package main

import (
	"database/sql"
	"fmt"
	"log"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/golang-jwt/jwt/v5"
	"github.com/labstack/echo/v4"
	"golang.org/x/crypto/bcrypt"
)

type App struct {
	DB *sql.DB
}

func HandleError(c echo.Context, err *AppError) error {
	log.Printf("[%s] %s", err.Code, err.Error())

	return c.JSON(err.HTTPStatus, err.ToResponse())
}

func getClaims(c echo.Context) (*Claims, error) {
	user, ok := c.Get("user").(*jwt.Token)
	if !ok {
		return nil, fmt.Errorf("JWT token missing or invalid")
	}

	claims, ok := user.Claims.(*Claims)
	if !ok {
		return nil, fmt.Errorf("failed to parse JWT claims")
	}

	return claims, nil
}

func isDuplicateError(err error) bool {
	return err != nil && (err.Error() == "UNIQUE constraint failed" ||
		strings.Contains(err.Error(), "UNIQUE") ||
		strings.Contains(err.Error(), "duplicate"))
}

func (app *App) LoginHandler(c echo.Context) error {
	var req LoginRequest
	if err := c.Bind(&req); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Login-Daten"))
	}

	if req.Username == "" {
		return HandleError(c, ErrMissingFieldMsg("Benutzername"))
	}
	if req.Password == "" {
		return HandleError(c, ErrMissingFieldMsg("Passwort"))
	}

	user, err := GetUserByUsername(app.DB, req.Username)
	if err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrInvalidCredentialsMsg())
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	if err := bcrypt.CompareHashAndPassword([]byte(user.Password), []byte(req.Password)); err != nil {
		return HandleError(c, ErrInvalidCredentialsMsg())
	}

	token, err := createToken(user.ID, user.Username, user.IsAdmin)
	if err != nil {
		return HandleError(c, ErrInternalMsg(err))
	}

	response := LoginResponse{
		Token:    token,
		Username: user.Username,
		IsAdmin:  user.IsAdmin,
	}

	return c.JSON(http.StatusOK, response)
}

func (app *App) GetSchedulesHandler(c echo.Context) error {
	schedules, err := GetAllSchedules(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	return c.JSON(http.StatusOK, schedules)
}

func (app *App) CreateScheduleHandler(c echo.Context) error {
	var schedule Schedule
	if err := c.Bind(&schedule); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Stundenplan-Daten"))
	}

	if schedule.StartTime == "" {
		return HandleError(c, ErrMissingFieldMsg("Startzeit"))
	}
	if schedule.EndTime == "" {
		return HandleError(c, ErrMissingFieldMsg("Endzeit"))
	}
	if schedule.Title == "" {
		return HandleError(c, ErrMissingFieldMsg("Titel"))
	}

	if err := CreateSchedule(app.DB, &schedule); err != nil {
		if isDuplicateError(err) {
			return HandleError(c, ErrAlreadyExistsMsg("Stundenplan-Eintrag"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.JSON(http.StatusCreated, map[string]string{"message": "Stundenplan erstellt"})
}

func (app *App) DeleteScheduleHandler(c echo.Context) error {
	id, err := strconv.Atoi(c.QueryParam("id"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Stundenplan-ID"))
	}

	if err := DeleteSchedule(app.DB, id); err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Stundenplan"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusNoContent)
}

func (app *App) GetYearlyHoursSummaryHandler(c echo.Context) error {
	hours, err := GetYearlyHoursSummary(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	if hours == nil {
		hours = []WeeklyHours{}
	}
	return c.JSON(http.StatusOK, hours)
}

func (app *App) AdminCreateTimeEntryHandler(c echo.Context) error {
	var req struct {
		UserID int     `json:"user_id"`
		Date   string  `json:"date"`
		Hours  float64 `json:"hours"`
		Type   string  `json:"type"`
	}

	if err := c.Bind(&req); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Zeiteintrag-Daten"))
	}

	if req.UserID == 0 {
		return HandleError(c, ErrMissingFieldMsg("Benutzer"))
	}
	if req.Date == "" {
		return HandleError(c, ErrMissingFieldMsg("Datum"))
	}
	if req.Hours == 0 {
		return HandleError(c, ErrMissingFieldMsg("Stunden"))
	}

	entry := TimeEntry{
		UserID:    req.UserID,
		Date:      req.Date,
		StartTime: "00:00",
		EndTime:   "00:00",
		Type:      "manual",
	}

	if err := CreateManualTimeEntry(app.DB, &entry, req.Hours); err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusNoContent)
}

