Source/Plugin/McpServer.cpp

#include "McpServer.h"
#include "PluginBridgeProcessor.h"

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

using json = nlohmann::json;

McpServer::McpServer(int port, PluginBridgeProcessor& processor)
    : server(std::make_unique<httplib::Server>()), port(port), processor(processor)
{
    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},
            {"plugin", processor.isPluginLoaded() ? processor.getLoadedPluginName().toStdString() : "none"},
            {"params", processor.getLoadedPluginParamCount()}
        };
        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(); }

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","0.3.0"}}}
        }}
    };
    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","Show loaded plugin info"},
                 {"inputSchema",{{"type","object"},{"properties",json::object()}}}},
                {{"name","search_param"},{"description","Search params by keyword"},
                 {"inputSchema",{{"type","object"},{"properties",{
                    {"keyword",{{"type","string"},{"description","e.g. 'gain', 'band 1', 'cutoff'"}}}
                 }},{"required",json::array({"keyword"})}}}},
                {{"name","get_params"},{"description","Get param values by index"},
                 {"inputSchema",{{"type","object"},{"properties",{
                    {"ids",{{"type","array"},{"items",{{"type","integer"}}}}}
                 }},{"required",json::array({"ids"})}}}},
                {{"name","set_params"},{"description","Set params (batch, 0.0-1.0)"},
                 {"inputSchema",{{"type","object"},{"properties",{
                    {"values",{{"type","object"},{"description","index→value map"}}}
                 }},{"required",json::array({"values"})}}}},
                {{"name","get_analysis"},{"description","Real-time audio analysis (future)"},
                 {"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 (!processor.isPluginLoaded())
    {
        resultText = "no plugin loaded";
        isError = true;
    }
    else if (toolName == "list_plugins")
    {
        json info = {
            {"name", processor.getLoadedPluginName().toStdString()},
            {"params", processor.getLoadedPluginParamCount()},
            {"path", processor.getLastPluginPath().toStdString()}
        };
        resultText = info.dump();
    }
    else if (toolName == "search_param")
    {
        auto keyword = args.value("keyword", "");
        auto results = processor.searchParams(juce::String(keyword));

        json arr = json::array();
        for (auto& p : results)
        {
            arr.push_back({
                {"i", p.index},
                {"id", p.id.toStdString()},
                {"n", p.name.toStdString()},
                {"v", std::round(p.value * 1000.0f) / 1000.0f},
                {"t", p.displayText.toStdString()}
            });
        }
        resultText = arr.dump();
    }
    else if (toolName == "get_params")
    {
        std::vector<int> ids;
        for (auto& id : args["ids"])
            ids.push_back(id.get<int>());

        auto results = processor.getParams(ids);

        json values = json::object();
        for (auto& [idx, val] : results)
            values[std::to_string(idx)] = std::round(val * 1000.0f) / 1000.0f;

        resultText = values.dump();
    }
    else if (toolName == "set_params")
    {
        std::map<int, float> values;
        for (auto& [key, val] : args["values"].items())
            values[std::stoi(key)] = val.get<float>();

        bool ok = processor.setParams(values);
        resultText = ok ? "ok" : "set failed";
    }
    else if (toolName == "get_analysis")
    {
        resultText = "silent"; // Sprint 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();
}