tankstopp-app/internal/database/db.go

package database

import (
	"fmt"
	"log"
	"os"
	"tankstopp/internal/models"
	"time"

	"golang.org/x/crypto/bcrypt"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

type DB struct {
	conn *gorm.DB
}

// NewDB creates a new database connection using GORM with configuration
func NewDB(config *Config) (*DB, error) {
	// Validate configuration
	if err := config.Validate(); err != nil {
		return nil, fmt.Errorf("invalid configuration: %w", err)
	}

	// Configure GORM
	gormConfig := &gorm.Config{
		Logger:                                   logger.Default.LogMode(config.LogLevel),
		PrepareStmt:                              config.PrepareStmt,
		DisableForeignKeyConstraintWhenMigrating: config.DisableForeignKeyCheck,
		IgnoreRelationshipsWhenMigrating:         config.IgnoreRelationshipsWhenMigrating,
		QueryFields:                              config.QueryFields,
		CreateBatchSize:                          config.CreateBatchSize,
		DryRun:                                   config.DryRun,
	}

	// Configure slow query logging
	if config.SlowQueryLog > 0 {
		env := os.Getenv("ENV")
		isDev := env == "development" || env == "dev" || env == ""

		customLogger := logger.New(
			log.New(os.Stdout, "\r\n", log.LstdFlags), // io writer
			logger.Config{
				SlowThreshold:             config.SlowQueryLog,
				LogLevel:                  config.LogLevel,
				IgnoreRecordNotFoundError: true,
				Colorful:                  isDev,
			},
		)
		gormConfig.Logger = customLogger
	}

	conn, err := gorm.Open(sqlite.Open(config.DatabasePath), gormConfig)
	if err != nil {
		return nil, fmt.Errorf("failed to open database: %w", err)
	}

	// Get underlying SQL DB to configure connection pool
	sqlDB, err := conn.DB()
	if err != nil {
		return nil, fmt.Errorf("failed to get underlying sql.DB: %w", err)
	}

	// Set connection pool settings from configuration
	sqlDB.SetMaxIdleConns(config.MaxIdleConns)
	sqlDB.SetMaxOpenConns(config.MaxOpenConns)
	sqlDB.SetConnMaxLifetime(config.ConnMaxLifetime)
	sqlDB.SetConnMaxIdleTime(config.ConnMaxIdleTime)

	db := &DB{conn: conn}

	// Run migrations if enabled
	if config.AutoMigrate {
		if err := db.migrate(); err != nil {
			return nil, fmt.Errorf("failed to migrate database: %w", err)
		}
	}

	return db, nil
}

// NewDBWithDefaults creates a new database connection with default configuration
func NewDBWithDefaults(databasePath string) (*DB, error) {
	config := DefaultConfig()
	config.DatabasePath = databasePath
	return NewDB(config)
}

// NewDBFromEnv creates a new database connection using environment variables
func NewDBFromEnv() (*DB, error) {
	config := LoadFromEnv()
	return NewDB(config)
}

// NewDBFromConfig creates a new database connection using configuration file
func NewDBFromConfig(configPath string) (*DB, error) {
	config := LoadFromConfig(configPath)
	return NewDB(config)
}

// Close closes the database connection
func (db *DB) Close() error {
	sqlDB, err := db.conn.DB()
	if err != nil {
		return err
	}
	return sqlDB.Close()
}

// migrate runs database migrations
func (db *DB) migrate() error {
	// Auto-migrate the schema
	return db.conn.AutoMigrate(&models.User{}, &models.Vehicle{}, &models.FuelStop{})
}

