Add support for channel categories (#907)

commit a85c5814a7
Author: Christopher F <computerizedtaco@gmail.com>
Date:   Sat Jan 6 22:25:48 2018 -0500

    Code cleanup

commit 4b243fd3dd
Author: Christopher F <computerizedtaco@gmail.com>
Date:   Sat Jan 6 22:08:28 2018 -0500

    Add support for channel categories (#907)

    commit 41ed9106f2
    Author: mrspits4ever <spits.lucas@gmail.com>
    Date:   Thu Dec 14 20:02:57 2017 +0100

        removed mentioning support for RestCategoryChannel, added channels property to SocketCategoryChannel

    commit 71142c3108
    Merge: 4589d731 678a7238
    Author: mrspits4ever <spits.lucas@gmail.com>
    Date:   Wed Dec 13 21:17:53 2017 +0100

        Merge branch 'dev' of https://github.com/RogueException/Discord.Net into feature/channel-categories

    commit 4589d73187
    Author: mrspits4ever <spits.lucas@gmail.com>
    Date:   Wed Dec 13 21:17:46 2017 +0100

        adressed requested changes

    commit d59b038efa
    Author: pegasy <pegasy@users.noreply.github.com>
    Date:   Mon Sep 25 18:53:23 2017 +0200

        Renamed classes / properties / methods to use CategoryChannel instead of ChannelCategory to be consistant with how text / voice channels are named.

    commit 5c4777dc8c
    Author: pegasy <pegasy@users.noreply.github.com>
    Date:   Sun Sep 24 19:08:25 2017 +0200

        removed Guild from class name for ChannelCategory
        Renamed all properties to use Category instead of Parent
        Throw exception on GetUsers / GetInvites etc for categories

    commit e18bd8c799
    Author: pegasy <pegasy@users.noreply.github.com>
    Date:   Sun Sep 24 15:49:51 2017 +0200

        Add support for channel categories (as its own channel type)

experiment/Discord.Net.Rpc/Entities/Channels/RpcGuildChannel.cs

@@ -10,6 +10,7 @@ namespace Discord.Rpc
     {
         public ulong GuildId { get; }
         public int Position { get; private set; }
+        public ulong? CategoryId { get; private set; }
 
         internal RpcGuildChannel(DiscordRpcClient discord, ulong id, ulong guildId)
             : base(discord, id)
@@ -57,6 +58,12 @@ namespace Discord.Rpc
         public override string ToString() => Name;
 
         //IGuildChannel
+        public Task<ICategoryChannel> GetCategoryAsync()
+        {
+            //Always fails
+            throw new InvalidOperationException("Unable to return this entity's parent unless it was fetched through that object.");
+        }
+
         IGuild IGuildChannel.Guild
         {
             get

src/Discord.Net.Core/Entities/Channels/GuildChannelProperties.cs

@@ -26,5 +26,9 @@
         /// Move the channel to the following position. This is 0-based!
         /// </summary>
         public Optional<int> Position { get; set; }
+        /// <summary>
+        /// Sets the category for this channel
+        /// </summary>
+        public Optional<ulong?> CategoryId { get; set; }
     }
 }

src/Discord.Net.Core/Entities/Channels/ICategoryChannel.cs

@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord
+{
+    public interface ICategoryChannel : IGuildChannel
+    {
+    }
+}

src/Discord.Net.Core/Entities/Channels/IGuildChannel.cs

@@ -9,6 +9,10 @@ namespace Discord
         /// <summary> Gets the position of this channel in the guild's channel list, relative to others of the same type. </summary>
         int Position { get; }
 
+        /// <summary> Gets the parentid (category) of this channel in the guild's channel list. </summary>
+        ulong? CategoryId { get; }
+        /// <summary> Gets the parent channel (category) of this channel. </summary>
+        Task<ICategoryChannel> GetCategoryAsync();
         /// <summary> Gets the guild this channel is a member of. </summary>
         IGuild Guild { get; }
         /// <summary> Gets the id of the guild this channel is a member of. </summary>
@@ -23,7 +27,7 @@ namespace Discord
         Task<IInviteMetadata> CreateInviteAsync(int? maxAge = 86400, int? maxUses = default(int?), bool isTemporary = false, bool isUnique = false, RequestOptions options = null);
         /// <summary> Returns a collection of all invites to this channel. </summary>
         Task<IReadOnlyCollection<IInviteMetadata>> GetInvitesAsync(RequestOptions options = null);
-        
+
         /// <summary> Modifies this guild channel. </summary>
         Task ModifyAsync(Action<GuildChannelProperties> func, RequestOptions options = null);
 

