package service

import (
	"fmt"
	"log"
	"sort"
	"strconv"
	"strings"
	"time"

	"homework-manager/internal/database"
)

// TelegramUpdate is the top-level object sent by Telegram to the webhook.
type TelegramUpdate struct {
	UpdateID      int64             `json:"update_id"`
	Message       *TelegramMessage  `json:"message,omitempty"`
	CallbackQuery *TelegramCallback `json:"callback_query,omitempty"`
}

// TelegramMessage is an incoming text message from a user.
type TelegramMessage struct {
	MessageID int64        `json:"message_id"`
	From      TelegramUser `json:"from"`
	Chat      TelegramChat `json:"chat"`
	Text      string       `json:"text"`
}

// TelegramChat holds the chat metadata.
type TelegramChat struct {
	ID   int64  `json:"id"`
	Type string `json:"type"`
}

// TelegramUser holds basic sender information.
type TelegramUser struct {
	ID        int64  `json:"id"`
	FirstName string `json:"first_name"`
}

// TelegramCallback is sent when the user presses an inline keyboard button.
type TelegramCallback struct {
	ID      string           `json:"id"`
	From    TelegramUser     `json:"from"`
	Message *TelegramMessage `json:"message,omitempty"`
	Data    string           `json:"data"`
}

// TelegramService handles incoming Telegram updates and drives bot interactions.
type TelegramService struct {
	notifService      *NotificationService
	assignmentService *AssignmentService
}

// NewTelegramService creates a TelegramService.
func NewTelegramService(notifService *NotificationService, assignmentService *AssignmentService) *TelegramService {
	return &TelegramService{
		notifService:      notifService,
		assignmentService: assignmentService,
	}
}

// HandleUpdate routes an incoming Telegram update to the appropriate handler.
func (s *TelegramService) HandleUpdate(update TelegramUpdate) {
	switch {
	case update.Message != nil:
		s.handleMessage(update.Message)
	case update.CallbackQuery != nil:
		s.handleCallbackQuery(update.CallbackQuery)
	}
}

// --- Message handlers ---

func (s *TelegramService) handleMessage(msg *TelegramMessage) {
	chatID := strconv.FormatInt(msg.Chat.ID, 10)
	text := strings.TrimSpace(msg.Text)
	if text == "" {
		return
	}

	userID, err := s.notifService.FindUserIDByChatID(chatID)
	if err != nil {
		_ = s.notifService.SendTelegramNotification(chatID,
			"このBotはSuper Homework Managerと連携されていません。\nアプリのプロフィール画面でChat IDを登録してください。")
		return
	}

	parts := strings.SplitN(text, " ", 2)
	cmd := strings.ToLower(parts[0])
	args := ""
	if len(parts) > 1 {
		args = strings.TrimSpace(parts[1])
	}

	switch cmd {
	case "/add":
		s.handleAdd(chatID, userID, args)
	case "/list":
		s.handleList(chatID, userID)
	case "/done":
		s.handleDone(chatID, userID, args)
	case "/help", "/start":
		s.handleHelp(chatID)
	default:
		_ = s.notifService.SendTelegramNotification(chatID,
			fmt.Sprintf("不明なコマンドです: %s\n\n%s", escapeHTML(cmd), addUsageShort()))
	}
}

func (s *TelegramService) handleAdd(chatID string, userID uint, args string) {
	if args == "" {
		_ = s.notifService.SendTelegramNotification(chatID, helpText())
		return
	}

	title, dueDate, subject, priority, err := ParseAddCommand(args)
	if err != nil {
		if err.Error() == "usage" {
			_ = s.notifService.SendTelegramNotification(chatID, addUsageShort())
			return
		}
		_ = s.notifService.SendTelegramNotification(chatID,
			fmt.Sprintf("❌ %s\n\n%s", err.Error(), addUsageShort()))
		return
	}

	assignment, err := s.assignmentService.Create(
		userID, title, "", subject, priority, dueDate, nil, false, nil, true,
	)
	if err != nil {
		log.Printf("telegram /add error userID=%d: %v", userID, err)
		_ = s.notifService.SendTelegramNotification(chatID, "❌ 課題の登録に失敗しました。")
		return
	}

	softDue := assignment.GetEffectiveSoftDueDate()
	priorityLabel := map[string]string{"high": "高", "medium": "中", "low": "低"}[priority]

	var sb strings.Builder
	fmt.Fprintf(&sb, "✅ 課題を登録しました\n\n📌 <b>%s</b>", escapeHTML(title))
	if subject != "" {
		fmt.Fprintf(&sb, "\n科目: %s", escapeHTML(subject))
	}
	fmt.Fprintf(&sb, "\n優先度: %s\nガチ期限: %s\n自分の期限: %s（2日前）",
		priorityLabel,
		dueDate.Format("2006/01/02 15:04"),
		softDue.Format("2006/01/02 15:04"),
	)

	keyboard := &InlineKeyboardMarkup{
		InlineKeyboard: [][]InlineKeyboardButton{
			{{Text: "🗑 取り消す", CallbackData: fmt.Sprintf("undo:%d", assignment.ID)}},
		},
	}
	_ = s.notifService.SendMessageWithKeyboard(chatID, sb.String(), keyboard)
}

