
+
+	if user == nil {
+		responses.NotFoundResponse(c, "User not found")
+		return
+	}
+
+	// Convert to DTO
+	userDTO := convertUserToDTO(user)
+
+	responses.SuccessResponse(c, http.StatusOK, userDTO)
+}
+
+// CreateUser handles POST /users
+//
+//	@Summary		Create a new user
+//	@Description	Create a new user
+//	@Tags			users
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			user	body		dto.UserCreateDto	true	"User data"
+//	@Success		201		{object}	utils.Response{data=dto.UserDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/users [post]
+func (h *UserHandler) CreateUser(c *gin.Context) {
+	utils.HandleCreate(c, createUserWrapper, convertUserToDTO, "user")
+}
+
+// UpdateUser handles PUT /users/:id
+//
+//	@Summary		Update a user
+//	@Description	Update an existing user
+//	@Tags			users
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id		path		string				true	"User ID"
+//	@Param			user	body		dto.UserUpdateDto	true	"User data"
+//	@Success		200		{object}	utils.Response{data=dto.UserDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		404		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/users/{id} [put]
+func (h *UserHandler) UpdateUser(c *gin.Context) {
+	utils.HandleUpdate(c, models.UpdateUser, convertUserToDTO, prepareUserUpdate, "user")
+}
+
+// DeleteUser handles DELETE /users/:id
+//
+//	@Summary		Delete a user
+//	@Description	Delete a user by their ID
+//	@Tags			users
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Param			id	path		string	true	"User ID"
+//	@Success		204	{object}	utils.Response
+//	@Failure		400	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/users/{id} [delete]
+func (h *UserHandler) DeleteUser(c *gin.Context) {
+	utils.HandleDelete(c, models.DeleteUser, "user")
+}
+
+// Login handles POST /auth/login
+//
+//	@Summary		Login
+//	@Description	Authenticate a user and get a JWT token
+//	@Tags			auth
+//	@Accept			json
+//	@Produce		json
+//	@Param			credentials	body		dto.LoginDto	true	"Login credentials"
+//	@Success		200			{object}	utils.Response{data=dto.TokenDto}
+//	@Failure		400			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		401			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500			{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/auth/login [post]
+func (h *UserHandler) Login(c *gin.Context) {
+	// Parse request body
+	var loginDTO dto.LoginDto
+	if err := c.ShouldBindJSON(&loginDTO); err != nil {
+		responses.BadRequestResponse(c, "Invalid request body: "+err.Error())
+		return
+	}
+
+	// Authenticate user
+	user, err := models.AuthenticateUser(c.Request.Context(), loginDTO.Email, loginDTO.Password)
+	if err != nil {
+		responses.UnauthorizedResponse(c, "Invalid login credentials")
+		return
+	}
+
+	// Generate JWT token
+	token, err := middleware.GenerateToken(user, c)
+	if err != nil {
+		responses.InternalErrorResponse(c, "Error generating token: "+err.Error())
+		return
+	}
+
+	// Return token
+	tokenDTO := dto.TokenDto{
+		Token: token,
+		User:  convertUserToDTO(user),
+	}
+
+	responses.SuccessResponse(c, http.StatusOK, tokenDTO)
+}
+
+// Register handles POST /auth/register
+//
+//	@Summary		Register
+//	@Description	Register a new user and get a JWT token
+//	@Tags			auth
+//	@Accept			json
+//	@Produce		json
+//	@Param			user	body		dto.UserCreateDto	true	"User data"
+//	@Success		201		{object}	utils.Response{data=dto.TokenDto}
+//	@Failure		400		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500		{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/auth/register [post]
+func (h *UserHandler) Register(c *gin.Context) {
+	// Parse request body
+	var userCreateDTO dto.UserCreateDto
+	if err := c.ShouldBindJSON(&userCreateDTO); err != nil {
+		responses.BadRequestResponse(c, "Invalid request body: "+err.Error())
+		return
+	}
+
+	// Convert DTO to model
+	userCreate := convertCreateDTOToModel(userCreateDTO)
+
+	// Create user in the database
+	user, err := models.CreateUser(c.Request.Context(), userCreate)
+	if err != nil {
+		responses.InternalErrorResponse(c, "Error creating user: "+err.Error())
+		return
+	}
+
+	// Generate JWT token
+	token, err := middleware.GenerateToken(user, c)
+	if err != nil {
+		responses.InternalErrorResponse(c, "Error generating token: "+err.Error())
+		return
+	}
+
+	// Return token
+	tokenDTO := dto.TokenDto{
+		Token: token,
+		User:  convertUserToDTO(user),
+	}
+
+	responses.SuccessResponse(c, http.StatusCreated, tokenDTO)
+}
+
+// GetCurrentUser handles GET /auth/me
+//
+//	@Summary		Get current user
+//	@Description	Get the currently authenticated user
+//	@Tags			auth
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=dto.UserDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/auth/me [get]
+func (h *UserHandler) GetCurrentUser(c *gin.Context) {
+	// Get user ID from context (set by AuthMiddleware)
+	userID, err := middleware.GetUserIDFromContext(c)
+	if err != nil {
+		responses.UnauthorizedResponse(c, "User not authenticated")
+		return
+	}
+
+	// Get user from the database
+	user, err := models.GetUserByID(c.Request.Context(), userID)
+	if err != nil {
+		responses.InternalErrorResponse(c, "Error retrieving user: "+err.Error())
+		return
+	}
+
+	if user == nil {
+		responses.NotFoundResponse(c, "User not found")
+		return
+	}
+
+	// Convert to DTO
+	userDTO := convertUserToDTO(user)
+
+	responses.SuccessResponse(c, http.StatusOK, userDTO)
+}
+
+// Helper functions for DTO conversion
+
+func convertUserToDTO(user *models.User) dto.UserDto {
+	var companyID *string
+	if user.CompanyID != nil {
+		s := user.CompanyID.String()
+		companyID = &s
+	}
+	return dto.UserDto{
+		ID:         user.ID.String(),
+		CreatedAt:  user.CreatedAt,
+		UpdatedAt:  user.UpdatedAt,
+		Email:      user.Email,
+		Role:       user.Role,
+		CompanyID:  companyID,
+		HourlyRate: user.HourlyRate,
+	}
+}
+
+// prepareUserUpdate prepares the user update object by parsing the ID, binding the JSON, and converting the DTO to a model
+func prepareUserUpdate(c *gin.Context) (models.UserUpdate, error) {
+	// Parse ID from URL
+	idStr := c.Param("id")
+	id, err := types.ULIDFromString(idStr)
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid user ID format")
+		return models.UserUpdate{}, err
+	}
+
+	// Parse request body
+	var userUpdateDTO dto.UserUpdateDto
+	if err := utils.BindJSON(c, &userUpdateDTO); err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return models.UserUpdate{}, err
+	}
+
+	// Convert DTO to Model
+	update := models.UserUpdate{
+		ID: id,
+	}
+
+	if userUpdateDTO.Email != nil {
+		update.Email = userUpdateDTO.Email
+	}
+	if userUpdateDTO.Password != nil {
+		update.Password = userUpdateDTO.Password
+	}
+	if userUpdateDTO.Role != nil {
+		update.Role = userUpdateDTO.Role
+	}
+
+	if userUpdateDTO.CompanyID.Valid {
+		if userUpdateDTO.CompanyID.Value != nil {
+			companyID, err := types.ULIDFromString(*userUpdateDTO.CompanyID.Value)
+			if err != nil {
+				responses.BadRequestResponse(c, "Invalid company ID format")
+				return models.UserUpdate{}, err
+			}
+			update.CompanyID = types.NewNullable(companyID)
+		} else {
+			update.CompanyID = types.Null[types.ULID]()
+		}
+	}
+
+	if userUpdateDTO.HourlyRate != nil {
+		update.HourlyRate = userUpdateDTO.HourlyRate
+	}
+
+	return update, nil
+}
+
+func convertCreateDTOToModel(dto dto.UserCreateDto) models.UserCreate {
+	var companyID *types.ULID
+	if dto.CompanyID != nil {
+		wrapper, _ := types.ULIDFromString(*dto.CompanyID) // Ignoring error, validation happens in the model
+		companyID = &wrapper
+	}
+
+	return models.UserCreate{
+		Email:      dto.Email,
+		Password:   dto.Password,
+		Role:       dto.Role,
+		CompanyID:  companyID,
+		HourlyRate: dto.HourlyRate,
+	}
+}
+
+// createUserWrapper is a wrapper function for models.CreateUser that takes a DTO as input
+func createUserWrapper(ctx context.Context, createDTO dto.UserCreateDto) (*models.User, error) {
+	// Convert DTO to model
+	userCreate := convertCreateDTOToModel(createDTO)
+
+	// Call the original function
+	return models.CreateUser(ctx, userCreate)
+}

backend/internal/api/middleware/api_key_middleware.go

@@ -0,0 +1,35 @@
+package middleware
+
+import (
+	"github.com/gin-gonic/gin"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/config"
+)
+
+// APIKeyMiddleware checks for a valid API key if configured
+func APIKeyMiddleware(cfg *config.Config) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// Skip if no API key is configured
+		if cfg.APIKey == "" {
+			c.Next()
+			return
+		}
+
+		// Get API key from header
+		apiKey := c.GetHeader("X-API-Key")
+		if apiKey == "" {
+			responses.UnauthorizedResponse(c, "API key is required")
+			c.Abort()
+			return
+		}
+
+		// Validate API key
+		if apiKey != cfg.APIKey {
+			responses.UnauthorizedResponse(c, "Invalid API key")
+			c.Abort()
+			return
+		}
+
+		c.Next()
+	}
+}

backend/internal/api/middleware/jwt_auth.go

@@ -0,0 +1,364 @@
+package middleware
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/config"
+	"github.com/timetracker/backend/internal/models"
+	"github.com/timetracker/backend/internal/types"
+)
+
+var (
+	signKey   *rsa.PrivateKey
+	verifyKey *rsa.PublicKey
+)
+
+// InitJWTKeys initializes the JWT keys
+func InitJWTKeys() error {
+	cfg := config.MustLoadConfig()
+
+	// If a secret is provided, we'll use HMAC-SHA256, so no need for certificates
+	if cfg.JWTConfig.Secret != "" {
+		println("Using HMAC-SHA256 for JWT")
+		return nil
+	}
+
+	// Check if keys exist
+	privKeyPath := filepath.Join(cfg.JWTConfig.KeyDir, cfg.JWTConfig.PrivKeyFile)
+	pubKeyPath := filepath.Join(cfg.JWTConfig.KeyDir, cfg.JWTConfig.PubKeyFile)
+
+	keysExist := fileExists(privKeyPath) && fileExists(pubKeyPath)
+
+	// Generate keys if they don't exist and KeyGenerate is true
+	if !keysExist && cfg.JWTConfig.KeyGenerate {
+		println("Generating RSA keys")
+		if err := generateRSAKeys(cfg.JWTConfig); err != nil {
+			return fmt.Errorf("failed to generate RSA keys: %w", err)
+		}
+	} else if !keysExist {
+		return errors.New("JWT keys not found and key generation is disabled")
+	}
+
+	// Load keys
+	var err error
+	signKey, err = loadPrivateKey(privKeyPath)
+	if err != nil {
+		return fmt.Errorf("failed to load private key: %w", err)
+	}
+
+	verifyKey, err = loadPublicKey(pubKeyPath)
+	if err != nil {
+		return fmt.Errorf("failed to load public key: %w", err)
+	}
+
+	return nil
+}
+
+// fileExists checks if a file exists
+func fileExists(path string) bool {
+	_, err := os.Stat(path)
+	return !os.IsNotExist(err)
+}
+
+// generateRSAKeys generates RSA keys and saves them to disk
+func generateRSAKeys(cfg models.JWTConfig) error {
+	// Create key directory if it doesn't exist
+	if err := os.MkdirAll(cfg.KeyDir, 0700); err != nil {
+		return fmt.Errorf("failed to create key directory: %w", err)
+	}
+
+	// Generate private key
+	privateKey, err := rsa.GenerateKey(rand.Reader, cfg.KeyBits)
+	if err != nil {
+		return fmt.Errorf("failed to generate private key: %w", err)
+	}
+
+	// Save private key
+	privKeyPath := filepath.Join(cfg.KeyDir, cfg.PrivKeyFile)
+	privKeyFile, err := os.OpenFile(privKeyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return fmt.Errorf("failed to create private key file: %w", err)
+	}
+	defer privKeyFile.Close()
+
+	privKeyPEM := &pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(privateKey),
+	}
+
+	if err := pem.Encode(privKeyFile, privKeyPEM); err != nil {
+		return fmt.Errorf("failed to encode private key: %w", err)
+	}
+
+	// Save public key
+	pubKeyPath := filepath.Join(cfg.KeyDir, cfg.PubKeyFile)
+	pubKeyFile, err := os.OpenFile(pubKeyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return fmt.Errorf("failed to create public key file: %w", err)
+	}
+	defer pubKeyFile.Close()
+
+	pubKeyPEM := &pem.Block{
+		Type:  "RSA PUBLIC KEY",
+		Bytes: x509.MarshalPKCS1PublicKey(&privateKey.PublicKey),
+	}
+
+	if err := pem.Encode(pubKeyFile, pubKeyPEM); err != nil {
+		return fmt.Errorf("failed to encode public key: %w", err)
+	}
+
+	return nil
+}
+
+// loadPrivateKey loads a private key from a file
+func loadPrivateKey(path string) (*rsa.PrivateKey, error) {
+	keyData, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read private key file: %w", err)
+	}
+
+	block, _ := pem.Decode(keyData)
+	if block == nil {
+		return nil, errors.New("failed to parse PEM block containing the private key")
+	}
+
+	privateKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse private key: %w", err)
+	}
+
+	return privateKey, nil
+}
+
+// loadPublicKey loads a public key from a file
+func loadPublicKey(path string) (*rsa.PublicKey, error) {
+	keyData, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read public key file: %w", err)
+	}
+
+	block, _ := pem.Decode(keyData)
+	if block == nil {
+		return nil, errors.New("failed to parse PEM block containing the public key")
+	}
+
+	publicKey, err := x509.ParsePKCS1PublicKey(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse public key: %w", err)
+	}
+
+	return publicKey, nil
+}
+
+// Claims represents the JWT claims
+type Claims struct {
+	UserID    string  `json:"userId"`
+	Email     string  `json:"email"`
+	Role      string  `json:"role"`
+	CompanyID *string `json:"companyId"`
+	jwt.RegisteredClaims
+}
+
+// AuthMiddleware checks if the user is authenticated
+func AuthMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// Get the token from cookie
+		tokenString, err := c.Cookie("jwt")
+		if err != nil {
+			responses.UnauthorizedResponse(c, "Authentication cookie is required")
+			c.Abort()
+			return
+		}
+
+		claims, err := validateToken(tokenString)
+		if err != nil {
+			responses.UnauthorizedResponse(c, "Invalid or expired token")
+			c.Abort()
+			return
+		}
+
+		// Store user information in the context
+		c.Set("userID", claims.UserID)
+		c.Set("email", claims.Email)
+		c.Set("role", claims.Role)
+		c.Set("companyID", claims.CompanyID)
+
+		c.Next()
+	}
+}
+
+// RoleMiddleware checks if the user has the required role
+func RoleMiddleware(roles ...string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		userRole, exists := c.Get("role")
+		if !exists {
+			responses.UnauthorizedResponse(c, "User role not found in context")
+			c.Abort()
+			return
+		}
+
+		// Check if the user's role is in the allowed roles
+		roleStr, ok := userRole.(string)
+		if !ok {
+			responses.InternalErrorResponse(c, "Invalid role type in context")
+			c.Abort()
+			return
+		}
+
+		allowed := false
+		for _, role := range roles {
+			if roleStr == role {
+				allowed = true
+				break
+			}
+		}
+
+		if !allowed {
+			responses.ForbiddenResponse(c, "Insufficient permissions")
+			c.Abort()
+			return
+		}
+
+		c.Next()
+	}
+}
+
+// GenerateToken creates a new JWT token for a user
+func GenerateToken(user *models.User, c *gin.Context) (string, error) {
+	// Create the claims
+	var companyId *string
+	if user.CompanyID != nil {
+		wrapper := user.CompanyID.String()
+		companyId = &wrapper
+	}
+	claims := Claims{
+		UserID:    user.ID.String(),
+		Email:     user.Email,
+		Role:      user.Role,
+		CompanyID: companyId,
+		RegisteredClaims: jwt.RegisteredClaims{
+			ExpiresAt: jwt.NewNumericDate(time.Now().Add(config.MustLoadConfig().JWTConfig.TokenDuration)),
+			IssuedAt:  jwt.NewNumericDate(time.Now()),
+			NotBefore: jwt.NewNumericDate(time.Now()),
+		},
+	}
+
+	cfg := config.MustLoadConfig()
+	var token *jwt.Token
+	var tokenString string
+	var err error
+
+	// Choose signing method based on configuration
+	if cfg.JWTConfig.Secret != "" {
+		// Use HMAC-SHA256 if a secret is provided
+		token = jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+		tokenString, err = token.SignedString([]byte(cfg.JWTConfig.Secret))
+	} else {
+		// Use RSA if no secret is provided
+		token = jwt.NewWithClaims(jwt.SigningMethodRS256, claims)
+		tokenString, err = token.SignedString(signKey)
+	}
+
+	if err != nil {
+		return "", err
+	}
+
+	// Set the cookie
+	c.SetCookie("jwt", tokenString, int(cfg.JWTConfig.TokenDuration.Seconds()), "/", "", true, true)
+
+	return tokenString, nil
+}
+
+// validateToken validates a JWT token and returns the claims
+func validateToken(tokenString string) (*Claims, error) {
+	cfg := config.MustLoadConfig()
+
+	// Parse the token
+	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (any, error) {
+		// Check which signing method was used
+		if _, ok := token.Method.(*jwt.SigningMethodHMAC); ok {
+			// HMAC method was used, validate with secret
+			if cfg.JWTConfig.Secret == "" {
+				return nil, errors.New("HMAC signing method used but no secret configured")
+			}
+			return []byte(cfg.JWTConfig.Secret), nil
+		} else if _, ok := token.Method.(*jwt.SigningMethodRSA); ok {
+			// RSA method was used, validate with public key
+			if verifyKey == nil {
+				return nil, errors.New("RSA signing method used but no public key loaded")
+			}
+			return verifyKey, nil
+		}
+
+		return nil, errors.New("unexpected signing method")
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	// Check if the token is valid
+	if !token.Valid {
+		return nil, errors.New("invalid token")
+	}
+
+	// Get the claims
+	claims, ok := token.Claims.(*Claims)
+	if !ok {
+		return nil, errors.New("invalid claims")
+	}
+
+	return claims, nil
+}
+
+// GetUserIDFromContext extracts the user ID from the context
+func GetUserIDFromContext(c *gin.Context) (types.ULID, error) {
+	userID, exists := c.Get("userID")
+	if !exists {
+		return types.ULID{}, errors.New("user ID not found in context")
+	}
+
+	userIDStr, ok := userID.(string)
+	if !ok {
+		return types.ULID{}, errors.New("invalid user ID type in context")
+	}
+
+	id, err := ulid.Parse(userIDStr)
+	if err != nil {
+		return types.ULID{}, err
+	}
+
+	return types.FromULID(id), nil
+}
+
+// GetCompanyIDFromContext extracts the company ID from the context
+func GetCompanyIDFromContext(c *gin.Context) (types.ULID, error) {
+	companyID, exists := c.Get("companyID")
+	if !exists {
+		return types.ULID{}, errors.New("company ID not found in context")
+	}
+
+	companyIDStr, ok := companyID.(string)
+	if !ok {
+		return types.ULID{}, errors.New("invalid company ID type in context")
+	}
+
+	id, err := ulid.Parse(companyIDStr)
+	if err != nil {
+		return types.ULID{}, err
+	}
+
+	return types.FromULID(id), nil
+}

