package main

import (
	"database/sql"
	"fmt"
	"log"
	"sort"
	"strconv"
	"strings"
	"time"

	"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)
	createIndexes(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,
		  yearly_hours REAL NOT NULL DEFAULT 1800.0,  -- 40 Stunden/Woche * 45 Schulwochen
		  created_at DATETIME DEFAULT CURRENT_TIMESTAMP
		)`,
		`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,
			created_at DATETIME DEFAULT CURRENT_TIMESTAMP
		)`,
		`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)
		)`,
		`CREATE TABLE IF NOT EXISTS audit_logs (
			id INTEGER PRIMARY KEY AUTOINCREMENT,
			user_id INTEGER NOT NULL,
			action TEXT NOT NULL,
			details TEXT,
			created_at DATETIME DEFAULT CURRENT_TIMESTAMP
		)`,
	}

	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, yearly_hours)
		VALUES (?, ?, ?, ?, ?)`,
		1, "admin", string(hash), true, 40.0,
	)
	if err != nil {
		log.Fatal(err)
	}
}

func createIndexes(db *sql.DB) {
	indexes := []string{
		`CREATE INDEX IF NOT EXISTS idx_time_entries_user_date ON time_entries(user_id, date)`,
		`CREATE INDEX IF NOT EXISTS idx_time_entries_date ON time_entries(date)`,
		`CREATE INDEX IF NOT EXISTS idx_audit_logs_user ON audit_logs(user_id)`,
		`CREATE INDEX IF NOT EXISTS idx_audit_logs_created ON audit_logs(created_at)`,
		`CREATE INDEX IF NOT EXISTS idx_schedules_day ON schedules(day_of_week)`,
	}

	for _, idx := range indexes {
		if _, err := db.Exec(idx); err != nil {
			log.Printf("Warning: Failed to create index: %v", err)
		}
	}
}

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

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

func CreateUser(db *sql.DB, username, hashedPassword string, isAdmin bool, yearlyHours float64) error {
	_, err := db.Exec("INSERT INTO users (username, password, is_admin, yearly_hours) VALUES (?, ?, ?, ?)",
		username, hashedPassword, isAdmin, yearlyHours)
	return err
}

func GetAllUsers(db *sql.DB) ([]User, error) {
	rows, err := db.Query("SELECT id, username, is_admin, yearly_hours FROM users ORDER BY username")
	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, &u.YearlyHours); err != nil {
			continue
		}
		users = append(users, u)
	}
	return users, nil
}

func UpdateUser(db *sql.DB, userID int, yearlyHours float64) error {
	_, err := db.Exec("UPDATE users SET yearly_hours = ? WHERE id = ?",
		yearlyHours, userID)
	return err
}

func ResetUserPassword(db *sql.DB, userID int, hashedPassword string) error {
	_, err := db.Exec("UPDATE users SET password = ? WHERE id = ?", hashedPassword, userID)
	return err
}

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 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 UpdateTimeEntry(db *sql.DB, entryID int, date, startTime, endTime, entryType string) error {
	_, err := db.Exec("UPDATE time_entries SET date = ?, start_time = ?, end_time = ?, type = ? WHERE id = ?",
		date, startTime, endTime, entryType, entryID)
	return err
}

func DeleteTimeEntry(db *sql.DB, entryID int) error {
	_, err := db.Exec("DELETE FROM time_entries WHERE id = ?", entryID)
	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,
            te.date,
            te.start_time,
            te.end_time,
            te.type,
            u.yearly_hours
        FROM time_entries te
        JOIN users u ON te.user_id = u.id
        ORDER BY te.date DESC
    `)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	hoursMap := make(map[string]*WeeklyHours)
	userYearlyHours := make(map[int]float64)

	for rows.Next() {
		var userID int
		var username, dateStr, startTime, endTime, entryType string
		var yearlyHours float64

		if err := rows.Scan(&userID, &username, &dateStr, &startTime, &endTime, &entryType, &yearlyHours); err != nil {
			continue
		}

		userYearlyHours[userID] = yearlyHours

		t, err := time.Parse("2006-01-02", dateStr)
		if err != nil {
			continue
		}

		year, week := t.ISOWeek()

		var hours float64
		if entryType == "lesson" {
			hours = 1.0
		} else {
			hours = calculateHoursDiff(startTime, endTime)
		}

		key := fmt.Sprintf("%d_%d_%d", userID, year, week)
		if existing, exists := hoursMap[key]; exists {
			existing.TotalHours += hours
		} else {
			hoursMap[key] = &WeeklyHours{
				UserID:     userID,
				Username:   username,
				Year:       year,
				Week:       week,
				TotalHours: hours,
			}
		}
	}

	yearlyTotals := make(map[int]float64)
	for _, h := range hoursMap {
		yearlyTotals[h.UserID] += h.TotalHours
	}

	for _, h := range hoursMap {
		h.YearlyTarget = userYearlyHours[h.UserID]
		h.YearlyActual = yearlyTotals[h.UserID]

		h.WeeklyTarget = h.YearlyTarget / 45.0
		h.RemainingYearly = h.YearlyTarget - h.YearlyActual
	}

	var result []WeeklyHours
	for _, h := range hoursMap {
		result = append(result, *h)
	}

	sort.Slice(result, func(i, j int) bool {
		if result[i].Year != result[j].Year {
			return result[i].Year > result[j].Year
		}
		if result[i].Week != result[j].Week {
			return result[i].Week > result[j].Week
		}
		return result[i].Username < result[j].Username
	})

	return result, nil
}

func GetYearlyHoursSummary(db *sql.DB) ([]WeeklyHours, error) {
	users, err := GetAllUsers(db)
	if err != nil {
		return nil, err
	}

	entries, err := GetAllTimeEntries(db)
	if err != nil {
		return nil, err
	}

	userTotals := make(map[int]float64)
	usernames := make(map[int]string)

	for _, entry := range entries {
		var hours float64
		if entry.Type == "lesson" {
			hours = 1.0
		} else {
			hours = calculateHoursDiff(entry.StartTime, entry.EndTime)
		}
		userTotals[entry.UserID] += hours
		usernames[entry.UserID] = entry.Username
	}

	var result []WeeklyHours
	for _, user := range users {
		if !user.IsAdmin {
			total := userTotals[user.ID]
			remaining := user.YearlyHours - total

			result = append(result, WeeklyHours{
				UserID:          user.ID,
				Username:        user.Username,
				Year:            time.Now().Year(),
				Week:            0,
				TotalHours:      total,
				YearlyTarget:    user.YearlyHours,
				YearlyActual:    total,
				RemainingYearly: remaining,
			})
		}
	}

	sort.Slice(result, func(i, j int) bool {
		return result[i].Username < result[j].Username
	})

	return result, nil
}

func calculateHoursDiff(startTime, endTime string) float64 {
	parseTime := func(timeStr string) float64 {
		parts := strings.Split(timeStr, ":")
		if len(parts) != 2 {
			return 0
		}

		hours, err1 := strconv.ParseFloat(parts[0], 64)
		minutes, err2 := strconv.ParseFloat(parts[1], 64)

		if err1 != nil || err2 != nil {
			return 0
		}

		return hours + (minutes / 60.0)
	}

	start := parseTime(startTime)
	end := parseTime(endTime)

	if end > start {
		return end - start
	}
	return 0
}

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
}