package main

import (
	"database/sql"
	"fmt"
	"log"

	"golang.org/x/crypto/bcrypt"
	_ "modernc.org/sqlite"
)

func InitDB(filepath string) *sql.DB {
	db, err := sql.Open("sqlite", filepath)
	if err != nil {
		log.Fatal(err)
	}

	if err = db.Ping(); err != nil {
		log.Fatal(err)
	}

	createTables(db)
	return db
}

func createTables(db *sql.DB) {
	queries := []string{
		`CREATE TABLE IF NOT EXISTS users (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            username TEXT UNIQUE NOT NULL,
            password TEXT NOT NULL,
            is_admin BOOLEAN NOT NULL DEFAULT 0
        )`,
		`CREATE TABLE IF NOT EXISTS schedules (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            day_of_week INTEGER NOT NULL,
            start_time TEXT NOT NULL,
            end_time TEXT NOT NULL,
            type TEXT NOT NULL,
            title TEXT NOT NULL
        )`,
		`CREATE TABLE IF NOT EXISTS time_entries (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id INTEGER NOT NULL,
            schedule_id INTEGER NOT NULL,
            date TEXT NOT NULL,
            type TEXT NOT NULL,
            start_time TEXT NOT NULL,
            end_time TEXT NOT NULL,
            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
            FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE,
            FOREIGN KEY (schedule_id) REFERENCES schedules(id)
        )`,
	}

	for _, query := range queries {
		if _, err := db.Exec(query); err != nil {
			log.Fatal(err)
		}
	}

	hash, _ := bcrypt.GenerateFromPassword([]byte("admin123"), bcrypt.DefaultCost)
	_, err := db.Exec(`
    INSERT OR IGNORE INTO users (id, username, password, is_admin)
    VALUES (?, ?, ?, ?)`,
		1, "admin", string(hash), true,
	)
	if err != nil {
		log.Fatal(err)
	}
}

func GetUserByUsername(db *sql.DB, username string) (*User, error) {
	user := &User{}
	err := db.QueryRow("SELECT id, username, password, is_admin FROM users WHERE username = ?", username).
		Scan(&user.ID, &user.Username, &user.Password, &user.IsAdmin)
	if err != nil {
		return nil, err
	}
	return user, nil
}

func CreateUser(db *sql.DB, username, hashedPassword string, isAdmin bool) error {
	_, err := db.Exec("INSERT INTO users (username, password, is_admin) VALUES (?, ?, ?)",
		username, hashedPassword, isAdmin)
	return err
}

func GetAllUsers(db *sql.DB) ([]User, error) {
	rows, err := db.Query("SELECT id, username, is_admin FROM users")
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var users []User
	for rows.Next() {
		var u User
		if err := rows.Scan(&u.ID, &u.Username, &u.IsAdmin); err != nil {
			continue
		}
		users = append(users, u)
	}
	return users, nil
}

func CreateSchedule(db *sql.DB, schedule *Schedule) error {
	_, err := db.Exec("INSERT INTO schedules (day_of_week, start_time, end_time, type, title) VALUES (?, ?, ?, ?, ?)",
		schedule.DayOfWeek, schedule.StartTime, schedule.EndTime, schedule.Type, schedule.Title)
	return err
}

func GetAllSchedules(db *sql.DB) ([]Schedule, error) {
	rows, err := db.Query("SELECT id, day_of_week, start_time, end_time, type, title FROM schedules ORDER BY day_of_week, start_time")
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var schedules []Schedule
	for rows.Next() {
		var s Schedule
		if err := rows.Scan(&s.ID, &s.DayOfWeek, &s.StartTime, &s.EndTime, &s.Type, &s.Title); err != nil {
			continue
		}
		schedules = append(schedules, s)
	}
	return schedules, nil
}

func DeleteSchedule(db *sql.DB, id int) error {
	_, err := db.Exec("DELETE FROM schedules WHERE id = ?", id)
	return err
}

func CreateTimeEntry(db *sql.DB, entry *TimeEntry) error {
	_, err := db.Exec("INSERT INTO time_entries (user_id, schedule_id, date, type, start_time, end_time) VALUES (?, ?, ?, ?, ?, ?)",
		entry.UserID, entry.ScheduleID, entry.Date, entry.Type, entry.StartTime, entry.EndTime)
	return err
}

func GetTimeEntriesByUser(db *sql.DB, userID int) ([]TimeEntry, error) {
	rows, err := db.Query(`
        SELECT te.id, te.user_id, te.schedule_id, te.date, te.type, te.start_time, te.end_time, te.created_at, u.username 
        FROM time_entries te
        JOIN users u ON te.user_id = u.id
        WHERE te.user_id = ? 
        ORDER BY te.date DESC, te.created_at DESC
    `, userID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var entries []TimeEntry
	for rows.Next() {
		var e TimeEntry
		if err := rows.Scan(&e.ID, &e.UserID, &e.ScheduleID, &e.Date, &e.Type, &e.StartTime, &e.EndTime, &e.CreatedAt, &e.Username); err != nil {
			continue
		}
		entries = append(entries, e)
	}
	return entries, nil
}

