import { Server } from '@modelcontextprotocol/sdk/server/index.js';
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import { ListToolsRequestSchema, CallToolRequestSchema } from '@modelcontextprotocol/sdk/types.js';
import { externalRegistry } from './external-registry.js';
import { buildCtxFromAgent } from './context.js';
import { recordAudit } from '../db/repos/audit_stub.js';

// --- transport-free helpers (exported for tests) ---
export function listExternalTools() {
  return externalRegistry.listTools().map(({ name, description, input_schema }) =>
    ({ name, description, input_schema }));
}
export async function callExternalTool(name, args, ctx) {
  const tool = externalRegistry.getTool(name);
  if (!tool) throw new Error(`Unknown tool: ${name}`);
  return tool.handler(args, ctx);
}

// --- MCP server factory (one per request in stateless mode) ---
export function createExternalMcpServer(ctx) {
  const server = new Server(
    { name: 'void-external', version: '1.0.0' },
    { capabilities: { tools: {} } }
  );
  server.setRequestHandler(ListToolsRequestSchema, () => ({
    tools: listExternalTools().map(({ name, description, input_schema }) =>
      ({ name, description, inputSchema: input_schema }))
  }));
  server.setRequestHandler(CallToolRequestSchema, async (request) => {
    const { name, arguments: args = {} } = request.params;
    try {
      const result = await callExternalTool(name, args, ctx);
      recordAudit(ctx.actor, 'mcp_tool_call', 'agent', ctx.agent.id, null,
        { tool: name, space_id: ctx.space_id }).catch(() => {});
      return { content: [{ type: 'text', text: JSON.stringify(result) }], structuredContent: result };
    } catch (err) {
      return { content: [{ type: 'text', text: err.message ?? String(err) }], isError: true };
    }
  });
  return server;
}

// --- Express handler: stateless Streamable HTTP. Requires req.mcpAgent (mcpAuth). ---
export async function handleMcp(req, res) {
  const ctx = buildCtxFromAgent(req.mcpAgent);
  const server = createExternalMcpServer(ctx);
  const transport = new StreamableHTTPServerTransport({
    sessionIdGenerator: undefined,   // stateless
    enableJsonResponse: true
  });
  res.on('close', () => { try { transport.close(); } catch { /* */ } try { server.close(); } catch { /* */ } });
  await server.connect(transport);
  await transport.handleRequest(req, res, req.body);
}