func (s *TelegramService) handleList(chatID string, userID uint) {
	assignments, err := s.assignmentService.GetPendingByUser(userID)
	if err != nil {
		_ = s.notifService.SendTelegramNotification(chatID, "❌ 課題一覧の取得に失敗しました。")
		return
	}

	if len(assignments) == 0 {
		_ = s.notifService.SendTelegramNotification(chatID, "✨ 未完了の課題はありません！")
		return
	}

	totalCount := len(assignments)
	sort.Slice(assignments, func(i, j int) bool {
		return assignments[i].DueDate.Before(assignments[j].DueDate)
	})
	if len(assignments) > 5 {
		assignments = assignments[:5]
	}

	var sb strings.Builder
	if totalCount > 5 {
		fmt.Fprintf(&sb, "📋 未完了課題（%d件中上位5件）\n\n", totalCount)
	} else {
		fmt.Fprintf(&sb, "📋 未完了課題（%d件）\n\n", totalCount)
	}

	for _, a := range assignments {
		fmt.Fprintf(&sb, "%s <b>#%d</b> %s\n", priorityEmoji(a.Priority), a.ID, escapeHTML(a.Title))
		if a.Subject != "" {
			fmt.Fprintf(&sb, "　科目: %s\n", escapeHTML(a.Subject))
		}
		fmt.Fprintf(&sb, "　%s %s\n\n", a.DueDate.Format("1/2 15:04"), formatTimeUntil(a.DueDate))
	}

	sb.WriteString("完了: /done &lt;番号&gt;")
	_ = s.notifService.SendTelegramNotification(chatID, sb.String())
}

func (s *TelegramService) handleDone(chatID string, userID uint, args string) {
	args = strings.TrimPrefix(strings.TrimSpace(args), "#")
	id, err := strconv.ParseUint(args, 10, 64)
	if err != nil || id == 0 {
		_ = s.notifService.SendTelegramNotification(chatID,
			"❌ 使い方: /done &lt;課題番号&gt;\n例: /done 42\n\n課題番号は /list で確認できます。")
		return
	}

	assignment, err := s.assignmentService.GetByID(userID, uint(id))
	if err != nil {
		_ = s.notifService.SendTelegramNotification(chatID, "❌ 課題が見つかりませんでした。")
		return
	}
	if assignment.IsCompleted {
		_ = s.notifService.SendTelegramNotification(chatID, "ℹ️ この課題はすでに完了済みです。")
		return
	}

	if _, err := s.assignmentService.ToggleComplete(userID, uint(id)); err != nil {
		_ = s.notifService.SendTelegramNotification(chatID, "❌ 完了処理に失敗しました。")
		return
	}

	_ = s.notifService.SendTelegramNotification(chatID,
		fmt.Sprintf("✅ 完了！お疲れ様！\n\n【%s】", escapeHTML(assignment.Title)))
}

func (s *TelegramService) handleHelp(chatID string) {
	_ = s.notifService.SendTelegramNotification(chatID, helpText())
}

// --- Callback query handlers ---

// handleCallbackQuery processes inline button presses.
func (s *TelegramService) handleCallbackQuery(cb *TelegramCallback) {
	chatID := strconv.FormatInt(cb.From.ID, 10)

	userID, err := s.notifService.FindUserIDByChatID(chatID)
	if err != nil {
		_ = s.notifService.AnswerCallbackQuery(cb.ID, "ユーザーが見つかりません")
		return
	}

	parts := strings.SplitN(cb.Data, ":", 2)
	if len(parts) != 2 {
		_ = s.notifService.AnswerCallbackQuery(cb.ID, "")
		return
	}

	action := parts[0]
	assignmentID, err := strconv.ParseUint(parts[1], 10, 64)
	if err != nil || assignmentID == 0 {
		_ = s.notifService.AnswerCallbackQuery(cb.ID, "")
		return
	}

	var msgID int64
	if cb.Message != nil {
		msgID = cb.Message.MessageID
	}

	switch action {
	case "done":
		s.callbackDone(chatID, userID, uint(assignmentID), cb.ID, msgID)
	case "snooze15":
		s.callbackSnooze(chatID, userID, uint(assignmentID), 15, cb.ID, msgID)
	case "working":
		s.callbackSnooze(chatID, userID, uint(assignmentID), 60, cb.ID, msgID)
	case "undo":
		s.callbackUndo(chatID, userID, uint(assignmentID), cb.ID, msgID)
	default:
		_ = s.notifService.AnswerCallbackQuery(cb.ID, "")
	}
}

func (s *TelegramService) callbackDone(chatID string, userID uint, assignmentID uint, cbID string, msgID int64) {
	assignment, err := s.assignmentService.GetByID(userID, assignmentID)
	if err != nil {
		_ = s.notifService.AnswerCallbackQuery(cbID, "課題が見つかりません")
		return
	}
	if assignment.IsCompleted {
		_ = s.notifService.AnswerCallbackQuery(cbID, "すでに完了済みです")
		_ = s.notifService.EditMessageRemoveKeyboard(chatID, msgID)
		return
	}
	if _, err := s.assignmentService.ToggleComplete(userID, assignmentID); err != nil {
		_ = s.notifService.AnswerCallbackQuery(cbID, "エラーが発生しました")
		return
	}
	_ = s.notifService.AnswerCallbackQuery(cbID, "✅ 完了！お疲れ様！")
	_ = s.notifService.EditMessageRemoveKeyboard(chatID, msgID)
}