// CreateFuelStop inserts a new fuel stop into the database
func (db *DB) CreateFuelStop(stop *models.FuelStop) error {
	// Set timestamps
	now := time.Now()
	stop.CreatedAt = now
	stop.UpdatedAt = now

	result := db.conn.Create(stop)
	if result.Error != nil {
		return fmt.Errorf("failed to create fuel stop: %w", result.Error)
	}

	return nil
}

// GetFuelStops retrieves all fuel stops for a specific user from the database
func (db *DB) GetFuelStops(userID uint) ([]models.FuelStop, error) {
	var stops []models.FuelStop

	result := db.conn.Preload("Vehicle").Where("user_id = ?", userID).
		Order("date DESC").
		Find(&stops)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to get fuel stops: %w", result.Error)
	}

	return stops, nil
}

// GetFuelStopsByVehicle retrieves all fuel stops for a specific vehicle
func (db *DB) GetFuelStopsByVehicle(vehicleID, userID uint) ([]models.FuelStop, error) {
	var stops []models.FuelStop

	result := db.conn.Where("vehicle_id = ? AND user_id = ?", vehicleID, userID).
		Order("date DESC").
		Find(&stops)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to get fuel stops by vehicle: %w", result.Error)
	}

	return stops, nil
}

// GetFuelStopByID retrieves a fuel stop by its ID and user ID
func (db *DB) GetFuelStopByID(id, userID uint) (*models.FuelStop, error) {
	var stop models.FuelStop

	result := db.conn.Where("id = ? AND user_id = ?", id, userID).First(&stop)
	if result.Error != nil {
		if result.Error == gorm.ErrRecordNotFound {
			return nil, nil // Return nil when record not found
		}
		return nil, fmt.Errorf("failed to get fuel stop: %w", result.Error)
	}

	return &stop, nil
}

// UpdateFuelStop updates an existing fuel stop
func (db *DB) UpdateFuelStop(stop *models.FuelStop) error {
	// Update timestamp
	stop.UpdatedAt = time.Now()

	result := db.conn.Model(stop).
		Where("id = ? AND user_id = ?", stop.ID, stop.UserID).
		Updates(stop)

	if result.Error != nil {
		return fmt.Errorf("failed to update fuel stop: %w", result.Error)
	}

	if result.RowsAffected == 0 {
		return fmt.Errorf("fuel stop not found or access denied")
	}

	return nil
}

// DeleteFuelStop deletes a fuel stop by its ID and user ID
func (db *DB) DeleteFuelStop(id, userID uint) error {
	result := db.conn.Where("id = ? AND user_id = ?", id, userID).Delete(&models.FuelStop{})
	if result.Error != nil {
		return fmt.Errorf("failed to delete fuel stop: %w", result.Error)
	}

	if result.RowsAffected == 0 {
		return fmt.Errorf("fuel stop not found or access denied")
	}

	return nil
}

// CreateVehicle creates a new vehicle for a user
func (db *DB) CreateVehicle(vehicle *models.Vehicle) error {
	// Set timestamps
	now := time.Now()
	vehicle.CreatedAt = now
	vehicle.UpdatedAt = now

	result := db.conn.Create(vehicle)
	if result.Error != nil {
		return fmt.Errorf("failed to create vehicle: %w", result.Error)
	}

	return nil
}

// GetVehicles retrieves all vehicles for a specific user
func (db *DB) GetVehicles(userID uint) ([]models.Vehicle, error) {
	var vehicles []models.Vehicle

	result := db.conn.Where("user_id = ?", userID).
		Order("is_active DESC, name ASC").
		Find(&vehicles)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to get vehicles: %w", result.Error)
	}

	return vehicles, nil
}

// GetActiveVehicles retrieves only active vehicles for a specific user
func (db *DB) GetActiveVehicles(userID uint) ([]models.Vehicle, error) {
	var vehicles []models.Vehicle

	result := db.conn.Where("user_id = ? AND is_active = ?", userID, true).
		Order("name ASC").
		Find(&vehicles)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to get active vehicles: %w", result.Error)
	}

	return vehicles, nil
}

// GetVehicleByID retrieves a vehicle by its ID and user ID
func (db *DB) GetVehicleByID(id, userID uint) (*models.Vehicle, error) {
	var vehicle models.Vehicle

