refactor: restructure database initialization and migration logic, moving to models package

backend/cmd/migrate/main.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/timetracker/backend/internal/config"
 	"github.com/timetracker/backend/internal/db"
+	"github.com/timetracker/backend/internal/models"
 	"gorm.io/gorm/logger"
 )
 
@@ -102,7 +103,7 @@ func main() {
 
 	// Run migrations
 	fmt.Println("Running database migrations...")
-	if err = db.MigrateDB(); err != nil {
+	if err = models.MigrateDB(); err != nil {
 		log.Fatalf("Error migrating database: %v", err)
 	}
 	fmt.Println("✓ Database migrations completed successfully")

backend/internal/db/db.go

@@ -2,6 +2,7 @@ package db
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"log"
 	"time"
@@ -15,53 +16,30 @@ import (
 // Global variable for the DB connection
 var db *gorm.DB
 
+// ErrDBNotInitialized is returned when a database operation is attempted before initialization
+var ErrDBNotInitialized = errors.New("database not initialized")
+
 // InitDB initializes the database connection (once at startup)
 // with the provided configuration
 func InitDB(config config.DatabaseConfig) error {
-	// Create DSN (Data Source Name)
-	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)
-
-	// 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
-	var err error
-	db, err = gorm.Open(postgres.Open(dsn), &gorm.Config{
-		Logger: gormLogger,
-	})
+	// Create connection using the default database name
+	gormDB, err := createConnection(config, config.DBName)
 	if err != nil {
-		return fmt.Errorf("error connecting to the database: %w", err)
+		return err
 	}
 
+	// Set the global db instance
+	db = gormDB
+
 	// 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)
-
-	return nil
+	return configureConnectionPool(db, config)
 }
 
-// GetEngine returns the DB instance, possibly with context
+// GetEngine returns the DB instance with context
 func GetEngine(ctx context.Context) *gorm.DB {
 	if db == nil {
-		panic("database not initialized")
+		panic(ErrDBNotInitialized)
 	}
-	// If a special transaction is in ctx, you could check it here
 	return db.WithContext(ctx)
 }
 
@@ -82,3 +60,67 @@ func CloseDB() error {
 
 	return nil
 }
+
+// GetGormDB is used for special cases like database creation
+func GetGormDB(dbConfig config.DatabaseConfig, dbName string) (*gorm.DB, error) {
+	return createConnection(dbConfig, dbName)
+}
+
+// MigrateDB performs database migrations for all models
+// This is a placeholder that will be called by models.MigrateDB
+func MigrateDB() error {
+	if db == nil {
+		return ErrDBNotInitialized
+	}
+	// The actual migration is implemented in models.MigrateDB
+	// This is just a placeholder to make the migrate/main.go file work
+	return errors.New("MigrateDB should be called from models package")
+}
+
+// createConnection creates a new database connection with the given configuration
+func createConnection(dbConfig config.DatabaseConfig, dbName string) (*gorm.DB, error) {
+	// Create DSN (Data Source Name)
+	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 := createGormLogger(dbConfig)
+
+	// Establish database connection with custom logger
+	gormDB, 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 gormDB, nil
+}
+
+// createGormLogger creates a configured GORM logger instance
+func createGormLogger(dbConfig config.DatabaseConfig) logger.Interface {
+	return 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
+		},
+	)
+}
+
+// configureConnectionPool sets up the connection pool parameters
+func configureConnectionPool(db *gorm.DB, config config.DatabaseConfig) error {
+	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)
+
+	return nil
+}