backend/internal/api/responses/response.go

@@ -0,0 +1,85 @@
+package responses
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+)
+
+// Response is a standardized API response structure
+type Response struct {
+	Success bool        `json:"success"`
+	Data    interface{} `json:"data,omitempty"`
+	Error   *ErrorInfo  `json:"error,omitempty"`
+}
+
+// ErrorInfo contains detailed error information
+type ErrorInfo struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+// ErrorResponse codes
+const (
+	ErrorCodeValidation   = "VALIDATION_ERROR"
+	ErrorCodeNotFound     = "NOT_FOUND"
+	ErrorCodeUnauthorized = "UNAUTHORIZED"
+	ErrorCodeForbidden    = "FORBIDDEN"
+	ErrorCodeInternal     = "INTERNAL_ERROR"
+	ErrorCodeBadRequest   = "BAD_REQUEST"
+	ErrorCodeConflict     = "CONFLICT"
+)
+
+// SuccessResponse sends a successful response with data
+func SuccessResponse(c *gin.Context, statusCode int, data interface{}) {
+	c.JSON(statusCode, Response{
+		Success: true,
+		Data:    data,
+	})
+}
+
+// ErrorResponse sends an error response
+func ErrorResponse(c *gin.Context, statusCode int, errorCode string, message string) {
+	c.JSON(statusCode, Response{
+		Success: false,
+		Error: &ErrorInfo{
+			Code:    errorCode,
+			Message: message,
+		},
+	})
+}
+
+// BadRequestResponse sends a 400 Bad Request response
+func BadRequestResponse(c *gin.Context, message string) {
+	ErrorResponse(c, http.StatusBadRequest, ErrorCodeBadRequest, message)
+}
+
+// ValidationErrorResponse sends a 400 Bad Request response for validation errors
+func ValidationErrorResponse(c *gin.Context, message string) {
+	ErrorResponse(c, http.StatusBadRequest, ErrorCodeValidation, message)
+}
+
+// NotFoundResponse sends a 404 Not Found response
+func NotFoundResponse(c *gin.Context, message string) {
+	ErrorResponse(c, http.StatusNotFound, ErrorCodeNotFound, message)
+}
+
+// UnauthorizedResponse sends a 401 Unauthorized response
+func UnauthorizedResponse(c *gin.Context, message string) {
+	ErrorResponse(c, http.StatusUnauthorized, ErrorCodeUnauthorized, message)
+}
+
+// ForbiddenResponse sends a 403 Forbidden response
+func ForbiddenResponse(c *gin.Context, message string) {
+	ErrorResponse(c, http.StatusForbidden, ErrorCodeForbidden, message)
+}
+
+// InternalErrorResponse sends a 500 Internal Server Error response
+func InternalErrorResponse(c *gin.Context, message string) {
+	ErrorResponse(c, http.StatusInternalServerError, ErrorCodeInternal, message)
+}
+
+// ConflictResponse sends a 409 Conflict response
+func ConflictResponse(c *gin.Context, message string) {
+	ErrorResponse(c, http.StatusConflict, ErrorCodeConflict, message)
+}

backend/internal/api/routes/router.go

@@ -0,0 +1,110 @@
+package routes
+
+import (
+	"github.com/gin-gonic/gin"
+	"github.com/timetracker/backend/internal/api/handlers"
+	"github.com/timetracker/backend/internal/api/middleware"
+	"github.com/timetracker/backend/internal/config"
+)
+
+// SetupRouter configures all the routes for the API
+func SetupRouter(r *gin.Engine, cfg *config.Config) {
+	// Create handlers
+	// Apply API key middleware to all API routes
+	r.Use(middleware.APIKeyMiddleware(cfg))
+	userHandler := handlers.NewUserHandler()
+	activityHandler := handlers.NewActivityHandler()
+	companyHandler := handlers.NewCompanyHandler()
+	customerHandler := handlers.NewCustomerHandler()
+	projectHandler := handlers.NewProjectHandler()
+	timeEntryHandler := handlers.NewTimeEntryHandler()
+
+	// API routes
+	api := r.Group("/api")
+	{
+		// Auth routes (public)
+		auth := api.Group("/auth")
+		{
+			auth.POST("/login", userHandler.Login)
+			auth.POST("/register", userHandler.Register)
+		}
+
+		// Protected routes
+		protected := api.Group("")
+		protected.Use(middleware.AuthMiddleware())
+		{
+			// Auth routes (protected)
+			protectedAuth := protected.Group("/auth")
+			{
+				protectedAuth.GET("/me", userHandler.GetCurrentUser)
+			}
+
+			// User routes
+			users := protected.Group("/users")
+			{
+				users.GET("", userHandler.GetUsers)
+				users.GET("/:id", userHandler.GetUserByID)
+				users.POST("", middleware.RoleMiddleware("admin"), userHandler.CreateUser)
+				users.PUT("/:id", middleware.RoleMiddleware("admin"), userHandler.UpdateUser)
+				users.DELETE("/:id", middleware.RoleMiddleware("admin"), userHandler.DeleteUser)
+			}
+
+			// Activity routes
+			activities := protected.Group("/activities")
+			{
+				activities.GET("", activityHandler.GetActivities)
+				activities.GET("/:id", activityHandler.GetActivityByID)
+				activities.POST("", middleware.RoleMiddleware("admin"), activityHandler.CreateActivity)
+				activities.PUT("/:id", middleware.RoleMiddleware("admin"), activityHandler.UpdateActivity)
+				activities.DELETE("/:id", middleware.RoleMiddleware("admin"), activityHandler.DeleteActivity)
+			}
+
+			// Company routes
+			companies := protected.Group("/companies")
+			{
+				companies.GET("", companyHandler.GetCompanies)
+				companies.GET("/:id", companyHandler.GetCompanyByID)
+				companies.POST("", middleware.RoleMiddleware("admin"), companyHandler.CreateCompany)
+				companies.PUT("/:id", middleware.RoleMiddleware("admin"), companyHandler.UpdateCompany)
+				companies.DELETE("/:id", middleware.RoleMiddleware("admin"), companyHandler.DeleteCompany)
+			}
+
+			// Customer routes
+			customers := protected.Group("/customers")
+			{
+				customers.GET("", customerHandler.GetCustomers)
+				customers.GET("/:id", customerHandler.GetCustomerByID)
+				customers.GET("/company/:companyId", customerHandler.GetCustomersByCompanyID)
+				customers.POST("", middleware.RoleMiddleware("admin"), customerHandler.CreateCustomer)
+				customers.PUT("/:id", middleware.RoleMiddleware("admin"), customerHandler.UpdateCustomer)
+				customers.DELETE("/:id", middleware.RoleMiddleware("admin"), customerHandler.DeleteCustomer)
+			}
+
+			// Project routes
+			projects := protected.Group("/projects")
+			{
+				projects.GET("", projectHandler.GetProjects)
+				projects.GET("/with-customers", projectHandler.GetProjectsWithCustomers)
+				projects.GET("/:id", projectHandler.GetProjectByID)
+				projects.GET("/customer/:customerId", projectHandler.GetProjectsByCustomerID)
+				projects.POST("", middleware.RoleMiddleware("admin"), projectHandler.CreateProject)
+				projects.PUT("/:id", middleware.RoleMiddleware("admin"), projectHandler.UpdateProject)
+				projects.DELETE("/:id", middleware.RoleMiddleware("admin"), projectHandler.DeleteProject)
+			}
+
+			// Time Entry routes
+			timeEntries := protected.Group("/time-entries")
+			{
+				timeEntries.GET("", timeEntryHandler.GetTimeEntries)
+				timeEntries.GET("/me", timeEntryHandler.GetMyTimeEntries)
+				timeEntries.GET("/range", timeEntryHandler.GetTimeEntriesByDateRange)
+				timeEntries.GET("/:id", timeEntryHandler.GetTimeEntryByID)
+				timeEntries.GET("/user/:userId", timeEntryHandler.GetTimeEntriesByUserID)
+				timeEntries.GET("/project/:projectId", timeEntryHandler.GetTimeEntriesByProjectID)
+				timeEntries.POST("", timeEntryHandler.CreateTimeEntry)
+				timeEntries.PUT("/:id", timeEntryHandler.UpdateTimeEntry)
+				timeEntries.DELETE("/:id", timeEntryHandler.DeleteTimeEntry)
+			}
+		}
+	}
+}

