initial implementation

src/Discord.Net.Core/DiscordConfig.cs

@@ -132,6 +132,16 @@ namespace Discord
         /// </returns>
         public const int MaxAuditLogEntriesPerBatch = 100;
 
+        /// <summary>
+        ///     Returns the max number of stickers that can be sent on a message.
+        /// </summary>
+        public const int MaxStickersPerMessage = 3;
+
+        /// <summary>
+        ///     Returns the max number of embeds that can be sent on a message.
+        /// </summary>
+        public const int MaxEmbedsPerMessage = 10;
+
         /// <summary>
         ///     Gets or sets how a request should act in the case of an error, by default.
         /// </summary>

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

@@ -26,6 +26,8 @@ namespace Discord
         /// <summary> The channel is a stage voice channel. </summary>
         Stage = 13,
         /// <summary> The channel is a guild directory used in hub servers. (Unreleased)</summary>
-        GuildDirectory = 14
+        GuildDirectory = 14,
+        /// <summary> The channel is a forum channel containing multiple threads. </summary>
+        Forum = 15
     }
 }

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

@@ -0,0 +1,101 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord
+{
+    public interface IForumChannel : IGuildChannel, IMentionable
+    {
+        /// <summary>
+        ///     Gets a value that indicates whether the channel is NSFW.
+        /// </summary>
+        /// <returns>
+        ///     <c>true</c> if the channel has the NSFW flag enabled; otherwise <c>false</c>.
+        /// </returns>
+        bool IsNsfw { get; }
+
+        /// <summary>
+        ///     Gets the current topic for this text channel.
+        /// </summary>
+        /// <returns>
+        ///     A string representing the topic set in the channel; <c>null</c> if none is set.
+        /// </returns>
+        string Topic { get; }
+
+        /// <summary>
+        ///     Gets the default archive duration for a newly created post.
+        /// </summary>
+        ThreadArchiveDuration DefaultAutoArchiveDuration { get; }
+
+        /// <summary>
+        ///     Gets a collection of tags inside of this forum channel.
+        /// </summary>
+        IReadOnlyCollection<ForumTag> Tags { get; }
+
+        /// <summary>
+        ///     Creates a new post (thread) within the forum.
+        /// </summary>
+        /// <param name="title">The title of the post.</param>
+        /// <param name="archiveDuration">The archive duration of the post.</param>
+        /// <param name="message">
+        ///     The starting message of the post. The content of the message supports full markdown.
+        /// </param>
+        /// <param name="slowmode">The slowmode for the posts thread.</param>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents the asynchronous creation operation.
+        /// </returns>
+        Task<IThreadChannel> CreatePostAsync(string title, ThreadArchiveDuration archiveDuration, Message message, int? slowmode = null, RequestOptions options = null);
+
+        /// <summary>
+        ///     Gets a collection of active threads within this forum channel.
+        /// </summary>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents an asynchronous get operation for retrieving the threads. The task result contains
+        ///     a collection of active threads.
+        /// </returns>
+        Task<IReadOnlyCollection<IThreadChannel>> GetActiveThreadsAsync(RequestOptions options = null);
+
+        /// <summary>
+        ///     Gets a collection of publicly archived threads within this forum channel.
+        /// </summary>
+        /// <param name="limit">The optional limit of how many to get.</param>
+        /// <param name="before">The optional date to return threads created before this timestamp.</param>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents an asynchronous get operation for retrieving the threads. The task result contains
+        ///     a collection of publicly archived threads.
+        /// </returns>
+        Task<IReadOnlyCollection<IThreadChannel>> GetPublicArchivedThreadsAsync(int? limit = null, DateTimeOffset? before = null, RequestOptions options = null);
+
+        /// <summary>
+        ///     Gets a collection of privatly archived threads within this forum channel.
+        /// </summary>
+        /// <remarks>
+        ///     The bot requires the <see cref="GuildPermission.ManageThreads"/> permission in order to execute this request.
+        /// </remarks>
+        /// <param name="limit">The optional limit of how many to get.</param>
+        /// <param name="before">The optional date to return threads created before this timestamp.</param>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents an asynchronous get operation for retrieving the threads. The task result contains
+        ///     a collection of privatly archived threads.
+        /// </returns>
+        Task<IReadOnlyCollection<IThreadChannel>> GetPrivateArchivedThreadsAsync(int? limit = null, DateTimeOffset? before = null, RequestOptions options = null);
+
+        /// <summary>
+        ///     Gets a collection of privatly archived threads that the current bot has joined within this forum channel.
+        /// </summary>
+        /// <param name="limit">The optional limit of how many to get.</param>
+        /// <param name="before">The optional date to return threads created before this timestamp.</param>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents an asynchronous get operation for retrieving the threads. The task result contains
+        ///     a collection of privatly archived threads.
+        /// </returns>
+        Task<IReadOnlyCollection<IThreadChannel>> GetJoinedPrivateArchivedThreadsAsync(int? limit = null, DateTimeOffset? before = null, RequestOptions options = null);
+    }
+}

