package store

import (
	"context"
	"database/sql"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
	"time"

	"golang.org/x/text/cases"
	"golang.org/x/text/language"
	_ "modernc.org/sqlite"
)

const (
	TagWork  = "work"
	TagBreak = "break"
)

type TimeEntry struct {
	ID        int64
	Tag       string
	StartTime time.Time
	EndTime   sql.NullTime
}

type Store struct {
	db     *sql.DB
	dbPath string
}

func NewStore() (*Store, error) {
	dbPath, err := ensureDatabasePath()
	if err != nil {
		return nil, fmt.Errorf("could not determine database path: %w", err)
	}

	slog.Debug("Using database at:", "path", dbPath)

	db, err := sql.Open("sqlite", fmt.Sprintf("%s?_pragma=journal_mode(WAL)", dbPath))
	if err != nil {
		return nil, fmt.Errorf("failed to open database '%s': %w", dbPath, err)
	}

	if err = db.Ping(); err != nil {
		db.Close()
		return nil, fmt.Errorf("failed to connect to database '%s': %w", dbPath, err)
	}

	if err := migrate(db); err != nil {
		db.Close()
		return nil, fmt.Errorf("migration failed: %w", err)
	}

	return &Store{db: db, dbPath: dbPath}, nil
}

func migrate(db *sql.DB) error {
	createTableSQL := `
	CREATE TABLE IF NOT EXISTS time_entries (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		tag TEXT NOT NULL CHECK(tag <> ''),
		start_time DATETIME NOT NULL,
		end_time DATETIME NULL,
		CHECK (end_time IS NULL OR end_time >= start_time)
	);`
	if _, err := db.Exec(createTableSQL); err != nil {
		return fmt.Errorf("failed to create table 'time_entries': %w", err)
	}

	createIndexSQL := `CREATE INDEX IF NOT EXISTS idx_time_entries_start_time ON time_entries (start_time);`
	if _, err := db.Exec(createIndexSQL); err != nil {
		slog.Warn("Failed to create index on start_time:", "error", err)
	}
	return nil
}

func ensureDatabasePath() (string, error) {
	configDir, err := os.UserConfigDir()
	if err != nil {
		return "", fmt.Errorf("could not get user config dir: %w", err)
	}
	workConfigDir := filepath.Join(configDir, "work")
	if err := os.MkdirAll(workConfigDir, 0o750); err != nil {
		return "", fmt.Errorf("failed to create config directory '%s': %w", workConfigDir, err)
	}
	return filepath.Join(workConfigDir, "worktime.sqlite"), nil
}

func (s *Store) Close() error {
	if s.db != nil {
		slog.Debug("Closing database connection", "path", s.dbPath)
		return s.db.Close()
	}
	return nil
}

func (s *Store) stopCurrentEntry(ctx context.Context, now time.Time) (bool, error) {
	query := `UPDATE time_entries SET end_time = ? WHERE end_time IS NULL;`
	result, err := s.db.ExecContext(ctx, query, now)
	if err != nil {
		return false, fmt.Errorf("failed to execute stop current entry query: %w", err)
	}

	rowsAffected, err := result.RowsAffected()
	if err != nil {
		return false, fmt.Errorf("failed to get affected rows: %w", err)
	}
	return rowsAffected > 0, nil
}

func (s *Store) StartTracking(ctx context.Context, tag string) error {
	if tag == "" {
		return fmt.Errorf("cannot start tracking with an empty tag")
	}

	now := time.Now()
	stopped, err := s.stopCurrentEntry(ctx, now)
	if err != nil {
		return err
	}
	if stopped {
		slog.Info("Stopped previous time entry.")
	}

	query := `INSERT INTO time_entries (tag, start_time, end_time) VALUES (?, ?, NULL);`
	_, err = s.db.ExecContext(ctx, query, tag, now)
	if err != nil {
		return fmt.Errorf("failed to start tracking tag '%s': %w", tag, err)
	}
	slog.Info(fmt.Sprintf("Started tracking: %s", tag))
	return nil
}