src/Discord.Net.Core/Entities/Guilds/IGuild.cs

@@ -84,6 +84,7 @@ namespace Discord
         Task<IReadOnlyCollection<ITextChannel>> GetTextChannelsAsync(CacheMode mode = CacheMode.AllowDownload, RequestOptions options = null);
         Task<ITextChannel> GetTextChannelAsync(ulong id, CacheMode mode = CacheMode.AllowDownload, RequestOptions options = null);
         Task<IReadOnlyCollection<IVoiceChannel>> GetVoiceChannelsAsync(CacheMode mode = CacheMode.AllowDownload, RequestOptions options = null);
+        Task<IReadOnlyCollection<ICategoryChannel>> GetCategoriesAsync(CacheMode mode = CacheMode.AllowDownload, RequestOptions options = null);
         Task<IVoiceChannel> GetVoiceChannelAsync(ulong id, CacheMode mode = CacheMode.AllowDownload, RequestOptions options = null);
         Task<IVoiceChannel> GetAFKChannelAsync(CacheMode mode = CacheMode.AllowDownload, RequestOptions options = null);
         Task<ITextChannel> GetSystemChannelAsync(CacheMode mode = CacheMode.AllowDownload, RequestOptions options = null);
@@ -93,6 +94,8 @@ namespace Discord
         Task<ITextChannel> CreateTextChannelAsync(string name, RequestOptions options = null);
         /// <summary> Creates a new voice channel. </summary>
         Task<IVoiceChannel> CreateVoiceChannelAsync(string name, RequestOptions options = null);
+        /// <summary> Creates a new channel category. </summary>
+        Task<ICategoryChannel> CreateCategoryAsync(string name, RequestOptions options = null);
 
         Task<IReadOnlyCollection<IGuildIntegration>> GetIntegrationsAsync(RequestOptions options = null);
         Task<IGuildIntegration> CreateIntegrationAsync(ulong id, string type, RequestOptions options = null);

src/Discord.Net.Rest/API/Common/Channel.cs

@@ -23,6 +23,8 @@ namespace Discord.API
         public Optional<int> Position { get; set; }
         [JsonProperty("permission_overwrites")]
         public Optional<Overwrite[]> PermissionOverwrites { get; set; }
+        [JsonProperty("parent_id")]
+        public ulong? CategoryId { get; set; }
 
         //TextChannel
         [JsonProperty("topic")]

src/Discord.Net.Rest/API/Rest/ModifyGuildChannelParams.cs

@@ -10,5 +10,7 @@ namespace Discord.API.Rest
         public Optional<string> Name { get; set; }
         [JsonProperty("position")]
         public Optional<int> Position { get; set; }
+        [JsonProperty("parent_id")]
+        public Optional<ulong?> CategoryId { get; set; }
     }
 }

src/Discord.Net.Rest/Entities/Channels/ChannelHelper.cs

@@ -14,13 +14,13 @@ namespace Discord.Rest
     internal static class ChannelHelper
     {
         //General
-        public static async Task DeleteAsync(IChannel channel, BaseDiscordClient client, 
+        public static async Task DeleteAsync(IChannel channel, BaseDiscordClient client,
             RequestOptions options)
-        { 
+        {
             await client.ApiClient.DeleteChannelAsync(channel.Id, options).ConfigureAwait(false);
         }
-        public static async Task<Model> ModifyAsync(IGuildChannel channel, BaseDiscordClient client, 
-            Action<GuildChannelProperties> func, 
+        public static async Task<Model> ModifyAsync(IGuildChannel channel, BaseDiscordClient client,
+            Action<GuildChannelProperties> func,
             RequestOptions options)
         {
             var args = new GuildChannelProperties();
@@ -28,12 +28,13 @@ namespace Discord.Rest
             var apiArgs = new API.Rest.ModifyGuildChannelParams
             {
                 Name = args.Name,
-                Position = args.Position
+                Position = args.Position,
+                CategoryId = args.CategoryId
             };
             return await client.ApiClient.ModifyGuildChannelAsync(channel.Id, apiArgs, options).ConfigureAwait(false);
         }
-        public static async Task<Model> ModifyAsync(ITextChannel channel, BaseDiscordClient client, 
-            Action<TextChannelProperties> func, 
+        public static async Task<Model> ModifyAsync(ITextChannel channel, BaseDiscordClient client,
+            Action<TextChannelProperties> func,
             RequestOptions options)
         {
             var args = new TextChannelProperties();
@@ -42,13 +43,14 @@ namespace Discord.Rest
             {
                 Name = args.Name,
                 Position = args.Position,
+                CategoryId = args.CategoryId,
                 Topic = args.Topic,
                 IsNsfw = args.IsNsfw
             };
             return await client.ApiClient.ModifyGuildChannelAsync(channel.Id, apiArgs, options).ConfigureAwait(false);
         }
-        public static async Task<Model> ModifyAsync(IVoiceChannel channel, BaseDiscordClient client, 
-            Action<VoiceChannelProperties> func, 
+        public static async Task<Model> ModifyAsync(IVoiceChannel channel, BaseDiscordClient client,
+            Action<VoiceChannelProperties> func,
             RequestOptions options)
         {
             var args = new VoiceChannelProperties();
@@ -58,6 +60,7 @@ namespace Discord.Rest
                 Bitrate = args.Bitrate,
                 Name = args.Name,
                 Position = args.Position,
+                CategoryId = args.CategoryId,
                 UserLimit = args.UserLimit.IsSpecified ? (args.UserLimit.Value ?? 0) : Optional.Create<int>()
             };
             return await client.ApiClient.ModifyGuildChannelAsync(channel.Id, apiArgs, options).ConfigureAwait(false);
@@ -87,7 +90,7 @@ namespace Discord.Rest
         }
 
