package toc

import (
	"log"
	"sync"
	"time"

	"tgchanbot/internal/storage"

	tele "gopkg.in/telebot.v3"
)

type Manager struct {
	storage  *storage.Storage
	bot      *tele.Bot
	chanID   int64
	debounce time.Duration

	mu      sync.Mutex
	pending bool
	timer   *time.Timer
	stopCh  chan struct{}
}

func NewManager(store *storage.Storage, bot *tele.Bot, chanID int64, debounce time.Duration) *Manager {
	return &Manager{
		storage:  store,
		bot:      bot,
		chanID:   chanID,
		debounce: debounce,
		stopCh:   make(chan struct{}),
	}
}

func (m *Manager) TriggerUpdate() {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.pending = true

	if m.timer != nil {
		m.timer.Stop()
	}

	m.timer = time.AfterFunc(m.debounce, func() {
		m.doUpdate()
	})
}

func (m *Manager) doUpdate() {
	m.mu.Lock()
	m.pending = false
	m.mu.Unlock()

	content, err := m.Render()
	if err != nil {
		log.Printf("TOC render error: %v", err)
		return
	}

	if err := m.updateMessage(content); err != nil {
		log.Printf("TOC update error: %v", err)
	}
}

func (m *Manager) updateMessage(content string) error {
	chat := &tele.Chat{ID: m.chanID}

	msgID, err := m.storage.GetTocMsgID()
	if err != nil {
		return err
	}

	if msgID == 0 {
		msg, err := m.bot.Send(chat, content, tele.ModeMarkdown, tele.NoPreview)
		if err != nil {
			return err
		}
		return m.storage.SetTocMsgID(msg.ID)
	}

	existingMsg := &tele.Message{
		ID:   msgID,
		Chat: chat,
	}

	_, err = m.bot.Edit(existingMsg, content, tele.ModeMarkdown, tele.NoPreview)
	if err != nil {
		if err == tele.ErrMessageNotModified {
			return nil
		}
		if err.Error() == "telegram: message to edit not found (400)" {
			msg, err := m.bot.Send(chat, content, tele.ModeMarkdown, tele.NoPreview)
			if err != nil {
				return err
			}
			return m.storage.SetTocMsgID(msg.ID)
		}
		return err
	}

	return nil
}

func (m *Manager) Stop() {
	m.mu.Lock()
	defer m.mu.Unlock()

	if m.timer != nil {
		m.timer.Stop()
	}

	close(m.stopCh)
}