Fix resource subscription handling (#89)

* Fix resource subscription handling
Add resource subscription tests

* Fix typo

* Typo

* small fixes

* Fix concurrency issue with test

* Align with specification schemas

src/mcpdotnet/Client/McpClientExtensions.cs

@@ -227,7 +227,7 @@ public static class McpClientExtensions
     {
         Throw.IfNull(client);
 
-        return client.SendRequestAsync<dynamic>(
+        return client.SendRequestAsync<EmptyResult>(
             CreateRequest("resources/subscribe", new() { ["uri"] = uri }),
             cancellationToken);
     }
@@ -242,7 +242,7 @@ public static class McpClientExtensions
     {
         Throw.IfNull(client);
 
-        return client.SendRequestAsync<dynamic>(
+        return client.SendRequestAsync<EmptyResult>(
             CreateRequest("resources/unsubscribe", new() { ["uri"] = uri }),
             cancellationToken);
     }

src/mcpdotnet/Configuration/McpServerBuilderExtensions.Handler.cs

@@ -107,7 +107,7 @@ public static partial class McpServerBuilderExtensions
     /// </summary>
     /// <param name="builder">The builder instance.</param>
     /// <param name="handler">The handler.</param>
-    public static IMcpServerBuilder WithSubscribeToResourcesHandler(this IMcpServerBuilder builder, Func<RequestContext<string>, CancellationToken, Task> handler)
+    public static IMcpServerBuilder WithSubscribeToResourcesHandler(this IMcpServerBuilder builder, Func<RequestContext<SubscribeRequestParams>, CancellationToken, Task<EmptyResult>> handler)
     {
         Throw.IfNull(builder);
 
@@ -120,7 +120,7 @@ public static partial class McpServerBuilderExtensions
     /// </summary>
     /// <param name="builder">The builder instance.</param>
     /// <param name="handler">The handler.</param>
-    public static IMcpServerBuilder WithUnsubscribeFromResourcesHandler(this IMcpServerBuilder builder, Func<RequestContext<string>, CancellationToken, Task> handler)
+    public static IMcpServerBuilder WithUnsubscribeFromResourcesHandler(this IMcpServerBuilder builder, Func<RequestContext<UnsubscribeRequestParams>, CancellationToken, Task<EmptyResult>> handler)
     {
         Throw.IfNull(builder);
 

src/mcpdotnet/Protocol/Types/Capabilities.cs

@@ -126,13 +126,13 @@ public record ResourcesCapability
     /// Gets or sets the handler for subscribe to resources messages.
     /// </summary>
     [JsonIgnore]
-    public Func<RequestContext<string>, CancellationToken, Task>? SubscribeToResourcesHandler { get; init; }
+    public Func<RequestContext<SubscribeRequestParams>, CancellationToken, Task<EmptyResult>>? SubscribeToResourcesHandler { get; init; }
 
     /// <summary>
     /// Gets or sets the handler for unsubscribe from resources messages.
     /// </summary>
     [JsonIgnore]
-    public Func<RequestContext<string>, CancellationToken, Task>? UnsubscribeFromResourcesHandler { get; init; }
+    public Func<RequestContext<UnsubscribeRequestParams>, CancellationToken, Task<EmptyResult>>? UnsubscribeFromResourcesHandler { get; init; }
 }
 
 /// <summary>

src/mcpdotnet/Protocol/Types/CompleteResult.cs

@@ -0,0 +1,16 @@
+using System.Text.Json.Serialization;
+
+namespace McpDotNet.Protocol.Types;
+
+/// <summary>
+/// The server's response to a completion/complete request
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public class CompleteResult
+{
+    /// <summary>
+    /// The completion object containing the completion values.
+    /// </summary>
+    [JsonPropertyName("completion")]
+    public Completion Completion { get; set; } = new Completion();
+}

src/mcpdotnet/Protocol/Types/EmptyResult.cs

@@ -0,0 +1,10 @@
+namespace McpDotNet.Protocol.Types;
+
+/// <summary>
+/// An empty result object.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public class EmptyResult
+{
+
+}

src/mcpdotnet/Protocol/Types/Reference.cs

@@ -66,15 +66,3 @@ public class Reference
         return true;
     }
 }
-
-/// <summary>
-/// The server's response to a completion/complete request
-/// </summary>
-public class CompleteResult
-{
-    /// <summary>
-    /// The completion object containing the completion values.
-    /// </summary>
-    [JsonPropertyName("completion")]
-    public Completion Completion { get; set; } = new Completion();
-}

src/mcpdotnet/Protocol/Types/ResourceUpdatedNotificationParams.cs

@@ -0,0 +1,14 @@
+namespace McpDotNet.Protocol.Types;
+
+/// <summary>
+/// Sent from the server as the payload of "notifications/resources/updated" notifications whenever a subscribed resource changes.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public class ResourceUpdatedNotificationParams
+{
+    /// <summary>
+    /// The URI of the resource to subscribe to. The URI can use any protocol; it is up to the server how to interpret it.
+    /// </summary>
+    [System.Text.Json.Serialization.JsonPropertyName("uri")]
+    public string? Uri { get; init; }
+}

