package repository

import (
	"database/sql"
	"errors"
	"time"

	"github.com/daniil/homelab-api/internal/model"
	"github.com/jmoiron/sqlx"
	"github.com/lib/pq"
)

var ErrHabitNotFound = errors.New("habit not found")
var ErrLogNotFound = errors.New("log not found")

type HabitRepository struct {
	db *sqlx.DB
}

func NewHabitRepository(db *sqlx.DB) *HabitRepository {
	return &HabitRepository{db: db}
}

func (r *HabitRepository) Create(habit *model.Habit) error {
	query := `
		INSERT INTO habits (user_id, name, description, color, icon, frequency, target_days, target_count, reminder_time, start_date)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
		RETURNING id, created_at, updated_at`

	targetDays := pq.Array(habit.TargetDays)
	if len(habit.TargetDays) == 0 {
		targetDays = pq.Array([]int{0, 1, 2, 3, 4, 5, 6})
	}

	return r.db.QueryRow(query,
		habit.UserID,
		habit.Name,
		habit.Description,
		habit.Color,
		habit.Icon,
		habit.Frequency,
		targetDays,
		habit.TargetCount,
		habit.ReminderTime,
		habit.StartDate,
	).Scan(&habit.ID, &habit.CreatedAt, &habit.UpdatedAt)
}

func (r *HabitRepository) GetByID(id, userID int64) (*model.Habit, error) {
	var habit model.Habit
	var targetDays pq.Int64Array

	query := `
		SELECT id, user_id, name, description, color, icon, frequency, target_days, target_count, reminder_time, start_date, is_archived, created_at, updated_at
		FROM habits WHERE id = $1 AND user_id = $2`

	err := r.db.QueryRow(query, id, userID).Scan(
		&habit.ID, &habit.UserID, &habit.Name, &habit.Description,
		&habit.Color, &habit.Icon, &habit.Frequency, &targetDays,
		&habit.TargetCount, &habit.ReminderTime, &habit.StartDate, &habit.IsArchived, &habit.CreatedAt, &habit.UpdatedAt,
	)

	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return nil, ErrHabitNotFound
		}
		return nil, err
	}

	habit.TargetDays = make([]int, len(targetDays))
	for i, v := range targetDays {
		habit.TargetDays[i] = int(v)
	}
	habit.ProcessForJSON()

	return &habit, nil
}

func (r *HabitRepository) ListByUser(userID int64, includeArchived bool) ([]model.Habit, error) {
	query := `
		SELECT id, user_id, name, description, color, icon, frequency, target_days, target_count, reminder_time, start_date, is_archived, created_at, updated_at
		FROM habits WHERE user_id = $1`

	if !includeArchived {
		query += " AND is_archived = FALSE"
	}
	query += " ORDER BY created_at DESC"

	rows, err := r.db.Query(query, userID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var habits []model.Habit
	for rows.Next() {
		var habit model.Habit
		var targetDays pq.Int64Array

		if err := rows.Scan(
			&habit.ID, &habit.UserID, &habit.Name, &habit.Description,
			&habit.Color, &habit.Icon, &habit.Frequency, &targetDays,
			&habit.TargetCount, &habit.ReminderTime, &habit.StartDate, &habit.IsArchived, &habit.CreatedAt, &habit.UpdatedAt,
		); err != nil {
			return nil, err
		}

		habit.TargetDays = make([]int, len(targetDays))
		for i, v := range targetDays {
			habit.TargetDays[i] = int(v)
		}
		habit.ProcessForJSON()

		habits = append(habits, habit)
	}

	return habits, nil
}

func (r *HabitRepository) GetHabitsWithReminder(reminderTime string, weekday int) ([]model.Habit, error) {
	query := `
		SELECT h.id, h.user_id, h.name, h.description, h.color, h.icon, h.frequency, h.target_days, h.target_count, h.reminder_time, h.start_date, h.is_archived, h.created_at, h.updated_at
		FROM habits h
		JOIN users u ON h.user_id = u.id
		WHERE h.reminder_time = $1
		AND h.is_archived = false
		AND u.telegram_chat_id IS NOT NULL
		AND u.notifications_enabled = true
		AND (
			h.frequency = 'daily' 
			OR (h.frequency = 'weekly' AND $2 = ANY(h.target_days))
			OR h.frequency = 'interval'
			OR h.frequency = 'custom'
		)`