	result := db.conn.Where("id = ? AND user_id = ?", id, userID).First(&vehicle)
	if result.Error != nil {
		if result.Error == gorm.ErrRecordNotFound {
			return nil, nil // Return nil when vehicle not found
		}
		return nil, fmt.Errorf("failed to get vehicle: %w", result.Error)
	}

	return &vehicle, nil
}

// UpdateVehicle updates an existing vehicle
func (db *DB) UpdateVehicle(vehicle *models.Vehicle) error {
	// Update timestamp
	vehicle.UpdatedAt = time.Now()

	result := db.conn.Model(vehicle).
		Where("id = ? AND user_id = ?", vehicle.ID, vehicle.UserID).
		Updates(vehicle)

	if result.Error != nil {
		return fmt.Errorf("failed to update vehicle: %w", result.Error)
	}

	if result.RowsAffected == 0 {
		return fmt.Errorf("vehicle not found or access denied")
	}

	return nil
}

// DeleteVehicle deletes a vehicle by its ID and user ID
func (db *DB) DeleteVehicle(id, userID uint) error {
	// Check if vehicle has fuel stops
	var count int64
	if err := db.conn.Model(&models.FuelStop{}).Where("vehicle_id = ?", id).Count(&count).Error; err != nil {
		return fmt.Errorf("failed to check fuel stops: %w", err)
	}

	if count > 0 {
		return fmt.Errorf("cannot delete vehicle with existing fuel stops")
	}

	result := db.conn.Where("id = ? AND user_id = ?", id, userID).Delete(&models.Vehicle{})
	if result.Error != nil {
		return fmt.Errorf("failed to delete vehicle: %w", result.Error)
	}

	if result.RowsAffected == 0 {
		return fmt.Errorf("vehicle not found or access denied")
	}

	return nil
}

// GetVehicleWithFuelStops retrieves a vehicle with its fuel stops
func (db *DB) GetVehicleWithFuelStops(vehicleID, userID uint) (*models.Vehicle, error) {
	var vehicle models.Vehicle

	result := db.conn.Preload("FuelStops", func(db *gorm.DB) *gorm.DB {
		return db.Order("date DESC")
	}).Where("id = ? AND user_id = ?", vehicleID, userID).First(&vehicle)

	if result.Error != nil {
		if result.Error == gorm.ErrRecordNotFound {
			return nil, nil
		}
		return nil, fmt.Errorf("failed to get vehicle with fuel stops: %w", result.Error)
	}

	return &vehicle, nil
}

// GetVehicleCount returns the total number of vehicles for a user
func (db *DB) GetVehicleCount(userID uint) (int64, error) {
	var count int64
	result := db.conn.Model(&models.Vehicle{}).Where("user_id = ?", userID).Count(&count)
	if result.Error != nil {
		return 0, fmt.Errorf("failed to count vehicles: %w", result.Error)
	}
	return count, nil
}

// ValidateVehicle validates vehicle data before creation/update
func (db *DB) ValidateVehicle(vehicle *models.Vehicle) error {
	if vehicle.UserID == 0 {
		return fmt.Errorf("user ID is required")
	}

	// Check if user exists
	exists, err := db.UserExists(vehicle.UserID)
	if err != nil {
		return fmt.Errorf("failed to validate user: %w", err)
	}
	if !exists {
		return fmt.Errorf("user does not exist")
	}

	if vehicle.Name == "" {
		return fmt.Errorf("vehicle name is required")
	}

	if len(vehicle.Name) > 100 {
		return fmt.Errorf("vehicle name must be 100 characters or less")
	}

	if vehicle.Make != "" && len(vehicle.Make) > 50 {
		return fmt.Errorf("vehicle make must be 50 characters or less")
	}

	if vehicle.Model != "" && len(vehicle.Model) > 50 {
		return fmt.Errorf("vehicle model must be 50 characters or less")
	}

	if vehicle.LicensePlate != "" && len(vehicle.LicensePlate) > 20 {
		return fmt.Errorf("license plate must be 20 characters or less")
	}

