Support "MESSAGE_REACTION_REMOVE_ALL" dispatch

src/Discord.Net.WebSocket/API/Gateway/RemoveAllReactionsEvent.cs

@@ -0,0 +1,12 @@
+using Newtonsoft.Json;
+
+namespace Discord.API.Gateway
+{
+    public class RemoveAllReactionsEvent
+    {
+        [JsonProperty("channel_id")]
+        public ulong ChannelId { get; set; }
+        [JsonProperty("message_id")]
+        public ulong MessageId { get; set; }
+    }
+}

src/Discord.Net.WebSocket/DiscordSocketClient.Events.cs

@@ -83,6 +83,12 @@ namespace Discord.WebSocket
             remove { _reactionRemovedEvent.Remove(value); }
         }
         private readonly AsyncEvent<Func<ulong, Optional<SocketUserMessage>, SocketReaction, Task>> _reactionRemovedEvent = new AsyncEvent<Func<ulong, Optional<SocketUserMessage>, SocketReaction, Task>>();
+        public event Func<ulong, Optional<SocketUserMessage>, Task> ReactionsCleared
+        {
+            add { _reactionsClearedEvent.Add(value); }
+            remove { _reactionsClearedEvent.Remove(value); }
+        }
+        private readonly AsyncEvent<Func<ulong, Optional<SocketUserMessage>, Task>> _reactionsClearedEvent = new AsyncEvent<Func<ulong, Optional<SocketUserMessage>, Task>>();
 
         //Roles
         public event Func<SocketRole, Task> RoleCreated

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -1306,7 +1306,7 @@ namespace Discord.WebSocket
                                 break;
                             case "MESSAGE_REACTION_ADD":
                                 {
-                                    await _gatewayLogger.DebugAsync("Received Disbatch (MESSAGE_REACTION_ADD)").ConfigureAwait(false);
+                                    await _gatewayLogger.DebugAsync("Received Dispatch (MESSAGE_REACTION_ADD)").ConfigureAwait(false);
 
                                     var data = (payload as JToken).ToObject<GatewayReaction>(_serializer);
                                     var channel = State.GetChannel(data.ChannelId) as ISocketMessageChannel;
@@ -1333,7 +1333,7 @@ namespace Discord.WebSocket
                                 }
                             case "MESSAGE_REACTION_REMOVE":
                                 {
-                                    await _gatewayLogger.DebugAsync("Received Disbatch (MESSAGE_REACTION_REMOVE)").ConfigureAwait(false);
+                                    await _gatewayLogger.DebugAsync("Received Dispatch (MESSAGE_REACTION_REMOVE)").ConfigureAwait(false);
 
                                     var data = (payload as JToken).ToObject<GatewayReaction>(_serializer);
                                     var channel = State.GetChannel(data.ChannelId) as ISocketMessageChannel;
@@ -1355,6 +1355,31 @@ namespace Discord.WebSocket
                                         await _gatewayLogger.WarningAsync("MESSAGE_REACTION_REMOVE referenced an unknown channel.").ConfigureAwait(false);
                                         return;
                                     }
+                                    break;
+                                }
+                            case "MESSAGE_REACTION_REMOVE_ALL":
+                                {
+                                    await _gatewayLogger.DebugAsync("Received Dispatch (MESSAGE_REACTION_REMOVE_ALL)").ConfigureAwait(false);
+
+                                    var data = (payload as JToken).ToObject<RemoveAllReactionsEvent>(_serializer);
+                                    var channel = State.GetChannel(data.ChannelId) as ISocketMessageChannel;
+                                    if (channel != null)
+                                    {
+                                        SocketUserMessage cachedMsg = channel.GetCachedMessage(data.MessageId) as SocketUserMessage;
+                                        if (cachedMsg != null)
+                                        {
+                                            cachedMsg.ClearReactions();
+                                            await _reactionsClearedEvent.InvokeAsync(data.MessageId, cachedMsg).ConfigureAwait(false);
+                                            return;
+                                        }
+                                        await _reactionsClearedEvent.InvokeAsync(data.MessageId, Optional.Create<SocketUserMessage>());
+                                    }
+                                    else
+                                    {
+                                        await _gatewayLogger.WarningAsync("MESSAGE_REACTION_REMOVE_ALL referenced an unknown channel.").ConfigureAwait(false);
+                                        return;
+                                    }
+
                                     break;
                                 }
                             case "MESSAGE_DELETE_BULK":

src/Discord.Net.WebSocket/Entities/Messages/SocketUserMessage.cs

@@ -122,6 +122,10 @@ namespace Discord.WebSocket
             if (_reactions.Contains(reaction))
                 _reactions.Remove(reaction);
         }
+        internal void ClearReactions()
+        {
+            _reactions.Clear();
+        }
 
         public Task ModifyAsync(Action<ModifyMessageParams> func, RequestOptions options = null)
             => MessageHelper.ModifyAsync(this, Discord, func, options);