backend/internal/api/utils/handler_utils.go

@@ -0,0 +1,286 @@
+package utils
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/timetracker/backend/internal/api/responses"
+	"github.com/timetracker/backend/internal/types"
+)
+
+// ParseID parses an ID from the URL parameter and converts it to a types.ULID
+func ParseID(c *gin.Context, paramName string) (types.ULID, error) {
+	idStr := c.Param(paramName)
+	return types.ULIDFromString(idStr)
+}
+
+// BindJSON binds the request body to the provided struct
+func BindJSON(c *gin.Context, obj interface{}) error {
+	if err := c.ShouldBindJSON(obj); err != nil {
+		return fmt.Errorf("invalid request body: %w", err)
+	}
+	return nil
+}
+
+// ConvertToDTO converts a slice of models to a slice of DTOs using the provided conversion function
+func ConvertToDTO[M any, D any](models []M, convertFn func(*M) D) []D {
+	dtos := make([]D, len(models))
+	for i, model := range models {
+		// Create a copy of the model to avoid issues with loop variable capture
+		modelCopy := model
+		dtos[i] = convertFn(&modelCopy)
+	}
+	return dtos
+}
+
+// HandleGetAll is a generic function to handle GET all entities endpoints
+func HandleGetAll[M any, D any](
+	c *gin.Context,
+	getAllFn func(ctx context.Context) ([]M, error),
+	convertFn func(*M) D,
+	entityName string,
+) {
+	// Get entities from the database
+	entities, err := getAllFn(c.Request.Context())
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error retrieving %s: %s", entityName, err.Error()))
+		return
+	}
+
+	// Convert to DTOs
+	dtos := ConvertToDTO(entities, convertFn)
+
+	responses.SuccessResponse(c, 200, dtos)
+}
+
+// HandleGetByID is a generic function to handle GET entity by ID endpoints
+func HandleGetByID[M any, D any](
+	c *gin.Context,
+	getByIDFn func(ctx context.Context, id types.ULID) (*M, error),
+	convertFn func(*M) D,
+	entityName string,
+) {
+	// Parse ID from URL
+	id, err := ParseID(c, "id")
+	if err != nil {
+		responses.BadRequestResponse(c, fmt.Sprintf("Invalid %s ID format", entityName))
+		return
+	}
+
+	// Get entity from the database
+	entity, err := getByIDFn(c.Request.Context(), id)
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error retrieving %s: %s", entityName, err.Error()))
+		return
+	}
+
+	if entity == nil {
+		responses.NotFoundResponse(c, fmt.Sprintf("%s not found", entityName))
+		return
+	}
+
+	// Convert to DTO
+	dto := convertFn(entity)
+
+	responses.SuccessResponse(c, 200, dto)
+}
+
+// HandleCreate is a generic function to handle POST entity endpoints
+func HandleCreate[C any, M any, D any](
+	c *gin.Context,
+	createFn func(ctx context.Context, create C) (*M, error),
+	convertFn func(*M) D,
+	entityName string,
+) {
+	// Parse request body
+	var createDTO C
+	if err := BindJSON(c, &createDTO); err != nil {
+		responses.BadRequestResponse(c, err.Error())
+		return
+	}
+
+	// Create entity in the database
+	entity, err := createFn(c.Request.Context(), createDTO)
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error creating %s: %s", entityName, err.Error()))
+		return
+	}
+
+	// Convert to DTO
+	dto := convertFn(entity)
+
+	responses.SuccessResponse(c, 201, dto)
+}
+
+// HandleDelete is a generic function to handle DELETE entity endpoints
+func HandleDelete(
+	c *gin.Context,
+	deleteFn func(ctx context.Context, id types.ULID) error,
+	entityName string,
+) {
+	// Parse ID from URL
+	id, err := ParseID(c, "id")
+	if err != nil {
+		responses.BadRequestResponse(c, fmt.Sprintf("Invalid %s ID format", entityName))
+		return
+	}
+
+	// Delete entity from the database
+	err = deleteFn(c.Request.Context(), id)
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error deleting %s: %s", entityName, err.Error()))
+		return
+	}
+
+	responses.SuccessResponse(c, 204, nil)
+}
+
+// HandleUpdate is a generic function to handle PUT entity endpoints
+// It takes a prepareUpdateFn that handles parsing the ID, binding the JSON, and converting the DTO to a model update object
+func HandleUpdate[U any, M any, D any](
+	c *gin.Context,
+	updateFn func(ctx context.Context, update U) (*M, error),
+	convertFn func(*M) D,
+	prepareUpdateFn func(*gin.Context) (U, error),
+	entityName string,
+) {
+	// Prepare the update object (parse ID, bind JSON, convert DTO to model)
+	update, err := prepareUpdateFn(c)
+	if err != nil {
+		// The prepareUpdateFn should handle setting the appropriate error response
+		return
+	}
+
+	// Update entity in the database
+	entity, err := updateFn(c.Request.Context(), update)
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error updating %s: %s", entityName, err.Error()))
+		return
+	}
+
+	if entity == nil {
+		responses.NotFoundResponse(c, fmt.Sprintf("%s not found", entityName))
+		return
+	}
+
+	// Convert to DTO
+	dto := convertFn(entity)
+
+	responses.SuccessResponse(c, http.StatusOK, dto)
+}
+
+// HandleGetByFilter is a generic function to handle GET entities by a filter parameter
+func HandleGetByFilter[M any, D any](
+	c *gin.Context,
+	getByFilterFn func(ctx context.Context, filterID types.ULID) ([]M, error),
+	convertFn func(*M) D,
+	entityName string,
+	paramName string,
+) {
+	// Parse filter ID from URL
+	filterID, err := ParseID(c, paramName)
+	if err != nil {
+		responses.BadRequestResponse(c, fmt.Sprintf("Invalid %s ID format", paramName))
+		return
+	}
+
+	// Get entities from the database
+	entities, err := getByFilterFn(c.Request.Context(), filterID)
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error retrieving %s: %s", entityName, err.Error()))
+		return
+	}
+
+	// Convert to DTOs
+	dtos := ConvertToDTO(entities, convertFn)
+
+	responses.SuccessResponse(c, http.StatusOK, dtos)
+}
+
+// HandleGetByUserID is a specialized function to handle GET entities by user ID
+func HandleGetByUserID[M any, D any](
+	c *gin.Context,
+	getByUserIDFn func(ctx context.Context, userID types.ULID) ([]M, error),
+	convertFn func(*M) D,
+	entityName string,
+) {
+	// Get user ID from context (set by AuthMiddleware)
+	userID, exists := c.Get("userID")
+	if !exists {
+		responses.UnauthorizedResponse(c, "User not authenticated")
+		return
+	}
+
+	userIDStr, ok := userID.(string)
+	if !ok {
+		responses.InternalErrorResponse(c, "Invalid user ID type in context")
+		return
+	}
+
+	parsedUserID, err := types.ULIDFromString(userIDStr)
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error parsing user ID: %s", err.Error()))
+		return
+	}
+
+	// Get entities from the database
+	entities, err := getByUserIDFn(c.Request.Context(), parsedUserID)
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error retrieving %s: %s", entityName, err.Error()))
+		return
+	}
+
+	// Convert to DTOs
+	dtos := ConvertToDTO(entities, convertFn)
+
+	responses.SuccessResponse(c, http.StatusOK, dtos)
+}
+
+// HandleGetByDateRange is a specialized function to handle GET entities by date range
+func HandleGetByDateRange[M any, D any](
+	c *gin.Context,
+	getByDateRangeFn func(ctx context.Context, start, end time.Time) ([]M, error),
+	convertFn func(*M) D,
+	entityName string,
+) {
+	// Parse date range from query parameters
+	startStr := c.Query("start")
+	endStr := c.Query("end")
+
+	if startStr == "" || endStr == "" {
+		responses.BadRequestResponse(c, "Start and end dates are required")
+		return
+	}
+
+	start, err := time.Parse(time.RFC3339, startStr)
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid start date format. Use ISO 8601 format (e.g., 2023-01-01T00:00:00Z)")
+		return
+	}
+
+	end, err := time.Parse(time.RFC3339, endStr)
+	if err != nil {
+		responses.BadRequestResponse(c, "Invalid end date format. Use ISO 8601 format (e.g., 2023-01-01T00:00:00Z)")
+		return
+	}
+
+	if end.Before(start) {
+		responses.BadRequestResponse(c, "End date cannot be before start date")
+		return
+	}
+
+	// Get entities from the database
+	entities, err := getByDateRangeFn(c.Request.Context(), start, end)
+	if err != nil {
+		responses.InternalErrorResponse(c, fmt.Sprintf("Error retrieving %s: %s", entityName, err.Error()))
+		return
+	}
+
+	// Convert to DTOs
+	dtos := ConvertToDTO(entities, convertFn)
+
+	responses.SuccessResponse(c, http.StatusOK, dtos)
+}

backend/internal/config/config.go

@@ -0,0 +1,131 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/joho/godotenv"
+	"github.com/timetracker/backend/internal/models"
+	"gorm.io/gorm/logger"
+)
+
+// Config represents the application configuration
+type Config struct {
+	Database  models.DatabaseConfig
+	JWTConfig models.JWTConfig
+	APIKey    string
+}
+
+// LoadConfig loads configuration from environment variables and .env file
+func LoadConfig() (*Config, error) {
+	// Try loading .env file, but don't fail if it doesn't exist
+	_ = godotenv.Load()
+
+	cfg := &Config{
+		Database:  models.DefaultDatabaseConfig(),
+		JWTConfig: models.JWTConfig{},
+	}
+
+	// Load database configuration
+	if err := loadDatabaseConfig(cfg); err != nil {
+		return nil, fmt.Errorf("failed to load database config: %w", err)
+	}
+
+	// Load JWT configuration
+	if err := loadJWTConfig(cfg); err != nil {
+		return nil, fmt.Errorf("failed to load JWT config: %w", err)
+	}
+
+	// Load API key
+	cfg.APIKey = getEnv("API_KEY", "")
+
+	return cfg, nil
+}
+
+// loadJWTConfig loads JWT configuration from environment
+func loadJWTConfig(cfg *Config) error {
+	cfg.JWTConfig.Secret = getEnv("JWT_SECRET", "")
+	defaultDuration := 24 * time.Hour
+	durationStr := getEnv("JWT_TOKEN_DURATION", defaultDuration.String())
+
+	duration, err := time.ParseDuration(durationStr)
+	if err != nil {
+		return fmt.Errorf("invalid JWT_TOKEN_DURATION: %w", err)
+	}
+	cfg.JWTConfig.TokenDuration = duration
+
+	keyGenerateStr := getEnv("JWT_KEY_GENERATE", "true")
+	keyGenerate, err := strconv.ParseBool(keyGenerateStr)
+	if err != nil {
+		return fmt.Errorf("invalid JWT_KEY_GENERATE: %w", err)
+	}
+	cfg.JWTConfig.KeyGenerate = keyGenerate
+
+	cfg.JWTConfig.KeyDir = getEnv("JWT_KEY_DIR", "./keys")
+	cfg.JWTConfig.PrivKeyFile = getEnv("JWT_PRIV_KEY_FILE", "jwt.key")
+	cfg.JWTConfig.PubKeyFile = getEnv("JWT_PUB_KEY_FILE", "jwt.key.pub")
+
+	keyBitsStr := getEnv("JWT_KEY_BITS", "2048")
+	keyBits, err := strconv.Atoi(keyBitsStr)
+	if err != nil {
+		return fmt.Errorf("invalid JWT_KEY_BITS: %w", err)
+	}
+	cfg.JWTConfig.KeyBits = keyBits
+
+	return nil
+}
+
+// loadDatabaseConfig loads database configuration from environment
+func loadDatabaseConfig(cfg *Config) error {
+	// Required fields
+	cfg.Database.Host = getEnv("DB_HOST", cfg.Database.Host)
+	cfg.Database.User = getEnv("DB_USER", cfg.Database.User)
+	cfg.Database.Password = getEnv("DB_PASSWORD", cfg.Database.Password)
+	cfg.Database.DBName = getEnv("DB_NAME", cfg.Database.DBName)
+	cfg.Database.SSLMode = getEnv("DB_SSLMODE", cfg.Database.SSLMode)
+
+	// Optional fields with parsing
+	if port := getEnv("DB_PORT", ""); port != "" {
+		portInt, err := strconv.Atoi(port)
+		if err != nil || portInt <= 0 {
+			return errors.New("invalid DB_PORT value")
+		}
+		cfg.Database.Port = portInt
+	}
+
+	// Log level based on environment
+	if os.Getenv("ENVIRONMENT") == "production" {
+		cfg.Database.LogLevel = logger.Error
+	} else {
+		cfg.Database.LogLevel = logger.Info
+	}
+
+	// Validate required fields
+	if cfg.Database.Host == "" || cfg.Database.User == "" ||
+		cfg.Database.Password == "" || cfg.Database.DBName == "" {
+		return errors.New("missing required database configuration")
+	}
+
+	return nil
+}
+
+// getEnv gets an environment variable with fallback
+func getEnv(key, fallback string) string {
+	if value, exists := os.LookupEnv(key); exists {
+		return value
+	}
+	return fallback
+}
+
+// MustLoadConfig loads configuration or panics on failure
+func MustLoadConfig() *Config {
+	cfg, err := LoadConfig()
+	if err != nil {
+		log.Fatalf("Failed to load config: %v", err)
+	}
+	return cfg
+}

backend/internal/dtos/activity_dto.go

@@ -1,30 +0,0 @@
-package dto
-
-import (
-	"time"
-
-	"github.com/oklog/ulid/v2"
-)
-
-type ActivityDto struct {
-	ID           ulid.ULID `json:"id"`
-	CreatedAt    time.Time `json:"createdAt"`
-	UpdatedAt    time.Time `json:"updatedAt"`
-	LastEditorID ulid.ULID `json:"lastEditorID"`
-	Name         string    `json:"name"`
-	BillingRate  float64   `json:"billingRate"`
-}
-
-type ActivityCreateDto struct {
-	Name        string  `json:"name"`
-	BillingRate float64 `json:"billingRate"`
-}
-
-type ActivityUpdateDto struct {
-	ID           ulid.ULID  `json:"id"`
-	CreatedAt    *time.Time `json:"createdAt"`
-	UpdatedAt    *time.Time `json:"updatedAt"`
-	LastEditorID *ulid.ULID `json:"lastEditorID"`
-	Name         *string    `json:"name"`
-	BillingRate  *float64   `json:"billingRate"`
-}

backend/internal/dtos/auth_dto.go

@@ -1,6 +0,0 @@
-package dto
-
-type AuthDto struct {
-	Email    string `json:"email"`
-	Password string `json:"password"`
-}

backend/internal/dtos/company_dto.go

@@ -1,27 +0,0 @@
-package dto
-
-import (
-	"time"
-
-	"github.com/oklog/ulid/v2"
-)
-
-type CompanyDto struct {
-	ID           ulid.ULID `json:"id"`
-	CreatedAt    time.Time `json:"createdAt"`
-	UpdatedAt    time.Time `json:"updatedAt"`
-	LastEditorID ulid.ULID `json:"lastEditorID"`
-	Name         string    `json:"name"`
-}
-
-type CompanyCreateDto struct {
-	Name string `json:"name"`
-}
-
-type CompanyUpdateDto struct {
-	ID           ulid.ULID  `json:"id"`
-	CreatedAt    *time.Time `json:"createdAt"`
-	UpdatedAt    *time.Time `json:"updatedAt"`
-	LastEditorID *ulid.ULID `json:"lastEditorID"`
-	Name         *string    `json:"name"`
-}

backend/internal/dtos/customer_dto.go

@@ -1,30 +0,0 @@
-package dto
-
-import (
-	"time"
-
-	"github.com/oklog/ulid/v2"
-)
-
-type CustomerDto struct {
-	ID           ulid.ULID `json:"id"`
-	CreatedAt    time.Time `json:"createdAt"`
-	UpdatedAt    time.Time `json:"updatedAt"`
-	LastEditorID ulid.ULID `json:"lastEditorID"`
-	Name         string    `json:"name"`
-	CompanyID    int       `json:"companyId"`
-}
-
-type CustomerCreateDto struct {
-	Name      string `json:"name"`
-	CompanyID int    `json:"companyId"`
-}
-
-type CustomerUpdateDto struct {
-	ID           ulid.ULID  `json:"id"`
-	CreatedAt    *time.Time `json:"createdAt"`
-	UpdatedAt    *time.Time `json:"updatedAt"`
-	LastEditorID *ulid.ULID `json:"lastEditorID"`
-	Name         *string    `json:"name"`
-	CompanyID    *int       `json:"companyId"`
-}