	if vehicle.FuelType != "" && len(vehicle.FuelType) > 50 {
		return fmt.Errorf("fuel type must be 50 characters or less")
	}

	if vehicle.Year < 0 || vehicle.Year > time.Now().Year()+1 {
		return fmt.Errorf("invalid vehicle year")
	}

	return nil
}

// CreateVehicleWithValidation creates a vehicle with validation
func (db *DB) CreateVehicleWithValidation(vehicle *models.Vehicle) error {
	if err := db.ValidateVehicle(vehicle); err != nil {
		return fmt.Errorf("validation failed: %w", err)
	}

	return db.CreateVehicle(vehicle)
}

// GetFuelStopStats calculates statistics for fuel consumption for a specific user
func (db *DB) GetFuelStopStats(userID uint) (*models.FuelStopStats, error) {
	stats := &models.FuelStopStats{}

	// Get basic statistics
	var result struct {
		TotalStops   int64   `json:"total_stops"`
		TotalLiters  float64 `json:"total_liters"`
		TotalSpent   float64 `json:"total_spent"`
		AveragePrice float64 `json:"average_price"`
		TotalTripKm  float64 `json:"total_trip_km"`
		MinOdometer  int     `json:"min_odometer"`
		MaxOdometer  int     `json:"max_odometer"`
	}

	err := db.conn.Model(&models.FuelStop{}).
		Select(`
			COUNT(*) as total_stops,
			COALESCE(SUM(liters), 0) as total_liters,
			COALESCE(SUM(total_price), 0) as total_spent,
			COALESCE(AVG(price_per_l), 0) as average_price,
			COALESCE(SUM(trip_length), 0) as total_trip_km,
			COALESCE(MIN(odometer), 0) as min_odometer,
			COALESCE(MAX(odometer), 0) as max_odometer
		`).
		Where("user_id = ?", userID).
		Scan(&result).Error

	if err != nil {
		return nil, fmt.Errorf("failed to get fuel stop stats: %w", err)
	}

	stats.TotalStops = int(result.TotalStops)
	stats.TotalLiters = result.TotalLiters
	stats.TotalSpent = result.TotalSpent
	stats.AveragePrice = result.AveragePrice

	// Get the last fillup
	var lastStop models.FuelStop
	err = db.conn.Where("user_id = ?", userID).
		Order("date DESC").
		First(&lastStop).Error

	if err != nil && err != gorm.ErrRecordNotFound {
		return nil, fmt.Errorf("failed to get last fillup: %w", err)
	}

	if err != gorm.ErrRecordNotFound {
		stats.LastFillup = &lastStop
	}

	// Calculate average consumption using trip length (preferred) or odometer difference (fallback)
	if stats.TotalStops > 1 {
		// Primary method: Use trip length if available
		if result.TotalTripKm > 0 {
			stats.AverageConsumption = (stats.TotalLiters / result.TotalTripKm) * 100
		} else if result.MaxOdometer > result.MinOdometer {
			// Fallback method: Use odometer difference
			distanceDriven := result.MaxOdometer - result.MinOdometer
			if distanceDriven > 0 {
				stats.AverageConsumption = (stats.TotalLiters / float64(distanceDriven)) * 100
			}
		}
	}

	return stats, nil

}

// CreateUser creates a new user in the database
func (db *DB) CreateUser(user *models.User) error {
	// Hash the password
	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(user.Password), bcrypt.DefaultCost)
	if err != nil {
		return fmt.Errorf("failed to hash password: %w", err)
	}

	user.PasswordHash = string(hashedPassword)
	user.Password = "" // Clear the plain text password