func (app *App) GetUsersHandler(c echo.Context) error {
	users, err := GetAllUsers(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	if users == nil {
		users = []User{}
	}
	return c.JSON(http.StatusOK, users)
}

func (app *App) DeleteUserHandler(c echo.Context) error {
	id, err := strconv.Atoi(c.QueryParam("id"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Benutzer-ID"))
	}

	if id == 1 {
		return HandleError(c, ErrProtectedUserMsg())
	}

	if err := DeleteUser(app.DB, id); err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Benutzer"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusNoContent)
}

func (app *App) CreateTimeEntryHandler(c echo.Context) error {
	claims, err := getClaims(c)
	if err != nil {
		return HandleError(c, ErrUnauthorizedMsg())
	}

	var entry TimeEntry
	if err := c.Bind(&entry); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Zeiteintrag-Daten"))
	}

	if entry.Date == "" {
		return HandleError(c, ErrMissingFieldMsg("Datum"))
	}
	if entry.StartTime == "" {
		return HandleError(c, ErrMissingFieldMsg("Startzeit"))
	}
	if entry.EndTime == "" {
		return HandleError(c, ErrMissingFieldMsg("Endzeit"))
	}

	entry.UserID = claims.UserID

	if err := CreateTimeEntry(app.DB, &entry); err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.JSON(http.StatusCreated, map[string]string{"message": "Zeiteintrag erstellt"})
}

func (app *App) GetMyTimeEntriesHandler(c echo.Context) error {
	claims, err := getClaims(c)
	if err != nil {
		return HandleError(c, ErrUnauthorizedMsg())
	}

	entries, err := GetTimeEntriesByUser(app.DB, claims.UserID)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	if entries == nil {
		entries = []TimeEntry{}
	}

	return c.JSON(http.StatusOK, entries)
}

func (app *App) GetWeekDates(c echo.Context) error {
	year, err := strconv.Atoi(c.QueryParam("year"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Jahr"))
	}

	week, err := strconv.Atoi(c.QueryParam("week"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Woche"))
	}

	if week < 1 || week > 53 {
		return HandleError(c, ErrInvalidInputMsg("Woche (muss zwischen 1 und 53 liegen)"))
	}

	dates := calculateWeekDates(year, week)
	return c.JSON(http.StatusOK, dates)
}

func (app *App) CheckWeekHasEntries(c echo.Context) error {
	claims, err := getClaims(c)
	if err != nil {
		return HandleError(c, ErrUnauthorizedMsg())
	}

	year, err := strconv.Atoi(c.QueryParam("year"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Jahr"))
	}

	week, err := strconv.Atoi(c.QueryParam("week"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Woche"))
	}

	hasEntries, err := CheckUserHasEntriesForWeek(app.DB, claims.UserID, year, week)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.JSON(http.StatusOK, map[string]bool{"has_entries": hasEntries})
}

func (app *App) GetAllTimeEntriesHandler(c echo.Context) error {
	entries, err := GetAllTimeEntries(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	if entries == nil {
		entries = []TimeEntry{}
	}
	return c.JSON(http.StatusOK, entries)
}

func (app *App) GetWeeklyHoursHandler(c echo.Context) error {
	hours, err := GetWeeklyHours(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	if hours == nil {
		hours = []WeeklyHours{}
	}
	return c.JSON(http.StatusOK, hours)
}

func (app *App) DeleteWeekEntries(c echo.Context) error {
	claims, err := getClaims(c)
	if err != nil {
		return HandleError(c, ErrUnauthorizedMsg())
	}

	year, err := strconv.Atoi(c.QueryParam("year"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Jahr"))
	}

	week, err := strconv.Atoi(c.QueryParam("week"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Woche"))
	}

	if err := DeleteTimeEntriesByUserAndWeek(app.DB, claims.UserID, year, week); err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusNoContent)
}

type WeekDates struct {
	Year  int               `json:"year"`
	Week  int               `json:"week"`
	Dates map[string]string `json:"dates"`
	Range string            `json:"range"`
}

func calculateWeekDates(year, week int) WeekDates {
	jan4 := time.Date(year, time.January, 4, 0, 0, 0, 0, time.UTC)

	weekday := int(jan4.Weekday())
	if weekday == 0 {
		weekday = 7
	}
	daysToMonday := weekday - 1
	mondayWeek1 := jan4.AddDate(0, 0, -daysToMonday)

	targetMonday := mondayWeek1.AddDate(0, 0, (week-1)*7)