backend/internal/dtos/project_dto.go

@@ -1,30 +0,0 @@
-package dto
-
-import (
-	"time"
-
-	"github.com/oklog/ulid/v2"
-)
-
-type ProjectDto struct {
-	ID           ulid.ULID `json:"id"`
-	CreatedAt    time.Time `json:"createdAt"`
-	UpdatedAt    time.Time `json:"updatedAt"`
-	LastEditorID ulid.ULID `json:"lastEditorID"`
-	Name         string    `json:"name"`
-	CustomerID   int       `json:"customerId"`
-}
-
-type ProjectCreateDto struct {
-	Name       string `json:"name"`
-	CustomerID int    `json:"customerId"`
-}
-
-type ProjectUpdateDto struct {
-	ID           ulid.ULID  `json:"id"`
-	CreatedAt    *time.Time `json:"createdAt"`
-	UpdatedAt    *time.Time `json:"updatedAt"`
-	LastEditorID *ulid.ULID `json:"lastEditorID"`
-	Name         *string    `json:"name"`
-	CustomerID   *int       `json:"customerId"`
-}

backend/internal/dtos/timeentry_dto.go

@@ -1,45 +0,0 @@
-package dto
-
-import (
-	"time"
-
-	"github.com/oklog/ulid/v2"
-)
-
-type TimeEntryDto struct {
-	ID           ulid.ULID `json:"id"`
-	CreatedAt    time.Time `json:"createdAt"`
-	UpdatedAt    time.Time `json:"updatedAt"`
-	LastEditorID ulid.ULID `json:"lastEditorID"`
-	UserID       int       `json:"userId"`
-	ProjectID    int       `json:"projectId"`
-	ActivityID   int       `json:"activityId"`
-	Start        time.Time `json:"start"`
-	End          time.Time `json:"end"`
-	Description  string    `json:"description"`
-	Billable     int       `json:"billable"` // Percentage (0-100)
-}
-
-type TimeEntryCreateDto struct {
-	UserID      int       `json:"userId"`
-	ProjectID   int       `json:"projectId"`
-	ActivityID  int       `json:"activityId"`
-	Start       time.Time `json:"start"`
-	End         time.Time `json:"end"`
-	Description string    `json:"description"`
-	Billable    int       `json:"billable"` // Percentage (0-100)
-}
-
-type TimeEntryUpdateDto struct {
-	ID           ulid.ULID  `json:"id"`
-	CreatedAt    *time.Time `json:"createdAt"`
-	UpdatedAt    *time.Time `json:"updatedAt"`
-	LastEditorID *ulid.ULID `json:"lastEditorID"`
-	UserID       *int       `json:"userId"`
-	ProjectID    *int       `json:"projectId"`
-	ActivityID   *int       `json:"activityId"`
-	Start        *time.Time `json:"start"`
-	End          *time.Time `json:"end"`
-	Description  *string    `json:"description"`
-	Billable     *int       `json:"billable"` // Percentage (0-100)
-}

backend/internal/dtos/user_dto.go

@@ -1,38 +0,0 @@
-package dto
-
-import (
-	"time"
-
-	"github.com/oklog/ulid/v2"
-)
-
-type UserDto struct {
-	ID           ulid.ULID `json:"id"`
-	CreatedAt    time.Time `json:"createdAt"`
-	UpdatedAt    time.Time `json:"updatedAt"`
-	LastEditorID ulid.ULID `json:"lastEditorID"`
-	Email        string    `json:"email"`
-	Role         string    `json:"role"`
-	CompanyID    int       `json:"companyId"`
-	HourlyRate   float64   `json:"hourlyRate"`
-}
-
-type UserCreateDto struct {
-	Email      string  `json:"email"`
-	Password   string  `json:"password"`
-	Role       string  `json:"role"`
-	CompanyID  int     `json:"companyId"`
-	HourlyRate float64 `json:"hourlyRate"`
-}
-
-type UserUpdateDto struct {
-	ID           ulid.ULID  `json:"id"`
-	CreatedAt    *time.Time `json:"createdAt"`
-	UpdatedAt    *time.Time `json:"updatedAt"`
-	LastEditorID *ulid.ULID `json:"lastEditorID"`
-	Email        *string    `json:"email"`
-	Password     *string    `json:"password"`
-	Role         *string    `json:"role"`
-	CompanyID    *int       `json:"companyId"`
-	HourlyRate   *float64   `json:"hourlyRate"`
-}

backend/internal/models/activity.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"errors"
 
-	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/types"
 	"gorm.io/gorm"
 )
 
@@ -22,7 +22,7 @@ func (Activity) TableName() string {
 
 // ActivityUpdate contains the updatable fields of an Activity
 type ActivityUpdate struct {
-	ID          ulid.ULID `gorm:"-"` // Use "-" to indicate that this field should be ignored
+	ID          types.ULID `gorm:"-"` // Use "-" to indicate that this field should be ignored
 	Name        *string    `gorm:"column:name"`
 	BillingRate *float64   `gorm:"column:billing_rate"`
 }
@@ -34,7 +34,7 @@ type ActivityCreate struct {
 }
 
 // GetActivityByID finds an Activity by its ID
-func GetActivityByID(ctx context.Context, id ulid.ULID) (*Activity, error) {
+func GetActivityByID(ctx context.Context, id types.ULID) (*Activity, error) {
 	var activity Activity
 	result := GetEngine(ctx).Where("id = ?", id).First(&activity)
 	if result.Error != nil {
@@ -90,7 +90,7 @@ func UpdateActivity(ctx context.Context, update ActivityUpdate) (*Activity, erro
 }
 
 // DeleteActivity deletes an Activity by its ID
-func DeleteActivity(ctx context.Context, id ulid.ULID) error {
+func DeleteActivity(ctx context.Context, id types.ULID) error {
 	result := GetEngine(ctx).Delete(&Activity{}, id)
 	return result.Error
 }

backend/internal/models/base.go

@@ -5,11 +5,12 @@ import (
 	"time"
 
 	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/types"
 	"gorm.io/gorm"
 )
 
 type EntityBase struct {
-	ID        ulid.ULID      `gorm:"type:uuid;primaryKey"`
+	ID        types.ULID     `gorm:"type:bytea;primaryKey"`
 	CreatedAt time.Time      `gorm:"index"`
 	UpdatedAt time.Time      `gorm:"index"`
 	DeletedAt gorm.DeletedAt `gorm:"index"`
@@ -17,10 +18,11 @@ type EntityBase struct {
 
 // BeforeCreate is called by GORM before creating a record
 func (eb *EntityBase) BeforeCreate(tx *gorm.DB) error {
-	if eb.ID.Compare(ulid.ULID{}) == 0 { // If ID is empty
-		// Generate a new ULID
+	if eb.ID.Compare(types.ULID{}) == 0 { // If ID is empty
+		// Generate a new types.ULID
 		entropy := ulid.Monotonic(rand.New(rand.NewSource(time.Now().UnixNano())), 0)
-		eb.ID = ulid.MustNew(ulid.Timestamp(time.Now()), entropy)
+		newID := ulid.MustNew(ulid.Timestamp(time.Now()), entropy)
+		eb.ID = types.ULID{ULID: newID}
 	}
 	return nil
 }

backend/internal/models/company.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"errors"
 
-	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/types"
 	"gorm.io/gorm"
 )
 
@@ -26,12 +26,12 @@ type CompanyCreate struct {
 
 // CompanyUpdate contains the updatable fields of a company
 type CompanyUpdate struct {
-	ID   ulid.ULID `gorm:"-"` // Exclude from updates
+	ID   types.ULID `gorm:"-"` // Exclude from updates
 	Name *string    `gorm:"column:name"`
 }
 
 // GetCompanyByID finds a company by its ID
-func GetCompanyByID(ctx context.Context, id ulid.ULID) (*Company, error) {
+func GetCompanyByID(ctx context.Context, id types.ULID) (*Company, error) {
 	var company Company
 	result := GetEngine(ctx).Where("id = ?", id).First(&company)
 	if result.Error != nil {
@@ -95,7 +95,7 @@ func UpdateCompany(ctx context.Context, update CompanyUpdate) (*Company, error)
 }
 
 // DeleteCompany deletes a company by its ID
-func DeleteCompany(ctx context.Context, id ulid.ULID) error {
+func DeleteCompany(ctx context.Context, id types.ULID) error {
 	result := GetEngine(ctx).Delete(&Company{}, id)
 	return result.Error
 }

backend/internal/models/customer.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"errors"
 
-	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/types"
 	"gorm.io/gorm"
 )
 
@@ -12,7 +12,8 @@ import (
 type Customer struct {
 	EntityBase
 	Name        string      `gorm:"column:name"`
-	CompanyID int    `gorm:"column:company_id"`
+	CompanyID   *types.ULID `gorm:"type:bytea;column:company_id"`
+	OwnerUserID *types.ULID `gorm:"type:bytea;column:owner_user_id"`
 }
 
 // TableName specifies the table name for GORM
@@ -23,18 +24,20 @@ func (Customer) TableName() string {
 // CustomerCreate contains the fields for creating a new customer
 type CustomerCreate struct {
 	Name        string
-	CompanyID int
+	CompanyID   *types.ULID
+	OwnerUserID *types.ULID
 }
 
 // CustomerUpdate contains the updatable fields of a customer
 type CustomerUpdate struct {
-	ID        ulid.ULID `gorm:"-"` // Exclude from updates
+	ID          types.ULID  `gorm:"-"` // Exclude from updates
 	Name        *string     `gorm:"column:name"`
-	CompanyID *int      `gorm:"column:company_id"`
+	CompanyID   *types.ULID `gorm:"column:company_id"`
+	OwnerUserID *types.ULID `gorm:"column:owner_user_id"`
 }
 
 // GetCustomerByID finds a customer by its ID
-func GetCustomerByID(ctx context.Context, id ulid.ULID) (*Customer, error) {
+func GetCustomerByID(ctx context.Context, id types.ULID) (*Customer, error) {
 	var customer Customer
 	result := GetEngine(ctx).Where("id = ?", id).First(&customer)
 	if result.Error != nil {
@@ -90,7 +93,7 @@ func UpdateCustomer(ctx context.Context, update CustomerUpdate) (*Customer, erro
 }
 
 // DeleteCustomer deletes a customer by its ID
-func DeleteCustomer(ctx context.Context, id ulid.ULID) error {
+func DeleteCustomer(ctx context.Context, id types.ULID) error {
 	result := GetEngine(ctx).Delete(&Customer{}, id)
 	return result.Error
 }

backend/internal/models/db.go

@@ -4,11 +4,14 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log"
 	"reflect"
 	"strings"
+	"time"
 
 	"gorm.io/driver/postgres" // For PostgreSQL
 	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
 )
 
 // Global variable for the DB connection
@@ -22,6 +25,26 @@ type DatabaseConfig struct {
 	Password     string
 	DBName       string
 	SSLMode      string
+	MaxIdleConns int           // Maximum number of idle connections
+	MaxOpenConns int           // Maximum number of open connections
+	MaxLifetime  time.Duration // Maximum lifetime of a connection
+	LogLevel     logger.LogLevel
+}
+
+// DefaultDatabaseConfig returns a default configuration with sensible values
+func DefaultDatabaseConfig() DatabaseConfig {
+	return DatabaseConfig{
+		Host:         "localhost",
+		Port:         5432,
+		User:         "timetracker",
+		Password:     "password",
+		DBName:       "timetracker",
+		SSLMode:      "disable",
+		MaxIdleConns: 10,
+		MaxOpenConns: 100,
+		MaxLifetime:  time.Hour,
+		LogLevel:     logger.Info,
+	}
 }
 
 // InitDB initializes the database connection (once at startup)
@@ -31,22 +54,118 @@ func InitDB(config DatabaseConfig) error {
 	dsn := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=%s",
 		config.Host, config.Port, config.User, config.Password, config.DBName, config.SSLMode)
 
-	// Establish database connection
-	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{})
+	// Configure GORM logger
+	gormLogger := logger.New(
+		log.New(log.Writer(), "\r\n", log.LstdFlags), // io writer
+		logger.Config{
+			SlowThreshold:             200 * time.Millisecond, // Slow SQL threshold
+			LogLevel:                  config.LogLevel,        // Log level
+			IgnoreRecordNotFoundError: true,                   // Ignore ErrRecordNotFound error for logger
+			Colorful:                  true,                   // Enable color
+		},
+	)
+
+	// Establish database connection with custom logger
+	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
+		Logger: gormLogger,
+	})
 	if err != nil {
 		return fmt.Errorf("error connecting to the database: %w", err)
 	}
 
+	// Configure connection pool
+	sqlDB, err := db.DB()
+	if err != nil {
+		return fmt.Errorf("error getting database connection: %w", err)
+	}
+
+	// Set connection pool parameters
+	sqlDB.SetMaxIdleConns(config.MaxIdleConns)
+	sqlDB.SetMaxOpenConns(config.MaxOpenConns)
+	sqlDB.SetConnMaxLifetime(config.MaxLifetime)
+
 	defaultDB = db
 	return nil
 }
 
+// MigrateDB performs database migrations for all models
+func MigrateDB() error {
+	if defaultDB == nil {
+		return errors.New("database not initialized")
+	}
+
+	log.Println("Starting database migration...")
+
+	// Add all models that should be migrated here
+	err := defaultDB.AutoMigrate(
+		&Company{},
+		&User{},
+		&Customer{},
+		&Project{},
+		&Activity{},
+		&TimeEntry{},
+	)
+
+	if err != nil {
+		return fmt.Errorf("error migrating database: %w", err)
+	}
+
+	log.Println("Database migration completed successfully")
+	return nil
+}
+
 // GetEngine returns the DB instance, possibly with context
 func GetEngine(ctx context.Context) *gorm.DB {
+	if defaultDB == nil {
+		panic("database not initialized")
+	}
 	// If a special transaction is in ctx, you could check it here
 	return defaultDB.WithContext(ctx)
 }
 