func (s *Store) StopTracking(ctx context.Context) error {
	now := time.Now()
	stopped, err := s.stopCurrentEntry(ctx, now)
	if err != nil {
		return err
	}
	if stopped {
		slog.Info(fmt.Sprintf("Stopped tracking at %s", now.Format(time.RFC3339)))
	} else {
		slog.Info("No active time entry found to stop.")
	}
	return nil
}

func (s *Store) LogFullDay(ctx context.Context, tag string, date time.Time) error {
	if tag == "" {
		return fmt.Errorf("cannot log full day with an empty tag")
	}
	tag = strings.ToLower(tag)
	location := date.Location()
	dayStart := time.Date(date.Year(), date.Month(), date.Day(), 0, 0, 0, 0, location)
	dayEnd := dayStart.Add(24 * time.Hour)

	_, err := s.stopCurrentEntry(ctx, dayStart)
	if err != nil {
		slog.Warn("Failed to stop current entry before logging full day", "error", err)
	}

	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()

	query := `INSERT INTO time_entries (tag, start_time, end_time) VALUES (?, ?, ?);`
	if _, err := tx.ExecContext(ctx, query, tag, dayStart, dayEnd); err != nil {
		return fmt.Errorf("failed to insert full-day entry: %w", err)
	}

	if err := tx.Commit(); err != nil {
		return fmt.Errorf("failed to commit transaction: %w", err)
	}

	titleCaser := cases.Title(language.English)
	slog.Info(fmt.Sprintf("Successfully logged full day entry: Tag='%s', Date='%s'", tag, dayStart.Format("2006-01-02")))
	fmt.Printf("Successfully logged '%s' for %s.\n", titleCaser.String(tag), dayStart.Format("2006-01-02"))
	return nil
}

func (s *Store) GetEntriesInRange(ctx context.Context, start, end time.Time) ([]TimeEntry, error) {
	if start.IsZero() || end.IsZero() || end.Before(start) {
		return nil, fmt.Errorf("invalid time range: start=%v, end=%v", start, end)
	}

	query := `
	SELECT id, tag, start_time, end_time
	FROM time_entries
	WHERE start_time >= ? AND start_time < ?
	ORDER BY start_time ASC;`

	rows, err := s.db.QueryContext(ctx, query, start, end)
	if err != nil {
		return nil, fmt.Errorf("failed to query entries in range [%v, %v): %w", start, end, err)
	}
	defer rows.Close()

	var entries []TimeEntry
	for rows.Next() {
		var entry TimeEntry
		if err := rows.Scan(&entry.ID, &entry.Tag, &entry.StartTime, &entry.EndTime); err != nil {
			return nil, fmt.Errorf("failed to scan entry row: %w", err)
		}
		entries = append(entries, entry)
	}

	if err = rows.Err(); err != nil {
		return nil, fmt.Errorf("error during row iteration: %w", err)
	}

	return entries, nil
}

func (s *Store) CalculateSummary(ctx context.Context, period string) (map[string]time.Duration, error) {
	start, end := GetTimeRangeFromPeriod(period)
	if start.IsZero() {
		return nil, fmt.Errorf("invalid period string: '%s'", period)
	}

	query := `
	SELECT id, tag, start_time, end_time
	FROM time_entries
	WHERE (end_time IS NULL OR end_time > ?)
	  AND start_time < ?
	ORDER BY start_time ASC;`

	rows, err := s.db.QueryContext(ctx, query, start, end)
	if err != nil {
		return nil, fmt.Errorf("failed to query entries: %w", err)
	}
	defer rows.Close()

	summary := make(map[string]time.Duration)
	now := time.Now()

	for rows.Next() {
		var entry TimeEntry
		if err := rows.Scan(&entry.ID, &entry.Tag, &entry.StartTime, &entry.EndTime); err != nil {
			return nil, fmt.Errorf("failed to scan entry: %w", err)
		}

		effStart := entry.StartTime
		if effStart.Before(start) {
			effStart = start
		}
		effEnd := now
		if entry.EndTime.Valid {
			effEnd = entry.EndTime.Time
		}
		if effEnd.After(end) {
			effEnd = end
		}

		if effEnd.After(effStart) {
			summary[entry.Tag] += effEnd.Sub(effStart)
		}
	}
	return summary, rows.Err()
}

