package bot

import (
	"context"
	"fmt"
	"log/slog"
	"strings"
	"sync"
	"time"

	bot "github.com/go-telegram/bot"
	"github.com/go-telegram/bot/models"

	"worktimeBot/internal/db"
)

const rateLimitInterval = 1 * time.Second

type pendingNote struct {
	eventID   int64
	createdAt time.Time
}

// Handler holds the bot instance, database store, user allowlist, and rate-limit state.
type Handler struct {
	Bot          *bot.Bot
	DB           *db.Store
	AllowedUsers map[int64]bool
	lastMsgTime  map[int64]time.Time
	pendingNotes map[int64]*pendingNote
	mu           sync.Mutex
}

// NewHandler creates a Handler and starts the rate-limit cleanup goroutine.
func NewHandler(bot *bot.Bot, store *db.Store, allowed map[int64]bool) *Handler {
	h := &Handler{
		Bot:          bot,
		DB:           store,
		AllowedUsers: allowed,
		lastMsgTime:  make(map[int64]time.Time),
		pendingNotes: make(map[int64]*pendingNote),
	}
	go h.periodicCleanup()
	return h
}

// periodicCleanup runs in the background, purging stale rate-limit entries and pending notes every 10 seconds.
func (h *Handler) periodicCleanup() {
	for {
		time.Sleep(10 * time.Second)
		h.mu.Lock()
		cutoff := time.Now().Add(-rateLimitInterval * 2)
		for uid, t := range h.lastMsgTime {
			if t.Before(cutoff) {
				delete(h.lastMsgTime, uid)
			}
		}
		noteCutoff := time.Now().Add(-5 * time.Minute)
		for chatID, pn := range h.pendingNotes {
			if pn.createdAt.Before(noteCutoff) {
				delete(h.pendingNotes, chatID)
			}
		}
		h.mu.Unlock()
	}
}

type actionFunc func(int64) (string, error)

// isRateLimited returns true if the user has sent a message within the last rateLimitInterval.
func (h *Handler) isRateLimited(userID int64) bool {
	h.mu.Lock()
	defer h.mu.Unlock()
	now := time.Now()
	if last, ok := h.lastMsgTime[userID]; ok && now.Sub(last) < rateLimitInterval {
		return true
	}
	h.lastMsgTime[userID] = now
	return false
}

// handleActionMsg runs an action function and sends the result as a new message.
func (h *Handler) handleActionMsg(ctx context.Context, msg *models.Message, fn actionFunc) {
	text, err := fn(msg.Chat.ID)
	if err != nil {
		h.sendText(ctx, msg.Chat.ID, err.Error())
		return
	}
	kb := mainKeyboard()
	h.sendWithKB(ctx, msg.Chat.ID, text, kb)
}

// handleActionCallback runs an action function and edits the callback message with the result.
func (h *Handler) handleActionCallback(ctx context.Context, chatID int64, msgID int, callbackID string, fn actionFunc) {
	defer h.answerCb(ctx, callbackID)
	text, err := fn(chatID)
	if err != nil {
		text = err.Error()
	}
	kb := backKeyboard()
	h.editText(ctx, chatID, msgID, text, &kb)
}

// HandleMessage routes incoming text messages to the appropriate handler.
func (h *Handler) HandleMessage(ctx context.Context, msg *models.Message) {
	if len(h.AllowedUsers) > 0 && !h.AllowedUsers[msg.Chat.ID] {
		return
	}
	if msg.Text == "" {
		return
	}
	user, err := h.getOrCreateUser(msg.Chat.ID)
	if err != nil {
		return
	}
	if h.isRateLimited(user.ID) {
		return
	}
	slog.Info("message", "chat_id", msg.Chat.ID, "text", msg.Text)