+// CloseDB closes the database connection
+func CloseDB() error {
+	if defaultDB == nil {
+		return nil
+	}
+
+	sqlDB, err := defaultDB.DB()
+	if err != nil {
+		return fmt.Errorf("error getting database connection: %w", err)
+	}
+
+	if err := sqlDB.Close(); err != nil {
+		return fmt.Errorf("error closing database connection: %w", err)
+	}
+
+	return nil
+}
+
+func GetGormDB(dbConfig DatabaseConfig, dbName string) (*gorm.DB, error) {
+	dsn := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=%s",
+		dbConfig.Host, dbConfig.Port, dbConfig.User, dbConfig.Password, dbName, dbConfig.SSLMode)
+
+	// Configure GORM logger
+	gormLogger := logger.New(
+		log.New(log.Writer(), "\r\n", log.LstdFlags), // io writer
+		logger.Config{
+			SlowThreshold:             200 * time.Millisecond, // Slow SQL threshold
+			LogLevel:                  dbConfig.LogLevel,      // Log level
+			IgnoreRecordNotFoundError: true,                   // Ignore ErrRecordNotFound error for logger
+			Colorful:                  true,                   // Enable color
+		},
+	)
+
+	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
+		Logger: gormLogger,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("error connecting to the database: %w", err)
+	}
+
+	return db, nil
+}
+
 // UpdateModel updates a model based on the set pointer fields
 func UpdateModel(ctx context.Context, model any, updates any) error {
 	updateValue := reflect.ValueOf(updates)

backend/internal/models/jwt.go

@@ -0,0 +1,13 @@
+package models
+
+import "time"
+
+type JWTConfig struct {
+	Secret        string        `env:"JWT_SECRET" default:""`
+	TokenDuration time.Duration `env:"JWT_TOKEN_DURATION" default:"24h"`
+	KeyGenerate   bool          `env:"JWT_KEY_GENERATE" default:"true"`
+	KeyDir        string        `env:"JWT_KEY_DIR" default:"./keys"`
+	PrivKeyFile   string        `env:"JWT_PRIV_KEY_FILE" default:"jwt.key"`
+	PubKeyFile    string        `env:"JWT_PUB_KEY_FILE" default:"jwt.key.pub"`
+	KeyBits       int           `env:"JWT_KEY_BITS" default:"2048"`
+}

backend/internal/models/project.go

@@ -5,7 +5,7 @@ import (
 	"errors"
 	"fmt"
 
-	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/types"
 	"gorm.io/gorm"
 )
 
@@ -13,7 +13,7 @@ import (
 type Project struct {
 	EntityBase
 	Name       string      `gorm:"column:name;not null"`
-	CustomerID ulid.ULID `gorm:"column:customer_id;type:uuid;not null"`
+	CustomerID *types.ULID `gorm:"column:customer_id;type:bytea;not null"`
 
 	// Relationships (for Eager Loading)
 	Customer *Customer `gorm:"foreignKey:CustomerID"`
@@ -27,14 +27,14 @@ func (Project) TableName() string {
 // ProjectCreate contains the fields for creating a new project
 type ProjectCreate struct {
 	Name       string
-	CustomerID ulid.ULID
+	CustomerID *types.ULID
 }
 
 // ProjectUpdate contains the updatable fields of a project
 type ProjectUpdate struct {
-	ID         ulid.ULID  `gorm:"-"` // Exclude from updates
+	ID         types.ULID  `gorm:"-"` // Exclude from updates
 	Name       *string     `gorm:"column:name"`
-	CustomerID *ulid.ULID `gorm:"column:customer_id"`
+	CustomerID *types.ULID `gorm:"column:customer_id"`
 }
 
 // Validate checks if the Create struct contains valid data
@@ -43,7 +43,7 @@ func (pc *ProjectCreate) Validate() error {
 		return errors.New("project name cannot be empty")
 	}
 	// Check for valid CustomerID
-	if pc.CustomerID.Compare(ulid.ULID{}) == 0 {
+	if pc.CustomerID.Compare(types.ULID{}) == 0 {
 		return errors.New("customerID cannot be empty")
 	}
 	return nil
@@ -58,7 +58,7 @@ func (pu *ProjectUpdate) Validate() error {
 }
 
 // GetProjectByID finds a project by its ID
-func GetProjectByID(ctx context.Context, id ulid.ULID) (*Project, error) {
+func GetProjectByID(ctx context.Context, id types.ULID) (*Project, error) {
 	var project Project
 	result := GetEngine(ctx).Where("id = ?", id).First(&project)
 	if result.Error != nil {
@@ -71,7 +71,7 @@ func GetProjectByID(ctx context.Context, id ulid.ULID) (*Project, error) {
 }
 
 // GetProjectWithCustomer loads a project with the associated customer information
-func GetProjectWithCustomer(ctx context.Context, id ulid.ULID) (*Project, error) {
+func GetProjectWithCustomer(ctx context.Context, id types.ULID) (*Project, error) {
 	var project Project
 	result := GetEngine(ctx).Preload("Customer").Where("id = ?", id).First(&project)
 	if result.Error != nil {
@@ -104,9 +104,9 @@ func GetAllProjectsWithCustomers(ctx context.Context) ([]Project, error) {
 }
 
 // GetProjectsByCustomerID returns all projects of a specific customer
-func GetProjectsByCustomerID(ctx context.Context, customerID ulid.ULID) ([]Project, error) {
+func GetProjectsByCustomerID(ctx context.Context, customerId types.ULID) ([]Project, error) {
 	var projects []Project
-	result := GetEngine(ctx).Where("customer_id = ?", customerID).Find(&projects)
+	result := GetEngine(ctx).Where("customer_id = ?", customerId.ULID).Find(&projects)
 	if result.Error != nil {
 		return nil, result.Error
 	}
@@ -121,13 +121,15 @@ func CreateProject(ctx context.Context, create ProjectCreate) (*Project, error)
 	}
 
 	// Check if the customer exists
-	customer, err := GetCustomerByID(ctx, create.CustomerID)
+	if create.CustomerID == nil {
+		customer, err := GetCustomerByID(ctx, *create.CustomerID)
 		if err != nil {
 			return nil, fmt.Errorf("error checking the customer: %w", err)
 		}
 		if customer == nil {
 			return nil, errors.New("the specified customer does not exist")
 		}
+	}
 
 	project := Project{
 		Name:       create.Name,
@@ -177,7 +179,7 @@ func UpdateProject(ctx context.Context, update ProjectUpdate) (*Project, error)
 }
 
 // DeleteProject deletes a project by its ID
-func DeleteProject(ctx context.Context, id ulid.ULID) error {
+func DeleteProject(ctx context.Context, id types.ULID) error {
 	// Here you could check if dependent entities exist
 	result := GetEngine(ctx).Delete(&Project{}, id)
 	if result.Error != nil {

backend/internal/models/timeentry.go

@@ -6,16 +6,16 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/types"
 	"gorm.io/gorm"
 )
 
 // TimeEntry represents a time entry in the system
 type TimeEntry struct {
 	EntityBase
-	UserID      ulid.ULID `gorm:"column:user_id;type:uuid;not null;index"`
-	ProjectID   ulid.ULID `gorm:"column:project_id;type:uuid;not null;index"`
-	ActivityID  ulid.ULID `gorm:"column:activity_id;type:uuid;not null;index"`
+	UserID      types.ULID `gorm:"column:user_id;type:bytea;not null;index"`
+	ProjectID   types.ULID `gorm:"column:project_id;type:bytea;not null;index"`
+	ActivityID  types.ULID `gorm:"column:activity_id;type:bytea;not null;index"`
 	Start       time.Time  `gorm:"column:start;not null"`
 	End         time.Time  `gorm:"column:end;not null"`
 	Description string     `gorm:"column:description"`
@@ -34,9 +34,9 @@ func (TimeEntry) TableName() string {
 
 // TimeEntryCreate contains the fields for creating a new time entry
 type TimeEntryCreate struct {
-	UserID      ulid.ULID
-	ProjectID   ulid.ULID
-	ActivityID  ulid.ULID
+	UserID      types.ULID
+	ProjectID   types.ULID
+	ActivityID  types.ULID
 	Start       time.Time
 	End         time.Time
 	Description string
@@ -45,10 +45,10 @@ type TimeEntryCreate struct {
 
 // TimeEntryUpdate contains the updatable fields of a time entry
 type TimeEntryUpdate struct {
-	ID          ulid.ULID  `gorm:"-"` // Exclude from updates
-	UserID      *ulid.ULID `gorm:"column:user_id"`
-	ProjectID   *ulid.ULID `gorm:"column:project_id"`
-	ActivityID  *ulid.ULID `gorm:"column:activity_id"`
+	ID          types.ULID  `gorm:"-"` // Exclude from updates
+	UserID      *types.ULID `gorm:"column:user_id"`
+	ProjectID   *types.ULID `gorm:"column:project_id"`
+	ActivityID  *types.ULID `gorm:"column:activity_id"`
 	Start       *time.Time  `gorm:"column:start"`
 	End         *time.Time  `gorm:"column:end"`
 	Description *string     `gorm:"column:description"`
@@ -58,13 +58,13 @@ type TimeEntryUpdate struct {
 // Validate checks if the Create struct contains valid data
 func (tc *TimeEntryCreate) Validate() error {
 	// Check for empty IDs
-	if tc.UserID.Compare(ulid.ULID{}) == 0 {
+	if tc.UserID.Compare(types.ULID{}) == 0 {
 		return errors.New("userID cannot be empty")
 	}
-	if tc.ProjectID.Compare(ulid.ULID{}) == 0 {
+	if tc.ProjectID.Compare(types.ULID{}) == 0 {
 		return errors.New("projectID cannot be empty")
 	}
-	if tc.ActivityID.Compare(ulid.ULID{}) == 0 {
+	if tc.ActivityID.Compare(types.ULID{}) == 0 {
 		return errors.New("activityID cannot be empty")
 	}
 
@@ -103,7 +103,7 @@ func (tu *TimeEntryUpdate) Validate() error {
 }
 
 // GetTimeEntryByID finds a time entry by its ID
-func GetTimeEntryByID(ctx context.Context, id ulid.ULID) (*TimeEntry, error) {
+func GetTimeEntryByID(ctx context.Context, id types.ULID) (*TimeEntry, error) {
 	var timeEntry TimeEntry
 	result := GetEngine(ctx).Where("id = ?", id).First(&timeEntry)
 	if result.Error != nil {
@@ -116,7 +116,7 @@ func GetTimeEntryByID(ctx context.Context, id ulid.ULID) (*TimeEntry, error) {
 }
 
 // GetTimeEntryWithRelations loads a time entry with all associated data
-func GetTimeEntryWithRelations(ctx context.Context, id ulid.ULID) (*TimeEntry, error) {
+func GetTimeEntryWithRelations(ctx context.Context, id types.ULID) (*TimeEntry, error) {
 	var timeEntry TimeEntry
 	result := GetEngine(ctx).
 		Preload("User").
@@ -146,7 +146,7 @@ func GetAllTimeEntries(ctx context.Context) ([]TimeEntry, error) {
 }
 
 // GetTimeEntriesByUserID returns all time entries of a user
-func GetTimeEntriesByUserID(ctx context.Context, userID ulid.ULID) ([]TimeEntry, error) {
+func GetTimeEntriesByUserID(ctx context.Context, userID types.ULID) ([]TimeEntry, error) {
 	var timeEntries []TimeEntry
 	result := GetEngine(ctx).Where("user_id = ?", userID).Find(&timeEntries)
 	if result.Error != nil {
@@ -156,7 +156,7 @@ func GetTimeEntriesByUserID(ctx context.Context, userID ulid.ULID) ([]TimeEntry,
 }
 
 // GetTimeEntriesByProjectID returns all time entries of a project
-func GetTimeEntriesByProjectID(ctx context.Context, projectID ulid.ULID) ([]TimeEntry, error) {
+func GetTimeEntriesByProjectID(ctx context.Context, projectID types.ULID) ([]TimeEntry, error) {
 	var timeEntries []TimeEntry
 	result := GetEngine(ctx).Where("project_id = ?", projectID).Find(&timeEntries)
 	if result.Error != nil {
@@ -181,7 +181,7 @@ func GetTimeEntriesByDateRange(ctx context.Context, start, end time.Time) ([]Tim
 }
 
 // SumBillableHoursByProject calculates the billable hours per project
-func SumBillableHoursByProject(ctx context.Context, projectID ulid.ULID) (float64, error) {
+func SumBillableHoursByProject(ctx context.Context, projectID types.ULID) (float64, error) {
 	type Result struct {
 		TotalHours float64
 	}
@@ -247,7 +247,7 @@ func CreateTimeEntry(ctx context.Context, create TimeEntryCreate) (*TimeEntry, e
 }
 
 // validateReferences checks if all referenced entities exist
-func validateReferences(tx *gorm.DB, userID, projectID, activityID ulid.ULID) error {
+func validateReferences(tx *gorm.DB, userID, projectID, activityID types.ULID) error {
 	// Check user
 	var userCount int64
 	if err := tx.Model(&User{}).Where("id = ?", userID).Count(&userCount).Error; err != nil {
@@ -351,7 +351,7 @@ func UpdateTimeEntry(ctx context.Context, update TimeEntryUpdate) (*TimeEntry, e
 }
 
 // DeleteTimeEntry deletes a time entry by its ID
-func DeleteTimeEntry(ctx context.Context, id ulid.ULID) error {
+func DeleteTimeEntry(ctx context.Context, id types.ULID) error {
 	result := GetEngine(ctx).Delete(&TimeEntry{}, id)
 	if result.Error != nil {
 		return fmt.Errorf("error deleting the time entry: %w", result.Error)

backend/internal/models/user.go

@@ -11,7 +11,7 @@ import (
 
 	"slices"
 
-	"github.com/oklog/ulid/v2"
+	"github.com/timetracker/backend/internal/types"
 	"golang.org/x/crypto/argon2"
 	"gorm.io/gorm"
 )
@@ -40,7 +40,7 @@ type User struct {
 	Salt       string      `gorm:"column:salt;not null;type:varchar(64)"`  // Base64-encoded Salt
 	Hash       string      `gorm:"column:hash;not null;type:varchar(128)"` // Base64-encoded Hash
 	Role       string      `gorm:"column:role;not null;default:'user'"`
-	CompanyID  ulid.ULID `gorm:"column:company_id;type:uuid;not null;index"`
+	CompanyID  *types.ULID `gorm:"column:company_id;type:bytea;index"`
 	HourlyRate float64     `gorm:"column:hourly_rate;not null;default:0"`
 
 	// Relationship for Eager Loading
@@ -57,17 +57,17 @@ type UserCreate struct {
 	Email      string
 	Password   string
 	Role       string
-	CompanyID  ulid.ULID
+	CompanyID  *types.ULID
 	HourlyRate float64
 }
 
 // UserUpdate contains the updatable fields of a user
 type UserUpdate struct {
-	ID         ulid.ULID  `gorm:"-"` // Exclude from updates
+	ID         types.ULID                 `gorm:"-"` // Exclude from updates
 	Email      *string                    `gorm:"column:email"`
 	Password   *string                    `gorm:"-"` // Not stored directly in DB
 	Role       *string                    `gorm:"column:role"`
-	CompanyID  *ulid.ULID `gorm:"column:company_id"`
+	CompanyID  types.Nullable[types.ULID] `gorm:"column:company_id"`
 	HourlyRate *float64                   `gorm:"column:hourly_rate"`
 }
 
@@ -202,7 +202,7 @@ func (uc *UserCreate) Validate() error {
 		}
 	}
 
-	if uc.CompanyID.Compare(ulid.ULID{}) == 0 {
+	if uc.CompanyID.Compare(types.ULID{}) == 0 {
 		return errors.New("companyID cannot be empty")
 	}
 
@@ -288,7 +288,7 @@ func (uu *UserUpdate) Validate() error {
 }
 
 // GetUserByID finds a user by their ID
-func GetUserByID(ctx context.Context, id ulid.ULID) (*User, error) {
+func GetUserByID(ctx context.Context, id types.ULID) (*User, error) {
 	var user User
 	result := GetEngine(ctx).Where("id = ?", id).First(&user)
 	if result.Error != nil {
@@ -314,7 +314,7 @@ func GetUserByEmail(ctx context.Context, email string) (*User, error) {
 }
 
