// Package tg provides Telegram bot functionality for RSMon.
package tg

import (
	"errors"
	"fmt"
	"log"
	"net/http"
	"os"
	"strconv"
	"strings"
	"time"

	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"

	"rocketgit.ru/rsmon/worker/app/models"
)

var bot *tgbotapi.BotAPI

type silentTelegramLogger struct{}

func (silentTelegramLogger) Println(...interface{})        {}
func (silentTelegramLogger) Printf(string, ...interface{}) {}

func init() {
	_ = tgbotapi.SetLogger(silentTelegramLogger{})
}

const (
	defaultBaseURL     = "https://rsmon.ru"
	telegramAPITimeout = 15 * time.Second
)

func telegramAPIEndpoint(rawURL string) string {
	if rawURL == "" {
		return tgbotapi.APIEndpoint
	}
	return strings.TrimRight(rawURL, "/") + "/bot%s/%s"
}

func newBotAPI(token, apiURL string) (*tgbotapi.BotAPI, error) {
	return tgbotapi.NewBotAPIWithClient(token, telegramAPIEndpoint(apiURL), &http.Client{Timeout: telegramAPITimeout})
}

func botAPIForCredential(cred *models.NotificationCredential) (*tgbotapi.BotAPI, error) {
	if cred == nil {
		return nil, errors.New("telegram credential is nil")
	}
	token, err := cred.GetSecret()
	if err != nil {
		return nil, fmt.Errorf("telegram credential secret: %w", err)
	}
	apiURL := ""
	if cred.APIURL != nil {
		apiURL = *cred.APIURL
	}
	client, err := newBotAPI(token, apiURL)
	if err != nil {
		return nil, err
	}
	client.Debug = false
	return client, nil
}

// GetContact finds or creates a contact for the given Telegram chat.
func GetContact(kind, name string, chatID int64) (models.Contact, error) {
	contact := models.Contact{}

	if kind == "supergroup" {
		kind = "group"
	}
	ckind := "telegram_" + kind
	cvalue := strconv.FormatInt(chatID, 10)

	models.DB().Where("kind = ? AND value = ?", ckind, cvalue).Find(&contact)

	contact.Kind = ckind
	contact.Value = cvalue
	contact.Name = name
	if contact.Token == "" {
		contact.SetToken()
	}
	err := models.DB().Save(&contact).Error

	return contact, err
}

// Init initializes the Telegram bot API client.
func Init() error {
	if bot == nil {
		client, err := defaultBotAPI()
		if err != nil {
			return err
		}
		bot = client
	}
	return nil
}

func defaultBotAPI() (*tgbotapi.BotAPI, error) {
	creds, err := models.EnabledCredentialsByKind(models.CredentialKindTelegram)
	if err != nil {
		return nil, err
	}
	if len(creds) == 0 {
		return nil, errors.New("telegram bot not configured")
	}
	return botAPIForCredential(&creds[0])
}

func botAPIForCredentialID(id int64) (*tgbotapi.BotAPI, error) {
	if id <= 0 {
		return defaultBotAPI()
	}
	cred, err := models.FindCredential(id)
	if err != nil {
		return nil, err
	}
	if cred.Kind != models.CredentialKindTelegram {
		return nil, fmt.Errorf("credential %d is %q, not telegram", id, cred.Kind)
	}
	if cred.Enabled != nil && !*cred.Enabled {
		return nil, fmt.Errorf("credential %d is disabled", id)
	}
	return botAPIForCredential(cred)
}

// SendMessage sends a Telegram message to the given chat ID string.
func SendMessage(chatIDStr, message string) error {
	var err error

	iChatID, err := strconv.ParseInt(chatIDStr, 10, 64)
	if err != nil {
		return err
	}
	err = Init()
	if err != nil {
		return err
	}
	msg := tgbotapi.NewMessage(iChatID, "")
	msg.Text = message

	_, err = bot.Send(msg)
	recordSentMessage(iChatID, message, err)
	if err != nil {
		log.Println(err)
	}
	return err
}