         //Messages
-        public static async Task<RestMessage> GetMessageAsync(IMessageChannel channel, BaseDiscordClient client, 
+        public static async Task<RestMessage> GetMessageAsync(IMessageChannel channel, BaseDiscordClient client,
             ulong id, RequestOptions options)
         {
             var guildId = (channel as IGuildChannel)?.GuildId;
@@ -98,7 +101,7 @@ namespace Discord.Rest
             var author = GetAuthor(client, guild, model.Author.Value, model.WebhookId.ToNullable());
             return RestMessage.Create(client, channel, author, model);
         }
-        public static IAsyncEnumerable<IReadOnlyCollection<RestMessage>> GetMessagesAsync(IMessageChannel channel, BaseDiscordClient client, 
+        public static IAsyncEnumerable<IReadOnlyCollection<RestMessage>> GetMessagesAsync(IMessageChannel channel, BaseDiscordClient client,
             ulong? fromMessageId, Direction dir, int limit, RequestOptions options)
         {
             if (dir == Direction.Around)
@@ -124,7 +127,7 @@ namespace Discord.Rest
                     foreach (var model in models)
                     {
                         var author = GetAuthor(client, guild, model.Author.Value, model.WebhookId.ToNullable());
-                        builder.Add(RestMessage.Create(client, channel, author, model));                        
+                        builder.Add(RestMessage.Create(client, channel, author, model));
                     }
                     return builder.ToImmutable();
                 },
@@ -180,7 +183,7 @@ namespace Discord.Rest
             var args = new UploadFileParams(stream) { Filename = filename, Content = text, IsTTS = isTTS };
             var model = await client.ApiClient.UploadFileAsync(channel.Id, args, options).ConfigureAwait(false);
             return RestUserMessage.Create(client, channel, client.CurrentUser, model);
-        }     
+        }
 
         public static async Task DeleteMessagesAsync(ITextChannel channel, BaseDiscordClient client,
             IEnumerable<ulong> messageIds, RequestOptions options)
@@ -277,7 +280,7 @@ namespace Discord.Rest
         {
             await client.ApiClient.TriggerTypingIndicatorAsync(channel.Id, options).ConfigureAwait(false);
         }
-        public static IDisposable EnterTypingState(IMessageChannel channel, BaseDiscordClient client, 
+        public static IDisposable EnterTypingState(IMessageChannel channel, BaseDiscordClient client,
             RequestOptions options)
             => new TypingNotifier(client, channel, options);
 

src/Discord.Net.Rest/Entities/Channels/ChannelType.cs

@@ -5,6 +5,7 @@
         Text = 0,
         DM = 1,
         Voice = 2,
-        Group = 3
+        Group = 3,
+        Category = 4
     }
 }