src/Discord.Net.Core/Entities/ForumTag.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord
+{
+    /// <summary>
+    ///     A struct representing a forum channel tag.
+    /// </summary>
+    public struct ForumTag
+    {
+        /// <summary>
+        ///     Gets the Id of the tag.
+        /// </summary>
+        public ulong Id { get; }
+
+        /// <summary>
+        ///     Gets the name of the tag.
+        /// </summary>
+        public string Name { get; }
+
+        /// <summary>
+        ///     Gets the emoji of the tag or <see langword="null"/> if none is set.
+        /// </summary>
+        public IEmote Emoji { get; }
+
+        internal ForumTag(ulong id, string name, ulong? emojiId, string emojiName)
+        {
+            if (emojiId.HasValue && emojiId.Value != 0)
+                Emoji = new Emote(emojiId.Value, emojiName, false);
+            else if (emojiName != null)
+                Emoji = new Emoji(name);
+            else
+                Emoji = null;
+
+            Id = id;
+            Name = name;
+        }
+    }
+}

src/Discord.Net.Core/Entities/Messages/Message.cs

@@ -0,0 +1,74 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord
+{
+    /// <summary>
+    ///     Represents a message created by a <see cref="MessageBuilder"/> that can be sent to a channel. 
+    /// </summary>
+    public sealed class Message
+    {
+        /// <summary>
+        ///     Gets the content of the message.
+        /// </summary>
+        public string Content { get; }
+
+        /// <summary>
+        ///     Gets whether or not this message should be read by a text-to-speech engine.
+        /// </summary>
+        public bool IsTTS { get; }
+
+        /// <summary>
+        ///     Gets a collection of embeds sent along with this message.
+        /// </summary>
+        public IReadOnlyCollection<Embed> Embeds { get; }
+
+        /// <summary>
+        ///     Gets the allowed mentions for this message.
+        /// </summary>
+        public AllowedMentions AllowedMentions { get; }
+
+        /// <summary>
+        ///     Gets the message reference (reply to) for this message.
+        /// </summary>
+        public MessageReference MessageReference { get; }
+
+        /// <summary>
+        ///     Gets the components of this message.
+        /// </summary>
+        public MessageComponent Components { get; }
+
+        /// <summary>
+        ///     Gets a collection of sticker ids that will be sent with this message.
+        /// </summary>
+        public IReadOnlyCollection<ulong> StickerIds { get; }
+
+        /// <summary>
+        ///     Gets a collection of files sent with this message.
+        /// </summary>
+        public IReadOnlyCollection<FileAttachment> Attachments { get; }
+
+        /// <summary>
+        ///     Gets the message flags for this message.
+        /// </summary>
+        public MessageFlags Flags { get; }
+
+        internal Message(string content, bool istts, IReadOnlyCollection<Embed> embeds, AllowedMentions allowedMentions,
+            MessageReference messagereference, MessageComponent components, IReadOnlyCollection<ulong> stickerIds,
+            IReadOnlyCollection<FileAttachment> attachments, MessageFlags flags)
+        {
+            Content = content;
+            IsTTS = istts;
+            Embeds = embeds;
+            AllowedMentions = allowedMentions;
+            MessageReference = messagereference;
+            Components = components;
+            StickerIds = stickerIds;
+            Attachments = attachments;
+            Flags = flags;
+        }
+    }
+}