	// Set timestamps
	now := time.Now()
	user.CreatedAt = now
	user.UpdatedAt = now

	result := db.conn.Create(user)
	if result.Error != nil {
		return fmt.Errorf("failed to create user: %w", result.Error)
	}

	return nil
}

// GetUserByUsername retrieves a user by username
func (db *DB) GetUserByUsername(username string) (*models.User, error) {
	var user models.User

	result := db.conn.Where("username = ?", username).First(&user)
	if result.Error != nil {
		if result.Error == gorm.ErrRecordNotFound {
			return nil, nil // Return nil when user not found
		}
		return nil, fmt.Errorf("failed to get user by username: %w", result.Error)
	}

	return &user, nil
}

// GetUserByID retrieves a user by ID
func (db *DB) GetUserByID(id uint) (*models.User, error) {
	var user models.User

	result := db.conn.First(&user, id)
	if result.Error != nil {
		if result.Error == gorm.ErrRecordNotFound {
			return nil, nil // Return nil when user not found
		}
		return nil, fmt.Errorf("failed to get user by ID: %w", result.Error)
	}

	return &user, nil
}

// UpdateUser updates an existing user
func (db *DB) UpdateUser(user *models.User) error {
	// Update timestamp
	user.UpdatedAt = time.Now()

	result := db.conn.Model(user).
		Select("email", "base_currency", "updated_at").
		Updates(user)

	if result.Error != nil {
		return fmt.Errorf("failed to update user: %w", result.Error)
	}

	if result.RowsAffected == 0 {
		return fmt.Errorf("user not found")
	}

	return nil
}

// UpdateUserPassword updates a user's password
func (db *DB) UpdateUserPassword(user *models.User, newPassword string) error {
	// Hash the new password
	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(newPassword), bcrypt.DefaultCost)
	if err != nil {
		return fmt.Errorf("failed to hash password: %w", err)
	}

	// Update timestamp
	now := time.Now()

	// Update only the password hash and updated_at fields
	result := db.conn.Model(user).
		Updates(map[string]interface{}{
			"password_hash": string(hashedPassword),
			"updated_at":    now,
		})

	if result.Error != nil {
		return fmt.Errorf("failed to update password: %w", result.Error)
	}

	if result.RowsAffected == 0 {
		return fmt.Errorf("user not found")
	}

	// Update the user object with new password hash
	user.PasswordHash = string(hashedPassword)
	user.UpdatedAt = now

	return nil
}

// GetUserByEmail retrieves a user by email
func (db *DB) GetUserByEmail(email string) (*models.User, error) {
	var user models.User

	result := db.conn.Where("email = ?", email).First(&user)
	if result.Error != nil {
		if result.Error == gorm.ErrRecordNotFound {
			return nil, nil // Return nil when user not found
		}
		return nil, fmt.Errorf("failed to get user by email: %w", result.Error)
	}

	return &user, nil
}

// GetUserWithFuelStops retrieves a user with their fuel stops
func (db *DB) GetUserWithFuelStops(userID uint) (*models.User, error) {
	var user models.User

	result := db.conn.Preload("FuelStops", func(db *gorm.DB) *gorm.DB {
		return db.Order("date DESC")
	}).Preload("Vehicles").First(&user, userID)

	if result.Error != nil {
		if result.Error == gorm.ErrRecordNotFound {
			return nil, nil
		}
		return nil, fmt.Errorf("failed to get user with fuel stops: %w", result.Error)
	}

	return &user, nil
}

// GetFuelStopsWithPagination retrieves fuel stops with pagination
func (db *DB) GetFuelStopsWithPagination(userID uint, limit, offset int) ([]models.FuelStop, int64, error) {
	var stops []models.FuelStop
	var total int64

	// Get total count
	err := db.conn.Model(&models.FuelStop{}).
		Where("user_id = ?", userID).
		Count(&total).Error

	if err != nil {
		return nil, 0, fmt.Errorf("failed to count fuel stops: %w", err)
	}

