Add message reaction collectors & abstract collectors (#1335)

* message reaction collectors

* docs cleanup

* abstraction

* remove pointless method

* rename reaction collector creator method

* docs and stuff

* fix docs & build

* backwards compatibility, fix docs

* fix docs

* remove deprecated comments

* betterer docs again

* Fix documentation

* Fix Alias to not break depreciated code

src/structures/Message.js

@@ -2,6 +2,7 @@ const Mentions = require('./MessageMentions');
 const Attachment = require('./MessageAttachment');
 const Embed = require('./MessageEmbed');
 const MessageReaction = require('./MessageReaction');
+const ReactionCollector = require('./ReactionCollector');
 const Util = require('../util/Util');
 const Collection = require('../util/Collection');
 const Constants = require('../util/Constants');
@@ -245,6 +246,47 @@ class Message {
       });
   }
 
+  /**
+   * Creates a reaction collector.
+   * @param {CollectorFilter} filter The filter to apply.
+   * @param {ReactionCollectorOptions} [options={}] Options to send to the collector.
+   * @returns {ReactionCollector}
+   * @example
+   * // create a reaction collector
+   * const collector = message.createReactionCollector(
+   *  (reaction, user) => reaction.emoji.id === '👌' && user.id === 'someID',
+   *  { time: 15000 }
+   * );
+   * collector.on('collect', r => console.log(`Collected ${r.emoji.name}`));
+   * collector.on('end', collected => console.log(`Collected ${collected.size} items`));
+   */
+  createReactionCollector(filter, options = {}) {
+    return new ReactionCollector(this, filter, options);
+  }
+
+  /**
+   * An object containing the same properties as CollectorOptions, but a few more:
+   * @typedef {ReactionCollectorOptions} AwaitReactionsOptions
+   * @property {string[]} [errors] Stop/end reasons that cause the promise to reject
+   */
+
+  /**
+   * Similar to createCollector but in promise form. Resolves with a collection of reactions that pass the specified
+   * filter.
+   * @param {CollectorFilter} filter The filter function to use
+   * @param {AwaitReactionsOptions} [options={}] Optional options to pass to the internal collector
+   * @returns {Promise<Collection<string, MessageReaction>>}
+   */
+  awaitReactions(filter, options = {}) {
+    return new Promise((resolve, reject) => {
+      const collector = this.createReactionCollector(filter, options);
+      collector.once('end', (reactions, reason) => {
+        if (options.errors && options.errors.includes(reason)) reject(reactions);
+        else resolve(reactions);
+      });
+    });
+  }
+
   /**
    * An array of cached versions of the message, including the current version.
    * Sorted from latest (first) to oldest (last).