[LLC -> Channel] Segregate sendMessage api call and state handling

Signed-off-by: Sahil Kumar <[email protected]>

packages/stream_chat/lib/src/api/channel.dart

@@ -338,18 +338,9 @@ class Channel {
         message = await attachmentsUploadCompleter.future;
       }
 
-      final response = await _client.post(
-        '$_channelURL/message',
-        data: {
-          'message': message.toJson(),
-        },
-      );
-
-      final res = _client.decode(response.data, SendMessageResponse.fromJson);
-
-      state?.addMessage(res.message);
-
-      return res;
+      final response = await _client.sendMessage(message, id, type);
+      state?.addMessage(response.message);
+      return response;
     } catch (error) {
       if (error is DioError && error.type != DioErrorType.RESPONSE) {
         state?.retryQueue?.add([message]);

packages/stream_chat/lib/src/client.dart

@@ -1246,6 +1246,16 @@ class StreamChatClient {
     return decode(response.data, EmptyResponse.fromJson);
   }
 
+  /// Sends the message to the given channel
+  Future<SendMessageResponse> sendMessage(
+      Message message, String channelId, String channelType) async {
+    final response = await post(
+      '/channels/$channelType/$channelId/message',
+      data: {'message': message},
+    );
+    return decode(response.data, SendMessageResponse.fromJson);
+  }
+
   /// Update the given message
   Future<UpdateMessageResponse> updateMessage(Message message) async {
     final response = await post(