Fix interop/API type mismatches: RtcDataChannel width, SetLocalDescription spec alignment

WebRtcInterop/RtcDataChannel.cpp

@@ -67,14 +67,14 @@ namespace WebRtcInterop
 		return GetNativeDataChannelInterface(true)->ordered();
 	}
 
-	Nullable<uint32_t> RtcDataChannel::MaxPacketLifeTime::get()
+	Nullable<uint16_t> RtcDataChannel::MaxPacketLifeTime::get()
 	{
-		return marshal_as<uint32_t>(GetNativeDataChannelInterface(true)->maxPacketLifeTime());
+		return marshal_as<uint16_t>(GetNativeDataChannelInterface(true)->maxPacketLifeTime());
 	}
 
-	Nullable<uint32_t> RtcDataChannel::MaxRetransmits::get()
+	Nullable<uint16_t> RtcDataChannel::MaxRetransmits::get()
 	{
-		return marshal_as<uint32_t>(GetNativeDataChannelInterface(true)->maxRetransmitsOpt());
+		return marshal_as<uint16_t>(GetNativeDataChannelInterface(true)->maxRetransmitsOpt());
 	}
 
 	String^ RtcDataChannel::Protocol::get()

WebRtcInterop/RtcDataChannel.h

@@ -20,8 +20,8 @@ namespace WebRtcInterop
 		// Inherited via RtcDataChannel
 		virtual property String^ Label { String^ get() override; }
 		virtual property bool Ordered { bool get() override; }
-		virtual property Nullable<uint32_t> MaxPacketLifeTime { Nullable<uint32_t> get() override; }
-		virtual property Nullable<uint32_t> MaxRetransmits { Nullable<uint32_t> get() override; }
+		virtual property Nullable<uint16_t> MaxPacketLifeTime { Nullable<uint16_t> get() override; }
+		virtual property Nullable<uint16_t> MaxRetransmits { Nullable<uint16_t> get() override; }
 		virtual property String^ Protocol { String^ get() override; }
 		virtual property bool Negotiated { bool get() override; }
 		virtual property Nullable<uint16_t> Id { Nullable<uint16_t> get() override; }

WebRtcInterop/RtcPeerConnection.cpp

@@ -104,10 +104,16 @@ namespace WebRtcInterop
 		return task;
 	}
 
-	Task^ RtcPeerConnection::SetLocalDescription(RtcSessionDescription description)
-	{
+	Task^ RtcPeerConnection::SetLocalDescription(Nullable<RtcLocalSessionDescriptionInit> description)
+	{
+		// TODO: Implement using two native overloads on PeerConnectionInterface:
+		//   - description is null, or description.Value.Type is null:
+		//       -> SetLocalDescription(observer)  [native creates offer/answer from signaling state]
+		//   - description.Value.Type has a value:
+		//       -> SetLocalDescription(unique_ptr<SessionDescriptionInterface>, observer)
+		// Add marshal_as<webrtc::SessionDescriptionInterface*>(RtcLocalSessionDescriptionInit) in
+		// MarshalPeerConnection.h to support the second path.
 		throw gcnew NotImplementedException();
-		// TODO: insert return statement here
 	}
 
 	Task^ RtcPeerConnection::SetRemoteDescription(RtcSessionDescription description)

WebRtcInterop/RtcPeerConnection.h

@@ -91,7 +91,7 @@ namespace WebRtcInterop
 		virtual Task^ AddIceCandidate(RtcIceCandidate^ candidate) override;
 		virtual void RestartIce() override;
 
