rss-tools @ d3bc404

package telegram

import (

	"bytes"

	"context"

	"encoding/binary"

	"encoding/gob"

	"fmt"

	"log/slog"

	"net/http"

	"strings"

	"time"

	"olexsmir.xyz/rss-tools/app"

)

type telegram struct {

	db        *app.Bucket

	messages  *app.Bucket

	client    *http.Client

	get       func(context.Context, string) (*http.Response, error)

	tg        *TelegramSDK

	allowedID int64

	logger    *slog.Logger

}

func Register(a *app.App) error {

	db, err := a.Bucket("telegram")

	if err != nil {

		return err

	}

	messages, err := a.Bucket("telegram:messages")

	if err != nil {

		return err

	}

	t := &telegram{

		db:        db,

		messages:  messages,

		client:    a.Client,

		get:       a.Get,

		tg:        NewSDK(a.Client, a.Config.TGToken),

		allowedID: a.Config.TGUserID,

		logger:    a.Logger,

	}

	a.AddWorker(t.worker)

	a.Route("GET /telegram", t.handler)

	a.Logger.Info("telegram source registered")

	return nil

}

func (t *telegram) handler(w http.ResponseWriter, r *http.Request) {

	// todo: cache feed contruction

	// todo: dont include messages older than N days

	messages, err := t.loadMessages(r.Context())

	if err != nil {

		http.Error(w, "failed to load messages", http.StatusInternalServerError)

		return

	}

	feed := app.NewFeed("Telegram feed", "telegram-feed")

	for _, m := range messages {

		if changed := t.enrichMessageWithLinkTitles(r.Context(), m); changed {

			if err := t.saveMessage(m); err != nil {

				http.Error(w, "failed to update cached titles", http.StatusInternalServerError)

				return

			}

		}

		feed.Add(feedEntryFromMessage(m))

	}

	if err := feed.Render(w); err != nil {

		http.Error(w, "failed to render feed", http.StatusInternalServerError)

		return

	}

}

func (t *telegram) worker(ctx context.Context) error {

	t.logger.Info("starting telegram bot")

	offset, err := t.loadOffset()

	if err != nil {

		return err

	}

	for {

		updates, err := t.tg.GetUpdates(ctx, offset)

		if err != nil {

			t.logger.ErrorContext(ctx, "getUpdates failed", "err", err)

			select {

			case <-ctx.Done():

				return nil

			case <-time.After(5 * time.Second):

				continue

			}

		}

		for _, u := range updates {

			if u.Message != nil && u.Message.From != nil {

				t.logger.InfoContext(ctx, "message from", "user_id", u.Message.From.ID, "username", u.Message.From.Username, "msg", messageText(u.Message))

			}

			if u.Message == nil || u.Message.From == nil || u.Message.From.ID != t.allowedID {

				offset = u.UpdateID + 1

				continue

			}

			_ = t.enrichMessageWithLinkTitles(ctx, u.Message)

			if err := t.saveMessage(u.Message); err != nil {

				t.logger.ErrorContext(ctx, "failed to save message", "err", err)

			}

			if err := t.tg.SetReaction(ctx, u.Message.From.ID, u.Message.MessageID, "👍"); err != nil {

				slog.ErrorContext(ctx, "failed to set reaction", "err", err)

			}

			offset = u.UpdateID + 1

		}

		if err := t.saveOffset(offset); err != nil {

			slog.ErrorContext(ctx, "failed to save offset", "err", err)

		}

		select {

		case <-ctx.Done():

			return nil

		case <-time.After(time.Second):

		}

	}

}

func (t *telegram) saveOffset(offset int64) error {

	return t.db.Set([]byte("offset"), binary.BigEndian.AppendUint64(nil, uint64(offset)))

}

func (t *telegram) loadOffset() (int64, error) {

	val, err := t.db.Get([]byte("offset"))

	if err != nil || val == nil {

		return 0, err

	}

	return int64(binary.BigEndian.Uint64(val)), nil

}

func (t *telegram) saveMessage(m *Message) error {

	var buf bytes.Buffer

	if err := gob.NewEncoder(&buf).Encode(m); err != nil {

		return err

	}

	key := binary.BigEndian.AppendUint64(nil, uint64(m.MessageID))

	return t.messages.Set(key, buf.Bytes())