src/Discord.Net.Rest/Entities/Channels/RestCategoryChannel.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using Model = Discord.API.Channel;
+
+namespace Discord.Rest
+{
+    [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
+    public class RestCategoryChannel : RestGuildChannel, ICategoryChannel
+    {
+        internal RestCategoryChannel(BaseDiscordClient discord, IGuild guild, ulong id)
+            : base(discord, guild, id)
+        {
+        }
+        internal new static RestCategoryChannel Create(BaseDiscordClient discord, IGuild guild, Model model)
+        {
+            var entity = new RestCategoryChannel(discord, guild, model.Id);
+            entity.Update(model);
+            return entity;
+        }
+
+        private string DebuggerDisplay => $"{Name} ({Id}, Category)";
+
+        // IGuildChannel
+        IAsyncEnumerable<IReadOnlyCollection<IGuildUser>> IGuildChannel.GetUsersAsync(CacheMode mode, RequestOptions options)
+            => throw new NotSupportedException();
+        Task<IGuildUser> IGuildChannel.GetUserAsync(ulong id, CacheMode mode, RequestOptions options)
+            => throw new NotSupportedException();
+        Task<IInviteMetadata> IGuildChannel.CreateInviteAsync(int? maxAge, int? maxUses, bool isTemporary, bool isUnique, RequestOptions options)
+            => throw new NotSupportedException();
+        Task<IReadOnlyCollection<IInviteMetadata>> IGuildChannel.GetInvitesAsync(RequestOptions options)
+            => throw new NotSupportedException();
+
+        //IChannel
+        IAsyncEnumerable<IReadOnlyCollection<IUser>> IChannel.GetUsersAsync(CacheMode mode, RequestOptions options)
+            => throw new NotSupportedException();
+        Task<IUser> IChannel.GetUserAsync(ulong id, CacheMode mode, RequestOptions options)
+            => throw new NotSupportedException();
+    }
+}

src/Discord.Net.Rest/Entities/Channels/RestGuildChannel.cs

@@ -16,7 +16,7 @@ namespace Discord.Rest
         internal IGuild Guild { get; }
         public string Name { get; private set; }
         public int Position { get; private set; }
-
+        public ulong? CategoryId { get; private set; }
         public ulong GuildId => Guild.Id;
 
         internal RestGuildChannel(BaseDiscordClient discord, IGuild guild, ulong id)
@@ -32,6 +32,8 @@ namespace Discord.Rest
                     return RestTextChannel.Create(discord, guild, model);
                 case ChannelType.Voice:
                     return RestVoiceChannel.Create(discord, guild, model);
+                case ChannelType.Category:
+                    return RestCategoryChannel.Create(discord, guild, model);
                 default:
                     // TODO: Channel categories
                     return new RestGuildChannel(discord, guild, model.Id);
@@ -61,7 +63,14 @@ namespace Discord.Rest
         }
         public Task DeleteAsync(RequestOptions options = null)
             => ChannelHelper.DeleteAsync(this, Discord, options);
-        
+
+        public async Task<ICategoryChannel> GetCategoryAsync()
+        {
+            if (CategoryId.HasValue)
+                return (await Guild.GetChannelAsync(CategoryId.Value).ConfigureAwait(false)) as ICategoryChannel;
+            return null;
+        }
+
         public OverwritePermissions? GetPermissionOverwrite(IUser user)
         {
             for (int i = 0; i < _overwrites.Length; i++)
@@ -139,20 +148,20 @@ namespace Discord.Rest
             => await GetInvitesAsync(options).ConfigureAwait(false);
         async Task<IInviteMetadata> IGuildChannel.CreateInviteAsync(int? maxAge, int? maxUses, bool isTemporary, bool isUnique, RequestOptions options)
             => await CreateInviteAsync(maxAge, maxUses, isTemporary, isUnique, options).ConfigureAwait(false);
-        
-        OverwritePermissions? IGuildChannel.GetPermissionOverwrite(IRole role) 
+
+        OverwritePermissions? IGuildChannel.GetPermissionOverwrite(IRole role)
             => GetPermissionOverwrite(role);
         OverwritePermissions? IGuildChannel.GetPermissionOverwrite(IUser user)
             => GetPermissionOverwrite(user);
-        async Task IGuildChannel.AddPermissionOverwriteAsync(IRole role, OverwritePermissions permissions, RequestOptions options) 
+        async Task IGuildChannel.AddPermissionOverwriteAsync(IRole role, OverwritePermissions permissions, RequestOptions options)
             => await AddPermissionOverwriteAsync(role, permissions, options).ConfigureAwait(false);
-        async Task IGuildChannel.AddPermissionOverwriteAsync(IUser user, OverwritePermissions permissions, RequestOptions options) 
+        async Task IGuildChannel.AddPermissionOverwriteAsync(IUser user, OverwritePermissions permissions, RequestOptions options)
             => await AddPermissionOverwriteAsync(user, permissions, options).ConfigureAwait(false);
-        async Task IGuildChannel.RemovePermissionOverwriteAsync(IRole role, RequestOptions options) 
+        async Task IGuildChannel.RemovePermissionOverwriteAsync(IRole role, RequestOptions options)
             => await RemovePermissionOverwriteAsync(role, options).ConfigureAwait(false);
-        async Task IGuildChannel.RemovePermissionOverwriteAsync(IUser user, RequestOptions options) 
+        async Task IGuildChannel.RemovePermissionOverwriteAsync(IUser user, RequestOptions options)
             => await RemovePermissionOverwriteAsync(user, options).ConfigureAwait(false);
-        
+
         IAsyncEnumerable<IReadOnlyCollection<IGuildUser>> IGuildChannel.GetUsersAsync(CacheMode mode, RequestOptions options)
             => AsyncEnumerable.Empty<IReadOnlyCollection<IGuildUser>>(); //Overridden //Overridden in Text/Voice
         Task<IGuildUser> IGuildChannel.GetUserAsync(ulong id, CacheMode mode, RequestOptions options)