 // GetUserWithCompany loads a user with their company
-func GetUserWithCompany(ctx context.Context, id ulid.ULID) (*User, error) {
+func GetUserWithCompany(ctx context.Context, id types.ULID) (*User, error) {
 	var user User
 	result := GetEngine(ctx).Preload("Company").Where("id = ?", id).First(&user)
 	if result.Error != nil {
@@ -336,10 +336,22 @@ func GetAllUsers(ctx context.Context) ([]User, error) {
 	return users, nil
 }
 
+// getCompanyCondition builds the company condition for queries
+func getCompanyCondition(companyID *types.ULID) func(db *gorm.DB) *gorm.DB {
+	return func(db *gorm.DB) *gorm.DB {
+		if companyID == nil {
+			return db.Where("company_id IS NULL")
+		}
+		return db.Where("company_id = ?", *companyID)
+	}
+}
+
 // GetUsersByCompanyID returns all users of a company
-func GetUsersByCompanyID(ctx context.Context, companyID ulid.ULID) ([]User, error) {
+func GetUsersByCompanyID(ctx context.Context, companyID types.ULID) ([]User, error) {
 	var users []User
-	result := GetEngine(ctx).Where("company_id = ?", companyID).Find(&users)
+	// Apply the dynamic company condition
+	condition := getCompanyCondition(&companyID)
+	result := GetEngine(ctx).Scopes(condition).Find(&users)
 	if result.Error != nil {
 		return nil, result.Error
 	}
@@ -436,15 +448,17 @@ func UpdateUser(ctx context.Context, update UserUpdate) (*User, error) {
 		}
 
 		// If CompanyID is updated, check if it exists
-		if update.CompanyID != nil && update.CompanyID.Compare(user.CompanyID) != 0 {
+		if update.CompanyID.Valid && update.CompanyID.Value != nil {
+			if user.CompanyID == nil || *update.CompanyID.Value != *user.CompanyID {
 				var companyCount int64
-			if err := tx.Model(&Company{}).Where("id = ?", *update.CompanyID).Count(&companyCount).Error; err != nil {
+				if err := tx.Model(&Company{}).Where("id = ?", *update.CompanyID.Value).Count(&companyCount).Error; err != nil {
 					return fmt.Errorf("error checking company: %w", err)
 				}
 				if companyCount == 0 {
 					return errors.New("the specified company does not exist")
 				}
 			}
+		}
 
 		// If password is updated, rehash with new salt
 		if update.Password != nil {
@@ -472,8 +486,13 @@ func UpdateUser(ctx context.Context, update UserUpdate) (*User, error) {
 		if update.Role != nil {
 			updates["role"] = *update.Role
 		}
-		if update.CompanyID != nil {
-			updates["company_id"] = *update.CompanyID
+		if update.CompanyID.Valid {
+			if update.CompanyID.Value == nil {
+				updates["company_id"] = nil
+			} else {
+				updates["company_id"] = *update.CompanyID.Value
+			}
+
 		}
 		if update.HourlyRate != nil {
 			updates["hourly_rate"] = *update.HourlyRate
@@ -498,7 +517,7 @@ func UpdateUser(ctx context.Context, update UserUpdate) (*User, error) {
 }
 
 // DeleteUser deletes a user by their ID
-func DeleteUser(ctx context.Context, id ulid.ULID) error {
+func DeleteUser(ctx context.Context, id types.ULID) error {
 	// Here one could check if dependent entities exist
 	// e.g., don't delete if time entries still exist
 

backend/internal/types/nullable.go

@@ -0,0 +1,52 @@
+package types
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// Nullable[T] - Generischer Typ für optionale Werte (nullable fields)
+type Nullable[T any] struct {
+	Value *T   // Der tatsächliche Wert (kann nil sein)
+	Valid bool // Gibt an, ob der Wert gesetzt wurde
+}
+
+// NewNullable erstellt eine gültige Nullable-Instanz
+func NewNullable[T any](value T) Nullable[T] {
+	return Nullable[T]{Value: &value, Valid: true}
+}
+
+// Null erstellt eine leere Nullable-Instanz (ungesetzt)
+func Null[T any]() Nullable[T] {
+	return Nullable[T]{Valid: true}
+}
+
+func Undefined[T any]() Nullable[T] {
+	return Nullable[T]{Valid: false}
+}
+
+// MarshalJSON - Serialisiert `Nullable[T]` korrekt ins JSON-Format
+func (n Nullable[T]) MarshalJSON() ([]byte, error) {
+	if !n.Valid {
+		return []byte("null"), nil // Wenn nicht valid, dann NULL
+	}
+	return json.Marshal(n.Value) // Serialisiert den tatsächlichen Wert
+}
+
+// UnmarshalJSON - Deserialisiert JSON in `Nullable[T]`
+func (n *Nullable[T]) UnmarshalJSON(data []byte) error {
+	if string(data) == "null" {
+		n.Valid = true // Wert wurde gesetzt, aber auf NULL
+		n.Value = nil  // Explizit NULL setzen
+		return nil
+	}
+
+	var v T
+	if err := json.Unmarshal(data, &v); err != nil {
+		return fmt.Errorf("invalid JSON for Nullable: %w", err)
+	}
+
+	n.Value = &v
+	n.Valid = true
+	return nil
+}

backend/internal/types/ulid.go

@@ -0,0 +1,77 @@
+package types
+
+import (
+	"context"
+	"database/sql/driver"
+	"fmt"
+
+	"github.com/oklog/ulid/v2"
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+)
+
+// ULID wraps ulid.ULID to make it work nicely with GORM
+type ULID struct {
+	ulid.ULID
+}
+
+// NewULIDWrapper creates a new ULID with a new ULID
+func NewULIDWrapper() ULID {
+	return ULID{ULID: ulid.Make()}
+}
+
+// FromULID creates a ULID from a ulid.ULID
+func FromULID(id ulid.ULID) ULID {
+	return ULID{ULID: id}
+}
+
+// ULIDWrapperFromString creates a ULID from a string
+func ULIDFromString(id string) (ULID, error) {
+	parsed, err := ulid.Parse(id)
+	if err != nil {
+		return ULID{}, fmt.Errorf("failed to parse ULID string: %w", err)
+	}
+	return ULID{ULID: parsed}, nil
+}
+
+// Scan implements the sql.Scanner interface for ULID
+func (u *ULID) Scan(src any) error {
+	switch v := src.(type) {
+	case []byte:
+		// If it's exactly 16 bytes, it's the binary representation
+		if len(v) == 16 {
+			copy(u.ULID[:], v)
+			return nil
+		}
+		// Otherwise, try as string
+		return fmt.Errorf("cannot scan []byte of length %d into ULID", len(v))
+	case string:
+		parsed, err := ulid.Parse(v)
+		if err != nil {
+			return fmt.Errorf("failed to parse ULID: %w", err)
+		}
+		u.ULID = parsed
+		return nil
+	default:
+		return fmt.Errorf("cannot scan %T into ULID", src)
+	}
+}
+
+// Value implements the driver.Valuer interface for ULID
+// Returns the binary representation of the ULID for maximum efficiency
+func (u ULID) Value() (driver.Value, error) {
+	return u.ULID.Bytes(), nil
+}
+
+// GormValue implements the gorm.Valuer interface for ULID
+func (u ULID) GormValue(ctx context.Context, db *gorm.DB) clause.Expr {
+	return clause.Expr{
+		SQL:  "?",
+		Vars: []any{u.Bytes()},
+	}
+}
+
+// Compare implements comparison for ULID
+func (u ULID) Compare(other ULID) int {
+	return u.ULID.Compare(other.ULID)
+}

backend/scripts/fix_tygo.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+const (
+	dtoFilePath     = "../frontend/src/types/dto.ts"
+	importStatement = `import { Nullable } from "./nullable";`
+)
+
+func main() {
+	// Run Tygo first
+	fmt.Println("🔄 Running tygo...")
+	if err := runTygo(); err != nil {
+		fmt.Println("❌ Error running tygo:", err)
+		os.Exit(1)
+	}
+
+	// Read dto.ts file
+	content, err := os.ReadFile(dtoFilePath)
+	if err != nil {
+		fmt.Println("❌ Could not read dto.ts:", err)
+		os.Exit(1)
+	}
+
+	// Convert to string
+	dtoContent := string(content)
+
+	// Check if import already exists
+	if strings.Contains(dtoContent, importStatement) {
+		fmt.Println("ℹ️ Import already exists in dto.ts, skipping.")
+		return
+	}
+
+	// Add import statement at the beginning
+	newContent := importStatement + "\n" + dtoContent
+	if err := os.WriteFile(dtoFilePath, []byte(newContent), 0644); err != nil {
+		fmt.Println("❌ Error writing dto.ts:", err)
+		os.Exit(1)
+	}
+
+	fmt.Println("✅ Successfully added Nullable<T> import to dto.ts")
+}
+
+// Runs Tygo command
+func runTygo() error {
+	cmd := "tygo"
+	output, err := exec.Command(cmd, "generate").CombinedOutput()
+	if err != nil {
+		fmt.Println("Tygo output:", string(output))
+		return err
+	}
+	if len(output) > 0 {
+		fmt.Println("Tygo output:", string(output))
+		return nil
+	}
+	return nil
+}

backend/tygo.yaml

@@ -0,0 +1,7 @@
+packages:
+  - path: "github.com/timetracker/backend/internal/api/dto"
+    type_mappings:
+      "time.Time": "string"
+      "types.ULID": "string"
+      "types.Nullable": "Nullable"
+    output_path: ../frontend/src/types/dto.ts

backend/tygo.yml

@@ -1,6 +0,0 @@
-packages:
-  - path: github.com/timetracker/backend/dto
-    type_mappings:
-      "time.Time": "string"
-      "ulid.ULID": "string"
-    output_path: ../frontend/src/types/dto.ts

docker-compose.yml

@@ -0,0 +1,26 @@
+services:
+  db:
+    image: postgres:14
+    container_name: timetracker_db
+    restart: always
+    ports:
+      - "5432:5432"
+    environment:
+      POSTGRES_USER: timetracker
+      POSTGRES_PASSWORD: password
+      POSTGRES_DB: timetracker
+    volumes:
+      - db_data:/var/lib/postgresql/data
+  pgadmin:
+    image: dpage/pgadmin4
+    container_name: pgadmin
+    environment:
+      PGADMIN_DEFAULT_EMAIL: admin@example.com
+      PGADMIN_DEFAULT_PASSWORD: admin
+    ports:
+      - "8081:80"
+    depends_on:
+      - db
+
+volumes:
+  db_data:

docu/backend_architecture.md

@@ -2,7 +2,7 @@
 
 **Note:** This document describes a *conceptual* architecture and is not a final, binding requirement.
 
-The backend is written in Go and follows the principles of **Clean Architecture** and **Domain-Driven Design (DDD)**.
+The backend is written in Go using idiomatic Go patterns. While initially following Clean Architecture and DDD principles, we've adapted to a more pragmatic approach that better fits Go's conventions and reduces boilerplate code.
 