src/Discord.Net.Core/Entities/Messages/MessageBuilder.cs

@@ -0,0 +1,220 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord
+{
+    /// <summary>
+    ///     Represents a generic message builder that can build <see cref="Message"/>s.
+    /// </summary>
+    public class MessageBuilder
+    {
+        private string _content;
+        private List<ISticker> _stickers;
+        private List<EmbedBuilder> _embeds;
+
+        /// <summary>
+        ///     Gets or sets the content of this message
+        /// </summary>
+        /// <exception cref="ArgumentOutOfRangeException">The content is bigger than the <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
+        public string Content
+        {
+            get => _content;
+            set
+            {
+                if (_content?.Length > DiscordConfig.MaxMessageSize)
+                    throw new ArgumentOutOfRangeException(nameof(value), $"Message size must be less than or equal to {DiscordConfig.MaxMessageSize} characters");
+
+                _content = value;
+            }
+        }
+
+        /// <summary>
+        ///     Gets or sets whether or not this message is TTS.
+        /// </summary>
+        public bool IsTTS { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the embeds of this message.
+        /// </summary>
+        public List<EmbedBuilder> Embeds
+        {
+            get
+            {
+                if (_embeds == null)
+                    _embeds = new();
+                return _embeds;
+            }
+            set
+            {
+                if (value?.Count > DiscordConfig.MaxEmbedsPerMessage)
+                    throw new ArgumentOutOfRangeException(nameof(value), $"Embed count must be less than or equal to {DiscordConfig.MaxEmbedsPerMessage}");
+
+                _embeds = value;
+            }
+        }
+
+        /// <summary>
+        ///     Gets or sets the allowed mentions of this message.
+        /// </summary>
+        public AllowedMentions AllowedMentions { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the message reference (reply to) of this message.
+        /// </summary>
+        public MessageReference MessageReference { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the components of this message.
+        /// </summary>
+        public ComponentBuilder Components { get; set; } = new();
+
+        /// <summary>
+        ///     Gets or sets the stickers sent with this message.
+        /// </summary>
+        public List<ISticker> Stickers
+        {
+            get => _stickers;
+            set
+            {
+                if (value?.Count > DiscordConfig.MaxStickersPerMessage)
+                    throw new ArgumentOutOfRangeException(nameof(value), $"Sticker count must be less than or equal to {DiscordConfig.MaxStickersPerMessage}");
+
+                _stickers = value;
+            }
+        }
+
+        /// <summary>
+        ///     Gets or sets the files sent with this message.
+        /// </summary>
+        public List<FileAttachment> Files { get; set; } = new();
+
+        /// <summary>
+        ///     Gets or sets the message flags.
+        /// </summary>
+        public MessageFlags Flags { get; set; }
+
+        /// <summary>
+        ///     Sets the <see cref="Content"/> of this message.
+        /// </summary>
+        /// <param name="content">The content of the message.</param>
+        /// <returns>The current builder.</returns>
+        public MessageBuilder WithContent(string content)
+        {
+            Content = content;
+            return this;
+        }
+
+        /// <summary>
+        ///     Sets the <see cref="IsTTS"/> of this message.
+        /// </summary>
+        /// <param name="isTTS">whether or not this message is tts.</param>
+        /// <returns>The current builder.</returns>
+        public MessageBuilder WithTTS(bool isTTS)
+        {
+            IsTTS = isTTS;
+            return this;
+        }
+
+        public MessageBuilder WithEmbeds(params EmbedBuilder[] embeds)
+        {
+            Embeds = new(embeds);
+            return this;
+        }
+
+        public MessageBuilder AddEmbed(EmbedBuilder embed)
+        {
+            if (_embeds?.Count >= DiscordConfig.MaxEmbedsPerMessage)
+                throw new ArgumentOutOfRangeException(nameof(embed.Length), $"A message can only contain a maximum of {DiscordConfig.MaxEmbedsPerMessage} embeds");
+
+            _embeds ??= new();
+
+            _embeds.Add(embed);
+
+            return this;
+        }
+
+        public MessageBuilder WithAllowedMentions(AllowedMentions allowedMentions)
+        {
+            AllowedMentions = allowedMentions;
+            return this;
+        }
+
+        public MessageBuilder WithMessageReference(MessageReference reference)
+        {
+            MessageReference = reference;
+            return this;
+        }
+
+        public MessageBuilder WithMessageReference(IMessage message)
+        {
+            if (message != null)
+                MessageReference = new MessageReference(message.Id, message.Channel?.Id, ((IGuildChannel)message.Channel)?.GuildId);
+            return this;
+        }
+
+        public MessageBuilder WithComponentBuilder(ComponentBuilder builder)
+        {
+            Components = builder;
+            return this;
+        }
+
+        public MessageBuilder WithButton(ButtonBuilder button, int row = 0)
+        {
+            Components ??= new();
+            Components.WithButton(button, row);
+            return this;
+        }
+
+        public MessageBuilder WithButton(
+            string label = null,
+            string customId = null,
+            ButtonStyle style = ButtonStyle.Primary,
+            IEmote emote = null,
+            string url = null,
+            bool disabled = false,
+            int row = 0)
+        {
+            Components ??= new();
+            Components.WithButton(label, customId, style, emote, url, disabled, row);
+            return this;
+        }
+
+        public MessageBuilder WithSelectMenu(SelectMenuBuilder menu, int row = 0)
+        {
+            Components ??= new();
+            Components.WithSelectMenu(menu, row);
+            return this;
+        }
+
+        public MessageBuilder WithSelectMenu(string customId, List<SelectMenuOptionBuilder> options,
+            string placeholder = null, int minValues = 1, int maxValues = 1, bool disabled = false, int row = 0)
+        {
+            Components ??= new();
+            Components.WithSelectMenu(customId, options, placeholder, minValues, maxValues, disabled, row);
+            return this;
+        }
+
+        public Message Build()
+        {
+            var embeds = _embeds != null && _embeds.Count > 0
+                ? _embeds.Select(x => x.Build()).ToImmutableArray()
+                : ImmutableArray<Embed>.Empty;
+
+            return new Message(
+                _content,
+                IsTTS,
+                embeds,
+                AllowedMentions,
+                MessageReference,
+                Components?.Build(),
+                _stickers != null && _stickers.Any() ? _stickers.Select(x => x.Id).ToImmutableArray() : ImmutableArray<ulong>.Empty,
+                Files?.ToImmutableArray() ?? ImmutableArray<FileAttachment>.Empty,
+                Flags
+            );
+        }
+    }
+}