-		virtual Task^ SetLocalDescription(RtcSessionDescription description) override;
+		virtual Task^ SetLocalDescription(Nullable<RtcLocalSessionDescriptionInit> description) override;
 		virtual Task^ SetRemoteDescription(RtcSessionDescription description) override;
 
 		virtual RtcRtpSender^ AddTrack(WebRtcNet::Media::MediaStreamTrack^ track,

WebRtcNet.Api.UnitTests/RtcPeerConnectionContractTests.cs

@@ -79,15 +79,21 @@ public void RtcPeerConnection_Exposes_Nullable_Optional_SetLocalDescription_And_
 	{
 		var setLocalDescription = typeof(RtcPeerConnection).GetMethod(
 			nameof(RtcPeerConnection.SetLocalDescription),
-			new[] { typeof(RtcSessionDescription?) });
+			new[] { typeof(RtcLocalSessionDescriptionInit?) });
 		var addIceCandidate = typeof(RtcPeerConnection).GetMethod(
 			nameof(RtcPeerConnection.AddIceCandidate),
 			new[] { typeof(RtcIceCandidate) });
 
-		Assert.That(setLocalDescription, Is.Not.Null);
+		Assert.That(setLocalDescription, Is.Not.Null,
+			"SetLocalDescription must accept RtcLocalSessionDescriptionInit? (spec: RTCLocalSessionDescriptionInit, type optional)");
 		Assert.That(setLocalDescription!.GetParameters()[0].IsOptional, Is.True);
 		Assert.That(setLocalDescription.GetParameters()[0].DefaultValue, Is.Null);
 
+		// Verify the parameter is NOT the old RtcSessionDescription? type — type distinction is spec-required.
+		Assert.That(setLocalDescription.GetParameters()[0].ParameterType,
+			Is.Not.EqualTo(typeof(RtcSessionDescription?)),
+			"SetLocalDescription must use RtcLocalSessionDescriptionInit (RTCLocalSessionDescriptionInit), not RtcSessionDescription (RTCSessionDescriptionInit)");
+
 		Assert.That(addIceCandidate, Is.Not.Null);
 		Assert.That(addIceCandidate!.GetParameters()[0].IsOptional, Is.True);
 		Assert.That(addIceCandidate.GetParameters()[0].DefaultValue, Is.Null);

WebRtcNet.Api/RtcPeerConnection.cs

@@ -334,15 +334,16 @@ public static Task<RtcCertificate> GenerateCertificate(object keygenAlgorithm)
 
 	/// <summary>
 	/// The SetLocalDescription() method instructs the RtcPeerConnection to apply the supplied
-	/// <see cref="RtcSessionDescription">RtcSessionDescription</see> as the
+	/// <see cref="RtcLocalSessionDescriptionInit">description</see> as the
 	/// <see cref="LocalDescription">local description</see>.
 	/// </summary>
 	/// <param name="description">
-	/// A session description containing the SDP describing the local session, or null to let the implementation
-	/// infer and apply the next local description.
+	/// A local session description init whose <c>type</c> may be omitted to let the implementation
+	/// infer it from the current signaling state, or <see langword="null"/> to use the implementation's
+	/// default (equivalent to passing an empty <c>RTCLocalSessionDescriptionInit</c>).
 	/// </param>
 	/// <seealso href="https://www.w3.org/TR/webrtc/#dom-peerconnection-setlocaldescription" />
-	public abstract Task SetLocalDescription(RtcSessionDescription? description = null);
+	public abstract Task SetLocalDescription(RtcLocalSessionDescriptionInit? description = null);
 
 	/// <summary>
 	/// The SetRemoteDescription() method instructs the RTCPeerConnection to apply the supplied

WebRtcNet.Api/RtcSessionDescription.cs

@@ -1,3 +1,5 @@
+using System;
+
 namespace WebRtcNet;
 
