import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { FetchSSEServerTransport } from "./fetch-transport.server";
import { registerMcpTools } from "./mcp-tools.server";

type McpToolRegistrar = (server: McpServer) => void;

export const server = new McpServer(
  {
    name: "app-mcp",
    version: "1.0.0",
  },
  {
    capabilities: {
      tools: {},
    },
  }
);

// Register MCP tools
registerMcpTools(server);

// Tool registrar storage for app-specific tools
const toolRegistrars: McpToolRegistrar[] = [];

/**
 * Register a tool registrar that will add custom MCP tools.
 * This allows apps to extend the MCP server with their own tools.
 */
export function addToolRegistrar(registrar: McpToolRegistrar) {
  toolRegistrars.push(registrar);
  registrar(server);
}

const transports = new Map<string, FetchSSEServerTransport>();
const MAX_TRANSPORTS = 64;

export async function connect(sessionId?: string | null) {
  const transport = new FetchSSEServerTransport("/mcp", sessionId);
  transport.onclose = () => {
    transports.delete(transport.sessionId);
  };
  await server.connect(transport);
  pruneTransports();
  transports.set(transport.sessionId, transport);
  return transport;
}

export async function getTransport(sessionId: string) {
  return transports.get(sessionId);
}

function pruneTransports() {
  while (transports.size >= MAX_TRANSPORTS) {
    const oldestSessionId = transports.keys().next().value;
    if (!oldestSessionId) {
      return;
    }
    transports.delete(oldestSessionId);
  }
}