[Core] Stream Message (#795)

Author: DarkRRb

Lagrange.Core/Internal/Packets/Message/Element/Implementation/Extra/StreamExtra.cs

@@ -0,0 +1,11 @@
+using ProtoBuf;
+
+namespace Lagrange.Core.Internal.Packets.Message.Element.Implementation.Extra;
+
+[ProtoContract]
+public class StreamExtra
+{
+    [ProtoMember(43)] public ulong Field43 { get; init; }
+
+    [ProtoMember(103)] public ulong Sequence { get; init; }
+}

Lagrange.Core/Message/Entity/StreamEntity.cs

@@ -0,0 +1,47 @@
+using Lagrange.Core.Internal.Packets.Message.Element;
+using Lagrange.Core.Internal.Packets.Message.Element.Implementation;
+using Lagrange.Core.Internal.Packets.Message.Element.Implementation.Extra;
+using ProtoBuf;
+
+namespace Lagrange.Core.Message.Entity;
+
+public class StreamEntity : IMessageEntity
+{
+    public string Text { get; }
+
+    public StreamEntity(string text)
+    {
+        Text = text;
+    }
+
+    IEnumerable<Elem> IMessageEntity.PackElement()
+    {
+        byte[] extra;
+        using (MemoryStream stream = new())
+        {
+            Serializer.Serialize(stream, new StreamExtra
+            {
+                Field43 = (ulong)Random.Shared.NextInt64(),
+                Sequence = 1
+            });
+            extra = stream.ToArray();
+        }
+
+        return new Elem[] {
+            new() {
+                Text = new Text {
+                    Str = Text
+                }
+            },
+            new() {
+                GeneralFlags = new GeneralFlags {
+                    PbReserve = extra
+                }
+            }
+        };
+    }
+
+    IMessageEntity? IMessageEntity.UnpackElement(Elem elem) => throw new NotImplementedException();
+
+    string IMessageEntity.ToPreviewString() => $"[Stream] {Text}";
+}