backfill: add support for forward backfilling more than 100 messages

pkg/connector/backfill.go

@@ -153,56 +153,91 @@ func (tc *TelegramClient) FetchMessages(ctx context.Context, fetchParams bridgev
 	if fetchParams.Portal.Metadata.(*PortalMetadata).IsForumGeneral {
 		topicID = 1
 	}
-	var req bin.Object
 	if topicID == ids.TopicIDSpaceRoom {
 		return nil, nil
-	} else if topicID > 0 {
-		req = &tg.MessagesGetRepliesRequest{
-			Peer:     peer,
-			MsgID:    topicID,
-			Limit:    fetchParams.Count,
-			MinID:    minID,
-			OffsetID: offsetID,
-		}
-	} else {
-		req = &tg.MessagesGetHistoryRequest{
-			Peer:     peer,
-			Limit:    fetchParams.Count,
-			MinID:    minID,
-			OffsetID: offsetID,
-		}
 	}
-	if takeoutID != 0 {
-		req = &tg.InvokeWithTakeoutRequest{TakeoutID: takeoutID, Query: req}
-	}
-	log.Info().Any("req", req).Msg("Fetching messages")
-	msgs, err := APICallWithUpdates(ctx, tc, func() (tg.ModifiedMessagesMessages, error) {
-		var box tg.MessagesMessagesBox
-		// TODO a single request can only fetch 100 messages, use multiple requests if the requested count is higher
-		err = tc.client.Invoke(ctx, req, &box)
-		if err != nil {
-			return nil, err
-		}
-		msgs, ok := box.Messages.(tg.ModifiedMessagesMessages)
-		if !ok {
-			return nil, fmt.Errorf("unsupported messages type %T", box.Messages)
-		}
-		return msgs, nil
-	})
-	if err != nil {
-		if tgerr.Is(err, tg.ErrTakeoutInvalid) {
-			tc.metadata.TakeoutID = 0
-			err := tc.userLogin.Save(ctx)
-			if err != nil {
-				log.Err(err).Msg("Failed to save user login after clearing takeout ID")
-			} else {
-				log.Debug().Msg("Cleared invalid takeout ID")
+	limit := fetchParams.Count
+	const chunkLimit = 100
+	makeReq := func() bin.Object {
+		if topicID > 0 {
+			return &tg.MessagesGetRepliesRequest{
+				Peer:     peer,
+				MsgID:    topicID,
+				Limit:    min(limit, chunkLimit),
+				MinID:    minID,
+				OffsetID: offsetID,
+			}
+		}
+		return &tg.MessagesGetHistoryRequest{
+			Peer:     peer,
+			Limit:    min(limit, chunkLimit),
+			MinID:    minID,
+			OffsetID: offsetID,
+		}
+	}
+	var messages []tg.MessageClass
+	requestCount := 0
+	for limit > 0 {
+		requestCount++
+		req := makeReq()
+		if takeoutID != 0 {
+			req = &tg.InvokeWithTakeoutRequest{TakeoutID: takeoutID, Query: req}
+		}
+		log.Info().Any("req", req).Msg("Fetching messages")
+		resp, err := APICallWithUpdates(ctx, tc, func() (tg.ModifiedMessagesMessages, error) {
+			var box tg.MessagesMessagesBox
+			retry := true
+			attempts := 0
+			var err error
+			for retry && attempts < 5 {
+				retry, err = tgerr.FloodWait(ctx, tc.client.Invoke(ctx, req, &box))
+				attempts++
+			}
+			if err != nil {
+				return nil, err
+			}
+			msgs, ok := box.Messages.(tg.ModifiedMessagesMessages)
+			if !ok {
+				return nil, fmt.Errorf("unsupported messages type %T", box.Messages)
+			}
+			return msgs, nil
+		})
+		if err != nil {
+			if tgerr.Is(err, tg.ErrTakeoutInvalid) {
+				tc.metadata.TakeoutID = 0
+				err := tc.userLogin.Save(ctx)
+				if err != nil {
+					log.Err(err).Msg("Failed to save user login after clearing takeout ID")
+				} else {
+					log.Debug().Msg("Cleared invalid takeout ID")
+				}
+			}
+			return nil, err
+		}
+		newMessages := resp.GetMessages()
+		if messages == nil {
+			messages = newMessages
+		} else {
+			messages = append(messages, resp.GetMessages()...)
+		}
+		if len(newMessages) < chunkLimit || !fetchParams.Forward {
+			break
+		}
+		limit -= len(newMessages)
+		offsetID = newMessages[len(newMessages)-1].GetID()
+		if takeoutID == 0 {
+			waitTime := time.Duration(min(requestCount*2, 15)) * time.Second
+			log.Debug().
+				Dur("wait_time", waitTime).
+				Msg("Not using takeout, waiting before requesting another batch of messages")
+			select {
+			case <-time.After(waitTime):
+			case <-ctx.Done():
+				return nil, ctx.Err()
 			}
 		}
-		return nil, err
 	}
 
-	messages := msgs.GetMessages()
 	portal := fetchParams.Portal
 
 	// If the first message is the last read message, mark the chat as read