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -157,6 +157,15 @@ namespace Discord.Rest
             var model = await client.ApiClient.CreateGuildChannelAsync(guild.Id, args, options).ConfigureAwait(false);
             return RestVoiceChannel.Create(client, guild, model);
         }
+        public static async Task<RestCategoryChannel> CreateCategoryChannelAsync(IGuild guild, BaseDiscordClient client,
+            string name, RequestOptions options)
+        {
+            if (name == null) throw new ArgumentNullException(nameof(name));
+
+            var args = new CreateGuildChannelParams(name, ChannelType.Category);
+            var model = await client.ApiClient.CreateGuildChannelAsync(guild.Id, args, options).ConfigureAwait(false);
+            return RestCategoryChannel.Create(client, guild, model);
+        }
 
         //Integrations
         public static async Task<IReadOnlyCollection<RestGuildIntegration>> GetIntegrationsAsync(IGuild guild, BaseDiscordClient client,

src/Discord.Net.Rest/Entities/Guilds/RestGuild.cs

@@ -23,7 +23,7 @@ namespace Discord.Rest
         public VerificationLevel VerificationLevel { get; private set; }
         public MfaLevel MfaLevel { get; private set; }
         public DefaultMessageNotifications DefaultMessageNotifications { get; private set; }
-        
+
         public ulong? AFKChannelId { get; private set; }
         public ulong? EmbedChannelId { get; private set; }
         public ulong? SystemChannelId { get; private set; }
@@ -114,7 +114,7 @@ namespace Discord.Rest
             Update(model);
         }
         public async Task ModifyEmbedAsync(Action<GuildEmbedProperties> func, RequestOptions options = null)
-        { 
+        {
             var model = await GuildHelper.ModifyEmbedAsync(this, Discord, func, options).ConfigureAwait(false);
             Update(model);
         }
@@ -155,7 +155,7 @@ namespace Discord.Rest
         public Task<IReadOnlyCollection<RestGuildChannel>> GetChannelsAsync(RequestOptions options = null)
             => GuildHelper.GetChannelsAsync(this, Discord, options);
         public Task<RestGuildChannel> GetChannelAsync(ulong id, RequestOptions options = null)
-            => GuildHelper.GetChannelAsync(this, Discord, id, options);            
+            => GuildHelper.GetChannelAsync(this, Discord, id, options);
         public async Task<RestTextChannel> GetTextChannelAsync(ulong id, RequestOptions options = null)
         {
             var channel = await GuildHelper.GetChannelAsync(this, Discord, id, options).ConfigureAwait(false);
@@ -176,6 +176,11 @@ namespace Discord.Rest
             var channels = await GuildHelper.GetChannelsAsync(this, Discord, options).ConfigureAwait(false);
             return channels.Select(x => x as RestVoiceChannel).Where(x => x != null).ToImmutableArray();
         }
+        public async Task<IReadOnlyCollection<RestCategoryChannel>> GetCategoryChannelsAsync(RequestOptions options = null)
+        {
+            var channels = await GuildHelper.GetChannelsAsync(this, Discord, options).ConfigureAwait(false);
+            return channels.Select(x => x as RestCategoryChannel).Where(x => x != null).ToImmutableArray();
+        }
 
         public async Task<RestVoiceChannel> GetAFKChannelAsync(RequestOptions options = null)
         {
@@ -199,7 +204,7 @@ namespace Discord.Rest
         public async Task<RestGuildChannel> GetEmbedChannelAsync(RequestOptions options = null)
         {
             var embedId = EmbedChannelId;
-            if (embedId.HasValue) 
+            if (embedId.HasValue)
                 return await GuildHelper.GetChannelAsync(this, Discord, embedId.Value, options).ConfigureAwait(false);
             return null;
         }
@@ -217,6 +222,8 @@ namespace Discord.Rest
             => GuildHelper.CreateTextChannelAsync(this, Discord, name, options);
         public Task<RestVoiceChannel> CreateVoiceChannelAsync(string name, RequestOptions options = null)
             => GuildHelper.CreateVoiceChannelAsync(this, Discord, name, options);
+        public Task<RestCategoryChannel> CreateCategoryChannelAsync(string name, RequestOptions options = null)
+            => GuildHelper.CreateCategoryChannelAsync(this, Discord, name, options);
 