 ## Project Structure
 ```

docu/code_examples/api_handler.go

@@ -1,101 +0,0 @@
-// interfaces/http/handlers/time_entry_handler.go
-package main
-
-import (
-	"net/http"
-
-	"github.com/email/timetracker/internal/application/timetracking"
-	"github.com/email/timetracker/internal/interfaces/http/dto"
-	"github.com/email/timetracker/internal/interfaces/http/middleware"
-	"github.com/gin-gonic/gin"
-	"github.com/google/uuid"
-)
-
-// TimeEntryHandler behandelt HTTP-Anfragen für Zeitbuchungen
-type TimeEntryHandler struct {
-	createTimeEntryUseCase *timetracking.CreateTimeEntryUseCase
-	updateTimeEntryUseCase *timetracking.UpdateTimeEntryUseCase
-	listTimeEntriesUseCase *timetracking.ListTimeEntriesUseCase
-	deleteTimeEntryUseCase *timetracking.DeleteTimeEntryUseCase
-}
-
-// NewTimeEntryHandler erstellt einen neuen TimeEntryHandler
-func NewTimeEntryHandler(
-	createTimeEntryUseCase *timetracking.CreateTimeEntryUseCase,
-	updateTimeEntryUseCase *timetracking.UpdateTimeEntryUseCase,
-	listTimeEntriesUseCase *timetracking.ListTimeEntriesUseCase,
-	deleteTimeEntryUseCase *timetracking.DeleteTimeEntryUseCase,
-) *TimeEntryHandler {
-	return &TimeEntryHandler{
-		createTimeEntryUseCase: createTimeEntryUseCase,
-		updateTimeEntryUseCase: updateTimeEntryUseCase,
-		listTimeEntriesUseCase: listTimeEntriesUseCase,
-		deleteTimeEntryUseCase: deleteTimeEntryUseCase,
-	}
-}
-
-// RegisterRoutes registriert die Routen am Router
-func (h *TimeEntryHandler) RegisterRoutes(router *gin.RouterGroup) {
-	timeEntries := router.Group("/time-entries")
-	{
-		timeEntries.GET("", h.ListTimeEntries)
-		timeEntries.POST("", h.CreateTimeEntry)
-		timeEntries.GET("/:id", h.GetTimeEntry)
-		timeEntries.PUT("/:id", h.UpdateTimeEntry)
-		timeEntries.DELETE("/:id", h.DeleteTimeEntry)
-	}
-}
-
-// CreateTimeEntry behandelt die Erstellung einer neuen Zeitbuchung
-func (h *TimeEntryHandler) CreateTimeEntry(c *gin.Context) {
-	var req dto.CreateTimeEntryRequest
-	if err := c.ShouldBindJSON(&req); err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
-		return
-	}
-
-	// Tenant-ID aus dem Kontext extrahieren
-	companyID, exists := middleware.GetCompanyID(c)
-	if !exists {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "Company ID not found"})
-		return
-	}
-
-	// Benutzer-ID aus dem Kontext oder Request
-	var userID uuid.UUID
-	if req.UserID != nil {
-		userID = *req.UserID
-	} else {
-		currentUserID, exists := middleware.GetUserID(c)
-		if !exists {
-			c.JSON(http.StatusBadRequest, gin.H{"error": "User ID not found"})
-			return
-		}
-		userID = currentUserID
-	}
-
-	// Command erstellen
-	cmd := timetracking.CreateTimeEntryCommand{
-		UserID:             userID,
-		ProjectID:          req.ProjectID,
-		ActivityID:         req.ActivityID,
-		TaskID:             req.TaskID,
-		StartTime:          req.StartTime,
-		EndTime:            req.EndTime,
-		Description:        req.Description,
-		BillablePercentage: req.BillablePercentage,
-	}
-
-	// UseCase ausführen
-	result := h.createTimeEntryUseCase.Execute(c.Request.Context(), companyID, cmd)
-	if result.IsFailure() {
-		c.JSON(http.StatusInternalServerError, gin.H{"error": result.Error().Error()})
-		return
-	}
-
-	// TimeEntry in Response-DTO umwandeln
-	timeEntry := result.Value()
-	response := dto.MapTimeEntryToDTO(*timeEntry)
-
-	c.JSON(http.StatusCreated, response)
-}

docu/code_examples/fpgo_repository.go

@@ -1,52 +0,0 @@
-// domain/repositories/time_entry_repository.go
-package repositories
-
-import (
-	"context"
-	"time"
-
-	"github.com/email/timetracker/internal/domain/entities"
-	"github.com/email/timetracker/pkg/functional"
-	"github.com/google/uuid"
-)
-
-// TimeEntryFilter enthält Filter für die Suche nach Zeitbuchungen
-type TimeEntryFilter struct {
-	UserID     *uuid.UUID
-	ProjectID  *uuid.UUID
-	CustomerID *uuid.UUID
-	StartDate  *time.Time
-	EndDate    *time.Time
-	ActivityID *uuid.UUID
-	TaskID     *uuid.UUID
-}
-
-// TimeEntryRepository Interface für den Zugriff auf Zeitbuchungen
-type TimeEntryRepository interface {
-	// FindByID sucht eine Zeitbuchung anhand ihrer ID
-	FindByID(ctx context.Context, companyID, id uuid.UUID) functional.Result[*entities.TimeEntry]
-
-	// FindAll sucht alle Zeitbuchungen mit optionalen Filtern
-	FindAll(ctx context.Context, companyID uuid.UUID, filter TimeEntryFilter) functional.Result[[]entities.TimeEntry]
-
-	// Create erstellt eine neue Zeitbuchung
-	Create(ctx context.Context, entry *entities.TimeEntry) functional.Result[*entities.TimeEntry]
-
-	// Update aktualisiert eine bestehende Zeitbuchung
-	Update(ctx context.Context, entry *entities.TimeEntry) functional.Result[*entities.TimeEntry]
-
-	// Delete löscht eine Zeitbuchung
-	Delete(ctx context.Context, companyID, id uuid.UUID) functional.Result[bool]
-
-	// GetSummary berechnet eine Zusammenfassung der Zeitbuchungen
-	GetSummary(ctx context.Context, companyID uuid.UUID, filter TimeEntryFilter) functional.Result[TimeEntrySummary]
-}
-
-// TimeEntrySummary enthält zusammengefasste Informationen über Zeitbuchungen
-type TimeEntrySummary struct {
-	TotalDuration         int
-	TotalBillableDuration int
-	TotalAmount           float64
-	TotalBillableAmount   float64
-	EntriesCount          int
-}

docu/code_examples/fpgo_service.go

@@ -1,99 +0,0 @@
-// application/timetracking/create_time_entry.go
-package main
-
-import (
-	"context"
-	"time"
-
-	"github.com/email/timetracker/internal/domain/entities"
-	"github.com/email/timetracker/internal/domain/repositories"
-	"github.com/email/timetracker/pkg/functional"
-	"github.com/email/timetracker/pkg/validator"
-	"github.com/google/uuid"
-)
-
-// CreateTimeEntryCommand enthält die Daten zum Erstellen einer Zeitbuchung
-type CreateTimeEntryCommand struct {
-	UserID             uuid.UUID
-	ProjectID          uuid.UUID
-	ActivityID         uuid.UUID
-	TaskID             *uuid.UUID
-	StartTime          time.Time
-	EndTime            time.Time
-	Description        string
-	BillablePercentage int
-}
-
-// CreateTimeEntryUseCase repräsentiert den Anwendungsfall zum Erstellen einer Zeitbuchung
-type CreateTimeEntryUseCase struct {
-	timeEntryRepo repositories.TimeEntryRepository
-	projectRepo   repositories.ProjectRepository
-	activityRepo  repositories.ActivityRepository
-	userRepo      repositories.UserRepository
-}
-
-// NewCreateTimeEntryUseCase erstellt eine neue Instanz des UseCase
-func NewCreateTimeEntryUseCase(
-	timeEntryRepo repositories.TimeEntryRepository,
-	projectRepo repositories.ProjectRepository,
-	activityRepo repositories.ActivityRepository,
-	userRepo repositories.UserRepository,
-) *CreateTimeEntryUseCase {
-	return &CreateTimeEntryUseCase{
-		timeEntryRepo: timeEntryRepo,
-		projectRepo:   projectRepo,
-		activityRepo:  activityRepo,
-		userRepo:      userRepo,
-	}
-}
-
-// Execute führt den Anwendungsfall aus
-func (uc *CreateTimeEntryUseCase) Execute(ctx context.Context, companyID uuid.UUID, cmd CreateTimeEntryCommand) functional.Result[*entities.TimeEntry] {
-	// Validierung
-	if err := validator.ValidateStruct(cmd); err != nil {
-		return functional.Failure[*entities.TimeEntry](err)
-	}
-
-	// Überprüfen, ob Projekt existiert und zum gleichen Tenant gehört
-	projectResult := uc.projectRepo.FindByID(ctx, companyID, cmd.ProjectID)
-	if projectResult.IsFailure() {
-		return functional.Failure[*entities.TimeEntry](projectResult.Error())
-	}
-
-	// Überprüfen, ob Activity existiert und zum gleichen Tenant gehört
-	activityResult := uc.activityRepo.FindByID(ctx, companyID, cmd.ActivityID)
-	if activityResult.IsFailure() {
-		return functional.Failure[*entities.TimeEntry](activityResult.Error())
-	}
-	activity := activityResult.Value()
-
-	// Benutzer abrufen für den Stundensatz
-	userResult := uc.userRepo.FindByID(ctx, companyID, cmd.UserID)
-	if userResult.IsFailure() {
-		return functional.Failure[*entities.TimeEntry](userResult.Error())
-	}
-	user := userResult.Value()
-
-	// Berechnung der Dauer in Minuten
-	durationMinutes := int(cmd.EndTime.Sub(cmd.StartTime).Minutes())
-
-	// TimeEntry erstellen
-	timeEntry := &entities.TimeEntry{
-		TenantEntity: entities.TenantEntity{
-			CompanyID: companyID,
-		},
-		UserID:             cmd.UserID,
-		ProjectID:          cmd.ProjectID,
-		ActivityID:         cmd.ActivityID,
-		TaskID:             cmd.TaskID,
-		StartTime:          cmd.StartTime,
-		EndTime:            cmd.EndTime,
-		DurationMinutes:    durationMinutes,
-		Description:        cmd.Description,
-		BillablePercentage: cmd.BillablePercentage,
-		BillingRate:        activity.BillingRate,
-	}
-
-	// Speichern der TimeEntry
-	return uc.timeEntryRepo.Create(ctx, timeEntry)
-}

docu/code_examples/gorm_entities.go

@@ -1,104 +0,0 @@
-package models
-
-import (
-	"time"
-
-	"github.com/google/uuid"
-	"gorm.io/gorm"
-)
-
-// BaseEntity enthält gemeinsame Felder für alle Entitäten
-type BaseEntity struct {
-	ID        uuid.UUID      `gorm:"type:uuid;primary_key"`
-	CreatedAt time.Time      `gorm:"autoCreateTime"`
-	UpdatedAt time.Time      `gorm:"autoUpdateTime"`
-	DeletedAt gorm.DeletedAt `gorm:"index"`
-}
-
-// BeforeCreate setzt eine neue UUID vor dem Erstellen
-func (base *BaseEntity) BeforeCreate(tx *gorm.DB) error {
-	if base.ID == uuid.Nil {
-		base.ID = uuid.New()
-	}
-	return nil
-}
-
-// TenantEntity erweitert BaseEntity um Company-ID für Multi-Tenancy
-type TenantEntity struct {
-	BaseEntity
-	CompanyID uuid.UUID `gorm:"type:uuid;index:idx_tenant"`
-}
-
-// Role repräsentiert eine Benutzerrolle
-type Role struct {
-	BaseEntity
-	Name        string `gorm:"unique;not null"`
-	Description string
-	Permissions []Permission `gorm:"many2many:role_permissions;"`
-}
-
-// Permission repräsentiert eine einzelne Berechtigung
-type Permission struct {
-	BaseEntity
-	Resource string `gorm:"not null"`
-	Action   string `gorm:"not null"`
-	UniqueID string `gorm:"uniqueIndex"`
-}
-
-// User repräsentiert einen Benutzer im System
-type User struct {
-	TenantEntity
-	Email        string `gorm:"uniqueIndex;not null"`
-	FirstName    string
-	LastName     string
-	PasswordHash string    `gorm:"not null"`
-	RoleID       uuid.UUID `gorm:"type:uuid"`
-	Role         Role      `gorm:"foreignKey:RoleID"`
-	HourlyRate   float64
-	IsActive     bool `gorm:"default:true"`
-}
-
-// FullName gibt den vollständigen Namen des Benutzers zurück
-func (u User) FullName() string {
-	return u.FirstName + " " + u.LastName
-}
-
-// TimeEntry repräsentiert eine Zeitbuchung
-type TimeEntry struct {
-	TenantEntity
-	UserID             uuid.UUID  `gorm:"type:uuid;index:idx_user"`
-	User               User       `gorm:"foreignKey:UserID"`
-	ProjectID          uuid.UUID  `gorm:"type:uuid;index:idx_project"`
-	Project            Project    `gorm:"foreignKey:ProjectID"`
-	ActivityID         uuid.UUID  `gorm:"type:uuid"`
-	Activity           Activity   `gorm:"foreignKey:ActivityID"`
-	TaskID             *uuid.UUID `gorm:"type:uuid;null"`
-	Task               *Task      `gorm:"foreignKey:TaskID"`
-	StartTime          time.Time  `gorm:"not null;index:idx_time_range"`
-	EndTime            time.Time  `gorm:"not null;index:idx_time_range"`
-	DurationMinutes    int        `gorm:"not null"`
-	Description        string
-	BillablePercentage int `gorm:"default:100"`
-	BillingRate        float64
-}
-
-type Project struct {
-	TenantEntity
-	Name string
-}
-
-type Activity struct {
-	TenantEntity
-	Name string
-}
-
-type Task struct {
-	TenantEntity
-	Name string
-}
-
-// CalculateBillableAmount berechnet den abrechenbaren Betrag
-func (t TimeEntry) CalculateBillableAmount() float64 {
-	hours := float64(t.DurationMinutes) / 60.0
-	return hours * t.BillingRate * (float64(t.BillablePercentage) / 100.0)
-}

docu/code_examples/react_component.tsx

@@ -1,136 +0,0 @@
-// presentation/components/timeTracker/Timer/Timer.tsx
-import React, { useState, useEffect } from 'react';
-import { useTimeTracking } from '../../../hooks/useTimeTracking';
-import { pipe, Option, fromNullable } from '../../../../utils/fp/option';
-import { Button } from '../../common/Button';
-import { formatDuration } from '../../../../utils/date/dateUtils';
-
-interface TimerProps {
-    onComplete?: (duration: number) => void;
-}
-
-export const Timer: React.FC<TimerProps> = ({ onComplete }) => {
-    const [isRunning, setIsRunning] = useState(false);
-    const [startTime, setStartTime] = useState<Option<Date>>(Option.none());
-    const [elapsedTime, setElapsedTime] = useState(0);
-    const [selectedProject, setSelectedProject] = useState<Option<string>>(Option.none());
-    const [selectedActivity, setSelectedActivity] = useState<Option<string>>(Option.none());
-
-    const { lastTimeEntry, projects, activities } = useTimeTracking();
-
-    // Beim ersten Rendering die letzte Zeitbuchung laden
-    useEffect(() => {
-        pipe(
-            fromNullable(lastTimeEntry),
-            Option.map(entry => {
-                setSelectedProject(Option.some(entry.projectId));
-                setSelectedActivity(Option.some(entry.activityId));
-            })
-        );
-    }, [lastTimeEntry]);
-
-    // Timer-Logik
-    useEffect(() => {
-        let interval: NodeJS.Timeout | null = null;
-
-        if (isRunning) {
-            interval = setInterval(() => {
-                const now = new Date();
-                pipe(
-                    startTime,
-                    Option.map(start => {
-                        const diff = now.getTime() - start.getTime();
-                        setElapsedTime(Math.floor(diff / 1000));
-                    })
-                );
-            }, 1000);
-        } else if (interval) {
-            clearInterval(interval);
-        }
-
-        return () => {
-            if (interval) clearInterval(interval);
-        };
-    }, [isRunning, startTime]);
-
-    // Timer starten
-    const handleStart = () => {
-        setStartTime(Option.some(new Date()));
-        setIsRunning(true);
-    };
-
-    // Timer stoppen
-    const handleStop = () => {
-        setIsRunning(false);
-
-        // Prüfen, ob Projekt und Aktivität ausgewählt wurden
-        const projectId = pipe(
-            selectedProject,
-            Option.getOrElse(() => '')
-        );
-
-        const activityId = pipe(
-            selectedActivity,
-            Option.getOrElse(() => '')
-        );
-
-        if (projectId && activityId && onComplete) {
-            onComplete(elapsedTime);
-        }
-
-        // Timer zurücksetzen
-        setElapsedTime(0);
-        setStartTime(Option.none());
-    };
-
-    return (
-        <div className="bg-white rounded-lg shadow-md p-4">
-            <div className="text-4xl text-center font-mono mb-4">
-                {formatDuration(elapsedTime)}
-            </div>
-
-            <div className="grid grid-cols-2 gap-4 mb-4">
-                <div>
-                    <label className="block text-sm font-medium text-gray-700 mb-1">
-                        Projekt
-                    </label>
-                    <select
-                        className="w-full border border-gray-300 rounded-md px-3 py-2"
-                        value={pipe(selectedProject, Option.getOrElse(() => ''))}
-                        onChange={(e) => setSelectedProject(Option.some(e.target.value))}
-                        disabled={isRunning}
-                    >
-                        <option value="">Projekt auswählen</option>
-                        {projects.map((project) => (
-                            <option key={project.id} value={project.id}>
-                                {project.name}
-                            </option>
-                        ))}