func (s *Store) ShowSummary(ctx context.Context, period string) error {
	summary, err := s.CalculateSummary(ctx, period)
	if err != nil {
		return err
	}

	start, _ := GetTimeRangeFromPeriod(period)
	titlePeriod := period
	if !start.IsZero() {
		_, end := GetTimeRangeFromPeriod(period)
		if period == ":day" || period == "today" {
			titlePeriod = fmt.Sprintf("Today (%s)", start.Format("2006-01-02"))
		} else if period == ":week" {
			titlePeriod = fmt.Sprintf("Week starting %s", start.Format("Mon, 2006-01-02"))
		} else if period == ":month" {
			titlePeriod = fmt.Sprintf("Month %s", start.Format("January 2006"))
		} else if period == ":year" {
			titlePeriod = fmt.Sprintf("Year %d", start.Year())
		} else if _, err := time.Parse("2006-01-02", period); err == nil {
			titlePeriod = fmt.Sprintf("Day %s", start.Format("2006-01-02"))
		} else {
			titlePeriod = fmt.Sprintf("Period '%s' (%s to %s)", period, start.Format("2006-01-02"), end.Format("2006-01-02"))
		}
	}

	fmt.Printf("\nTime Summary for %s\n", titlePeriod)
	if len(summary) == 0 {
		fmt.Println("  No recorded time entries for this period.")
		return nil
	}

	tags := make([]string, 0, len(summary))
	for tag := range summary {
		tags = append(tags, tag)
	}

	titleCaser := cases.Title(language.English)
	totalDuration := time.Duration(0)
	fmt.Println("------------------------------")
	for _, tag := range tags {
		duration := summary[tag]
		fmt.Printf("  %-12s: %s\n", titleCaser.String(tag), formatDuration(duration))
		totalDuration += duration
	}
	fmt.Println("------------------------------")
	fmt.Printf("  Total         : %s\n\n", formatDuration(totalDuration))

	return nil
}

func formatDuration(d time.Duration) string {
	if d < 0 {
		d = -d
		sign := "-"
		d = d.Round(time.Second)
		h := int64(d.Hours())
		m := int64(d.Minutes()) % 60
		s := int64(d.Seconds()) % 60
		return fmt.Sprintf("%s%02d:%02d:%02d", sign, h, m, s)
	}
	d = d.Round(time.Second)
	h := int64(d.Hours())
	m := int64(d.Minutes()) % 60
	s := int64(d.Seconds()) % 60
	return fmt.Sprintf("%02d:%02d:%02d", h, m, s)
}

func GetTimeRangeFromPeriod(period string) (time.Time, time.Time) {
	now := time.Now()
	year, month, day := now.Date()
	loc := now.Location()

	normalizedPeriod := strings.ToLower(strings.TrimPrefix(period, ":"))

	switch normalizedPeriod {
	case "week":
		weekday := now.Weekday()
		daysToMonday := time.Duration(weekday - time.Monday)
		if weekday == time.Sunday {
			daysToMonday = 6
		}
		start := time.Date(year, month, day, 0, 0, 0, 0, loc).Add(-daysToMonday * 24 * time.Hour)
		end := start.Add(7 * 24 * time.Hour)
		return start, end
	case "month":
		start := time.Date(year, month, 1, 0, 0, 0, 0, loc)
		end := start.AddDate(0, 1, 0)
		return start, end
	case "year":
		start := time.Date(year, 1, 1, 0, 0, 0, 0, loc)
		end := start.AddDate(1, 0, 0)
		return start, end
	case "day", "today":
		start := time.Date(year, month, day, 0, 0, 0, 0, loc)
		end := start.AddDate(0, 0, 1)
		return start, end
	default:
		if t, err := time.ParseInLocation("2006-01-02", period, loc); err == nil {
			start := time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, loc)
			end := start.AddDate(0, 0, 1)
			return start, end
		}
		slog.Warn(fmt.Sprintf("Unrecognized period string '%s'. Cannot calculate time range.", period))
		return time.Time{}, time.Time{}
	}
}

func (s *Store) DB() *sql.DB {
	return s.db
}