         //Integrations
         public Task<IReadOnlyCollection<RestGuildIntegration>> GetIntegrationsAsync(RequestOptions options = null)
@@ -236,7 +243,7 @@ namespace Discord.Rest
             return null;
         }
 
-        public async Task<RestRole> CreateRoleAsync(string name, GuildPermissions? permissions = default(GuildPermissions?), Color? color = default(Color?), 
+        public async Task<RestRole> CreateRoleAsync(string name, GuildPermissions? permissions = default(GuildPermissions?), Color? color = default(Color?),
             bool isHoisted = false, RequestOptions options = null)
         {
             var role = await GuildHelper.CreateRoleAsync(this, Discord, name, permissions, color, isHoisted, options).ConfigureAwait(false);
@@ -320,6 +327,13 @@ namespace Discord.Rest
             else
                 return ImmutableArray.Create<IVoiceChannel>();
         }
+        async Task<IReadOnlyCollection<ICategoryChannel>> IGuild.GetCategoriesAsync(CacheMode mode, RequestOptions options)
+        {
+            if (mode == CacheMode.AllowDownload)
+                return await GetCategoryChannelsAsync(options).ConfigureAwait(false);
+            else
+                return null;
+        }
         async Task<IVoiceChannel> IGuild.GetVoiceChannelAsync(ulong id, CacheMode mode, RequestOptions options)
         {
             if (mode == CacheMode.AllowDownload)
@@ -359,6 +373,8 @@ namespace Discord.Rest
             => await CreateTextChannelAsync(name, options).ConfigureAwait(false);
         async Task<IVoiceChannel> IGuild.CreateVoiceChannelAsync(string name, RequestOptions options)
             => await CreateVoiceChannelAsync(name, options).ConfigureAwait(false);
+        async Task<ICategoryChannel> IGuild.CreateCategoryAsync(string name, RequestOptions options)
+            => await CreateCategoryChannelAsync(name, options).ConfigureAwait(false);
 
         async Task<IReadOnlyCollection<IGuildIntegration>> IGuild.GetIntegrationsAsync(RequestOptions options)
             => await GetIntegrationsAsync(options).ConfigureAwait(false);
@@ -368,7 +384,7 @@ namespace Discord.Rest
         async Task<IReadOnlyCollection<IInviteMetadata>> IGuild.GetInvitesAsync(RequestOptions options)
             => await GetInvitesAsync(options).ConfigureAwait(false);
 
-        IRole IGuild.GetRole(ulong id) 
+        IRole IGuild.GetRole(ulong id)
             => GetRole(id);
         async Task<IRole> IGuild.CreateRoleAsync(string name, GuildPermissions? permissions, Color? color, bool isHoisted, RequestOptions options)
             => await CreateRoleAsync(name, permissions, color, isHoisted, options).ConfigureAwait(false);

src/Discord.Net.Rpc/Entities/Channels/RpcCategoryChannel.cs

@@ -0,0 +1,36 @@
+using Discord.Rest;
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using Model = Discord.API.Rpc.Channel;
+
+namespace Discord.Rpc
+{
+    [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
+    public class RpcCategoryChannel : RpcGuildChannel, ICategoryChannel
+    {
+        public IReadOnlyCollection<RpcMessage> CachedMessages { get; private set; }
+
+        public string Mention => MentionUtils.MentionChannel(Id);
+
+        internal RpcCategoryChannel(DiscordRpcClient discord, ulong id, ulong guildId)
+            : base(discord, id, guildId)
+        {
+        }
+        internal new static RpcCategoryChannel Create(DiscordRpcClient discord, Model model)
+        {
+            var entity = new RpcCategoryChannel(discord, model.Id, model.GuildId.Value);
+            entity.Update(model);
+            return entity;
+        }
+        internal override void Update(Model model)
+        {
+            base.Update(model);
+            CachedMessages = model.Messages.Select(x => RpcMessage.Create(Discord, Id, x)).ToImmutableArray();
+        }
+    }
+}