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

@@ -66,5 +66,11 @@ namespace Discord.API
 
         [JsonProperty("member_count")]
         public Optional<int> MemberCount { get; set; }
+
+        //ForumChannel
+        [JsonProperty("available_tags")]
+        public Optional<ForumTags[]> ForumTags { get; set; }
+        [JsonProperty("default_auto_archive_duration")]
+        public Optional<ThreadArchiveDuration> DefaultAutoArchiveDuration { get; set; }
     }
 }

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

@@ -9,8 +9,5 @@ namespace Discord.API.Rest
 
         [JsonProperty("members")]
         public ThreadMember[] Members { get; set; }
-
-        [JsonProperty("has_more")]
-        public bool HasMore { get; set; }
     }
 }

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

@@ -0,0 +1,21 @@
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord.API
+{
+    internal class ForumTags
+    {
+        [JsonProperty("id")]
+        public ulong Id { get; set; }
+        [JsonProperty("name")]
+        public string Name { get; set; }
+        [JsonProperty("emoji_id")]
+        public Optional<ulong?> EmojiId { get; set; }
+        [JsonProperty("emoji_name")]
+        public Optional<string> EmojiName { get; set; }
+    }
+}

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

@@ -0,0 +1,94 @@
+using Discord.Net.Converters;
+using Discord.Net.Rest;
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord.API.Rest
+{
+    internal class CreateMultipartPostAsync
+    {
+        private static JsonSerializer _serializer = new JsonSerializer { ContractResolver = new DiscordContractResolver() };
+
+        public FileAttachment[] Files { get; }
+
+        public string Title { get; set; }
+        public ThreadArchiveDuration ArchiveDuration { get; set; }
+        public Optional<int?> Slowmode { get; set; }
+
+
+        public Optional<string> Content { get; set; }
+        public Optional<bool> IsTTS { get; set; }
+        public Optional<Embed[]> Embeds { get; set; }
+        public Optional<AllowedMentions> AllowedMentions { get; set; }
+        public Optional<ActionRowComponent[]> MessageComponent { get; set; }
+        public Optional<MessageFlags?> Flags { get; set; }
+        public Optional<ulong[]> Stickers { get; set; }
+
+        public CreateMultipartPostAsync(params FileAttachment[] attachments)
+        {
+            Files = attachments;
+        }
+
+        public IReadOnlyDictionary<string, object> ToDictionary()
+        {
+            var d = new Dictionary<string, object>();
+
+            var payload = new Dictionary<string, object>();
+
+            payload["title"] = Title;
+            payload["auto_archive_duration"] = ArchiveDuration;
+
+            if (Slowmode.IsSpecified)
+                payload["rate_limit_per_user"] = Slowmode.Value;
+            if (Content.IsSpecified)
+                payload["content"] = Content.Value;
+            if (IsTTS.IsSpecified)
+                payload["tts"] = IsTTS.Value;
+            if (Embeds.IsSpecified)
+                payload["embeds"] = Embeds.Value;
+            if (AllowedMentions.IsSpecified)
+                payload["allowed_mentions"] = AllowedMentions.Value;
+            if (MessageComponent.IsSpecified)
+                payload["components"] = MessageComponent.Value;
+            if (Stickers.IsSpecified)
+                payload["sticker_ids"] = Stickers.Value;
+            if (Flags.IsSpecified)
+                payload["flags"] = Flags.Value;
+
+            List<object> attachments = new();
+
+            for (int n = 0; n != Files.Length; n++)
+            {
+                var attachment = Files[n];
+
+                var filename = attachment.FileName ?? "unknown.dat";
+                if (attachment.IsSpoiler && !filename.StartsWith(AttachmentExtensions.SpoilerPrefix))
+                    filename = filename.Insert(0, AttachmentExtensions.SpoilerPrefix);
+                d[$"files[{n}]"] = new MultipartFile(attachment.Stream, filename);
+
+                attachments.Add(new
+                {
+                    id = (ulong)n,
+                    filename = filename,
+                    description = attachment.Description ?? Optional<string>.Unspecified
+                });
+            }
+
+            payload["attachments"] = attachments;
+
+            var json = new StringBuilder();
+            using (var text = new StringWriter(json))
+            using (var writer = new JsonTextWriter(text))
+                _serializer.Serialize(writer, payload);
+
+            d["payload_json"] = json.ToString();
+
+            return d;
+        }
+    }
+}

