Implement .NET gateway client sessions

clients/dotnet/MxGateway.Client/MxGatewayClient.cs

@@ -1,22 +1,44 @@
+using Grpc.Core;
 using Grpc.Net.Client;
 using MxGateway.Contracts.Proto;
 
 namespace MxGateway.Client;
 
 /// <summary>
-/// Provides the initial .NET client entry point and raw generated gRPC client.
+/// Provides the .NET client entry point for the public MXAccess Gateway gRPC API.
 /// </summary>
 public sealed class MxGatewayClient : IAsyncDisposable
 {
     private readonly GrpcChannel _channel;
+    private readonly IMxGatewayClientTransport _transport;
+    private bool _disposed;
 
-    private MxGatewayClient(GrpcChannel channel)
+    internal MxGatewayClient(
+        MxGatewayClientOptions options,
+        IMxGatewayClientTransport transport)
     {
-        _channel = channel;
-        RawClient = new MxAccessGateway.MxAccessGatewayClient(channel);
+        ArgumentNullException.ThrowIfNull(options);
+        options.Validate();
+
+        Options = options;
+        _transport = transport ?? throw new ArgumentNullException(nameof(transport));
+        _channel = null!;
     }
 
-    public MxAccessGateway.MxAccessGatewayClient RawClient { get; }
+    private MxGatewayClient(
+        GrpcChannel channel,
+        IMxGatewayClientTransport transport)
+    {
+        _channel = channel;
+        _transport = transport;
+        Options = transport.Options;
+    }
+
+    public MxGatewayClientOptions Options { get; }
+
+    public MxAccessGateway.MxAccessGatewayClient RawClient =>
+        _transport.RawClient
+        ?? throw new InvalidOperationException("The raw generated gRPC client is not available for this client instance.");
 
     public static MxGatewayClient Create(MxGatewayClientOptions options)
     {
@@ -30,12 +52,92 @@ public sealed class MxGatewayClient : IAsyncDisposable
                 LoggerFactory = options.LoggerFactory,
             });
 
-        return new MxGatewayClient(channel);
+        return new MxGatewayClient(
+            channel,
+            new GrpcMxGatewayClientTransport(
+                options,
+                new MxAccessGateway.MxAccessGatewayClient(channel)));
+    }
+
+    public async Task<MxGatewaySession> OpenSessionAsync(
+        OpenSessionRequest? request = null,
+        CancellationToken cancellationToken = default)
+    {
+        OpenSessionReply reply = await OpenSessionRawAsync(
+                request ?? new OpenSessionRequest(),
+                cancellationToken)
+            .ConfigureAwait(false);
+
+        return new MxGatewaySession(this, reply);
+    }
+
+    public Task<OpenSessionReply> OpenSessionRawAsync(
+        OpenSessionRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        ThrowIfDisposed();
+
+        return _transport.OpenSessionAsync(request, CreateCallOptions(cancellationToken));
+    }
+
+    public Task<CloseSessionReply> CloseSessionRawAsync(
+        CloseSessionRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        ThrowIfDisposed();
+
+        return _transport.CloseSessionAsync(request, CreateCallOptions(cancellationToken));
+    }
+
+    public Task<MxCommandReply> InvokeAsync(
+        MxCommandRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        ThrowIfDisposed();
+
+        return _transport.InvokeAsync(request, CreateCallOptions(cancellationToken));
+    }
+
+    public IAsyncEnumerable<MxEvent> StreamEventsAsync(
+        StreamEventsRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        ThrowIfDisposed();
+
+        return _transport.StreamEventsAsync(request, CreateCallOptions(cancellationToken));
     }
 
     public ValueTask DisposeAsync()
     {
-        _channel.Dispose();
+        if (_disposed)
+        {
+            return ValueTask.CompletedTask;
+        }
+
+        _disposed = true;
+        _channel?.Dispose();
         return ValueTask.CompletedTask;
     }
+
+    internal CallOptions CreateCallOptions(CancellationToken cancellationToken)
+    {
+        Metadata headers = new()
+        {
+            { "authorization", $"Bearer {Options.ApiKey}" },
+        };
+
+        return new CallOptions(
+            headers,
+            DateTime.UtcNow.Add(Options.DefaultCallTimeout),
+            cancellationToken);
+    }
+
+    private void ThrowIfDisposed()
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+    }
 }