}

func (t *telegram) loadMessages(ctx context.Context) ([]*Message, error) {

	var messages []*Message

	err := t.messages.ForEach(func(k, v []byte) error {

		var m Message

		if err := gob.NewDecoder(bytes.NewReader(v)).Decode(&m); err != nil {

			t.logger.WarnContext(ctx, "failed to decode telegram message, skipping", "key", fmt.Sprintf("%x", k), "err", err)

			return nil

		}

		messages = append(messages, &m)

		return nil

	})

	return messages, err

}

func (t *telegram) enrichMessageWithLinkTitles(ctx context.Context, m *Message) bool {

	text := messageText(m)

	if !isSingleLinkMessage(text) {

		return false

	}

	links := normalizeLinks(messageLinks(text))

	if len(links) == 0 {

		return false

	}

	if m.LinkTitles == nil {

		m.LinkTitles = make(map[string]string, len(links))

	}

	changed := false

	for _, link := range links {

		cachedTitle := normalizePageTitle(m.LinkTitles[link])

		if isMeaningfulPageTitle(cachedTitle) {

			continue

		}

		if cachedTitle != "" {

			delete(m.LinkTitles, link)

			changed = true

		}

		title, err := fetchPageTitle(ctx, t.get, link)

		if err != nil {

			t.logger.WarnContext(ctx, "failed to lookup page title", "url", link, "err", err)

			continue

		}

		m.LinkTitles[link] = title

		changed = true

	}

	return changed

}

func feedEntryFromMessage(m *Message) app.FeedEntry {

	updated := time.Unix(m.Date, 0)

	text := messageText(m)

	normalizedLinks := normalizeLinks(messageLinks(text))

	entryID := fmt.Sprintf("telegram-%d", m.MessageID)

	if videoID, ok := firstYouTubeVideoID(normalizedLinks); ok {

		entryID = "yt:video:" + videoID

	}

	if m.PhotoBase64 == "" {

		title := text

		if isSingleLinkMessage(text) {

			for _, link := range normalizedLinks {

				if t := strings.TrimSpace(m.LinkTitles[link]); t != "" {

					title = t

					break

				}

			}

		}

		if len(title) > 64 {

			title = title[:64] + "..."

		}

		content := text

		contentType := ""

		if len(normalizedLinks) > 0 {

			content, _ = linkifyMessageText(text)

			contentType = "html"

		}

		return app.FeedEntry{

			Title:       title,

			ID:          entryID,

			Links:       feedLinks(normalizedLinks),

			Content:     content,

			Updated:     updated,

			ContentType: contentType,

		}

	}

	parts := make([]string, 0, 2)

	if t := strings.TrimSpace(text); t != "" {

		linkified, _ := linkifyMessageText(t)

		parts = append(parts, "<p>"+linkified+"</p>")

	}

	mimeType := m.PhotoMIMEType

	if mimeType == "" {

		mimeType = "image/jpeg"

	}

	parts = append(parts, fmt.Sprintf(`<p><img src="data:%s;base64,%s" alt="telegram image"/></p>`, mimeType, m.PhotoBase64))

	return app.FeedEntry{

		Title:       fmt.Sprintf("🖼️ [%s]", updated.Format("2006-01-02")),

		ID:          entryID,

		Links:       feedLinks(normalizedLinks),

		Content:     strings.Join(parts, ""),

		ContentType: "html",

		Updated:     updated,

	}

}

func isSingleLinkMessage(text string) bool {

	links := findLinks(text)

	if len(links) != 1 {

		return false

	}

	link := links[0]

	if strings.TrimSpace(text[:link.start]) != "" {

		return false

	}

	after := strings.TrimSpace(text[link.end:])

	return trailingPunctRe.ReplaceAllString(after, "") == ""

}

func messageText(m *Message) string {

	if m == nil {

		return ""

	}

	if caption := strings.TrimSpace(m.Caption); caption != "" {

		return m.Caption

	}

	return m.Text

}