package db

import (
	"context"
	"errors"
	"fmt"
	"log"
	"time"

	"github.com/timetracker/backend/internal/config"
	"gorm.io/driver/postgres"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

// 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 connection using the default database name
	gormDB, err := createConnection(config, config.DBName)
	if err != nil {
		return err
	}

	// Set the global db instance
	db = gormDB

	// Configure connection pool
	return configureConnectionPool(db, config)
}

// GetEngine returns the DB instance with context
func GetEngine(ctx context.Context) *gorm.DB {
	if db == nil {
		panic(ErrDBNotInitialized)
	}
	return db.WithContext(ctx)
}

// CloseDB closes the database connection
func CloseDB() error {
	if db == nil {
		return nil
	}

	sqlDB, err := db.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
}

// 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
}