	// Check for pending note — intercepts plain text only, commands always pass through.
	h.mu.Lock()
	pn, hasPN := h.pendingNotes[msg.Chat.ID]
	if hasPN {
		delete(h.pendingNotes, msg.Chat.ID)
	}
	h.mu.Unlock()
	if hasPN && msg.Text[0] != '/' {
		loc := loadLocation(user.Timezone)
		event, err := h.getEventByID(user.ID, pn.eventID)
		if err == nil {
			if err := h.DB.SetEventNote(pn.eventID, msg.Text); err != nil {
				slog.Error("failed to save event note", "event_id", pn.eventID, "error", err)
			}
			date := time.Unix(event.OccurredAt, 0).In(loc).Format("2006-01-02")
			h.sendDayView(ctx, msg.Chat.ID, 0, user, date, loc, true)
		}
		return
	}

	if msg.Text[0] != '/' {
		h.sendText(ctx, msg.Chat.ID, "Unknown command")
		return
	}

	cmd := msg.Text
	if i := strings.IndexByte(msg.Text, ' '); i >= 0 {
		cmd = msg.Text[:i]
	}

	switch cmd {
	case "/start":
		h.handleStart(ctx, msg)
	case "/help":
		h.handleHelp(ctx, msg)
	case "/clockin":
		h.handleActionMsg(ctx, msg, h.clockIn)
	case "/clockout":
		h.handleActionMsg(ctx, msg, h.clockOut)
	case "/worktype":
		h.handleWorkTypeMsg(ctx, msg)
	case "/report":
		h.handleActionMsg(ctx, msg, h.report)
	case "/export":
		h.handleExport(ctx, msg)
	case "/dayoff":
		h.handleActionMsg(ctx, msg, h.dayOff)
	case "/history":
		h.handleHistoryMsg(ctx, msg)
	case "/edit":
		h.handleEditMsg(ctx, msg)
	case "/reporttoggle":
		h.handleActionMsg(ctx, msg, h.toggleReport)
	case "/setreporttime":
		h.handleSetReportTime(ctx, msg)
	case "/setaccent":
		h.handleAccentMsg(ctx, msg)
	case "/settimezone":
		h.handleSetTimezone(ctx, msg)
	case "/note":
		h.handleNoteMsg(ctx, msg)
	case "/summary":
		h.handleSummaryMsg(ctx, msg)
	case "/setbreak":
		h.handleSetBreakMsg(ctx, msg)
	default:
		h.sendText(ctx, msg.Chat.ID, "Unknown command")
	}
}

// HandleCallback routes inline callback queries to the appropriate handler.
func (h *Handler) HandleCallback(ctx context.Context, cb *models.CallbackQuery) {
	if len(h.AllowedUsers) > 0 && !h.AllowedUsers[cb.Message.Message.Chat.ID] {
		h.answerCbWithText(ctx, cb.ID, "Unauthorized")
		return
	}
	user, err := h.getOrCreateUser(cb.Message.Message.Chat.ID)
	if err != nil {
		h.answerCb(ctx, cb.ID)
		return
	}
	if h.isRateLimited(user.ID) {
		h.answerCb(ctx, cb.ID)
		return
	}
	slog.Info("callback", "chat_id", cb.Message.Message.Chat.ID, "data", cb.Data)
	chatID := cb.Message.Message.Chat.ID
	msgID := cb.Message.Message.ID

	switch cb.Data {
	case "clockin":
		h.handleActionCallback(ctx, chatID, msgID, cb.ID, h.clockIn)
	case "clockout":
		h.handleActionCallback(ctx, chatID, msgID, cb.ID, h.clockOut)
	case "worktype":
		h.workTypeCallback(ctx, chatID, msgID, cb.ID)
	case "report":
		h.handleActionCallback(ctx, chatID, msgID, cb.ID, h.report)
	case "export":
		h.exportCallback(ctx, chatID, msgID, cb.ID)
	case "noop":
		h.answerCb(ctx, cb.ID)
	case "dayoff":
		h.handleActionCallback(ctx, chatID, msgID, cb.ID, h.dayOff)
	case "settings":
		h.settingsCallback(ctx, chatID, msgID, cb.ID)
	case "caltype":
		h.calTypeCallback(ctx, chatID, msgID, cb.ID)
	case "accent":
		h.accentCallback(ctx, chatID, msgID, cb.ID)
	case "timezone":
		h.timezoneCallback(ctx, chatID, msgID, cb.ID)
	case "history":
		h.historyCallback(ctx, chatID, msgID, cb.ID)
	case "reporttoggle":
		h.handleActionCallback(ctx, chatID, msgID, cb.ID, h.toggleReport)
	case "reporttime":
		h.reportTimeCallback(ctx, chatID, msgID, cb.ID)
	case "breakthreshold":
		h.breakThresholdCallback(ctx, chatID, msgID, cb.ID)
	case "back_menu":
		h.backToMenu(ctx, chatID, msgID, cb.ID)
	case "back_settings":
		h.backToSettings(ctx, chatID, msgID, cb.ID)
	default:
		// Delegate prefixed callbacks to the appropriate sub-handler
		if len(cb.Data) > 9 && cb.Data[:9] == "worktype_" {
			h.selectWorkType(ctx, chatID, msgID, cb.ID, cb.Data[9:])
			return
		}
		if len(cb.Data) > 7 && cb.Data[:7] == "accent_" {
			h.selectAccent(ctx, chatID, msgID, cb.ID, cb.Data[7:])
			return
		}
		if len(cb.Data) > 8 && cb.Data[:8] == "caltype_" {
			h.selectCalendar(ctx, chatID, msgID, cb.ID, cb.Data[8:])
			return
		}
		if len(cb.Data) > 4 && cb.Data[:4] == "exp_" {
			h.handleExportCallback(ctx, chatID, msgID, cb.ID, cb.Data)
			return
		}
		h.handleHistoryCallback(ctx, chatID, msgID, cb.ID, cb.Data)
	}
}