	rows, err := r.db.Query(query, reminderTime, weekday)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var habits []model.Habit
	for rows.Next() {
		var habit model.Habit
		var targetDays pq.Int64Array

		if err := rows.Scan(
			&habit.ID, &habit.UserID, &habit.Name, &habit.Description,
			&habit.Color, &habit.Icon, &habit.Frequency, &targetDays,
			&habit.TargetCount, &habit.ReminderTime, &habit.StartDate, &habit.IsArchived, &habit.CreatedAt, &habit.UpdatedAt,
		); err != nil {
			return nil, err
		}

		habit.TargetDays = make([]int, len(targetDays))
		for i, v := range targetDays {
			habit.TargetDays[i] = int(v)
		}
		habit.ProcessForJSON()

		habits = append(habits, habit)
	}

	return habits, nil
}

// ShouldShowIntervalHabitToday checks if an interval habit should be shown today
func (r *HabitRepository) ShouldShowIntervalHabitToday(habitID, userID int64, intervalDays int, startDate sql.NullTime) (bool, error) {
	// Get the last log date for this habit
	var lastLogDate sql.NullTime
	err := r.db.Get(&lastLogDate, `
		SELECT MAX(date) FROM habit_logs WHERE habit_id = $1 AND user_id = $2
	`, habitID, userID)
	
	if err != nil && err != sql.ErrNoRows {
		return false, err
	}
	
	today := time.Now().Truncate(24 * time.Hour)
	
	// If no logs exist, check if today >= start_date (show on start_date)
	if !lastLogDate.Valid {
		if startDate.Valid {
			return !today.Before(startDate.Time.Truncate(24*time.Hour)), nil
		}
		return true, nil
	}
	
	// Calculate days since last log
	lastLog := lastLogDate.Time.Truncate(24 * time.Hour)
	daysSinceLastLog := int(today.Sub(lastLog).Hours() / 24)
	
	return daysSinceLastLog >= intervalDays, nil
}

func (r *HabitRepository) Update(habit *model.Habit) error {
	query := `
		UPDATE habits 
		SET name = $2, description = $3, color = $4, icon = $5, frequency = $6, 
			target_days = $7, target_count = $8, reminder_time = $9, start_date = $10, is_archived = $11, updated_at = CURRENT_TIMESTAMP
		WHERE id = $1 AND user_id = $12
		RETURNING updated_at`

	return r.db.QueryRow(query,
		habit.ID,
		habit.Name,
		habit.Description,
		habit.Color,
		habit.Icon,
		habit.Frequency,
		pq.Array(habit.TargetDays),
		habit.TargetCount,
		habit.ReminderTime,
		habit.StartDate,
		habit.IsArchived,
		habit.UserID,
	).Scan(&habit.UpdatedAt)
}

func (r *HabitRepository) Delete(id, userID int64) error {
	query := `DELETE FROM habits WHERE id = $1 AND user_id = $2`
	result, err := r.db.Exec(query, id, userID)
	if err != nil {
		return err
	}

	rows, _ := result.RowsAffected()
	if rows == 0 {
		return ErrHabitNotFound
	}

	return nil
}

// Logs

func (r *HabitRepository) CreateLog(log *model.HabitLog) error {
	query := `
		INSERT INTO habit_logs (habit_id, user_id, date, count, note)
		VALUES ($1, $2, $3, $4, $5)
		ON CONFLICT (habit_id, date) 
		DO UPDATE SET count = habit_logs.count + EXCLUDED.count, note = EXCLUDED.note
		RETURNING id, created_at`

	return r.db.QueryRow(query, log.HabitID, log.UserID, log.Date, log.Count, log.Note).
		Scan(&log.ID, &log.CreatedAt)
}

func (r *HabitRepository) GetLogs(habitID, userID int64, from, to time.Time) ([]model.HabitLog, error) {
	query := `
		SELECT id, habit_id, user_id, date, count, note, created_at
		FROM habit_logs 
		WHERE habit_id = $1 AND user_id = $2 AND date >= $3 AND date <= $4
		ORDER BY date DESC`

	var logs []model.HabitLog
	if err := r.db.Select(&logs, query, habitID, userID, from, to); err != nil {
		return nil, err
	}

