Add reaction fetching of users

src/client/rest/RESTMethods.js

@@ -751,6 +751,13 @@ class RESTMethods {
         .catch(reject);
     });
   }
+
+  getMessageReactionUsers(channelID, messageID, emoji, limit = 100) {
+    return new Promise((resolve, reject) => {
+      this.rest.makeRequest('get', Constants.Endpoints.messageReaction(channelID, messageID, emoji, limit), true)
+        .then(resolve, reject);
+    });
+  }
 }
 
 module.exports = RESTMethods;

src/structures/MessageReaction.js

@@ -108,6 +108,28 @@ class MessageReaction {
     const message = this.message;
     return message.client.rest.methods.removeMessageReaction(message.channel.id, message.id, this.emoji.identifier);
   }
+
+  /**
+   * Fetch all the users that gave this reaction. Resolves with a collection of users,
+   * mapped by their IDs.
+   * @returns {Promise<Collection<string, User>>}
+   */
+  fetchUsers() {
+    const message = this.message;
+    return new Promise((resolve, reject) => {
+      message.client.rest.methods.getMessageReactionUsers(message.channel.id, message.id, this.emoji.identifier)
+      .then(users => {
+        this.users = new Collection();
+        for (const rawUser of users) {
+          const user = this.message.client.dataManager.newUser(rawUser);
+          this.users.set(user.id, user);
+        }
+        this.count = this.users.size;
+        resolve(this.users);
+      })
+      .catch(reject);
+    });
+  }
 }
 
 module.exports = MessageReaction;

test/random.js

@@ -187,3 +187,19 @@ client.on('messageReactionRemove', (reaction, user) => {
   if (reaction.message.channel.id !== '222086648706498562') return;
   reaction.message.channel.sendMessage(`${user.username} removed reaction ${reaction.emoji}, count is now ${reaction.count}`);
 });
+
+client.on('message', m => {
+  if (m.content.startsWith('#reactions')) {
+    const mID = m.content.split(' ')[1];
+    m.channel.fetchMessage(mID).then(rM => {
+      for (const reaction of rM.reactions.values()) {
+        reaction.fetchUsers().then(users => {
+          m.channel.sendMessage(
+            `The following gave that message ${reaction.emoji}:\n` +
+            `${users.map(u => u.username).map(t => `- ${t}`).join('\n')}`
+          );
+        });
+      }
+    });
+  }
+});