	dates := make(map[string]string)
	weekDays := []string{"0", "1", "2", "3", "4"}

	var firstDate, lastDate time.Time
	for i, day := range weekDays {
		date := targetMonday.AddDate(0, 0, i)
		dates[day] = date.Format("2006-01-02")

		if i == 0 {
			firstDate = date
		}
		if i == 4 {
			lastDate = date
		}
	}

	rangeStr := firstDate.Format("2006-01-02") + " bis " + lastDate.Format("2006-01-02")

	return WeekDates{
		Year:  year,
		Week:  week,
		Dates: dates,
		Range: rangeStr,
	}
}

type BatchTimeEntryRequest struct {
	Entries []struct {
		ScheduleID int    `json:"schedule_id"`
		Date       string `json:"date"`
		Type       string `json:"type"`
		StartTime  string `json:"start_time"`
		EndTime    string `json:"end_time"`
	} `json:"entries"`
}

func (app *App) CreateBatchTimeEntriesHandler(c echo.Context) error {
	claims, err := getClaims(c)
	if err != nil {
		return HandleError(c, ErrUnauthorizedMsg())
	}

	var req BatchTimeEntryRequest
	if err := c.Bind(&req); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Zeiteintrag-Daten"))
	}

	if len(req.Entries) == 0 {
		return HandleError(c, ErrMissingFieldMsg("Zeiteinträge"))
	}

	tx, err := app.DB.Begin()
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare("INSERT INTO time_entries (user_id, schedule_id, date, type, start_time, end_time) VALUES (?, ?, ?, ?, ?, ?)")
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	defer stmt.Close()

	for _, entry := range req.Entries {
		_, err := stmt.Exec(claims.UserID, entry.ScheduleID, entry.Date, entry.Type, entry.StartTime, entry.EndTime)
		if err != nil {
			return HandleError(c, ErrDatabaseMsg(err))
		}
	}

	if err := tx.Commit(); err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.JSON(http.StatusCreated, map[string]string{"message": "Zeiteinträge erstellt"})
}

func (app *App) UpdateUserHandler(c echo.Context) error {
	userID, err := strconv.Atoi(c.Param("id"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Benutzer-ID"))
	}

	if userID == 1 {
		return HandleError(c, ErrProtectedUserMsg())
	}

	var req UpdateUserRequest
	if err := c.Bind(&req); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Benutzerdaten"))
	}

	if req.YearlyHours <= 0 {
		return HandleError(c, ErrInvalidInputMsg("Jahresarbeitsstunden (muss positiv sein)"))
	}

	if err := UpdateUser(app.DB, userID, req.YearlyHours); err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Benutzer"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusOK)
}

func (app *App) ResetPasswordHandler(c echo.Context) error {
	userID, err := strconv.Atoi(c.Param("id"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Benutzer-ID"))
	}

	var req ResetPasswordRequest
	if err := c.Bind(&req); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Passwort-Daten"))
	}

	if len(req.NewPassword) < 6 {
		return HandleError(c, ErrInvalidInputMsg("Passwort (mindestens 6 Zeichen)"))
	}

	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(req.NewPassword), bcrypt.DefaultCost)
	if err != nil {
		return HandleError(c, ErrInternalMsg(err))
	}

	if err := ResetUserPassword(app.DB, userID, string(hashedPassword)); err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Benutzer"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusOK)
}

func (app *App) UpdateTimeEntryHandler(c echo.Context) error {
	entryID, err := strconv.Atoi(c.Param("id"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Zeiteintrag-ID"))
	}

	var req UpdateTimeEntryRequest
	if err := c.Bind(&req); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Zeiteintrag-Daten"))
	}

	if req.Date == "" {
		return HandleError(c, ErrMissingFieldMsg("Datum"))
	}
	if req.StartTime == "" {
		return HandleError(c, ErrMissingFieldMsg("Startzeit"))
	}
	if req.EndTime == "" {
		return HandleError(c, ErrMissingFieldMsg("Endzeit"))
	}

	if err := UpdateTimeEntry(app.DB, entryID, req.Date, req.StartTime, req.EndTime, req.Type); err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Zeiteintrag"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusOK)
}

func (app *App) DeleteTimeEntryHandler(c echo.Context) error {
	entryID, err := strconv.Atoi(c.Param("id"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Zeiteintrag-ID"))
	}

	if err := DeleteTimeEntry(app.DB, entryID); err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Zeiteintrag"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusNoContent)
}

func (app *App) GetMyInfoHandler(c echo.Context) error {
	claims, err := getClaims(c)
	if err != nil {
		return HandleError(c, ErrUnauthorizedMsg())
	}