-                    </select>
-                </div>
-
-                <div>
-                    <label className="block text-sm font-medium text-gray-700 mb-1">
-                        Tätigkeit
-                    </label>
-                    <select
-                        className="w-full border border-gray-300 rounded-md px-3 py-2"
-                        value={pipe(selectedActivity, Option.getOrElse(() => ''))}
-                        onChange={(e) => setSelectedActivity(Option.some(e.target.value))}
-                        disabled={isRunning}
-                    >
-                        <option value="">Tätigkeit auswählen</option>
-                        {activities.map((activity) => (
-                            <option key={activity.id} value={activity.id}>
-                                {activity.name}
-                            </option>
-                        ))}
-                    </select>
-                </div>
-            </div>
-
-            <div className="flex justify-center">
-            </div>
-        </div>
-    );
-};

docu/database_schema.md

@@ -1,194 +0,0 @@
-# Database Schema (PostgreSQL)
-
-```sql
--- Multi-Tenant
-CREATE TABLE companies (
-    id UUID PRIMARY KEY,
-    name VARCHAR(255) NOT NULL,
-    address TEXT,
-    contact_email VARCHAR(255),
-    contact_phone VARCHAR(50),
-    logo_url TEXT,
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
--- Go structs for creating and updating customers
--- type CustomerCreate struct {
--- 	Name      string
--- 	CompanyID int
--- }
-
--- type CustomerUpdate struct {
--- 	ID        ulid.ULID
--- 	Name      *string
--- 	CompanyID *int
--- }
-
--- Go structs for creating and updating companies
--- type CompanyCreate struct {
--- 	Name string
--- }
-
--- type CompanyUpdate struct {
--- 	ID   ulid.ULID
--- 	Name *string
--- }
-
--- Go structs for creating and updating activities
--- type ActivityCreate struct {
--- 	Name        string
--- 	BillingRate float64
--- }
-
--- type ActivityUpdate struct {
--- 	ID          ulid.ULID
--- 	Name        *string
--- 	BillingRate *float64
--- }
-
--- Users and Roles
-CREATE TABLE roles (
-    id SERIAL PRIMARY KEY,
-    name VARCHAR(50) UNIQUE NOT NULL,
-    permissions JSONB
-);
-
-CREATE TABLE users (
-    id UUID PRIMARY KEY,
-    company_id UUID REFERENCES companies(id),
-    email VARCHAR(255) UNIQUE NOT NULL,
-    password_hash VARCHAR(255) NOT NULL,
-    first_name VARCHAR(100),
-    last_name VARCHAR(100),
-    role_id INTEGER REFERENCES roles(id),
-    hourly_rate DECIMAL(10, 2),
-    is_active BOOLEAN DEFAULT TRUE,
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
--- Customers
-CREATE TABLE customers (
-    id UUID PRIMARY KEY,
-    company_id UUID NOT NULL REFERENCES companies(id),
-    name VARCHAR(255) NOT NULL,
-    contact_person VARCHAR(255),
-    email VARCHAR(255),
-    phone VARCHAR(50),
-    address TEXT,
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
--- Projects
-CREATE TABLE projects (
-    id UUID PRIMARY KEY,
-    company_id UUID NOT NULL REFERENCES companies(id),
-    customer_id UUID REFERENCES customers(id),
-    name VARCHAR(255) NOT NULL,
-    description TEXT,
-    start_date DATE,
-    end_date DATE,
-    status VARCHAR(50),
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
--- Activities
-CREATE TABLE activities (
-    id UUID PRIMARY KEY,
-    company_id UUID NOT NULL REFERENCES companies(id),
-    name VARCHAR(255) NOT NULL,
-    description TEXT,
-    billing_rate DECIMAL(10, 2),
-    is_active BOOLEAN DEFAULT TRUE,
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
--- Time bookings
-CREATE TABLE time_entries (
-    id UUID PRIMARY KEY,
-    company_id UUID NOT NULL REFERENCES companies(id),
-    user_id UUID NOT NULL REFERENCES users(id),
-    project_id UUID NOT NULL REFERENCES projects(id),
-    activity_id UUID NOT NULL REFERENCES activities(id),
-    start_time TIMESTAMP NOT NULL,
-    end_time TIMESTAMP NOT NULL,
-    duration INTEGER NOT NULL, -- in minutes
-    description TEXT,
-    billable_percentage INTEGER NOT NULL DEFAULT 100,
-    billing_rate DECIMAL(10, 2),
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
--- Version 2: Sprint/Task Management
-CREATE TABLE sprints (
-    id UUID PRIMARY KEY,
-    project_id UUID NOT NULL REFERENCES projects(id),
-    name VARCHAR(255) NOT NULL,
-    start_date DATE NOT NULL,
-    end_date DATE NOT NULL,
-    status VARCHAR(50),
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
-CREATE TABLE task_statuses (
-    id SERIAL PRIMARY KEY,
-    company_id UUID NOT NULL REFERENCES companies(id),
-    name VARCHAR(100) NOT NULL,
-    color VARCHAR(7),
-    position INTEGER NOT NULL,
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
-CREATE TABLE tasks (
-    id UUID PRIMARY KEY,
-    company_id UUID NOT NULL REFERENCES companies(id),
-    project_id UUID NOT NULL REFERENCES projects(id),
-    sprint_id UUID REFERENCES sprints(id),
-    title VARCHAR(255) NOT NULL,
-    description TEXT,
-    assignee_id UUID REFERENCES users(id),
-    status_id INTEGER REFERENCES task_statuses(id),
-    priority VARCHAR(50),
-    estimate INTEGER, -- in minutes
-    due_date TIMESTAMP,
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
-CREATE TABLE kanban_boards (
-    id UUID PRIMARY KEY,
-    company_id UUID NOT NULL REFERENCES companies(id),
-    project_id UUID NOT NULL REFERENCES projects(id),
-    name VARCHAR(255) NOT NULL,
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
-CREATE TABLE kanban_columns (
-    id UUID PRIMARY KEY,
-    board_id UUID NOT NULL REFERENCES kanban_boards(id),
-    name VARCHAR(100) NOT NULL,
-    position INTEGER NOT NULL,
-    task_status_id INTEGER REFERENCES task_statuses(id),
-    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
-    updated_at TIMESTAMP NOT NULL DEFAULT NOW()
-);
-
--- Linking time entries and tasks
-ALTER TABLE time_entries ADD COLUMN task_id UUID REFERENCES tasks(id);
-
--- Indexes for performance
-CREATE INDEX idx_time_entries_user ON time_entries(user_id);
-CREATE INDEX idx_time_entries_project ON time_entries(project_id);
-CREATE INDEX idx_time_entries_date ON time_entries(start_time);
-CREATE INDEX idx_projects_company ON projects(company_id);
-CREATE INDEX idx_users_company ON users(company_id);
-CREATE INDEX idx_tasks_project ON tasks(project_id);
-CREATE INDEX idx_tasks_sprint ON tasks(sprint_id);

docu/deployment_devops.md

@@ -1,17 +0,0 @@
-# Deployment and DevOps
-
-## Containerization
-- Docker containers for backend and frontend
-- Docker Compose for development environment
-- Kubernetes manifests for production environment
-
-## CI/CD Pipeline
-- Automated tests (Unit, Integration, E2E)
-- Automated deployment
-- Version management
-
-## Monitoring and Logging
-- Prometheus for metrics
-- Grafana for visualization
-- ELK Stack or similar for logging
-- Alerting for critical events

docu/swagger_documentation.md

@@ -0,0 +1,84 @@
+# Swagger Documentation
+
+This document explains how to access and update the Swagger documentation for the Time Tracker API.
+
+## Accessing Swagger UI
+
+After starting the backend server, access the Swagger UI at:
+```
+http://localhost:8080/swagger/index.html
+```
+
+This interactive interface allows you to:
+- Browse all available API endpoints
+- See request parameters and response formats
+- Test API calls directly from the browser
+
+## Updating Swagger Documentation
+
+To update the Swagger documentation for the Time Tracker API, follow these steps:
+
+1. **Add or update Swagger annotations in your code**
+   - Annotations should be added as comments above handler functions
+   - Use the correct types in annotations (e.g., `dto.ActivityDto` instead of `utils.ActivityResponse`)
+   - Make sure all parameters, responses, and types are properly documented
+
+2. **Run the Swagger generation command**
+   ```bash
+   cd backend && swag init -g cmd/api/main.go --output docs
+   ```
+   
+   This command:
+   - Uses `swag` CLI tool to parse your code
+   - Looks for the main entry point in `cmd/api/main.go`
+   - Outputs the generated files to the `docs` directory
+
+3. **Verify the generated files**
+   The command will generate or update three files:
+   - `docs/docs.go` - Go code for the Swagger documentation
+   - `docs/swagger.json` - JSON representation of the API
+   - `docs/swagger.yaml` - YAML representation of the API
+
+4. **Common issues and solutions**
+   - If you encounter "cannot find type definition" errors, check that you're using the correct type names in your annotations
+   - If endpoints are missing, ensure they have proper Swagger annotations
+   - If you change the base path or other global settings, update them in the `main.go` file annotations
+
+## Swagger Annotation Examples
+
+### Main API Information
+
+In `main.go`:
+```go
+//	@title						Time Tracker API
+//	@version					1.0
+//	@description				This is a simple time tracker API.
+//	@host						localhost:8080
+//	@BasePath					/api
+//	@securityDefinitions.apikey	BearerAuth
+//	@in							header
+//	@name						Authorization
+```
+
+### Endpoint Documentation
+
+Example from a handler function:
+```go
+// GetActivities handles GET /activities
+//
+//	@Summary		Get all activities
+//	@Description	Get a list of all activities
+//	@Tags			activities
+//	@Accept			json
+//	@Produce		json
+//	@Security		BearerAuth
+//	@Success		200	{object}	utils.Response{data=[]dto.ActivityDto}
+//	@Failure		401	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Failure		500	{object}	utils.Response{error=utils.ErrorInfo}
+//	@Router			/activities [get]
+func (h *ActivityHandler) GetActivities(c *gin.Context) {
+    // Function implementation
+}
+```
+
+Remember that the Swagger documentation is generated from the annotations in your code, so keeping these annotations up-to-date is essential for accurate API documentation.

frontend/src/types/dto.ts

@@ -1,3 +1,4 @@
+import { Nullable } from "./nullable";
 // Code generated by tygo. DO NOT EDIT.
 
 //////////
@@ -24,6 +25,24 @@ export interface ActivityUpdateDto {
   billingRate?: number /* float64 */;
 }
 
+//////////
+// source: auth_dto.go
+
+/**
+ * LoginDto represents the login request
+ */
+export interface LoginDto {
+  email: string;
+  password: string;
+}
+/**
+ * TokenDto represents the response after successful authentication
+ */
+export interface TokenDto {
+  token: string;
+  user: UserDto;
+}
+
 //////////
 // source: company_dto.go
 
@@ -54,11 +73,12 @@ export interface CustomerDto {
   updatedAt: string;
   lastEditorID: string;
   name: string;
-  companyId: number /* int */;
+  companyId?: string;
+  owningUserID?: string;
 }
 export interface CustomerCreateDto {
   name: string;
-  companyId: number /* int */;
+  companyId?: string;
 }
 export interface CustomerUpdateDto {
   id: string;
@@ -66,7 +86,8 @@ export interface CustomerUpdateDto {
   updatedAt?: string;
   lastEditorID?: string;
   name?: string;
-  companyId?: number /* int */;
+  companyId?: Nullable<string>;
+  owningUserID?: Nullable<string>;
 }
 
 //////////
@@ -78,11 +99,11 @@ export interface ProjectDto {
   updatedAt: string;
   lastEditorID: string;
   name: string;
-  customerId: number /* int */;
+  customerId: string;
 }
 export interface ProjectCreateDto {
   name: string;
-  customerId: number /* int */;
+  customerId: string;
 }
 export interface ProjectUpdateDto {
   id: string;
@@ -90,7 +111,7 @@ export interface ProjectUpdateDto {
   updatedAt?: string;
   lastEditorID?: string;
   name?: string;
-  customerId?: number /* int */;
+  customerId?: string;
 }
 
 //////////
@@ -101,18 +122,18 @@ export interface TimeEntryDto {
   createdAt: string;
   updatedAt: string;
   lastEditorID: string;
-  userId: number /* int */;
-  projectId: number /* int */;
-  activityId: number /* int */;
+  userId: string;
+  projectId: string;
+  activityId: string;
   start: string;
   end: string;
   description: string;
   billable: number /* int */; // Percentage (0-100)
 }
 export interface TimeEntryCreateDto {
-  userId: number /* int */;
-  projectId: number /* int */;
-  activityId: number /* int */;
+  userId: string;
+  projectId: string;
+  activityId: string;
   start: string;
   end: string;
   description: string;
@@ -123,9 +144,9 @@ export interface TimeEntryUpdateDto {
   createdAt?: string;
   updatedAt?: string;
   lastEditorID?: string;
-  userId?: number /* int */;
-  projectId?: number /* int */;
-  activityId?: number /* int */;
+  userId?: string;
+  projectId?: string;
+  activityId?: string;
   start?: string;
   end?: string;
   description?: string;
@@ -141,16 +162,15 @@ export interface UserDto {
   updatedAt: string;
   lastEditorID: string;
   email: string;
-  password: string; // Note: In a real application, you would NEVER send the password in a DTO. This is just for demonstration.
   role: string;
-  companyId: number /* int */;
+  companyId?: string;
   hourlyRate: number /* float64 */;
 }
 export interface UserCreateDto {
   email: string;
-  password: string; // Note: In a real application, you would NEVER send the password in a DTO. This is just for demonstration.
+  password: string;
   role: string;
-  companyId: number /* int */;
+  companyId?: string;
   hourlyRate: number /* float64 */;
 }
 export interface UserUpdateDto {
@@ -159,8 +179,8 @@ export interface UserUpdateDto {
   updatedAt?: string;
   lastEditorID?: string;
   email?: string;
-  password?: string; // Note: In a real application, you would NEVER send the password in a DTO. This is just for demonstration.
+  password?: string;
   role?: string;
-  companyId?: number /* int */;
+  companyId?: Nullable<string>;
   hourlyRate?: number /* float64 */;
 }

frontend/src/types/nullable.ts

@@ -0,0 +1 @@
+export type Nullable<T> = T | null;

refactor_plan.md

@@ -0,0 +1,25 @@
+# Refactoring Plan for backend/internal/api/handlers
+
+## Goal
+
+Refactor the code in `backend/internal/api/handlers` to reduce repetition and create helper functions for boilerplate operations, utilizing functions from `backend/internal/api/utils/handler_utils.go` and creating new ones if necessary.
+
+## Analysis
+
+The following common patterns were identified in the handler files:
+
+1.  **Error Handling:** Each handler function repeats the same error handling pattern.
+2.  **DTO Binding:** Parsing the request body and handling potential errors.
+3.  **ID Parsing:** Parsing the ID from the URL and handling potential errors.
+4.  **DTO Conversion:** Converting between DTOs and models.
+5.  **Success Responses:** Calling `responses.SuccessResponse` with the appropriate HTTP status code and data.
+6.  **Not Found Responses:** Checking if a record exists and calling `responses.NotFoundResponse` if it doesn't.
+
+The `Update` handler is the most complex and has the most potential for refactoring.
+
+## Plan
+
+1.  **Implement a generic `HandleUpdate` function in `handler_utils.go`:** This function will encapsulate the common logic for updating entities, including parsing the ID, binding the JSON, converting the DTO to a model, calling the update function, and handling errors and not found cases. The function will also handle nullable fields correctly.
+2.  **Modify the existing handlers to use the new `HandleUpdate` function:** This will involve removing the duplicated code from each handler and calling the generic function instead.
+3.  **Create new helper functions in `handler_utils.go` if needed:** If there are any specific operations that are not covered by the existing utility functions, I will create new ones to handle them.
+