	// Get paginated results
	err = db.conn.Where("user_id = ?", userID).
		Order("date DESC").
		Limit(limit).
		Offset(offset).
		Find(&stops).Error

	if err != nil {
		return nil, 0, fmt.Errorf("failed to get fuel stops with pagination: %w", err)
	}

	return stops, total, nil
}

// GetFuelStopsByDateRange retrieves fuel stops within a date range
func (db *DB) GetFuelStopsByDateRange(userID uint, startDate, endDate time.Time) ([]models.FuelStop, error) {
	var stops []models.FuelStop

	result := db.conn.Where("user_id = ? AND date BETWEEN ? AND ?", userID, startDate, endDate).
		Order("date DESC").
		Find(&stops)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to get fuel stops by date range: %w", result.Error)
	}

	return stops, nil
}

// GetFuelStopsByFuelType retrieves fuel stops by fuel type
func (db *DB) GetFuelStopsByFuelType(userID uint, fuelType string) ([]models.FuelStop, error) {
	var stops []models.FuelStop

	result := db.conn.Where("user_id = ? AND fuel_type = ?", userID, fuelType).
		Order("date DESC").
		Find(&stops)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to get fuel stops by fuel type: %w", result.Error)
	}

	return stops, nil
}

// GetMonthlyStats retrieves monthly statistics for a user
func (db *DB) GetMonthlyStats(userID uint, year int) ([]models.MonthlyStats, error) {
	var stats []models.MonthlyStats

	query := `
		SELECT
			strftime('%m', date) as month,
			strftime('%Y', date) as year,
			COUNT(*) as total_stops,
			SUM(liters) as total_liters,
			SUM(total_price) as total_spent,
			AVG(price_per_l) as average_price
		FROM fuel_stops
		WHERE user_id = ? AND strftime('%Y', date) = ?
		GROUP BY strftime('%Y-%m', date)
		ORDER BY month
	`

	err := db.conn.Raw(query, userID, fmt.Sprintf("%d", year)).Scan(&stats).Error
	if err != nil {
		return nil, fmt.Errorf("failed to get monthly stats: %w", err)
	}

	return stats, nil
}

// BulkCreateFuelStops creates multiple fuel stops in a single transaction
func (db *DB) BulkCreateFuelStops(stops []models.FuelStop) error {
	if len(stops) == 0 {
		return nil
	}

	// Set timestamps for all stops
	now := time.Now()
	for i := range stops {
		stops[i].CreatedAt = now
		stops[i].UpdatedAt = now
	}

	// Use transaction for bulk insert
	return db.conn.Transaction(func(tx *gorm.DB) error {
		return tx.CreateInBatches(stops, 100).Error
	})
}

// DeleteAllUserData deletes all data for a user (for account deletion)
func (db *DB) DeleteAllUserData(userID uint) error {
	return db.conn.Transaction(func(tx *gorm.DB) error {
		// Delete all fuel stops first (due to foreign key constraint)
		if err := tx.Where("user_id = ?", userID).Delete(&models.FuelStop{}).Error; err != nil {
			return fmt.Errorf("failed to delete fuel stops: %w", err)
		}

		// Delete the user
		if err := tx.Delete(&models.User{}, userID).Error; err != nil {
			return fmt.Errorf("failed to delete user: %w", err)
		}

		return nil
	})
}

// HealthCheck performs a simple health check on the database
func (db *DB) HealthCheck() error {
	sqlDB, err := db.conn.DB()
	if err != nil {
		return fmt.Errorf("failed to get underlying sql.DB: %w", err)
	}

	return sqlDB.Ping()
}

// GetFuelStopCount returns the total number of fuel stops for a user
func (db *DB) GetFuelStopCount(userID uint) (int64, error) {
	var count int64
	result := db.conn.Model(&models.FuelStop{}).Where("user_id = ?", userID).Count(&count)
	if result.Error != nil {
		return 0, fmt.Errorf("failed to count fuel stops: %w", result.Error)
	}
	return count, nil
}

// GetLatestFuelStop returns the most recent fuel stop for a user
func (db *DB) GetLatestFuelStop(userID uint) (*models.FuelStop, error) {
	var stop models.FuelStop
	result := db.conn.Where("user_id = ?", userID).Order("date DESC").First(&stop)
	if result.Error != nil {
		if result.Error == gorm.ErrRecordNotFound {
			return nil, nil
		}
		return nil, fmt.Errorf("failed to get latest fuel stop: %w", result.Error)
	}
	return &stop, nil
}