// SendMessageWithToken is the credential-scoped variant used by the worker
// executor. It builds a one-shot bot client from the credential's BotToken +
// optional APIURL, then sends the message. Returns the bot's response error
// so callers can translate into retryable/permanent status.
func SendMessageWithToken(chatIDStr, message string, cred *models.NotificationCredential) error {
	if cred == nil {
		return errors.New("telegram credential is nil")
	}
	if cred.Kind != models.CredentialKindTelegram {
		return fmt.Errorf("credential %d is not telegram (kind=%s)", cred.ID, cred.Kind)
	}

	chatID, err := strconv.ParseInt(chatIDStr, 10, 64)
	if err != nil {
		return err
	}

	client, err := botAPIForCredential(cred)
	if err != nil {
		return err
	}

	msg := tgbotapi.NewMessage(chatID, message)
	_, err = client.Send(msg)
	recordSentMessage(chatID, message, err)
	return err
}

// Start starts the Telegram bot update loop.
func Start() {
	StartWithCredentialID(0)
}

// StartWithCredentialID starts the Telegram bot update loop for a specific credential.
func StartWithCredentialID(credentialID int64) {
	var err error
	if credentialID > 0 {
		bot, err = botAPIForCredentialID(credentialID)
	} else {
		err = Init()
	}
	if err != nil {
		log.Println(err)
		return
	}
	log.Printf("Authorized on account %s", bot.Self.UserName)
	SetBotCommands(bot)
	if _, err := bot.Request(tgbotapi.DeleteWebhookConfig{DropPendingUpdates: false}); err != nil {
		log.Println("telegram delete webhook:", err)
		return
	}

	u := tgbotapi.NewUpdate(0)
	u.Timeout = 10

	updates := bot.GetUpdatesChan(u)
	markBotOnline("")
	go heartbeat()

	for update := range updates {
		ProcessUpdate(bot, update)
	}
}

// ProcessWebhookUpdate handles one Telegram webhook update for a credential.
func ProcessWebhookUpdate(cred *models.NotificationCredential, update tgbotapi.Update) error {
	client, err := botAPIForCredential(cred)
	if err != nil {
		return err
	}
	ProcessUpdate(client, update)
	return nil
}

// SetCredentialCommands registers the slash command menu for a credential-backed bot.
func SetCredentialCommands(cred *models.NotificationCredential) error {
	client, err := botAPIForCredential(cred)
	if err != nil {
		return err
	}
	SetBotCommands(client)
	return nil
}

// ProcessUpdate handles one Telegram update from polling or webhook delivery.
func ProcessUpdate(client *tgbotapi.BotAPI, update tgbotapi.Update) {
	if update.Message == nil { // ignore any non-Message updates for now
		return
	}
	recordReceivedMessage(update.Message, nil)
	markBotOnline("")

	if !update.Message.IsCommand() {
		return
	}

	msg := tgbotapi.NewMessage(update.Message.Chat.ID, "")
	contact, err := contactForMessage(update.Message)
	if err != nil {
		msg.Text = "Внутренняя ошибка rsmon: " + err.Error()
		sendAndRecord(client, msg)
		return
	}

	msg.Text = commandResponse(update.Message, contact)
	sendAndRecord(client, msg)
}

func contactForMessage(message *tgbotapi.Message) (models.Contact, error) {
	var name string
	switch message.Chat.Type {
	case "private":
		name = strings.TrimSpace("@" + strings.TrimSpace(message.Chat.UserName+" "+message.Chat.FirstName+" "+message.Chat.LastName))
	case "group", "supergroup":
		name = message.Chat.Title
	default:
		return models.Contact{}, fmt.Errorf("unknown chat type: %s", message.Chat.Type)
	}
	return GetContact(message.Chat.Type, name, message.Chat.ID)
}

func commandResponse(message *tgbotapi.Message, contact models.Contact) string {
	baseURL := strings.TrimRight(os.Getenv("BASE_URL"), "/")
	if baseURL == "" {
		baseURL = defaultBaseURL
	}
	link := baseURL + "/telegram?token=" + contact.Token
	switch message.Command() {
	case "start":
		return "Для завершения добавления Telegram-уведомлений перейдите по ссылке:\n" + link +
			"\n\n/id - показать ID чата\n/info - статус привязки\n/settings - настройки\n/stop - отключить уведомления"
	case "id":
		return fmt.Sprintf("chat_id: %d\ntype: %s", message.Chat.ID, message.Chat.Type)
	case "info":
		return contactInfo(contact, link)
	case "settings":
		return "Настройки Telegram-контакта доступны в RSMon:\n" + link + "\n\n/stop - отключить уведомления для этого чата"
	case "stop":
		disabled, disableErr := disableChatNotifications(message.Chat.ID)
		if disableErr != nil {
			return "Не удалось отключить уведомления: " + disableErr.Error()
		}
		return fmt.Sprintf("Telegram-уведомления для этого чата отключены: %d", disabled)
	case "help":
		return helpText()
	default:
		return "Неизвестная команда. " + helpText()
	}
}