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

@@ -0,0 +1,44 @@
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discord.API.Rest
+{
+    internal class CreatePostParams
+    {
+        // thread
+        [JsonProperty("name")]
+        public string Title { get; set; }
+
+        [JsonProperty("auto_archive_duration")]
+        public ThreadArchiveDuration ArchiveDuration { get; set; }
+
+        [JsonProperty("rate_limit_per_user")]
+        public Optional<int?> Slowmode { get; set; }
+
+        // message
+        [JsonProperty("content")]
+        public string Content { get; set; }
+
+        [JsonProperty("tts")]
+        public Optional<bool> IsTTS { get; set; }
+
+        [JsonProperty("embeds")]
+        public Optional<Embed[]> Embeds { get; set; }
+
+        [JsonProperty("allowed_mentions")]
+        public Optional<AllowedMentions> AllowedMentions { get; set; }
+
+        [JsonProperty("components")]
+        public Optional<API.ActionRowComponent[]> Components { get; set; }
+
+        [JsonProperty("sticker_ids")]
+        public Optional<ulong[]> Stickers { get; set; }
+
+        [JsonProperty("flags")]
+        public Optional<MessageFlags> Flags { get; set; }
+    }
+}

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

@@ -37,7 +37,7 @@ namespace Discord.API.Rest
             if (Content.IsSpecified)
                 payload["content"] = Content.Value;
             if (IsTTS.IsSpecified)
-                payload["tts"] = IsTTS.Value.ToString();
+                payload["tts"] = IsTTS.Value;
             if (Nonce.IsSpecified)
                 payload["nonce"] = Nonce.Value;
             if (Embeds.IsSpecified)

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

@@ -50,7 +50,7 @@ namespace Discord.API.Rest
             if (Content.IsSpecified)
                 data["content"] = Content.Value;
             if (IsTTS.IsSpecified)
-                data["tts"] = IsTTS.Value.ToString();
+                data["tts"] = IsTTS.Value;
             if (MessageComponents.IsSpecified)
                 data["components"] = MessageComponents.Value;
             if (Embeds.IsSpecified)

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

@@ -36,7 +36,7 @@ namespace Discord.API.Rest
             if (Content.IsSpecified)
                 payload["content"] = Content.Value;
             if (IsTTS.IsSpecified)
-                payload["tts"] = IsTTS.Value.ToString();
+                payload["tts"] = IsTTS.Value;
             if (Nonce.IsSpecified)
                 payload["nonce"] = Nonce.Value;
             if (Username.IsSpecified)

src/Discord.Net.Rest/DiscordRestApiClient.cs

@@ -464,6 +464,24 @@ namespace Discord.API
         #endregion
 
         #region Threads
+        public async Task<Channel> CreatePostAsync(ulong channelId, CreatePostParams args, RequestOptions options = null)
+        {
+            Preconditions.NotEqual(channelId, 0, nameof(channelId));
+
+            var bucket = new BucketIds(channelId: channelId);
+
+            return await SendJsonAsync<Channel>("POST", () => $"channels/{channelId}/threads", args, bucket, options: options);
+        }
+
+        public async Task<Channel> CreatePostAsync(ulong channelId, CreateMultipartPostAsync args, RequestOptions options = null)
+        {
+            Preconditions.NotEqual(channelId, 0, nameof(channelId));
+
+            var bucket = new BucketIds(channelId: channelId);
+
+            return await SendMultipartAsync<Channel>("POST", () => $"channels/{channelId}/threads", args.ToDictionary(), bucket, options: options);
+        }
+
         public async Task<Channel> ModifyThreadAsync(ulong channelId, ModifyThreadParams args, RequestOptions options = null)
         {
             Preconditions.NotEqual(channelId, 0, nameof(channelId));
@@ -564,15 +582,15 @@ namespace Discord.API
             return await SendAsync<ThreadMember>("GET", () => $"channels/{channelId}/thread-members/{userId}", bucket, options: options).ConfigureAwait(false);
         }
 
