Add MCP sse/stdio transport types

Author: bandoti

common/CMakeLists.txt

@@ -79,6 +79,11 @@ add_library(${TARGET} STATIC
     ${CMAKE_CURRENT_SOURCE_DIR}/toolcall/handler.hpp
     ${CMAKE_CURRENT_SOURCE_DIR}/toolcall/mcp_messages.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/toolcall/mcp_messages.hpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/toolcall/mcp_transport.hpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/toolcall/mcp_sse_transport.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/toolcall/mcp_sse_transport.hpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/toolcall/mcp_stdio_transport.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/toolcall/mcp_stdio_transport.hpp
     )
 
 if (BUILD_SHARED_LIBS)

common/toolcall/handler.cpp

@@ -1,5 +1,7 @@
 
 #include "handler.hpp"
+#include "mcp_sse_transport.hpp"
+#include "mcp_stdio_transport.hpp"
 
 using json = toolcall::json;
 
@@ -97,16 +99,26 @@ toolcall::action toolcall::handler::last_action() const {
     return last_action_;
 }
 
-toolcall::mcp_impl::mcp_impl(std::string /*server_uri*/, tool_choice_t tool_choice)
-    : handler_impl(tool_choice)
+toolcall::mcp_impl::mcp_impl(std::string server_uri, tool_choice_t tool_choice)
+    : handler_impl(tool_choice),
+      transport_(new mcp_sse_transport(server_uri))
 {
-    // TODO
+    transport_->start();
+}
+
+toolcall::mcp_impl::mcp_impl(std::vector<std::string> argv, tool_choice_t tool_choice)
+    : handler_impl(tool_choice),
+      transport_(new mcp_stdio_transport(argv))
+{
+    transport_->start();
 }
 
 json toolcall::mcp_impl::tool_list() {
+    // Construct tools/list call and send to transport
     return json{};// TODO
 }
 
 toolcall::action toolcall::mcp_impl::call(const json & /*request*/, json & /*response*/) {
+    // Construct tool call and send to transport
     return toolcall::ACCEPT; // TODO
 }

common/toolcall/handler.hpp

@@ -93,11 +93,16 @@ namespace toolcall
         json tools_;
     };
 
+    class mcp_transport;
     class mcp_impl : public handler_impl {
     public:
         mcp_impl(std::string server_uri, tool_choice_t tool_choice);
+        mcp_impl(std::vector<std::string> argv, tool_choice_t tool_choice);
 
         virtual json tool_list() override;
         virtual action call(const json & request, json & response) override;
+
+    private:
+        std::unique_ptr<mcp_transport> transport_;
     };
 }

common/toolcall/mcp_messages.hpp

@@ -1,6 +1,7 @@
 #include <string>
 #include <optional>
 #include <vector>
+#include <variant>
 #include "../json.hpp"
 
 namespace mcp
@@ -212,4 +213,8 @@ namespace mcp
         tools_list tools_;
         std::string next_cursor_;
     };
+
+    using message_variant = std::variant<
+        initialize_request, initialize_response, initialized_notification,
+        tools_list_request, tools_list_response>;
 }

common/toolcall/mcp_sse_transport.cpp

@@ -0,0 +1,17 @@
+
+#include "mcp_sse_transport.hpp"
+
+toolcall::mcp_sse_transport::mcp_sse_transport(std::string server_uri)
+    : server_uri_(std::move(server_uri))
+{
+}
+
+void toolcall::mcp_sse_transport::start() {
+}
+
+void toolcall::mcp_sse_transport::stop() {
+}
+
+bool toolcall::mcp_sse_transport::send(const mcp::message_variant & /*request*/) {
+    return false;
+}

common/toolcall/mcp_sse_transport.hpp

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "mcp_transport.hpp"
+
+namespace toolcall
+{
+    class mcp_sse_transport : public mcp_transport {
+    public:
+        mcp_sse_transport(std::string server_uri);
+
+        virtual void start() override;
+        virtual void stop()  override;
+        virtual bool send(const mcp::message_variant & request) override;
+
+    private:
+        std::string server_uri_;
+    };
+}

common/toolcall/mcp_stdio_transport.cpp

@@ -0,0 +1,17 @@
+
+#include "mcp_stdio_transport.hpp"
+
+toolcall::mcp_stdio_transport::mcp_stdio_transport(std::vector<std::string> argv)
+    : argv_(std::move(argv))
+{
+}
+
+void toolcall::mcp_stdio_transport::start() {
+}
+
+void toolcall::mcp_stdio_transport::stop() {
+}
+
+bool toolcall::mcp_stdio_transport::send(const mcp::message_variant & /*request*/) {
+    return false;
+}

common/toolcall/mcp_stdio_transport.hpp

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "mcp_transport.hpp"
+
+#include <string>
+#include <vector>
+
+namespace toolcall
+{
+    class mcp_stdio_transport : public mcp_transport {
+    public:
+	mcp_stdio_transport(std::vector<std::string> argv);
+
+        virtual void start() override;
+        virtual void stop()  override;
+        virtual bool send(const mcp::message_variant & request) override;
+
+    private:
+        std::vector<std::string> argv_;
+    };
+}

common/toolcall/mcp_transport.hpp

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "mcp_messages.hpp"
+
+namespace toolcall
+{
+    class mcp_transport {
+    public:
+        using on_message_callback = std::function<void(const mcp::message_variant &)>;
+
+        virtual ~mcp_transport() = default;
+        virtual void start() = 0;
+        virtual void stop() = 0;
+        virtual bool send(const mcp::message_variant & request) = 0;
+
+        void on_received(on_message_callback callback) { callback_ = std::move(callback); }
+        const on_message_callback & on_received() const { return callback_; }
+
+    protected:
+        on_message_callback callback_;
+    };
+}