package service

import (
	"time"

	"accounting-app/internal/models"
	"accounting-app/internal/repository"
)

// StreakService handles business logic for user streaks
type StreakService struct {
	repo *repository.StreakRepository
}

// NewStreakService creates a new StreakService instance
func NewStreakService(repo *repository.StreakRepository) *StreakService {
	return &StreakService{repo: repo}
}

// GetStreakInfo returns the streak information for a user
func (s *StreakService) GetStreakInfo(userID uint) (*models.StreakInfo, error) {
	streak, err := s.repo.GetOrCreate(userID)
	if err != nil {
		return nil, err
	}

	now := time.Now()
	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())

	// Check if user has recorded today
	hasRecordToday, err := s.repo.HasTransactionOnDate(userID, today)
	if err != nil {
		return nil, err
	}

	// Determine message based on streak status
	var message string
	if hasRecordToday {
		if streak.CurrentStreak >= 7 {
			message = "太厉害了！连续记账一周以上 🔥"
		} else if streak.CurrentStreak >= 3 {
			message = "继续保持，养成好习惯！💪"
		} else {
			message = "今日已记账，明天继续哦 ✅"
		}
	} else {
		if streak.CurrentStreak > 0 {
			message = "今天还没有记账哦，别断了连续记录！"
		} else {
			message = "今天还没有记账哦，开始记录吧！"
		}
	}

	return &models.StreakInfo{
		CurrentStreak:   streak.CurrentStreak,
		LongestStreak:   streak.LongestStreak,
		TotalRecordDays: streak.TotalRecordDays,
		HasRecordToday:  hasRecordToday,
		Message:         message,
	}, nil
}

// UpdateStreak updates the streak when a transaction is created
// This should be called after a transaction is created
func (s *StreakService) UpdateStreak(userID uint, transactionDate time.Time) error {
	streak, err := s.repo.GetOrCreate(userID)
	if err != nil {
		return err
	}

	// Normalize transaction date to start of day
	txDate := time.Date(transactionDate.Year(), transactionDate.Month(), transactionDate.Day(), 0, 0, 0, 0, transactionDate.Location())
	now := time.Now()
	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())

	// Only update streak for today's date or past dates (not future)
	if txDate.After(today) {
		return nil // Don't update streak for future transactions
	}

	// If this is the first record ever
	if streak.LastRecordDate == nil {
		streak.CurrentStreak = 1
		streak.LongestStreak = 1
		streak.TotalRecordDays = 1
		streak.LastRecordDate = &txDate
		return s.repo.Update(streak)
	}

	lastDate := *streak.LastRecordDate
	lastDateNormalized := time.Date(lastDate.Year(), lastDate.Month(), lastDate.Day(), 0, 0, 0, 0, lastDate.Location())

	// If already recorded on this date, no update needed
	if txDate.Equal(lastDateNormalized) {
		return nil
	}

	// If recording for a new date
	if txDate.After(lastDateNormalized) {
		daysDiff := int(txDate.Sub(lastDateNormalized).Hours() / 24)

		if daysDiff == 1 {
			// Consecutive day - increment streak
			streak.CurrentStreak++
		} else {
			// Streak broken - reset to 1
			streak.CurrentStreak = 1
		}

		// Update longest streak if current is higher
		if streak.CurrentStreak > streak.LongestStreak {
			streak.LongestStreak = streak.CurrentStreak
		}

		// Increment total record days
		streak.TotalRecordDays++
		streak.LastRecordDate = &txDate
	} else {
		// Recording for a past date - just increment total if it's a new day
		hasRecord, err := s.repo.HasTransactionOnDate(userID, txDate)
		if err != nil {
			return err
		}
		// This is a bit tricky - we'd need to check if this specific date already has records
		// For simplicity, if it's a past date and we're adding a new transaction,
		// we'll just increment total (this might not be 100% accurate for edits)
		if !hasRecord {
			streak.TotalRecordDays++
		}
	}

	return s.repo.Update(streak)
}

// RecalculateStreak recalculates the entire streak from transaction history
// This is useful for fixing streak data or after bulk imports
func (s *StreakService) RecalculateStreak(userID uint) error {
	streak, err := s.repo.GetOrCreate(userID)
	if err != nil {
		return err
	}

	// Get all transaction dates for the user (last 365 days should be enough)
	now := time.Now()
	startDate := now.AddDate(-1, 0, 0) // 1 year ago

	dates, err := s.repo.GetTransactionDatesInRange(userID, startDate, now)
	if err != nil {
		return err
	}

	if len(dates) == 0 {
		// No transactions, reset streak
		streak.CurrentStreak = 0
		streak.LongestStreak = 0
		streak.TotalRecordDays = 0
		streak.LastRecordDate = nil
		return s.repo.Update(streak)
	}

	// Calculate streaks
	streak.TotalRecordDays = len(dates)

	// Find longest streak and current streak
	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())

	currentStreak := 1
	longestStreak := 1
	tempStreak := 1

	for i := 1; i < len(dates); i++ {
		prevDate := dates[i-1]
		currDate := dates[i]
		daysDiff := int(currDate.Sub(prevDate).Hours() / 24)

		if daysDiff == 1 {
			tempStreak++
			if tempStreak > longestStreak {
				longestStreak = tempStreak
			}
		} else {
			tempStreak = 1
		}
	}

	// Determine current streak (must include today or yesterday)
	lastRecordDate := dates[len(dates)-1]
	lastRecordNormalized := time.Date(lastRecordDate.Year(), lastRecordDate.Month(), lastRecordDate.Day(), 0, 0, 0, 0, lastRecordDate.Location())

	daysSinceLastRecord := int(today.Sub(lastRecordNormalized).Hours() / 24)

	if daysSinceLastRecord <= 1 {
		// Calculate current streak going backwards from last record
		currentStreak = 1
		for i := len(dates) - 2; i >= 0; i-- {
			currDate := dates[i+1]
			prevDate := dates[i]
			daysDiff := int(currDate.Sub(prevDate).Hours() / 24)

			if daysDiff == 1 {
				currentStreak++
			} else {
				break
			}
		}
	} else {
		// Streak is broken
		currentStreak = 0
	}

	streak.CurrentStreak = currentStreak
	streak.LongestStreak = longestStreak
	streak.LastRecordDate = &lastRecordNormalized

	return s.repo.Update(streak)
}

// CheckAndResetStreak checks if streak should be reset (called daily or on app open)
func (s *StreakService) CheckAndResetStreak(userID uint) error {
	streak, err := s.repo.GetOrCreate(userID)
	if err != nil {
		return err
	}

	if streak.LastRecordDate == nil {
		return nil
	}

	now := time.Now()
	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
	lastDate := *streak.LastRecordDate
	lastDateNormalized := time.Date(lastDate.Year(), lastDate.Month(), lastDate.Day(), 0, 0, 0, 0, lastDate.Location())

	daysDiff := int(today.Sub(lastDateNormalized).Hours() / 24)

	// If more than 1 day has passed without recording, reset streak
	if daysDiff > 1 {
		streak.CurrentStreak = 0
		return s.repo.Update(streak)
	}

	return nil
}

// GetContributionData returns daily transaction counts for the past year
func (s *StreakService) GetContributionData(userID uint) ([]models.DailyContribution, error) {
	now := time.Now()
	startDate := now.AddDate(-1, 0, 0) // 1 year ago

	return s.repo.GetDailyContribution(userID, startDate, now)
}