-        public async Task<ChannelThreads> GetActiveThreadsAsync(ulong channelId, RequestOptions options = null)
+        public async Task<ChannelThreads> GetActiveThreadsAsync(ulong guildId, RequestOptions options = null)
         {
-            Preconditions.NotEqual(channelId, 0, nameof(channelId));
+            Preconditions.NotEqual(guildId, 0, nameof(guildId));
 
             options = RequestOptions.CreateOrClone(options);
 
-            var bucket = new BucketIds(channelId: channelId);
+            var bucket = new BucketIds(guildId: guildId);
 
-            return await SendAsync<ChannelThreads>("GET", () => $"channels/{channelId}/threads/active", bucket, options: options);
+            return await SendAsync<ChannelThreads>("GET", () => $"guilds/{guildId}/threads/active", bucket, options: options);
         }
 
         public async Task<ChannelThreads> GetPublicArchivedThreadsAsync(ulong channelId, DateTimeOffset? before = null, int? limit = null, RequestOptions options = null)

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

@@ -1,5 +1,7 @@
 using Discord.API.Rest;
 using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
 using Model = Discord.API.Channel;
@@ -60,6 +62,33 @@ namespace Discord.Rest
             return await client.ApiClient.ModifyThreadAsync(channel.Id, apiArgs, options).ConfigureAwait(false);
         }
 
+        public static async Task<IReadOnlyCollection<RestThreadChannel>> GetActiveThreadsAsync(IGuild guild, BaseDiscordClient client, RequestOptions options)
+        {
+            var result = await client.ApiClient.GetActiveThreadsAsync(guild.Id, options).ConfigureAwait(false);
+            return result.Threads.Select(x => RestThreadChannel.Create(client, guild, x)).ToImmutableArray();
+        }
+
+        public static async Task<IReadOnlyCollection<RestThreadChannel>> GetPublicArchivedThreadsAsync(IGuildChannel channel, BaseDiscordClient client, int? limit = null,
+            DateTimeOffset? before = null, RequestOptions options = null)
+        {
+            var result = await client.ApiClient.GetPublicArchivedThreadsAsync(channel.Id, before, limit, options);
+            return result.Threads.Select(x => RestThreadChannel.Create(client, channel.Guild, x)).ToImmutableArray();
+        }
+
+        public static async Task<IReadOnlyCollection<RestThreadChannel>> GetPrivateArchivedThreadsAsync(IGuildChannel channel, BaseDiscordClient client, int? limit = null,
+            DateTimeOffset? before = null, RequestOptions options = null)
+        {
+            var result = await client.ApiClient.GetPrivateArchivedThreadsAsync(channel.Id, before, limit, options);
+            return result.Threads.Select(x => RestThreadChannel.Create(client, channel.Guild, x)).ToImmutableArray();
+        }
+
+        public static async Task<IReadOnlyCollection<RestThreadChannel>> GetJoinedPrivateArchivedThreadsAsync(IGuildChannel channel, BaseDiscordClient client, int? limit = null,
+            DateTimeOffset? before = null, RequestOptions options = null)
+        {
+            var result = await client.ApiClient.GetJoinedPrivateArchivedThreadsAsync(channel.Id, before, limit, options);
+            return result.Threads.Select(x => RestThreadChannel.Create(client, channel.Guild, x)).ToImmutableArray();
+        }
+
         public static async Task<RestThreadUser[]> GetUsersAsync(IThreadChannel channel, BaseDiscordClient client, RequestOptions options = null)
         {
             var users = await client.ApiClient.ListThreadMembersAsync(channel.Id, options);
@@ -73,5 +102,49 @@ namespace Discord.Rest
 
