Add delete_message_reactions + register event

Add the `delete_message_reactions` endpoint
(`DELETE /channels/{}/messages/{}/reactions`) and implement a method on
the `Message` struct for easy access, `delete_reactions`.

Register the `MESSAGE_REACTION_REMOVE_ALL` event and add an event
handler.

5 files changed, 52 insertions, 0 deletions

diff --git a/src/client/dispatch.rs b/src/client/dispatch.rs
index a629f33..875b9b3 100644
--- a/src/client/dispatch.rs
+++ b/src/client/dispatch.rs
@@ -513,6 +513,18 @@ pub fn dispatch(event: Result<Event>,
                 });
             }
         },
+        Ok(Event::ReactionRemoveAll(event)) => {
+            if let Some(ref handler) = handler!(on_reaction_remove_all, event_store) {
+                let context = context(Some(event.channel_id),
+                                      conn,
+                                      login_type);
+                let handler = handler.clone();
+
+                thread::spawn(move || {
+                    (handler)(context, event.channel_id, event.message_id);
+                });
+            }
+        },
         Ok(Event::Ready(event)) => {
             if let Some(ref handler) = handler!(on_ready, event_store) {
                 update!(update_with_ready, event);
diff --git a/src/client/event_store.rs b/src/client/event_store.rs
index 57f8dee..576fe29 100644
--- a/src/client/event_store.rs
+++ b/src/client/event_store.rs
@@ -57,6 +57,7 @@ pub struct EventStore {
     pub on_message_delete_bulk: Option<Arc<Fn(Context, ChannelId, Vec<MessageId>) + Send + Sync + 'static>>,
     pub on_reaction_add: Option<Arc<Fn(Context, Reaction) + Send + Sync + 'static>>,
     pub on_reaction_remove: Option<Arc<Fn(Context, Reaction) + Send + Sync + 'static>>,
+    pub on_reaction_remove_all: Option<Arc<Fn(Context, ChannelId, MessageId) + Send + Sync + 'static>>,
     pub on_message_update: Option<Arc<Fn(Context, MessageUpdateEvent) + Send + Sync + 'static>>,
     pub on_note_update: Option<Arc<Fn(Context, UserId, String) + Send + Sync + 'static>>,
     pub on_presence_replace: Option<Arc<Fn(Context, Vec<Presence>) + Send + Sync + 'static>>,
diff --git a/src/client/http/mod.rs b/src/client/http/mod.rs
index fa7e874..94fccce 100644
--- a/src/client/http/mod.rs
+++ b/src/client/http/mod.rs
@@ -282,6 +282,34 @@ pub fn delete_messages(channel_id: u64, map: Value) -> Result<()> {
                          channel_id))
 }
 
+/// Delete all of the [`Reaction`]s associated with a [`Message`].
+///
+/// # Examples
+///
+/// ```rust,no_run
+/// use serenity::client::http;
+/// use serenity::model::{ChannelId, MessageId};
+///
+/// let channel_id = ChannelId(7);
+/// let message_id = MessageId(8);
+///
+/// match http::delete_message_reactions(channel_id.0, message_id.0) {
+///     Ok(()) => println!("Reactions deleted"),
+///     Err(why) => println!("Error deleting reactions: {:?}", why),
+/// }
+/// ```
+///
+/// [`Message`]: ../../model/struct.Message.html
+/// [`Reaction`]: ../../model/struct.Reaction.html
+pub fn delete_message_reactions(channel_id: u64, message_id: u64)
+    -> Result<()> {
+    verify(204, request!(Route::ChannelsIdMessagesIdReactions(channel_id),
+                         delete,
+                         "/channels/{}/messages/{}/reactions",
+                         channel_id,
+                         message_id))
+}
+
 pub fn delete_permission(channel_id: u64, target_id: u64)
     -> Result<()> {
     verify(204, request!(Route::ChannelsIdPermissionsOverwriteId(channel_id),
diff --git a/src/client/http/ratelimiting.rs b/src/client/http/ratelimiting.rs
index 9928535..0302a7d 100644
--- a/src/client/http/ratelimiting.rs
+++ b/src/client/http/ratelimiting.rs
@@ -62,6 +62,7 @@ pub enum Route {
     ChannelsIdMessagesBulkDelete(u64),
     ChannelsIdMessagesId(u64),
     ChannelsIdMessagesIdAck(u64),
+    ChannelsIdMessagesIdReactions(u64),
     ChannelsIdMessagesIdReactionsUserIdType(u64),
     ChannelsIdPermissionsOverwriteId(u64),
     ChannelsIdPins(u64),
diff --git a/src/client/mod.rs b/src/client/mod.rs
index 77ec3e1..4db7a4e 100644
--- a/src/client/mod.rs
+++ b/src/client/mod.rs
@@ -713,6 +713,16 @@ impl Client {
             .on_reaction_remove = Some(Arc::new(handler))
     }
 
+    /// Attached a handler for when a [`ReactionRemoveAll`] is received.
+    ///
+    /// [`ReactionRemoveAll`]: ../model/enum.Event.html#variant.ReactionRemoveAll
+    pub fn on_reaction_remove_all<F>(&mut self, handler: F)
+        where F: Fn(Context, ChannelId, MessageId) + Send + Sync + 'static {
+        self.event_store.lock()
+            .unwrap()
+            .on_reaction_remove_all = Some(Arc::new(handler))
+    }
+
     /// Register an event to be called whenever a Ready event is received.
     ///
     /// Registering a handler for the ready event is good for noting when your