func (s *TelegramService) callbackSnooze(chatID string, userID uint, assignmentID uint, snoozeMin int, cbID string, msgID int64) {
	assignment, err := s.assignmentService.GetByID(userID, assignmentID)
	if err != nil {
		_ = s.notifService.AnswerCallbackQuery(cbID, "課題が見つかりません")
		return
	}
	if assignment.IsCompleted {
		_ = s.notifService.AnswerCallbackQuery(cbID, "すでに完了済みです")
		_ = s.notifService.EditMessageRemoveKeyboard(chatID, msgID)
		return
	}

	interval := getUrgentReminderInterval(assignment.Priority)
	// Set last_sent so that next fire happens after snoozeMin minutes.
	// Condition fires when: now - lastSent >= interval
	// We want it to fire at: T + snoozeMin
	// So set: lastSent = T + snoozeMin - interval
	newLastSent := time.Now().Add(time.Duration(snoozeMin)*time.Minute - interval)
	if err := database.GetDB().Model(assignment).Update("last_urgent_reminder_sent", newLastSent).Error; err != nil {
		_ = s.notifService.AnswerCallbackQuery(cbID, "エラーが発生しました")
		return
	}

	var label string
	if snoozeMin == 60 {
		label = "1時間後に通知します。頑張れ！"
	} else {
		label = fmt.Sprintf("%d分後に通知します", snoozeMin)
	}
	_ = s.notifService.AnswerCallbackQuery(cbID, label)
	_ = s.notifService.EditMessageRemoveKeyboard(chatID, msgID)
}

func (s *TelegramService) callbackUndo(chatID string, userID uint, assignmentID uint, cbID string, msgID int64) {
	assignment, err := s.assignmentService.GetByID(userID, assignmentID)
	if err != nil {
		_ = s.notifService.AnswerCallbackQuery(cbID, "課題が見つかりません")
		return
	}
	if time.Since(assignment.CreatedAt) > 60*time.Second {
		_ = s.notifService.AnswerCallbackQuery(cbID, "時間切れです（60秒以内のみ取り消し可能）")
		_ = s.notifService.EditMessageRemoveKeyboard(chatID, msgID)
		return
	}
	if err := s.assignmentService.Delete(userID, assignmentID); err != nil {
		_ = s.notifService.AnswerCallbackQuery(cbID, "エラーが発生しました")
		return
	}
	_ = s.notifService.AnswerCallbackQuery(cbID, "🗑 取り消しました")
	_ = s.notifService.EditMessageRemoveKeyboard(chatID, msgID)
}

// --- Text helpers ---

func priorityEmoji(p string) string {
	switch p {
	case "high":
		return "🚨"
	case "medium":
		return "⚠️"
	default:
		return "📌"
	}
}

func formatTimeUntil(t time.Time) string {
	d := time.Until(t)
	if d < 0 {
		return "（期限切れ）"
	}
	if d < time.Hour {
		return fmt.Sprintf("（あと%d分）", int(d.Minutes()))
	}
	if d < 24*time.Hour {
		return fmt.Sprintf("（あと%d時間）", int(d.Hours()))
	}
	return fmt.Sprintf("（あと%d日）", int(d.Hours()/24))
}

func escapeHTML(s string) string {
	s = strings.ReplaceAll(s, "&", "&amp;")
	s = strings.ReplaceAll(s, "<", "&lt;")
	s = strings.ReplaceAll(s, ">", "&gt;")
	return s
}

func helpText() string {
	return `📖 <b>Super Homework Manager Bot</b>

<b>コマンド一覧</b>

/add &lt;タイトル&gt; &lt;日付&gt; [時刻] [#科目] [!優先度]
  課題を追加します

/list
  未完了課題を一覧表示（最大5件）

/done &lt;番号&gt;
  課題を完了にします（/list の#番号）

/help
  このメッセージを表示

<b>日付の書き方</b>
  今日 / 明日 / 明後日
  月 火 水 木 金 土 日
  1/15 または 1月15日

<b>時刻の書き方</b>（省略時: 23:59）
  23:59 / 17時 / 17時30分

<b>オプション</b>
  #科目名 → 例: #数学
  !高 / !中 / !低 → 優先度（省略時: 中）

<b>例</b>
  /add レポート 金曜 23:59 #英語 !高
  /add 数学課題 明日
  /add 情報演習 1/20 17時`
}

func addUsageShort() string {
	return `使い方: /add &lt;タイトル&gt; &lt;日付&gt; [時刻] [#科目] [!優先度]

例:
  /add レポート 金曜 23:59 #英語 !高
  /add 数学課題 明日
  /add 情報演習 1/20 17時

詳細: /help`
}