             return RestThreadUser.Create(client, channel.Guild, model, channel);
         }
+
+        public static async Task<RestThreadChannel> CreatePostAsync(IForumChannel channel, BaseDiscordClient client, string title, ThreadArchiveDuration archiveDuration, Message message, int? slowmode = null, RequestOptions options = null)
+        {
+            Model model;
+
+            if (message.Attachments?.Any() ?? false)
+            {
+                var args = new CreateMultipartPostAsync(message.Attachments.ToArray())
+                {
+                    AllowedMentions = message.AllowedMentions.ToModel(),
+                    ArchiveDuration = archiveDuration,
+                    Content = message.Content,
+                    Embeds = message.Embeds.Any() ? message.Embeds.Select(x => x.ToModel()).ToArray() : Optional<API.Embed[]>.Unspecified,
+                    Flags = message.Flags,
+                    IsTTS = message.IsTTS,
+                    MessageComponent = message.Components?.Components?.Any() ?? false ? message.Components.Components.Select(x => new API.ActionRowComponent(x)).ToArray() : Optional<API.ActionRowComponent[]>.Unspecified,
+                    Slowmode = slowmode,
+                    Stickers = message.StickerIds?.Any() ?? false ? message.StickerIds.ToArray() : Optional<ulong[]>.Unspecified,
+                    Title = title
+                };
+
+                model = await client.ApiClient.CreatePostAsync(channel.Id, args, options).ConfigureAwait(false);
+            }
+            else
+            {
+                var args = new CreatePostParams()
+                {
+                    AllowedMentions = message.AllowedMentions.ToModel(),
+                    ArchiveDuration = archiveDuration,
+                    Content = message.Content,
+                    Embeds = message.Embeds.Any() ? message.Embeds.Select(x => x.ToModel()).ToArray() : Optional<API.Embed[]>.Unspecified,
+                    Flags = message.Flags,
+                    IsTTS = message.IsTTS,
+                    Components = message.Components?.Components?.Any() ?? false ? message.Components.Components.Select(x => new API.ActionRowComponent(x)).ToArray() : Optional<API.ActionRowComponent[]>.Unspecified,
+                    Slowmode = slowmode,
+                    Stickers = message.StickerIds?.Any() ?? false ? message.StickerIds.ToArray() : Optional<ulong[]>.Unspecified,
+                    Title = title
+                };
+
+                model = await client.ApiClient.CreatePostAsync(channel.Id, args, options);
+            }
+
+            return RestThreadChannel.Create(client, channel.Guild, model);
+        }
     }
 }

src/Discord.Net.Rest/Entities/Interactions/InteractionHelper.cs

@@ -352,7 +352,7 @@ namespace Discord.Rest
         #endregion
 
         #region Responses
-        public static async Task<Message> ModifyFollowupMessageAsync(BaseDiscordClient client, RestFollowupMessage message, Action<MessageProperties> func,
+        public static async Task<Discord.API.Message> ModifyFollowupMessageAsync(BaseDiscordClient client, RestFollowupMessage message, Action<MessageProperties> func,
             RequestOptions options = null)
         {
             var args = new MessageProperties();
@@ -394,7 +394,7 @@ namespace Discord.Rest
         }
         public static async Task DeleteFollowupMessageAsync(BaseDiscordClient client, RestFollowupMessage message, RequestOptions options = null)
             => await client.ApiClient.DeleteInteractionFollowupMessageAsync(message.Id, message.Token, options);
-        public static async Task<Message> ModifyInteractionResponseAsync(BaseDiscordClient client, string token, Action<MessageProperties> func,
+        public static async Task<API.Message> ModifyInteractionResponseAsync(BaseDiscordClient client, string token, Action<MessageProperties> func,
            RequestOptions options = null)
         {
             var args = new MessageProperties();

src/Discord.Net.Rest/Net/Converters/UInt64Converter.cs

@@ -1,4 +1,4 @@
-using Newtonsoft.Json;
+using Newtonsoft.Json;
 using System;
 using System.Globalization;
 
@@ -14,7 +14,7 @@ namespace Discord.Net.Converters
 
         public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
         {
-            return ulong.Parse((string)reader.Value, NumberStyles.None, CultureInfo.InvariantCulture);
+            return ulong.Parse(reader.Value?.ToString(), NumberStyles.None, CultureInfo.InvariantCulture);
         }
 
