Source/Plugin/McpServer.cpp

#include "McpServer.h"
#include "HelperConnection.h"
#include "../Shared/IPCProtocol.h"

#define CPPHTTPLIB_THREAD_POOL_COUNT 2
#include "httplib.h"
#include "json.hpp"

using json = nlohmann::json;

McpServer::McpServer(int port, HelperConnection& helper)
    : server(std::make_unique<httplib::Server>()), port(port), helper(helper)
{
    setupRoutes();
}

McpServer::~McpServer()
{
    stop();
}

void McpServer::setupRoutes()
{
    server->Post("/mcp", [this](const httplib::Request& req, httplib::Response& res) {
        res.set_header("Access-Control-Allow-Origin", "http://localhost");

        try {
            auto body = json::parse(req.body);
            std::string method = body.value("method", "");
            std::string responseStr;

            if (method == "initialize")
                responseStr = handleInitialize(req.body);
            else if (method == "notifications/initialized") {
                initialized = true;
                res.status = 204;
                return;
            }
            else if (method == "tools/list")
                responseStr = handleToolsList(req.body);
            else if (method == "tools/call")
                responseStr = handleToolsCall(req.body);
            else {
                json err = {{"jsonrpc","2.0"},{"id",body.value("id",json(nullptr))},
                           {"error",{{"code",-32601},{"message","Method not found"}}}};
                responseStr = err.dump();
            }

            if (!responseStr.empty())
                res.set_content(responseStr, "application/json");
        }
        catch (const json::exception&) {
            json err = {{"jsonrpc","2.0"},{"id",nullptr},
                       {"error",{{"code",-32700},{"message","Parse error"}}}};
            res.set_content(err.dump(), "application/json");
        }
    });

    server->Get("/health", [this](const httplib::Request&, httplib::Response& res) {
        json health = {
            {"status", "ok"},
            {"port", port},
            {"initialized", initialized},
            {"helper", helper.isHelperRunning() ? "connected" : "disconnected"}
        };
        res.set_content(health.dump(), "application/json");
    });

    server->Options("/mcp", [](const httplib::Request&, httplib::Response& res) {
        res.set_header("Access-Control-Allow-Origin", "http://localhost");
        res.set_header("Access-Control-Allow-Methods", "POST, OPTIONS");
        res.set_header("Access-Control-Allow-Headers", "Content-Type, Mcp-Session-Id");
        res.status = 204;
    });
}

void McpServer::start()
{
    if (running.load()) return;
    serverThread = std::thread([this]() {
        running.store(true);
        server->listen("127.0.0.1", port);
        running.store(false);
    });
    server->wait_until_ready();
}

void McpServer::stop()
{
    if (server && server->is_running()) server->stop();
    if (serverThread.joinable()) serverThread.join();
    running.store(false);
}

bool McpServer::isRunning() const { return running.load(); }

// --- Protocol Handlers ---

std::string McpServer::handleInitialize(const std::string& requestBody)
{
    auto body = json::parse(requestBody);
    sessionId = "pb-" + std::to_string(std::chrono::steady_clock::now().time_since_epoch().count());

    json response = {
        {"jsonrpc","2.0"},
        {"id", body.value("id", json(nullptr))},
        {"result", {
            {"protocolVersion","2025-06-18"},
            {"capabilities",{{"tools",{{"listChanged",false}}}}},
            {"serverInfo",{{"name","PluginBridge"},{"version","0.2.0"}}}
        }}
    };
    return response.dump();
}

std::string McpServer::handleToolsList(const std::string& requestBody)
{
    auto body = json::parse(requestBody);
    json response = {
        {"jsonrpc","2.0"},
        {"id", body.value("id", json(nullptr))},
        {"result",{
            {"tools", json::array({
                {{"name","list_plugins"},{"description","List loaded plugin"},
                 {"inputSchema",{{"type","object"},{"properties",json::object()}}}},
                {{"name","search_param"},{"description","Search params by keyword"},
                 {"inputSchema",{{"type","object"},{"properties",{
                    {"plugin",{{"type","string"}}},
                    {"keyword",{{"type","string"},{"description","e.g. 'gain', 'band 1', 'cutoff'"}}}
                 }},{"required",json::array({"plugin","keyword"})}}}},
                {{"name","get_params"},{"description","Get param values by ID"},
                 {"inputSchema",{{"type","object"},{"properties",{
                    {"plugin",{{"type","string"}}},
                    {"ids",{{"type","array"},{"items",{{"type","integer"}}}}}
                 }},{"required",json::array({"plugin","ids"})}}}},
                {{"name","set_params"},{"description","Set params (batch, 0.0-1.0)"},
                 {"inputSchema",{{"type","object"},{"properties",{
                    {"plugin",{{"type","string"}}},
                    {"values",{{"type","object"},{"description","id→value"}}}
                 }},{"required",json::array({"plugin","values"})}}}},
                {{"name","get_analysis"},{"description","Real-time audio analysis"},
                 {"inputSchema",{{"type","object"},{"properties",json::object()}}}}
            })}
        }}
    };
    return response.dump();
}

std::string McpServer::handleToolsCall(const std::string& requestBody)
{
    auto body = json::parse(requestBody);
    auto params = body["params"];
    std::string toolName = params["name"];
    auto args = params.value("arguments", json::object());

    std::string resultText;
    bool isError = false;

    if (!helper.isHelperRunning())
    {
        resultText = "helper not connected";
        isError = true;
    }
    else if (toolName == "list_plugins")
    {
        // Query helper for loaded plugin name
        auto resp = helper.sendCommand("{\"cmd\":\"search_param\",\"keyword\":\"\"}");
        // Just return what's loaded
        resultText = "[\"loaded plugin\"]"; // simplified — actual name comes from processor
    }
    else if (toolName == "search_param")
    {
        json cmd = {{"cmd","search_param"},{"keyword", args.value("keyword","")}};
        auto resp = helper.sendCommand(cmd.dump());
        try {
            auto j = json::parse(resp);
            if (j.value("ok", false))
                resultText = j["results"].dump();
            else
                resultText = j.value("error", "search failed");
        } catch (...) { resultText = "parse error"; isError = true; }
    }
    else if (toolName == "get_params")
    {
        json cmd = {{"cmd","get_params"},{"ids", args.value("ids", json::array())}};
        auto resp = helper.sendCommand(cmd.dump());
        try {
            auto j = json::parse(resp);
            if (j.value("ok", false))
                resultText = j["values"].dump();
            else
                resultText = "get failed";
        } catch (...) { resultText = "parse error"; isError = true; }
    }
    else if (toolName == "set_params")
    {
        json cmd = {{"cmd","set_params"},{"values", args.value("values", json::object())}};
        auto resp = helper.sendCommand(cmd.dump());
        try {
            auto j = json::parse(resp);
            resultText = j.value("ok", false) ? "ok" : "set failed";
        } catch (...) { resultText = "parse error"; isError = true; }
    }
    else if (toolName == "get_analysis")
    {
        resultText = "silent"; // Phase 4
    }
    else
    {
        resultText = "unknown tool: " + toolName;
        isError = true;
    }

    json response = {
        {"jsonrpc","2.0"},
        {"id", body.value("id", json(nullptr))},
        {"result",{
            {"content", json::array({{{"type","text"},{"text",resultText}}})},
            {"isError", isError}
        }}
    };
    return response.dump();
}