	return logs, nil
}

func (r *HabitRepository) DeleteLog(logID, userID int64) error {
	query := `DELETE FROM habit_logs WHERE id = $1 AND user_id = $2`
	result, err := r.db.Exec(query, logID, userID)
	if err != nil {
		return err
	}

	rows, _ := result.RowsAffected()
	if rows == 0 {
		return ErrLogNotFound
	}

	return nil
}

func (r *HabitRepository) GetUserLogsForDate(userID int64, date time.Time) ([]model.HabitLog, error) {
	query := `
		SELECT id, habit_id, user_id, date, count, note, created_at
		FROM habit_logs 
		WHERE user_id = $1 AND date = $2`

	var logs []model.HabitLog
	if err := r.db.Select(&logs, query, userID, date); err != nil {
		return nil, err
	}

	return logs, nil
}

func (r *HabitRepository) IsHabitCompletedToday(habitID, userID int64) (bool, error) {
	today := time.Now().Format("2006-01-02")
	var count int
	err := r.db.Get(&count, `SELECT COUNT(*) FROM habit_logs WHERE habit_id = $1 AND user_id = $2 AND date = $3`, habitID, userID, today)
	return count > 0, err
}

func (r *HabitRepository) GetStats(habitID, userID int64) (*model.HabitStats, error) {
	stats := &model.HabitStats{HabitID: habitID}

	// Get habit info
	habit, err := r.GetByID(habitID, userID)
	if err != nil {
		return nil, err
	}

	// Total logs
	r.db.Get(&stats.TotalLogs, `SELECT COUNT(*) FROM habit_logs WHERE habit_id = $1 AND user_id = $2`, habitID, userID)

	// This week (Monday-based)
	now := time.Now()
	weekday := int(now.Weekday())
	if weekday == 0 {
		weekday = 7
	}
	weekStart := now.AddDate(0, 0, -(weekday - 1)).Truncate(24 * time.Hour)
	r.db.Get(&stats.ThisWeek, `SELECT COUNT(*) FROM habit_logs WHERE habit_id = $1 AND user_id = $2 AND date >= $3`, habitID, userID, weekStart)

	// This month
	monthStart := time.Date(now.Year(), now.Month(), 1, 0, 0, 0, 0, time.UTC)
	r.db.Get(&stats.ThisMonth, `SELECT COUNT(*) FROM habit_logs WHERE habit_id = $1 AND user_id = $2 AND date >= $3`, habitID, userID, monthStart)

	// Streaks calculation (respecting target_days and interval)
	stats.CurrentStreak, stats.LongestStreak = r.calculateStreaksWithDays(habitID, userID, habit.Frequency, habit.TargetDays, habit.TargetCount)

	// Completion percentage since habit creation/start_date
	stats.CompletionPct = r.calculateCompletionPct(habit, stats.TotalLogs)

	return stats, nil
}

// calculateStreaksWithDays counts consecutive completions on expected days
func (r *HabitRepository) calculateStreaksWithDays(habitID, userID int64, frequency string, targetDays []int, targetCount int) (current, longest int) {
	query := `SELECT date FROM habit_logs WHERE habit_id = $1 AND user_id = $2 ORDER BY date DESC`

	var logDates []time.Time
	if err := r.db.Select(&logDates, query, habitID, userID); err != nil || len(logDates) == 0 {
		return 0, 0
	}

	// Convert log dates to map for quick lookup
	logMap := make(map[string]bool)
	for _, d := range logDates {
		logMap[d.Format("2006-01-02")] = true
	}

	// For interval habits, calculate streaks differently
	if (frequency == "interval" || frequency == "custom") && targetCount > 0 {
		return r.calculateIntervalStreaks(logDates, targetCount)
	}

	// Generate expected days from today backwards
	today := time.Now().Truncate(24 * time.Hour)
	expectedDays := r.getExpectedDays(today, frequency, targetDays, 365) // Look back up to 1 year

	if len(expectedDays) == 0 {
		return 0, 0
	}

	// Current streak: count from most recent expected day
	current = 0
	for _, day := range expectedDays {
		if logMap[day.Format("2006-01-02")] {
			current++
		} else {
			break
		}
	}