src/mcpdotnet/Protocol/Types/SubscribeRequestParams.cs

@@ -0,0 +1,14 @@
+namespace McpDotNet.Protocol.Types;
+
+/// <summary>
+/// Sent from the client to request updated notifications from the server whenever a particular primitive changes.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public class SubscribeRequestParams
+{
+    /// <summary>
+    /// The URI of the resource to subscribe to. The URI can use any protocol; it is up to the server how to interpret it.
+    /// </summary>
+    [System.Text.Json.Serialization.JsonPropertyName("uri")]
+    public string? Uri { get; init; }
+}

src/mcpdotnet/Protocol/Types/UnsubscribeRequestParams.cs

@@ -0,0 +1,14 @@
+namespace McpDotNet.Protocol.Types;
+
+/// <summary>
+/// Sent from the client to request not receiving updated notifications from the server whenever a primitive resource changes.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public class UnsubscribeRequestParams
+{
+    /// <summary>
+    /// The URI of the resource to unsubscribe fro. The URI can use any protocol; it is up to the server how to interpret it.
+    /// </summary>
+    [System.Text.Json.Serialization.JsonPropertyName("uri")]
+    public string? Uri { get; init; }
+}

src/mcpdotnet/Server/McpServer.cs

@@ -163,7 +163,8 @@ internal sealed class McpServer : McpJsonRpcEndpoint, IMcpServer
             throw new McpServerException("Resources capability was enabled with subscribe support, but SubscribeToResources and/or UnsubscribeFromResources handlers were not specified.");
         }
 
-        // TODO: Implement Subscribe support
+        SetRequestHandler<SubscribeRequestParams, EmptyResult>("resources/subscribe", request => subscribeHandler(new(this, request), cancellationToken));
+        SetRequestHandler<UnsubscribeRequestParams, EmptyResult>("resources/unsubscribe", request => unsubscribeHandler(new(this, request), cancellationToken));
     }
 
     private void SetPromptsHandler(McpServerOptions options)

src/mcpdotnet/Server/McpServerHandlers.cs

@@ -45,12 +45,12 @@ public sealed class McpServerHandlers
     /// <summary>
     /// Gets or sets the handler for subscribe to resources messages.
     /// </summary>
-    public Func<RequestContext<string>, CancellationToken, Task>? SubscribeToResourcesHandler { get; set; }
+    public Func<RequestContext<SubscribeRequestParams>, CancellationToken, Task<EmptyResult>>? SubscribeToResourcesHandler { get; set; }
 
     /// <summary>
     /// Gets or sets the handler for unsubscribe from resources messages.
     /// </summary>
-    public Func<RequestContext<string>, CancellationToken, Task>? UnsubscribeFromResourcesHandler { get; set; }
+    public Func<RequestContext<UnsubscribeRequestParams>, CancellationToken, Task<EmptyResult>>? UnsubscribeFromResourcesHandler { get; set; }
 
     /// <summary>
     /// Overwrite any handlers in McpServerOptions with non-null handlers from this instance.
@@ -77,25 +77,29 @@ public sealed class McpServerHandlers
 
         ResourcesCapability? resourcesCapability = options.Capabilities?.Resources;
         if (ListResourcesHandler is not null ||
-            ReadResourceHandler is not null ||
-            SubscribeToResourcesHandler is not null ||
-            UnsubscribeFromResourcesHandler is not null)
+            ReadResourceHandler is not null)
         {
             resourcesCapability = resourcesCapability is null ?
                 new()
                 {
                     ListResourcesHandler = ListResourcesHandler,
-                    ReadResourceHandler = ReadResourceHandler,
-                    SubscribeToResourcesHandler = SubscribeToResourcesHandler,
-                    UnsubscribeFromResourcesHandler = UnsubscribeFromResourcesHandler,
+                    ReadResourceHandler = ReadResourceHandler
                 } :
                 resourcesCapability with
                 {
                     ListResourcesHandler = ListResourcesHandler ?? resourcesCapability.ListResourcesHandler,
-                    ReadResourceHandler = ReadResourceHandler ?? resourcesCapability.ReadResourceHandler,
+                    ReadResourceHandler = ReadResourceHandler ?? resourcesCapability.ReadResourceHandler
+                };
+
+            if (SubscribeToResourcesHandler is not null || UnsubscribeFromResourcesHandler is not null)
+            {
+                resourcesCapability = resourcesCapability with
+                {
                     SubscribeToResourcesHandler = SubscribeToResourcesHandler ?? resourcesCapability.SubscribeToResourcesHandler,
                     UnsubscribeFromResourcesHandler = UnsubscribeFromResourcesHandler ?? resourcesCapability.UnsubscribeFromResourcesHandler,
+                    Subscribe = true
                 };
+            }
         }
 
         ToolsCapability? toolsCapability = options.Capabilities?.Tools;