Add interface type to channel types (#2567)

src/main/java/net/dv8tion/jda/api/entities/channel/ChannelType.java

@@ -28,69 +28,82 @@ public enum ChannelType
     /**
      * A {@link TextChannel TextChannel}, Guild-Only.
      */
-    TEXT(0, 0, true),
+    TEXT(TextChannel.class, 0, 0, true),
     /**
      * A {@link PrivateChannel PrivateChannel}.
      */
-    PRIVATE(1, -1),
+    PRIVATE(PrivateChannel.class, 1, -1),
     /**
      * A {@link VoiceChannel VoiceChannel}, Guild-Only.
      */
-    VOICE(2, 1, true),
+    VOICE(VoiceChannel.class, 2, 1, true),
     /**
      * A Group. (unused)
      */
-    GROUP(3, -1),
+    GROUP(GroupChannel.class, 3, -1),
     /**
      * A {@link Category Category}, Guild-Only.
      */
-    CATEGORY(4, 2, true),
+    CATEGORY(Category.class, 4, 2, true),
     /**
      * A {@link NewsChannel NewsChannel}, Guild-Only.
      */
-    NEWS(5, 0, true),
+    NEWS(NewsChannel.class, 5, 0, true),
     /**
      * A {@link StageChannel StageChannel}, Guild-Only.
      */
-    STAGE(13, 1, true),
+    STAGE(StageChannel.class, 13, 1, true),
 
-    GUILD_NEWS_THREAD(10, -1, true),
-    GUILD_PUBLIC_THREAD(11, -1, true),
-    GUILD_PRIVATE_THREAD(12, -1, true),
+    GUILD_NEWS_THREAD(ThreadChannel.class, 10, -1, true),
+    GUILD_PUBLIC_THREAD(ThreadChannel.class, 11, -1, true),
+    GUILD_PRIVATE_THREAD(ThreadChannel.class, 12, -1, true),
 
     /**
      * A {@link net.dv8tion.jda.api.entities.channel.concrete.ForumChannel ForumChannel}, Guild-Only.
      */
-    FORUM(15, 0, true),
+    FORUM(ForumChannel.class, 15, 0, true),
 
     /**
      * A {@link MediaChannel}, Guild-Only.
      */
-    MEDIA(16, 0, true),
+    MEDIA(MediaChannel.class, 16, 0, true),
 
     /**
      * Unknown Discord channel type.
      *
      * <p>This might be used in the case when a channel is not available in cache, like when sending webhook messages.
      */
-    UNKNOWN(-1, -2);
+    UNKNOWN(Channel.class, -1, -2);
 
     private final int sortBucket;
     private final int id;
     private final boolean isGuild;
+    private final Class<? extends Channel> clazz;
 
-    ChannelType(int id, int sortBucket)
+    ChannelType(Class<? extends Channel> clazz, int id, int sortBucket)
     {
-        this(id, sortBucket, false);
+        this(clazz, id, sortBucket, false);
     }
 
-    ChannelType(int id, int sortBucket, boolean isGuild)
+    ChannelType(Class<? extends Channel> clazz, int id, int sortBucket, boolean isGuild)
     {
+        this.clazz = clazz;
         this.id = id;
         this.sortBucket = sortBucket;
         this.isGuild = isGuild;
     }
 
+    /**
+     * The interface this channel type corresponds to.
+     *
+     * @return This channel type's interface
+     */
+    @Nonnull
+    public Class<? extends Channel> getInterface()
+    {
+        return this.clazz;
+    }
+
     /**
      * The sorting bucket for this channel type.
      *

src/main/java/net/dv8tion/jda/api/entities/channel/concrete/GroupChannel.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2015 Austin Keener, Michael Ritter, Florian Spieß, and the JDA contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.dv8tion.jda.api.entities.channel.concrete;
+
+import net.dv8tion.jda.api.entities.channel.middleman.MessageChannel;
+
+/**
+ * Represents a Group DM channel.
+ *
+ * <p><b>This is currently unused.</b>
+ */
+public interface GroupChannel extends MessageChannel
+{
+}