Add support for channel following (#514)

lib/Constants.js

@@ -155,3 +155,9 @@ module.exports.AuditLogActions = {
 
     MESSAGE_DELETE: 72
 };
+
+module.exports.MessageFlags = {
+    CROSSPOSTED: 1 << 0,
+    IS_CROSSPOST: 1 << 1,
+    SUPPRESS_EMBEDS: 1 << 2,
+};

lib/structures/Message.js

@@ -21,6 +21,11 @@ const User = require("./User");
 * @prop {Number?} editedTimestamp Timestamp of latest message edit
 * @prop {Boolean} tts Whether to play the message using TTS or not
 * @prop {Boolean} mentionEveryone Whether the message mentions everyone/here or not
+* @prop {Object?} messageReference An object containing the reference to the original message if it is a crossposted message
+* @prop {String} messageReference.messageID The id of the original message this message was crossposted from
+* @prop {String} messageReference.channelID The id of the channel this message was crossposted from
+* @prop {String} messageReference.guildID The id of the guild this message was crossposted from
+* @prop {Number} flags Message flags (see constants) 
 * @prop {Object[]} attachments Array of attachments
 * @prop {Object[]} embeds Array of embeds
 * @prop {Object?} activity The activity specified in the message
@@ -43,6 +48,19 @@ class Message extends Base {
         this.content = "";
         this.hit = !!data.hit;
         this.reactions = {};
+
+        if (data.message_reference) {
+            this.messageReference = {
+                messageID: data.message_reference.message_id,
+                channelID: data.message_reference.channel_id,
+                guildID: data.message_reference.guild_id,
+            };
+        } else {
+            this.messageReference = null;
+        }
+
+        this.flags = data.flags || 0;
+
         if(data.author) {
             if(data.author.discriminator !== "0000") {
                 this.author = client.users.add(data.author, client);
@@ -103,7 +121,9 @@ class Message extends Base {
             data.content = `${this.author.mention} just boosted the server!`;
         } else if(this.type === 9 || this.type === 10 || this.type === 11) {
             data.content = `${this.author.mention} just boosted the server! ${this.channel.guild ? this.channel.guild.name : data.guild_id} has achieved **Level ${this.type - 8}!**`;
-        }  else {
+        } else if(this.type === 12) {
+            data.content = `${this.author.mention} has added ${data.content} to this channel`;
+        } else {
             client.emit("warn", "Unhandled MESSAGE_CREATE type: " + JSON.stringify(data, null, 2));
         }