Implement robust history fetching

telegram/commands.go

@@ -988,24 +988,32 @@ func (c *Client) ProcessChatCommand(chatID int64, cmdline string) (string, bool)
 			}
 		}
 
-		var messages *client.Messages
+		var newMessages *client.Messages
+		var messages []*client.Message
 		var err error
-		for _ = range make([]struct{}, 2) {
+		var fromId int64
-			messages, err = c.client.GetChatHistory(&client.GetChatHistoryRequest{
+		for _ = range make([]struct{}, limit) { // safety limit
-				ChatId: chatID,
+			if len(messages) > 0 {
-				Limit:  limit,
+				fromId = messages[len(messages)-1].Id
+			}
+
+			newMessages, err = c.client.GetChatHistory(&client.GetChatHistoryRequest{
+				ChatId:        chatID,
+				FromMessageId: fromId,
+				Limit:         limit,
 			})
 			if err != nil {
 				return err.Error(), true
 			}
 
-			// TDlib yields only the latest message on the first request
+			messages = append(messages, newMessages.Messages...)
-			if !(len(messages.Messages) == 1 && limit > 1) {
+
+			if len(newMessages.Messages) == 0 || len(messages) >= int(limit) {
 				break
 			}
 		}
 
-		c.sendMessagesReverse(chatID, messages.Messages)
+		c.sendMessagesReverse(chatID, messages)
 	// chat members
 	case "members":
 		var query string