	user, err := GetUserByID(app.DB, claims.UserID)
	if err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Benutzer"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.JSON(http.StatusOK, user)
}

func (app *App) CreateUserHandler(c echo.Context) error {
	var req CreateUserRequest
	if err := c.Bind(&req); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Benutzerdaten"))
	}

	if req.Username == "" {
		return HandleError(c, ErrMissingFieldMsg("Benutzername"))
	}
	if req.Password == "" {
		return HandleError(c, ErrMissingFieldMsg("Passwort"))
	}
	if len(req.Password) < 6 {
		return HandleError(c, ErrInvalidInputMsg("Passwort (mindestens 6 Zeichen)"))
	}

	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(req.Password), bcrypt.DefaultCost)
	if err != nil {
		return HandleError(c, ErrInternalMsg(err))
	}

	if req.YearlyHours == 0 {
		req.YearlyHours = 60.0
	}

	if err := CreateUser(app.DB, req.Username, string(hashedPassword), req.IsAdmin, req.YearlyHours); err != nil {
		if isDuplicateError(err) {
			return HandleError(c, ErrAlreadyExistsMsg("Benutzername"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusCreated)
}

func (app *App) GetSchoolYearsHandler(c echo.Context) error {
	years, err := GetAllSchoolYears(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	if years == nil {
		years = []SchoolYear{}
	}
	return c.JSON(http.StatusOK, years)
}

func (app *App) CreateSchoolYearHandler(c echo.Context) error {
	var req CreateSchoolYearRequest
	if err := c.Bind(&req); err != nil {
		return HandleError(c, ErrInvalidInputMsg("Schuljahr-Daten"))
	}

	if req.Name == "" {
		return HandleError(c, ErrMissingFieldMsg("Name"))
	}
	if req.StartDate == "" {
		return HandleError(c, ErrMissingFieldMsg("Startdatum"))
	}
	if req.EndDate == "" {
		return HandleError(c, ErrMissingFieldMsg("Enddatum"))
	}

	if err := CreateSchoolYear(app.DB, req.Name, req.StartDate, req.EndDate); err != nil {
		if isDuplicateError(err) {
			return HandleError(c, ErrAlreadyExistsMsg("Schuljahr"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusCreated)
}

func (app *App) SetActiveSchoolYearHandler(c echo.Context) error {
	id, err := strconv.Atoi(c.Param("id"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Schuljahr-ID"))
	}

	if err := SetActiveSchoolYear(app.DB, id); err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Schuljahr"))
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusNoContent)
}

func (app *App) GetActiveSchoolYearHandler(c echo.Context) error {
	year, err := GetActiveSchoolYear(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	if year == nil {
		return c.JSON(http.StatusOK, map[string]any{"active": false})
	}
	return c.JSON(http.StatusOK, year)
}

func (app *App) GenerateYearlySummaryPDFHandler(c echo.Context) error {
	schoolYear, err := GetActiveSchoolYear(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}
	if schoolYear == nil {
		return HandleError(c, ErrNoActiveSchoolYearMsg())
	}

	summary, err := GetYearlyHoursSummary(app.DB)
	if err != nil {
		return HandleError(c, ErrDatabaseMsg(err))
	}

	pdfBytes, err := GenerateYearlySummaryPDF(schoolYear, summary)
	if err != nil {
		return HandleError(c, ErrInternalMsg(err))
	}

	filename := fmt.Sprintf("Jahresuebersicht_%s.pdf", schoolYear.Name)
	c.Response().Header().Set("Content-Type", "application/pdf")
	c.Response().Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))

	return c.Blob(http.StatusOK, "application/pdf", pdfBytes)
}

func (app *App) DeleteSchoolYearHandler(c echo.Context) error {
	id, err := strconv.Atoi(c.Param("id"))
	if err != nil {
		return HandleError(c, ErrInvalidInputMsg("Schuljahr-ID"))
	}

	if err := DeleteSchoolYear(app.DB, id); err != nil {
		if err == sql.ErrNoRows {
			return HandleError(c, ErrNotFoundMsg("Schuljahr"))
		}
		if err.Error() == "cannot delete active school year" {
			return HandleError(c, &AppError{
				Code:       "CANNOT_DELETE_ACTIVE_SCHOOL_YEAR",
				Message:    "Aktives Schuljahr kann nicht gelöscht werden",
				HTTPStatus: http.StatusBadRequest,
			})
		}
		return HandleError(c, ErrDatabaseMsg(err))
	}

	return c.NoContent(http.StatusNoContent)
}