src/Discord.Net.WebSocket/Entities/Channels/SocketCategoryChannel.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Discord.Audio;
+using Discord.Rest;
+using Model = Discord.API.Channel;
+
+namespace Discord.WebSocket
+{
+    [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
+    public class SocketCategoryChannel : SocketGuildChannel, ICategoryChannel
+    {
+        public override IReadOnlyCollection<SocketGuildUser> Users
+            => Guild.Users.Where(x => x.VoiceChannel?.Id == Id).ToImmutableArray();
+
+        public IReadOnlyCollection<SocketGuildChannel> Channels
+            => Guild.Channels.Where(x => x.CategoryId == CategoryId).ToImmutableArray();
+
+        internal SocketCategoryChannel(DiscordSocketClient discord, ulong id, SocketGuild guild)
+            : base(discord, id, guild)
+        {
+        }
+        internal new static SocketCategoryChannel Create(SocketGuild guild, ClientState state, Model model)
+        {
+            var entity = new SocketCategoryChannel(guild.Discord, model.Id, guild);
+            entity.Update(state, model);
+            return entity;
+        }
+
+        private string DebuggerDisplay => $"{Name} ({Id}, Category)";
+        internal new SocketCategoryChannel Clone() => MemberwiseClone() as SocketCategoryChannel;
+
+        // IGuildChannel
+        IAsyncEnumerable<IReadOnlyCollection<IGuildUser>> IGuildChannel.GetUsersAsync(CacheMode mode, RequestOptions options)
+            => throw new NotSupportedException();
+        Task<IGuildUser> IGuildChannel.GetUserAsync(ulong id, CacheMode mode, RequestOptions options)
+            => throw new NotSupportedException();
+        Task<IInviteMetadata> IGuildChannel.CreateInviteAsync(int? maxAge, int? maxUses, bool isTemporary, bool isUnique, RequestOptions options)
+            => throw new NotSupportedException();
+        Task<IReadOnlyCollection<IInviteMetadata>> IGuildChannel.GetInvitesAsync(RequestOptions options)
+            => throw new NotSupportedException();
+
+        //IChannel
+        IAsyncEnumerable<IReadOnlyCollection<IUser>> IChannel.GetUsersAsync(CacheMode mode, RequestOptions options)
+            => throw new NotSupportedException();
+        Task<IUser> IChannel.GetUserAsync(ulong id, CacheMode mode, RequestOptions options)
+            => throw new NotSupportedException();
+    }
+}

src/Discord.Net.WebSocket/Entities/Channels/SocketGuildChannel.cs

@@ -17,6 +17,9 @@ namespace Discord.WebSocket
         public SocketGuild Guild { get; }
         public string Name { get; private set; }
         public int Position { get; private set; }
+        public ulong? CategoryId { get; private set; }
+        public ICategoryChannel Category 
+            => CategoryId.HasValue ? Guild.GetChannel(CategoryId.Value) as ICategoryChannel : null;
 
         public IReadOnlyCollection<Overwrite> PermissionOverwrites => _overwrites;
         public new virtual IReadOnlyCollection<SocketGuildUser> Users => ImmutableArray.Create<SocketGuildUser>();
@@ -34,6 +37,8 @@ namespace Discord.WebSocket
                     return SocketTextChannel.Create(guild, state, model);
                 case ChannelType.Voice:
                     return SocketVoiceChannel.Create(guild, state, model);
+                case ChannelType.Category:
+                    return SocketCategoryChannel.Create(guild, state, model);
                 default:
                     // TODO: Proper implementation for channel categories
                     return new SocketGuildChannel(guild.Discord, model.Id, guild);
@@ -43,6 +48,7 @@ namespace Discord.WebSocket
         {
             Name = model.Name.Value;
             Position = model.Position.Value;
+            CategoryId = model.CategoryId;
 
             var overwrites = model.PermissionOverwrites.Value;
             var newOverwrites = ImmutableArray.CreateBuilder<Overwrite>(overwrites.Length);
@@ -129,6 +135,9 @@ namespace Discord.WebSocket
         IGuild IGuildChannel.Guild => Guild;
         ulong IGuildChannel.GuildId => Guild.Id;
 
