feat(battle-node): SocketIoFrame parse/encode for SIO2 incl. binary attachments

SVSim.UnitTests/BattleNode/Wire/SocketIoFrameTests.cs

@@ -0,0 +1,88 @@
+using System.Text.Json;
+using NUnit.Framework;
+using SVSim.BattleNode.Wire;
+
+namespace SVSim.UnitTests.BattleNode.Wire;
+
+[TestFixture]
+public class SocketIoFrameTests
+{
+    [Test]
+    public void Parse_ConnectPacket_HasNoPayload()
+    {
+        var frame = SocketIoFrame.Parse("0");
+        Assert.That(frame.Type, Is.EqualTo(SocketIoPacketType.Connect));
+        Assert.That(frame.AckId, Is.Null);
+        Assert.That(frame.AttachmentCount, Is.EqualTo(0));
+    }
+
+    [Test]
+    public void Parse_EventWithAck_ExtractsAckIdAndArgs()
+    {
+        var frame = SocketIoFrame.Parse("27[\"msg\",42]");
+        Assert.That(frame.Type, Is.EqualTo(SocketIoPacketType.Event));
+        Assert.That(frame.AckId, Is.EqualTo(7));
+        Assert.That(frame.EventName, Is.EqualTo("msg"));
+        Assert.That(frame.RawArgs[0].GetInt32(), Is.EqualTo(42));
+    }
+
+    [Test]
+    public void Parse_BinaryEvent_RecordsAttachmentCount_WithAttachments_Assembles()
+    {
+        var attachment = new byte[] { 0x01, 0x02, 0x03 };
+        var header = SocketIoFrame.Parse("51-[\"msg\",{\"_placeholder\":true,\"num\":0}]");
+        var assembled = header.WithAttachments(new[] { attachment });
+
+        Assert.That(assembled.Type, Is.EqualTo(SocketIoPacketType.BinaryEvent));
+        Assert.That(assembled.AckId, Is.Null);
+        Assert.That(assembled.AttachmentCount, Is.EqualTo(1));
+        Assert.That(assembled.BinaryAttachments[0], Is.EqualTo(attachment));
+        Assert.That(assembled.EventName, Is.EqualTo("msg"));
+    }
+
+    [Test]
+    public void Parse_BinaryEventWithAckId_ExtractsBoth()
+    {
+        var frame = SocketIoFrame.Parse("51-3[\"msg\",{\"_placeholder\":true,\"num\":0}]");
+        Assert.That(frame.Type, Is.EqualTo(SocketIoPacketType.BinaryEvent));
+        Assert.That(frame.AckId, Is.EqualTo(3));
+        Assert.That(frame.AttachmentCount, Is.EqualTo(1));
+    }
+
+    [Test]
+    public void Parse_AckResponse_ExtractsIdAndIntArg()
+    {
+        var frame = SocketIoFrame.Parse("37[123]");
+        Assert.That(frame.Type, Is.EqualTo(SocketIoPacketType.Ack));
+        Assert.That(frame.AckId, Is.EqualTo(7));
+        Assert.That(frame.RawArgs[0].GetInt32(), Is.EqualTo(123));
+    }
+
+    [Test]
+    public void Encode_BinaryEventWithAttachment_EmitsCountDashAndPlaceholder()
+    {
+        var attachment = new byte[] { 0xff };
+        var frame = SocketIoFrame.BinaryEventWithAttachments("synchronize", new[] { attachment });
+
+        var (text, bins) = frame.Encode();
+        Assert.That(text, Is.EqualTo("51-[\"synchronize\",{\"_placeholder\":true,\"num\":0}]"));
+        Assert.That(bins.Single(), Is.EqualTo(attachment));
+    }
+
+    [Test]
+    public void Encode_AckResponse_IsTypeIdAndArrayOfArgs()
+    {
+        var frame = SocketIoFrame.AckResponse(ackId: 7, arg: 123);
+        var (text, bins) = frame.Encode();
+
+        Assert.That(text, Is.EqualTo("37[123]"));
+        Assert.That(bins, Is.Empty);
+    }
+
+    [Test]
+    public void WithAttachments_CountMismatch_Throws()
+    {
+        var header = SocketIoFrame.Parse("51-[\"msg\",{\"_placeholder\":true,\"num\":0}]");
+        Assert.Throws<ArgumentException>(() => header.WithAttachments(Array.Empty<byte[]>()));
+    }
+}