// getOrCreateUser is a shortcut that delegates to the store.
func (h *Handler) getOrCreateUser(chatID int64) (*db.User, error) {
	return h.DB.GetOrCreateUser(chatID)
}

// getUserToday fetches the user and today's day record, using the user's timezone.
func (h *Handler) getUserToday(chatID int64) (*db.User, *db.Day, error) {
	user, err := h.getOrCreateUser(chatID)
	if err != nil {
		return nil, nil, err
	}
	loc, err := time.LoadLocation(user.Timezone)
	if err != nil {
		loc = time.UTC
	}
	today := time.Now().In(loc).Format("2006-01-02")
	day, err := h.DB.GetOrCreateDay(user.ID, today)
	if err != nil {
		return nil, nil, err
	}
	return user, day, nil
}

// handleStart shows the main menu with the user's current status.
func (h *Handler) handleStart(ctx context.Context, msg *models.Message) {
	user, err := h.getOrCreateUser(msg.Chat.ID)
	if err != nil {
		slog.Error("start: create user", "error", err)
		h.sendText(ctx, msg.Chat.ID, "Error setting up your profile")
		return
	}
	slog.Info("start", "user_id", user.ID, "chat_id", msg.Chat.ID)
	kb := mainKeyboard()
	h.sendWithKB(ctx, msg.Chat.ID, h.buildStatusText(msg.Chat.ID), kb)
}

// handleHelp shows the list of available commands.
func (h *Handler) handleHelp(ctx context.Context, msg *models.Message) {
	text := `Commands:
/start - Show main menu
/clockin - Clock in
/clockout - Clock out
/worktype - Select work type
/dayoff - Toggle day off
/report - Show today report
/export [YYYY-MM] - Export monthly report (current month if omitted)
/history - View calendar history
/edit YYYY-MM-DD - Edit a specific day
/note [YYYY-MM-DD] HH:MM <text> - Set note for an event
/summary [YYYY-MM] - Show monthly summary (current month if omitted)
/reporttoggle - Enable/disable auto report
/setreporttime HH:MM - Set daily report time
/setaccent - Select accent color
/settimezone <name> - Set your timezone (e.g. Asia/Tehran)
/setbreak <minutes> - Set minimum break threshold in minutes

Dates use your calendar type (Gregorian/Jalali/Hijri).
Buttons on the main menu also work.`
	h.sendText(ctx, msg.Chat.ID, text)
}