+        Task<ICategoryChannel> IGuildChannel.GetCategoryAsync()
+            => Task.FromResult(Category);
+
         async Task<IReadOnlyCollection<IInviteMetadata>> IGuildChannel.GetInvitesAsync(RequestOptions options)
             => await GetInvitesAsync(options).ConfigureAwait(false);
         async Task<IInviteMetadata> IGuildChannel.CreateInviteAsync(int? maxAge, int? maxUses, bool isTemporary, bool isUnique, RequestOptions options)

src/Discord.Net.WebSocket/Entities/Guilds/SocketGuild.cs

@@ -75,7 +75,7 @@ namespace Discord.WebSocket
                 return id.HasValue ? GetVoiceChannel(id.Value) : null;
             }
         }
-        public SocketGuildChannel EmbedChannel 
+        public SocketGuildChannel EmbedChannel
         {
             get
             {
@@ -95,6 +95,8 @@ namespace Discord.WebSocket
             => Channels.Select(x => x as SocketTextChannel).Where(x => x != null).ToImmutableArray();
         public IReadOnlyCollection<SocketVoiceChannel> VoiceChannels
             => Channels.Select(x => x as SocketVoiceChannel).Where(x => x != null).ToImmutableArray();
+        public IReadOnlyCollection<SocketCategoryChannel> CategoryChannels
+            => Channels.Select(x => x as SocketCategoryChannel).Where(x => x != null).ToImmutableArray();
         public SocketGuildUser CurrentUser => _members.TryGetValue(Discord.CurrentUser.Id, out SocketGuildUser member) ? member : null;
         public SocketRole EveryoneRole => GetRole(Id);
         public IReadOnlyCollection<SocketGuildChannel> Channels
@@ -317,6 +319,9 @@ namespace Discord.WebSocket
             => GuildHelper.CreateTextChannelAsync(this, Discord, name, options);
         public Task<RestVoiceChannel> CreateVoiceChannelAsync(string name, RequestOptions options = null)
             => GuildHelper.CreateVoiceChannelAsync(this, Discord, name, options);
+        public Task<RestCategoryChannel> CreateCategoryChannelAsync(string name, RequestOptions options = null)
+            => GuildHelper.CreateCategoryChannelAsync(this, Discord, name, options);
+
         internal SocketGuildChannel AddChannel(ClientState state, ChannelModel model)
         {
             var channel = SocketGuildChannel.Create(this, state, model);
@@ -348,7 +353,7 @@ namespace Discord.WebSocket
                 return value;
             return null;
         }
-        public Task<RestRole> CreateRoleAsync(string name, GuildPermissions? permissions = default(GuildPermissions?), Color? color = default(Color?), 
+        public Task<RestRole> CreateRoleAsync(string name, GuildPermissions? permissions = default(GuildPermissions?), Color? color = default(Color?),
             bool isHoisted = false, RequestOptions options = null)
             => GuildHelper.CreateRoleAsync(this, Discord, name, permissions, color, isHoisted, options);
         internal SocketRole AddRole(RoleModel model)
@@ -594,7 +599,7 @@ namespace Discord.WebSocket
             try
             {
                 await RepopulateAudioStreamsAsync().ConfigureAwait(false);
-                await _audioClient.StartAsync(url, Discord.CurrentUser.Id, voiceState.VoiceSessionId, token).ConfigureAwait(false);                
+                await _audioClient.StartAsync(url, Discord.CurrentUser.Id, voiceState.VoiceSessionId, token).ConfigureAwait(false);
             }
             catch (OperationCanceledException)
             {
@@ -651,6 +656,8 @@ namespace Discord.WebSocket
             => Task.FromResult<ITextChannel>(GetTextChannel(id));
         Task<IReadOnlyCollection<IVoiceChannel>> IGuild.GetVoiceChannelsAsync(CacheMode mode, RequestOptions options)
             => Task.FromResult<IReadOnlyCollection<IVoiceChannel>>(VoiceChannels);
+        Task<IReadOnlyCollection<ICategoryChannel>> IGuild.GetCategoriesAsync(CacheMode mode , RequestOptions options)
+            => Task.FromResult<IReadOnlyCollection<ICategoryChannel>>(CategoryChannels);
         Task<IVoiceChannel> IGuild.GetVoiceChannelAsync(ulong id, CacheMode mode, RequestOptions options)
             => Task.FromResult<IVoiceChannel>(GetVoiceChannel(id));
         Task<IVoiceChannel> IGuild.GetAFKChannelAsync(CacheMode mode, RequestOptions options)
@@ -665,6 +672,8 @@ namespace Discord.WebSocket
             => await CreateTextChannelAsync(name, options).ConfigureAwait(false);
         async Task<IVoiceChannel> IGuild.CreateVoiceChannelAsync(string name, RequestOptions options)
             => await CreateVoiceChannelAsync(name, options).ConfigureAwait(false);
+        async Task<ICategoryChannel> IGuild.CreateCategoryAsync(string name, RequestOptions options)
+            => await CreateCategoryChannelAsync(name, options).ConfigureAwait(false);
 
         async Task<IReadOnlyCollection<IGuildIntegration>> IGuild.GetIntegrationsAsync(RequestOptions options)
             => await GetIntegrationsAsync(options).ConfigureAwait(false);