	// Longest streak
	longest = 0
	streak := 0
	for _, day := range expectedDays {
		if logMap[day.Format("2006-01-02")] {
			streak++
			if streak > longest {
				longest = streak
			}
		} else {
			streak = 0
		}
	}

	return current, longest
}

// calculateIntervalStreaks calculates streaks for interval-based habits
func (r *HabitRepository) calculateIntervalStreaks(logDates []time.Time, intervalDays int) (current, longest int) {
	if len(logDates) == 0 {
		return 0, 0
	}

	today := time.Now().Truncate(24 * time.Hour)
	
	// Check if the most recent log is within the interval window from today
	lastLogDate := logDates[0].Truncate(24 * time.Hour)
	daysSinceLastLog := int(today.Sub(lastLogDate).Hours() / 24)
	
	// Current streak: if we're within interval, count consecutive logs that are within interval of each other
	current = 0
	if daysSinceLastLog < intervalDays {
		current = 1
		for i := 1; i < len(logDates); i++ {
			prevDate := logDates[i-1].Truncate(24 * time.Hour)
			currDate := logDates[i].Truncate(24 * time.Hour)
			daysBetween := int(prevDate.Sub(currDate).Hours() / 24)
			
			// If the gap is exactly the interval (or less, if done early), continue streak
			if daysBetween <= intervalDays {
				current++
			} else {
				break
			}
		}
	}

	// Longest streak calculation
	longest = 1
	streak := 1
	for i := 1; i < len(logDates); i++ {
		prevDate := logDates[i-1].Truncate(24 * time.Hour)
		currDate := logDates[i].Truncate(24 * time.Hour)
		daysBetween := int(prevDate.Sub(currDate).Hours() / 24)
		
		if daysBetween <= intervalDays {
			streak++
			if streak > longest {
				longest = streak
			}
		} else {
			streak = 1
		}
	}

	return current, longest
}

// getExpectedDays returns a list of days when the habit should be done, sorted descending
func (r *HabitRepository) getExpectedDays(from time.Time, frequency string, targetDays []int, maxDays int) []time.Time {
	var result []time.Time

	for i := 0; i < maxDays; i++ {
		day := from.AddDate(0, 0, -i)
		
		if frequency == "daily" {
			result = append(result, day)
		} else if frequency == "weekly" && len(targetDays) > 0 {
			weekday := int(day.Weekday())
			if weekday == 0 {
				weekday = 7 // Sunday = 7
			}
			for _, td := range targetDays {
				if td == weekday {
					result = append(result, day)
					break
				}
			}
		} else {
			result = append(result, day)
		}
	}

	return result
}

// calculateCompletionPct calculates completion percentage since habit start_date (or created_at)
func (r *HabitRepository) calculateCompletionPct(habit *model.Habit, totalLogs int) float64 {
	if totalLogs == 0 {
		return 0
	}

	// Use start_date if set, otherwise use created_at
	var startDate time.Time
	if habit.StartDate.Valid {
		startDate = habit.StartDate.Time.Truncate(24 * time.Hour)
	} else {
		startDate = habit.CreatedAt.Truncate(24 * time.Hour)
	}
	today := time.Now().Truncate(24 * time.Hour)

	expectedCount := 0
	
	// For interval habits, calculate expected differently
	if (habit.Frequency == "interval" || habit.Frequency == "custom") && habit.TargetCount > 0 {
		// Expected = (days since start) / interval + 1
		daysSinceStart := int(today.Sub(startDate).Hours()/24) + 1
		expectedCount = (daysSinceStart / habit.TargetCount) + 1
	} else {
		for d := startDate; !d.After(today); d = d.AddDate(0, 0, 1) {
			if habit.Frequency == "daily" {
				expectedCount++
			} else if habit.Frequency == "weekly" && len(habit.TargetDays) > 0 {
				weekday := int(d.Weekday())
				if weekday == 0 {
					weekday = 7
				}
				for _, td := range habit.TargetDays {
					if td == weekday {
						expectedCount++
						break
					}
				}
			} else {
				expectedCount++
			}
		}
	}

	if expectedCount == 0 {
		return 0
	}

	return float64(totalLogs) / float64(expectedCount) * 100
}

func (r *HabitRepository) IsHabitCompletedOnDate(habitID, userID int64, date time.Time) (bool, error) {
	dateStr := date.Format("2006-01-02")
	var count int
	err := r.db.Get(&count, `SELECT COUNT(*) FROM habit_logs WHERE habit_id = $1 AND user_id = $2 AND date = $3`, habitID, userID, dateStr)
	return count > 0, err
}