func GetAllTimeEntries(db *sql.DB) ([]TimeEntry, error) {
	rows, err := db.Query(`
        SELECT te.id, te.user_id, te.schedule_id, te.date, te.type, te.start_time, te.end_time, te.created_at, u.username 
        FROM time_entries te
        JOIN users u ON te.user_id = u.id
        ORDER BY te.date DESC, te.created_at DESC
    `)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var entries []TimeEntry
	for rows.Next() {
		var e TimeEntry
		if err := rows.Scan(&e.ID, &e.UserID, &e.ScheduleID, &e.Date, &e.Type, &e.StartTime, &e.EndTime, &e.CreatedAt, &e.Username); err != nil {
			continue
		}
		entries = append(entries, e)
	}
	return entries, nil
}

func GetWeeklyHours(db *sql.DB) ([]WeeklyHours, error) {
	rows, err := db.Query(`
        SELECT 
            te.user_id,
            u.username,
            -- ISO 8601 Wochennummer berechnen
            CASE 
                WHEN strftime('%j', date(te.date, '-' || ((strftime('%w', te.date) + 6) % 7) || ' days')) <= '3' 
                THEN CAST(strftime('%Y', date(te.date, '-' || ((strftime('%w', te.date) + 6) % 7) || ' days', '-4 days')) AS INTEGER)
                ELSE CAST(strftime('%Y', te.date) AS INTEGER)
            END as year,
            CASE 
                WHEN strftime('%j', date(te.date, '-' || ((strftime('%w', te.date) + 6) % 7) || ' days')) <= '3'
                THEN CAST((strftime('%j', date(te.date, '-' || ((strftime('%w', te.date) + 6) % 7) || ' days', '-4 days')) - 1) / 7 AS INTEGER) + 53
                ELSE CAST((strftime('%j', date(te.date, '-' || ((strftime('%w', te.date) + 6) % 7) || ' days')) - 1) / 7 AS INTEGER) + 1
            END as week,
            SUM(
                (CAST(substr(te.end_time, 1, 2) AS REAL) + CAST(substr(te.end_time, 4, 2) AS REAL) / 60.0) -
                (CAST(substr(te.start_time, 1, 2) AS REAL) + CAST(substr(te.start_time, 4, 2) AS REAL) / 60.0)
            ) as total_hours
        FROM time_entries te
        JOIN users u ON te.user_id = u.id
        GROUP BY te.user_id, u.username, week, year
        ORDER BY year DESC, week DESC, u.username
    `)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var hours []WeeklyHours
	for rows.Next() {
		var h WeeklyHours
		if err := rows.Scan(&h.UserID, &h.Username, &h.Year, &h.Week, &h.TotalHours); err != nil {
			continue
		}
		hours = append(hours, h)
	}
	return hours, nil
}

func DeleteUser(db *sql.DB, id int) error {
	if id == 1 {
		return fmt.Errorf("cannot delete admin user")
	}
	_, err := db.Exec("DELETE FROM users WHERE id = ?", id)
	return err
}

func DeleteTimeEntriesByUserAndWeek(db *sql.DB, userID int, year int, week int) error {
	dates := calculateWeekDates(year, week)

	var dateList []string
	for day := 0; day <= 4; day++ {
		dateList = append(dateList, dates.Dates[fmt.Sprintf("%d", day)])
	}

	query := `
        DELETE FROM time_entries 
        WHERE user_id = ? 
        AND date IN (?, ?, ?, ?, ?)
    `
	_, err := db.Exec(query, userID, dateList[0], dateList[1], dateList[2], dateList[3], dateList[4])
	return err
}

func CheckUserHasEntriesForWeek(db *sql.DB, userID int, year int, week int) (bool, error) {
	dates := calculateWeekDates(year, week)

	var dateList []string
	for day := 0; day <= 4; day++ {
		dateList = append(dateList, dates.Dates[fmt.Sprintf("%d", day)])
	}

	query := `
        SELECT COUNT(*) 
        FROM time_entries 
        WHERE user_id = ? 
        AND date IN (?, ?, ?, ?, ?)
    `

	var count int
	err := db.QueryRow(query, userID,
		dateList[0], dateList[1], dateList[2], dateList[3], dateList[4]).Scan(&count)

	if err != nil {
		log.Printf("Error checking entries: %v", err)
		return false, err
	}

	return count > 0, nil
}