         public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

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

@@ -0,0 +1,86 @@
+using Discord.Rest;
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Model = Discord.API.Channel;
+
+namespace Discord.WebSocket
+{
+    /// <summary>
+    ///     Represents a forum channel in a guild.
+    /// </summary>
+    public class SocketForumChannel : SocketGuildChannel, IForumChannel
+    {
+        /// <inheritdoc/>
+        public bool IsNsfw { get; private set; }
+
+        /// <inheritdoc/>
+        public string Topic { get; private set; }
+
+        /// <inheritdoc/>
+        public ThreadArchiveDuration DefaultAutoArchiveDuration { get; private set; }
+
+        /// <inheritdoc/>
+        public IReadOnlyCollection<ForumTag> Tags { get; private set; }
+
+        /// <inheritdoc/>
+        public string Mention => MentionUtils.MentionChannel(Id);
+
+        internal SocketForumChannel(DiscordSocketClient discord, ulong id, SocketGuild guild) : base(discord, id, guild) { }
+
+        internal new static SocketForumChannel Create(SocketGuild guild, ClientState state, Model model)
+        {
+            var entity = new SocketForumChannel(guild.Discord, model.Id, guild);
+            entity.Update(state, model);
+            return entity;
+        }
+
+        internal override void Update(ClientState state, Model model)
+        {
+            base.Update(state, model);
+            IsNsfw = model.Nsfw.GetValueOrDefault(false);
+            Topic = model.Topic.GetValueOrDefault();
+            DefaultAutoArchiveDuration = model.DefaultAutoArchiveDuration.GetValueOrDefault(ThreadArchiveDuration.OneDay);
+
+            Tags = model.ForumTags.GetValueOrDefault(new API.ForumTags[0]).Select(
+                x => new ForumTag(x.Id, x.Name, x.EmojiId.GetValueOrDefault(null), x.EmojiName.GetValueOrDefault())
+            ).ToImmutableArray();
+        }
+
+        /// <inheritdoc cref="IForumChannel.CreatePostAsync(string, ThreadArchiveDuration, Message, int?, RequestOptions)"/>
+        public Task<RestThreadChannel> CreatePostAsync(string title, ThreadArchiveDuration archiveDuration, Message message, int? slowmode = null, RequestOptions options = null)
+            => ThreadHelper.CreatePostAsync(this, Discord, title, archiveDuration, message, slowmode, options);
+
+        /// <inheritdoc cref="IForumChannel.GetActiveThreadsAsync(RequestOptions)"/>
+        public Task<IReadOnlyCollection<RestThreadChannel>> GetActiveThreadsAsync(RequestOptions options = null)
+            => ThreadHelper.GetActiveThreadsAsync(Guild, Discord, options);
+
+        /// <inheritdoc cref="IForumChannel.GetJoinedPrivateArchivedThreadsAsync(int?, DateTimeOffset?, RequestOptions)"/>
+        public Task<IReadOnlyCollection<RestThreadChannel>> GetJoinedPrivateArchivedThreadsAsync(int? limit = null, DateTimeOffset? before = null, RequestOptions options = null)
+            => ThreadHelper.GetJoinedPrivateArchivedThreadsAsync(this, Discord, limit, before, options);
+
+        /// <inheritdoc cref="IForumChannel.GetPrivateArchivedThreadsAsync(int?, DateTimeOffset?, RequestOptions)"/>
+        public Task<IReadOnlyCollection<RestThreadChannel>> GetPrivateArchivedThreadsAsync(int? limit = null, DateTimeOffset? before = null, RequestOptions options = null)
+            => ThreadHelper.GetPrivateArchivedThreadsAsync(this, Discord, limit, before, options);
+
+        /// <inheritdoc cref="IForumChannel.GetPublicArchivedThreadsAsync(int?, DateTimeOffset?, RequestOptions)"/>
+        public Task<IReadOnlyCollection<RestThreadChannel>> GetPublicArchivedThreadsAsync(int? limit = null, DateTimeOffset? before = null, RequestOptions options = null)
+            => ThreadHelper.GetPublicArchivedThreadsAsync(this, Discord, limit, before, options);
+
+        #region IForumChannel
+        async Task<IThreadChannel> IForumChannel.CreatePostAsync(string title, ThreadArchiveDuration archiveDuration, Message message, int? slowmode, RequestOptions options)
+            => await CreatePostAsync(title, archiveDuration, message, slowmode, options).ConfigureAwait(false);
+        async Task<IReadOnlyCollection<IThreadChannel>> IForumChannel.GetActiveThreadsAsync(RequestOptions options)
+            => await GetActiveThreadsAsync(options).ConfigureAwait(false);
+        async Task<IReadOnlyCollection<IThreadChannel>> IForumChannel.GetPublicArchivedThreadsAsync(int? limit, DateTimeOffset? before, RequestOptions options)
+            => await GetPublicArchivedThreadsAsync(limit, before, options).ConfigureAwait(false);
+        async Task<IReadOnlyCollection<IThreadChannel>> IForumChannel.GetPrivateArchivedThreadsAsync(int? limit, DateTimeOffset? before, RequestOptions options)
+            => await GetPrivateArchivedThreadsAsync(limit, before, options).ConfigureAwait(false);
+        async Task<IReadOnlyCollection<IThreadChannel>> IForumChannel.GetJoinedPrivateArchivedThreadsAsync(int? limit, DateTimeOffset? before, RequestOptions options)
+            => await GetJoinedPrivateArchivedThreadsAsync(limit, before, options).ConfigureAwait(false);
+        #endregion
+    }
+}

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

@@ -59,6 +59,7 @@ namespace Discord.WebSocket
                 ChannelType.Category => SocketCategoryChannel.Create(guild, state, model),
                 ChannelType.PrivateThread or ChannelType.PublicThread or ChannelType.NewsThread => SocketThreadChannel.Create(guild, state, model),
                 ChannelType.Stage => SocketStageChannel.Create(guild, state, model),
+                ChannelType.Forum => SocketForumChannel.Create(guild, state, model),
                 _ => new SocketGuildChannel(guild.Discord, model.Id, guild),
             };
         }