 /// <summary>
@@ -32,10 +34,12 @@ public enum RtcSdpType
 }
 
 /// <summary>
-/// Represents an SDP session description used by <see cref="RtcPeerConnection" /> operations.
+/// Represents an SDP session description produced by <see cref="RtcPeerConnection.CreateOffer"/> or
+/// <see cref="RtcPeerConnection.CreateAnswer"/>, or received from a remote peer via signaling.
+/// Models <c>RTCSessionDescriptionInit</c> where <c>type</c> is required.
 /// </summary>
-/// <seealso href="https://www.w3.org/TR/webrtc/#dom-rtcsessiondescriptioninit" />
-public struct RtcSessionDescription
+/// <seealso href="https://www.w3.org/TR/webrtc/#rtcsessiondescription-class" />
+public record struct RtcSessionDescription
 {
 	/// <summary>
 	/// Initializes a session description with a type and SDP payload.
@@ -51,10 +55,72 @@ public RtcSessionDescription(RtcSdpType type, string sdp)
 	/// <summary>
 	/// Gets the SDP description type.
 	/// </summary>
-	public readonly RtcSdpType Type;
+	/// <seealso href="https://www.w3.org/TR/webrtc/#dom-rtcsessiondescriptioninit-type" />
+	public RtcSdpType Type { get; init; }
+
+	/// <summary>
+	/// Gets the SDP payload string.
+	/// </summary>
+	/// <seealso href="https://www.w3.org/TR/webrtc/#dom-rtcsessiondescriptioninit-sdp" />
+	public string Sdp { get; init; } = string.Empty;
+
+	/// <summary>
+	/// Implicitly converts an <see cref="RtcLocalSessionDescriptionInit"/> to an
+	/// <see cref="RtcSessionDescription"/>. Throws if <see cref="RtcLocalSessionDescriptionInit.Type"/>
+	/// is <see langword="null"/>, as <see cref="Type"/> is required.
+	/// </summary>
+	/// <exception cref="InvalidOperationException">
+	/// Thrown when <see cref="RtcLocalSessionDescriptionInit.Type"/> is <see langword="null"/>.
+	/// </exception>
+	public static implicit operator RtcSessionDescription(RtcLocalSessionDescriptionInit description) =>
+		new(description.Type ?? throw new InvalidOperationException(
+				"Cannot convert RtcLocalSessionDescriptionInit to RtcSessionDescription: Type is null."),
+			description.Sdp);
+}
+
+/// <summary>
+/// The description passed to <see cref="RtcPeerConnection.SetLocalDescription"/>.
+/// Models <c>RTCLocalSessionDescriptionInit</c> where <c>type</c> is optional — the implementation
+/// may infer the type when it is omitted.
+/// </summary>
+/// <remarks>
+/// Implicitly converts from <see cref="RtcSessionDescription"/> so that the value returned by
+/// <see cref="RtcPeerConnection.CreateOffer"/> or <see cref="RtcPeerConnection.CreateAnswer"/>
+/// can be passed directly to <see cref="RtcPeerConnection.SetLocalDescription"/> without a cast.
+/// </remarks>
+/// <seealso href="https://www.w3.org/TR/webrtc/#dom-rtclocalsessiondescriptioninit" />
+public record struct RtcLocalSessionDescriptionInit
+{
+	/// <summary>
+	/// Initializes a local session description init with an optional type and SDP payload.
+	/// </summary>
+	/// <param name="type">
+	/// The SDP description type, or <see langword="null"/> to let the implementation infer the type
+	/// from the current signaling state.
+	/// </param>
+	/// <param name="sdp">The SDP payload text. Defaults to empty string.</param>
+	public RtcLocalSessionDescriptionInit(RtcSdpType? type = null, string sdp = "")
+	{
+		Type = type;
+		Sdp = sdp;
+	}
+
+	/// <summary>
+	/// Gets the SDP description type, or <see langword="null"/> if the implementation should infer it.
+	/// </summary>
+	/// <seealso href="https://www.w3.org/TR/webrtc/#dom-rtclocalsessiondescriptioninit-type" />
+	public RtcSdpType? Type { get; init; }
 
 	/// <summary>
 	/// Gets the SDP payload string.
 	/// </summary>
-	public readonly string Sdp;
-}
+	/// <seealso href="https://www.w3.org/TR/webrtc/#dom-rtclocalsessiondescriptioninit-sdp" />
+	public string Sdp { get; init; } = string.Empty;
+
+	/// <summary>
+	/// Implicitly converts an <see cref="RtcSessionDescription"/> (required type) to an
+	/// <see cref="RtcLocalSessionDescriptionInit"/> (optional type).
+	/// </summary>
+	public static implicit operator RtcLocalSessionDescriptionInit(RtcSessionDescription description) =>
+		new(description.Type, description.Sdp);
+}