func contactInfo(contact models.Contact, link string) string {
	bound := contact.UserID != nil || contact.AccountID != nil
	status := "не привязан"
	if bound {
		status = "привязан"
	}
	return fmt.Sprintf("Контакт: %s\nТип: %s\nID: %s\nСтатус: %s\nСсылка настройки: %s", contact.Name, contact.Kind, contact.Value, status, link)
}

func helpText() string {
	return "/start - подключить Telegram-уведомления\n" +
		"/id - показать ID чата\n" +
		"/info - информация о контакте\n" +
		"/settings - ссылка на настройки\n" +
		"/stop - отключить уведомления"
}

func sendAndRecord(client *tgbotapi.BotAPI, msg tgbotapi.MessageConfig) {
	_, err := client.Send(msg)
	recordSentMessage(msg.ChatID, msg.Text, err)
	if err != nil {
		log.Println(err)
	}
}

// SetBotCommands registers slash command menus for private and group chats.
func SetBotCommands(client *tgbotapi.BotAPI) {
	if client == nil {
		return
	}
	commands := []tgbotapi.BotCommand{
		{Command: "start", Description: "Подключить Telegram-уведомления"},
		{Command: "id", Description: "Показать ID чата"},
		{Command: "info", Description: "Информация о привязке"},
		{Command: "settings", Description: "Настройки контакта"},
		{Command: "stop", Description: "Отключить уведомления"},
		{Command: "help", Description: "Список команд"},
	}
	if _, err := client.Request(tgbotapi.NewSetMyCommands(commands...)); err != nil {
		log.Println("telegram set commands:", err)
	}
}

func heartbeat() {
	ticker := time.NewTicker(time.Minute)
	defer ticker.Stop()
	for range ticker.C {
		markBotOnline("")
	}
}

func markBotOnline(lastErr string) {
	now := time.Now()
	username := ""
	if bot != nil {
		username = bot.Self.UserName
	}
	status := models.TelegramBotStatus{}
	models.DB().Where("name = ?", models.TelegramBotStatusMain).
		FirstOrCreate(&status, models.TelegramBotStatus{Name: models.TelegramBotStatusMain})
	status.Username = username
	status.Online = true
	status.LastSeen = &now
	status.LastError = lastErr
	_ = models.DB().Save(&status).Error
}

func recordReceivedMessage(message *tgbotapi.Message, contactID *int64) {
	if message == nil || message.Chat == nil {
		return
	}
	username := ""
	if message.From != nil {
		username = message.From.UserName
	}
	record := models.TelegramBotMessage{
		Direction: models.TelegramBotMessageReceived,
		ChatID:    message.Chat.ID,
		ChatType:  message.Chat.Type,
		Username:  username,
		Text:      message.Text,
		Command:   message.Command(),
		ContactID: contactID,
		CreatedAt: time.Now(),
	}
	_ = models.DB().Create(&record).Error
}

func recordSentMessage(chatID int64, text string, sendErr error) {
	errorText := ""
	if sendErr != nil {
		errorText = sendErr.Error()
	}
	record := models.TelegramBotMessage{
		Direction: models.TelegramBotMessageSent,
		ChatID:    chatID,
		Text:      text,
		Error:     errorText,
		CreatedAt: time.Now(),
	}
	_ = models.DB().Create(&record).Error
}

func disableChatNotifications(chatID int64) (int64, error) {
	value := strconv.FormatInt(chatID, 10)
	result := models.DB().Model(&models.Contact{}).
		Where("kind IN ? AND value = ?", []string{"telegram_private", "telegram_group"}, value).
		Update("enabled", false)
	return result.RowsAffected, result.Error
}