// handleNoteMsg processes the /note command: /note [YYYY-MM-DD] HH:MM <text>
func (h *Handler) handleNoteMsg(ctx context.Context, msg *models.Message) {
	user, err := h.getOrCreateUser(msg.Chat.ID)
	if err != nil {
		h.sendText(ctx, msg.Chat.ID, "Error loading profile")
		return
	}
	loc := loadLocation(user.Timezone)

	parts := strings.Fields(msg.Text)
	if len(parts) < 3 {
		h.sendText(ctx, msg.Chat.ID, "Usage: /note [YYYY-MM-DD] HH:MM <text>")
		return
	}

	var dateStr string
	var timeStr string
	var noteParts []string

	// Check if first argument looks like a date
	if len(parts[1]) == 10 && parts[1][4] == '-' && parts[1][7] == '-' {
		dateStr = parts[1]
		timeStr = parts[2]
		noteParts = parts[3:]
	} else {
		dateStr = time.Now().In(loc).Format("2006-01-02")
		timeStr = parts[1]
		noteParts = parts[2:]
	}

	events, err := h.DB.EventsForDayByDate(user.ID, dateStr)
	if err != nil || len(events) == 0 {
		h.sendText(ctx, msg.Chat.ID, "No events found for that day")
		return
	}

	var targetEvent *db.Event
	for i := range events {
		t := time.Unix(events[i].OccurredAt, 0).In(loc).Format("15:04")
		if t == timeStr {
			targetEvent = &events[i]
			break
		}
	}
	if targetEvent == nil {
		h.sendText(ctx, msg.Chat.ID, "No event found at that time")
		return
	}

	note := strings.Join(noteParts, " ")
	if err := h.DB.SetEventNote(targetEvent.ID, note); err != nil {
		h.sendText(ctx, msg.Chat.ID, "Error saving note")
		return
	}
	h.sendText(ctx, msg.Chat.ID, "Note saved")
}

// handleWorkTypeMsg shows the work type picker for today.
func (h *Handler) handleWorkTypeMsg(ctx context.Context, msg *models.Message) {
	user, day, err := h.getUserToday(msg.Chat.ID)
	if err != nil {
		h.sendText(ctx, msg.Chat.ID, "Error loading work types")
		return
	}
	text, kb := h.buildWorkTypeKeyboard(user, day)
	h.sendWithKB(ctx, msg.Chat.ID, text, kb)
}

// workTypeCallback shows the work type picker (inline edit).
func (h *Handler) workTypeCallback(ctx context.Context, chatID int64, msgID int, callbackID string) {
	defer h.answerCb(ctx, callbackID)
	user, day, err := h.getUserToday(chatID)
	if err != nil {
		kb := backKeyboard()
		h.editText(ctx, chatID, msgID, "Error loading work types", &kb)
		return
	}
	text, kb := h.buildWorkTypeKeyboard(user, day)
	h.editText(ctx, chatID, msgID, text, &kb)
}

// buildWorkTypeKeyboard returns the work type selection keyboard.
func (h *Handler) buildWorkTypeKeyboard(user *db.User, day *db.Day) (string, models.InlineKeyboardMarkup) {
	wts, err := h.DB.GetWorkTypes()
	if err != nil || len(wts) == 0 {
		return "No work types available.", backKeyboard()
	}
	rows := [][]models.InlineKeyboardButton{}
	for _, wt := range wts {
		label := wt.Name
		if wt.ID == day.CurrentWorkTypeID {
			label = "> " + wt.Name
		}
		rows = append(rows, []models.InlineKeyboardButton{
			{Text: label, CallbackData: fmt.Sprintf("worktype_%d", wt.ID)},
		})
	}
	rows = append(rows, []models.InlineKeyboardButton{
		{Text: "Back to Menu", CallbackData: "back_menu"},
	})
	return "Select work type:", models.InlineKeyboardMarkup{InlineKeyboard: rows}
}

// selectWorkType updates the day's work type from a callback.
func (h *Handler) selectWorkType(ctx context.Context, chatID int64, msgID int, callbackID, idStr string) {
	defer h.answerCb(ctx, callbackID)
	_, day, err := h.getUserToday(chatID)
	if err != nil {
		return
	}
	var wtID int64
	if _, err := fmt.Sscanf(idStr, "%d", &wtID); err != nil {
		return
	}
	wt, err := h.DB.GetWorkType(wtID)
	if err != nil {
		return
	}
	day.CurrentWorkTypeID = wtID
	if err := h.DB.UpdateDay(day); err != nil {
		return
	}
	kb := backKeyboard()
	h.editText(ctx, chatID, msgID, fmt.Sprintf("Work type set to: %s", wt.Name), &kb)
}