// UserExists checks if a user exists by ID
func (db *DB) UserExists(userID uint) (bool, error) {
	var count int64
	result := db.conn.Model(&models.User{}).Where("id = ?", userID).Count(&count)
	if result.Error != nil {
		return false, fmt.Errorf("failed to check user existence: %w", result.Error)
	}
	return count > 0, nil
}

// ValidateFuelStop validates fuel stop data before creation/update
func (db *DB) ValidateFuelStop(stop *models.FuelStop) error {
	if stop.UserID == 0 {
		return fmt.Errorf("user ID is required")
	}

	// Check if user exists
	exists, err := db.UserExists(stop.UserID)
	if err != nil {
		return fmt.Errorf("failed to validate user: %w", err)
	}
	if !exists {
		return fmt.Errorf("user does not exist")
	}

	if stop.Date.IsZero() {
		return fmt.Errorf("date is required")
	}

	if stop.StationName == "" {
		return fmt.Errorf("station name is required")
	}

	if stop.Location == "" {
		return fmt.Errorf("location is required")
	}

	if stop.FuelType == "" {
		return fmt.Errorf("fuel type is required")
	}

	if stop.Liters <= 0 {
		return fmt.Errorf("liters must be greater than 0")
	}

	if stop.PricePerL <= 0 {
		return fmt.Errorf("price per liter must be greater than 0")
	}

	if stop.TotalPrice <= 0 {
		return fmt.Errorf("total price must be greater than 0")
	}

	if stop.Currency == "" {
		stop.Currency = "EUR" // Set default currency
	}

	if stop.TripLength < 0 {
		return fmt.Errorf("trip length cannot be negative")
	}

	if stop.VehicleID == 0 {
		return fmt.Errorf("vehicle is required")
	}

	// Check if vehicle exists and belongs to user
	vehicle, err := db.GetVehicleByID(stop.VehicleID, stop.UserID)
	if err != nil {
		return fmt.Errorf("failed to validate vehicle: %w", err)
	}
	if vehicle == nil {
		return fmt.Errorf("vehicle does not exist or access denied")
	}

	return nil
}

// CreateFuelStopWithValidation creates a fuel stop with validation
func (db *DB) CreateFuelStopWithValidation(stop *models.FuelStop) error {
	if err := db.ValidateFuelStop(stop); err != nil {
		return fmt.Errorf("validation failed: %w", err)
	}

	return db.CreateFuelStop(stop)
}

// GetFuelStopsWithUser retrieves fuel stops with user information preloaded
func (db *DB) GetFuelStopsWithUser(userID uint) ([]models.FuelStop, error) {
	var stops []models.FuelStop

	result := db.conn.Preload("User").Preload("Vehicle").
		Where("user_id = ?", userID).
		Order("date DESC").
		Find(&stops)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to get fuel stops with user: %w", result.Error)
	}

	return stops, nil
}

// SearchFuelStops performs a text search across station names and locations
func (db *DB) SearchFuelStops(userID uint, searchTerm string) ([]models.FuelStop, error) {
	var stops []models.FuelStop

	searchPattern := "%" + searchTerm + "%"
	result := db.conn.Where("user_id = ? AND (station_name LIKE ? OR location LIKE ?)",
		userID, searchPattern, searchPattern).
		Order("date DESC").
		Find(&stops)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to search fuel stops: %w", result.Error)
	}

	return stops, nil
}

// GetRecentFuelStops returns the most recent N fuel stops for a user
func (db *DB) GetRecentFuelStops(userID uint, limit int) ([]models.FuelStop, error) {
	var stops []models.FuelStop

	result := db.conn.Where("user_id = ?", userID).
		Order("date DESC").
		Limit(limit).
		Find(&stops)

	if result.Error != nil {
		return nil, fmt.Errorf("failed to get recent fuel stops: %w", result.Error)
	}

	return stops, nil
}