package repository

import (
	"errors"
	"time"

	"accounting-app/internal/models"

	"gorm.io/gorm"
)

// StreakRepository handles database operations for user streaks
type StreakRepository struct {
	db *gorm.DB
}

// NewStreakRepository creates a new StreakRepository instance
func NewStreakRepository(db *gorm.DB) *StreakRepository {
	return &StreakRepository{db: db}
}

// GetByUserID retrieves a user's streak record
func (r *StreakRepository) GetByUserID(userID uint) (*models.UserStreak, error) {
	var streak models.UserStreak
	if err := r.db.Where("user_id = ?", userID).First(&streak).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, nil // Return nil without error if not found
		}
		return nil, err
	}
	return &streak, nil
}

// Create creates a new streak record
func (r *StreakRepository) Create(streak *models.UserStreak) error {
	return r.db.Create(streak).Error
}

// Update updates an existing streak record
func (r *StreakRepository) Update(streak *models.UserStreak) error {
	return r.db.Save(streak).Error
}

// GetOrCreate retrieves existing streak record or creates a new one
func (r *StreakRepository) GetOrCreate(userID uint) (*models.UserStreak, error) {
	streak, err := r.GetByUserID(userID)
	if err != nil {
		return nil, err
	}

	if streak == nil {
		// Create new streak record
		streak = &models.UserStreak{
			UserID:          userID,
			CurrentStreak:   0,
			LongestStreak:   0,
			TotalRecordDays: 0,
		}
		if err := r.Create(streak); err != nil {
			return nil, err
		}
	}

	return streak, nil
}

// HasTransactionOnDate checks if user has any transaction on the given date
func (r *StreakRepository) HasTransactionOnDate(userID uint, date time.Time) (bool, error) {
	var count int64
	startOfDay := time.Date(date.Year(), date.Month(), date.Day(), 0, 0, 0, 0, date.Location())
	endOfDay := startOfDay.Add(24 * time.Hour)

	err := r.db.Model(&models.Transaction{}).
		Where("user_id = ? AND transaction_date >= ? AND transaction_date < ?", userID, startOfDay, endOfDay).
		Count(&count).Error

	if err != nil {
		return false, err
	}

	return count > 0, nil
}

// GetTransactionDatesInRange returns all dates with transactions in a date range
func (r *StreakRepository) GetTransactionDatesInRange(userID uint, startDate, endDate time.Time) ([]time.Time, error) {
	var dates []time.Time

	rows, err := r.db.Model(&models.Transaction{}).
		Select("DATE(transaction_date) as date").
		Where("user_id = ? AND transaction_date >= ? AND transaction_date <= ?", userID, startDate, endDate).
		Group("DATE(transaction_date)").
		Order("date ASC").
		Rows()

	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var date time.Time
		if err := rows.Scan(&date); err != nil {
			return nil, err
		}
		dates = append(dates, date)
	}

	return dates, nil
}

// GetDailyContribution returns daily transaction counts in a date range
func (r *StreakRepository) GetDailyContribution(userID uint, startDate, endDate time.Time) ([]models.DailyContribution, error) {
	var results []models.DailyContribution

	// SQLite uses strftime, MySQL/Postgres uses DATE()
	// Using a more generic approach compatible with SQLite (which is likely used locally)
	// For production readiness with multiple DBs, raw SQL might be safer or check dialect

	rows, err := r.db.Model(&models.Transaction{}).
		Select("DATE(transaction_date) as date, COUNT(*) as count").
		Where("user_id = ? AND transaction_date >= ? AND transaction_date <= ?", userID, startDate, endDate).
		Group("DATE(transaction_date)").
		Order("date ASC").
		Rows()

	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var dateStr string // Using string to handle potential format differences
		var count int
		// Scan into generic types then convert
		// Some drivers return date as time.Time, some as string/bytes
		// Let's try scan into string first (common for DATE() function result)
		// Or scan into interface{} to be safe
		if err := rows.Scan(&dateStr, &count); err != nil {
			// If string scan fails, try time.Time
			// Unfortunately we can't rewind rows. scan is one-way.
			// But usually drivers handle string conversion for DATE()
			// If this fails we might need to adjust based on specific DB driver
			return nil, err
		}
		// Normalize date string to YYYY-MM-DD (take first 10 chars if it includes time)
		if len(dateStr) > 10 {
			dateStr = dateStr[:10]
		}

		results = append(results, models.DailyContribution{
			Date:  dateStr,
			Count: count,
		})
	}

	return results, nil
}