Add middleware and authz support for server-side handlers (#733)

src/ModelContextProtocol.Core/Server/RequestServiceProvider.cs

@@ -0,0 +1,61 @@
+using Microsoft.Extensions.DependencyInjection;
+using ModelContextProtocol.Protocol;
+using System.Security.Claims;
+
+namespace ModelContextProtocol.Server;
+
+/// <summary>Augments a service provider with additional request-related services.</summary>
+internal sealed class RequestServiceProvider<TRequestParams>(RequestContext<TRequestParams> request) :
+    IServiceProvider,  IKeyedServiceProvider, IServiceProviderIsService, IServiceProviderIsKeyedService,
+    IDisposable,  IAsyncDisposable
+    where TRequestParams : RequestParams
+{
+    private readonly IServiceProvider? _innerServices = request.Services;
+
+    /// <summary>Gets the request associated with this instance.</summary>
+    public RequestContext<TRequestParams> Request => request;
+
+    /// <summary>Gets whether the specified type is in the list of additional types this service provider wraps around the one in a provided request's services.</summary>
+    public static bool IsAugmentedWith(Type serviceType) =>
+        serviceType == typeof(RequestContext<TRequestParams>) ||
+        serviceType == typeof(IMcpServer) ||
+        serviceType == typeof(IProgress<ProgressNotificationValue>) ||
+        serviceType == typeof(ClaimsPrincipal);
+
+    /// <inheritdoc />
+    public object? GetService(Type serviceType) =>
+        serviceType == typeof(RequestContext<TRequestParams>) ? request :
+        serviceType == typeof(IMcpServer) ? request.Server :
+        serviceType == typeof(IProgress<ProgressNotificationValue>) ?
+            (request.Params?.ProgressToken is { } progressToken ? new TokenProgress(request.Server, progressToken) : NullProgress.Instance) :
+        serviceType == typeof(ClaimsPrincipal) ? request.User :
+        _innerServices?.GetService(serviceType);
+
+    /// <inheritdoc />
+    public bool IsService(Type serviceType) =>
+        IsAugmentedWith(serviceType) ||
+        (_innerServices as IServiceProviderIsService)?.IsService(serviceType) is true;
+
+    /// <inheritdoc />
+    public bool IsKeyedService(Type serviceType, object? serviceKey) =>
+        (serviceKey is null && IsService(serviceType)) ||
+        (_innerServices as IServiceProviderIsKeyedService)?.IsKeyedService(serviceType, serviceKey) is true;
+
+    /// <inheritdoc />
+    public object? GetKeyedService(Type serviceType, object? serviceKey) =>
+        serviceKey is null ? GetService(serviceType) :
+        (_innerServices as IKeyedServiceProvider)?.GetKeyedService(serviceType, serviceKey);
+
+    /// <inheritdoc />
+    public object GetRequiredKeyedService(Type serviceType, object? serviceKey) =>
+        GetKeyedService(serviceType, serviceKey) ??
+        throw new InvalidOperationException($"No service of type '{serviceType}' with key '{serviceKey}' is registered.");
+
+    /// <inheritdoc />
+    public void Dispose() =>
+        (_innerServices as IDisposable)?.Dispose();
+
+    /// <inheritdoc />
+    public ValueTask DisposeAsync() =>
+        _innerServices is IAsyncDisposable asyncDisposable ? asyncDisposable.DisposeAsync() : default;
+}