// mainKeyboard returns the persistent inline menu.
func mainKeyboard() models.InlineKeyboardMarkup {
	return models.InlineKeyboardMarkup{
		InlineKeyboard: [][]models.InlineKeyboardButton{
			{
				{Text: "Clock In", CallbackData: "clockin"},
				{Text: "Clock Out", CallbackData: "clockout"},
			},
			{
				{Text: "Work Type", CallbackData: "worktype"},
				{Text: "Day Off", CallbackData: "dayoff"},
			},
			{
				{Text: "Report", CallbackData: "report"},
				{Text: "Export", CallbackData: "export"},
			},
			{
				{Text: "Settings", CallbackData: "settings"},
			},
		},
	}
}

// backKeyboard returns a simple "Back to Menu" button.
func backKeyboard() models.InlineKeyboardMarkup {
	return models.InlineKeyboardMarkup{
		InlineKeyboard: [][]models.InlineKeyboardButton{
			{{Text: "Back to Menu", CallbackData: "back_menu"}},
		},
	}
}

// formatDuration formats seconds as a human-readable duration (e.g. "7h 30m").
func formatDuration(seconds int64) string {
	hours := seconds / 3600
	mins := (seconds % 3600) / 60
	if hours > 0 {
		return fmt.Sprintf("%dh %dm", hours, mins)
	}
	return fmt.Sprintf("%dm", mins)
}

// sendText sends a plain text message to the given chat.
func (h *Handler) sendText(ctx context.Context, chatID int64, text string) {
	if _, err := h.Bot.SendMessage(ctx, &bot.SendMessageParams{ChatID: chatID, Text: text}); err != nil {
		slog.Warn("send text failed", "chat_id", chatID, "error", err)
	}
}

// editText edits an existing message, logging errors.
func (h *Handler) editText(ctx context.Context, chatID int64, msgID int, text string, kb *models.InlineKeyboardMarkup) {
	p := &bot.EditMessageTextParams{ChatID: chatID, MessageID: msgID, Text: text}
	if kb != nil {
		p.ReplyMarkup = kb
	}
	if _, err := h.Bot.EditMessageText(ctx, p); err != nil {
		slog.Warn("edit text failed", "chat_id", chatID, "msg_id", msgID, "error", err)
	}
}

// sendWithKB sends a message with an inline keyboard, logging errors.
func (h *Handler) sendWithKB(ctx context.Context, chatID int64, text string, kb models.InlineKeyboardMarkup) {
	if _, err := h.Bot.SendMessage(ctx, &bot.SendMessageParams{ChatID: chatID, Text: text, ReplyMarkup: kb}); err != nil {
		slog.Warn("send with keyboard failed", "chat_id", chatID, "error", err)
	}
}

// answerCb answers a callback query, logging errors.
func (h *Handler) answerCb(ctx context.Context, callbackID string) {
	if _, err := h.Bot.AnswerCallbackQuery(ctx, &bot.AnswerCallbackQueryParams{CallbackQueryID: callbackID}); err != nil {
		slog.Debug("answer callback failed", "error", err)
	}
}

// answerCbWithText answers a callback query with a toast message, logging errors.
func (h *Handler) answerCbWithText(ctx context.Context, callbackID, text string) {
	if _, err := h.Bot.AnswerCallbackQuery(ctx, &bot.AnswerCallbackQueryParams{CallbackQueryID: callbackID, Text: text}); err != nil {
		slog.Debug("answer callback with text failed", "error", err)
	}
}

// navMonth returns the (prevY, prevM, nextY, nextM) for month navigation.
func navMonth(year, month int) (prevY, prevM, nextY, nextM int) {
	prevY, prevM = year, month-1
	if prevM < 1 {
		prevM = 12
		prevY--
	}
	nextY, nextM = year, month+1
	if nextM > 12 {
		nextM = 1
		nextY++
	}
	return
}

// sendOrEdit sends a new message or edits an existing one depending on msgID.
func (h *Handler) sendOrEdit(ctx context.Context, chatID int64, msgID int, text string, kb *models.InlineKeyboardMarkup) {
	if msgID == 0 {
		if kb != nil {
			h.sendWithKB(ctx, chatID, text, *kb)
		} else {
			h.sendText(ctx, chatID, text)
		}
	} else {
		h.editText(ctx, chatID, msgID, text, kb)
	}
}