[Feature] Message Forwards (#2918)

* code

* no guild

* iTS ALIVE (THANKS aDVAITH)

Author: Misha-133

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

@@ -30,6 +30,11 @@ public interface IUserMessage : IMessage
         /// </remarks>
         IMessageInteractionMetadata InteractionMetadata { get; }
 
+        /// <summary>
+        ///     Gets a collection of partial messages that were forwarded with this message.
+        /// </summary>
+        IReadOnlyCollection<MessageSnapshot> ForwardedMessages { get; }
+        
         /// <summary>
         ///     Gets the poll sent with this message.
         /// </summary>

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

@@ -33,6 +33,11 @@ public class MessageReference
         /// </summary>
         public Optional<bool> FailIfNotExists { get; internal set; }
 
+        /// <summary>
+        ///     Gets the type of message reference.
+        /// </summary>
+        public Optional<MessageReferenceType> ReferenceType { get; internal set; }
+
         /// <summary>
         ///     Initializes a new instance of the <see cref="MessageReference"/> class.
         /// </summary>
@@ -48,12 +53,14 @@ public class MessageReference
         /// <param name="failIfNotExists">
         ///     Whether to error if the referenced message doesn't exist instead of sending as a normal (non-reply) message. Defaults to true.
         /// </param>
-        public MessageReference(ulong? messageId = null, ulong? channelId = null, ulong? guildId = null, bool? failIfNotExists = null)
+        public MessageReference(ulong? messageId = null, ulong? channelId = null, ulong? guildId = null, bool? failIfNotExists = null,
+            MessageReferenceType referenceType = MessageReferenceType.Default)
         {
             MessageId = messageId ?? Optional.Create<ulong>();
             InternalChannelId = channelId ?? Optional.Create<ulong>();
             GuildId = guildId ?? Optional.Create<ulong>();
             FailIfNotExists = failIfNotExists ?? Optional.Create<bool>();
+            ReferenceType = referenceType;
         }
 
         private string DebuggerDisplay

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

@@ -0,0 +1,17 @@
+namespace Discord;
+
+/// <summary>
+///     Determines how associated data is populated.
+/// </summary>
+public enum MessageReferenceType
+{
+    /// <summary>
+    ///     A standard reference used by replies.
+    /// </summary>
+    Default = 0,
+
+    /// <summary>
+    ///     Reference used to point to a message at a point in time.
+    /// </summary>
+    Forward = 1,
+}

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

@@ -0,0 +1,17 @@
+namespace Discord;
+
+/// <summary>
+///     Represents a snapshot of a message.
+/// </summary>
+public readonly struct MessageSnapshot
+{
+    /// <summary>
+    ///     Gets the partial message that was forwarded.
+    /// </summary>
+    public readonly IMessage Message;
+
+    internal MessageSnapshot(IMessage message)
+    {
+        Message = message;
+    }
+}

src/Discord.Net.Core/Utils/Preconditions.cs

@@ -98,7 +98,7 @@ public static void WebhookMessageAtLeastOneOf(string text = null, MessageCompone
         }
 
         public static void MessageAtLeastOneOf(string text = null, MessageComponent components = null, ICollection<IEmbed> embeds = null,
-                    ICollection<ISticker> stickers = null, IEnumerable<FileAttachment> attachments = null, PollProperties poll = null)
+                    ICollection<ISticker> stickers = null, IEnumerable<FileAttachment> attachments = null, PollProperties poll = null, MessageReference messageReference = null)
         {
             if (!string.IsNullOrEmpty(text))
                 return;
@@ -118,6 +118,9 @@ public static void MessageAtLeastOneOf(string text = null, MessageComponent comp
             if (poll is not null)
                 return;
 
+            if (messageReference?.ReferenceType.GetValueOrDefault(MessageReferenceType.Default) is MessageReferenceType.Forward)
+                return;
+
             throw new ArgumentException($"At least one of 'Content', 'Embeds', 'Components', 'Stickers', 'Attachments' or 'Poll' must be specified.");
         }
 

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

@@ -102,6 +102,9 @@ internal class Message
     [JsonProperty("interaction_metadata")]
     public Optional<MessageInteractionMetadata> InteractionMetadata { get; set; }
 
+    [JsonProperty("message_snapshots")]
+    public Optional<MessageSnapshot[]> MessageSnapshots { get; set; }
+  
     [JsonProperty("poll")]
     public Optional<Poll> Poll { get; set; }
 

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

@@ -4,6 +4,9 @@ namespace Discord.API
 {
     internal class MessageReference
     {
+        [JsonProperty("type")]
+        public Optional<MessageReferenceType> Type { get; set; }
+
         [JsonProperty("message_id")]
         public Optional<ulong> MessageId { get; set; }
 

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

@@ -0,0 +1,9 @@
+using Newtonsoft.Json;
+
+namespace Discord.API;
+
+internal class MessageSnapshot
+{
+    [JsonProperty("message")]
+    public Message Message { get; set; }
+}

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

@@ -284,7 +284,7 @@ public static async Task<RestUserMessage> SendMessageAsync(IMessageChannel chann
             Preconditions.AtMost(allowedMentions?.UserIds?.Count ?? 0, 100, nameof(allowedMentions.UserIds), "A max of 100 user Ids are allowed.");
             Preconditions.AtMost(embeds.Length, DiscordConfig.MaxEmbedsPerMessage, nameof(embeds), $"A max of {DiscordConfig.MaxEmbedsPerMessage} Embeds are allowed.");
 
-            Preconditions.MessageAtLeastOneOf(text, components, embeds, stickers, poll: poll);
+            Preconditions.MessageAtLeastOneOf(text, components, embeds, stickers, poll: poll, messageReference: messageReference);
             Preconditions.ValidatePoll(poll);
 
             // check that user flag and user Id list are exclusive, same with role flag and role Id list
@@ -400,7 +400,7 @@ public static async Task<RestUserMessage> SendFilesAsync(IMessageChannel channel
             Preconditions.AtMost(allowedMentions?.UserIds?.Count ?? 0, 100, nameof(allowedMentions.UserIds), "A max of 100 user Ids are allowed.");
             Preconditions.AtMost(embeds.Length, DiscordConfig.MaxEmbedsPerMessage, nameof(embeds), $"A max of {DiscordConfig.MaxEmbedsPerMessage} Embeds are allowed.");
 
-            Preconditions.MessageAtLeastOneOf(text, components, embeds, stickers, attachments, poll);
+            Preconditions.MessageAtLeastOneOf(text, components, embeds, stickers, attachments, poll, messageReference);
             Preconditions.ValidatePoll(poll);
 
             foreach (var attachment in attachments)

src/Discord.Net.Rest/Entities/Messages/RestMessage.cs

@@ -165,7 +165,8 @@ internal virtual void Update(Model model)
                     GuildId = model.Reference.Value.GuildId,
                     InternalChannelId = model.Reference.Value.ChannelId,
                     MessageId = model.Reference.Value.MessageId,
-                    FailIfNotExists = model.Reference.Value.FailIfNotExists
+                    FailIfNotExists = model.Reference.Value.FailIfNotExists,
+                    ReferenceType = model.Reference.Value.Type
                 };
             }