import { randomBytes, randomUUID } from 'node:crypto';
import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import { z } from 'zod';

function marker() {
  return randomBytes(12).toString('hex');
}

function createServer() {
  const server = new McpServer({ name: 'mcp-output-probe', version: '1.0.0' });
  const annotations = { readOnlyHint: true, destructiveHint: false, openWorldHint: false };
  const outputSchema = { probe_id: z.string(), structured_marker: z.string() };

  server.registerTool('probe_both', {
    description: 'Return independent diagnostic markers in text content and structured content. Report the exact markers you can see in the result.',
    inputSchema: {}, outputSchema, annotations,
  }, async () => {
    const probe_id = randomUUID();
    return {
      content: [{ type: 'text', text: JSON.stringify({ probe_id, text_marker: marker() }) }],
      structuredContent: { probe_id, structured_marker: marker() },
    };
  });

  server.registerTool('probe_text_only', {
    description: 'Control test: return a diagnostic marker using only text content. Report the exact marker you can see.',
    inputSchema: {}, annotations,
  }, async () => ({
    content: [{ type: 'text', text: JSON.stringify({ probe_id: randomUUID(), text_marker: marker() }) }],
  }));

  server.registerTool('probe_structured_only', {
    description: 'Control test: return a diagnostic marker using only structured content. Report the exact marker you can see.',
    inputSchema: {}, outputSchema, annotations,
  }, async () => ({
    content: [], structuredContent: { probe_id: randomUUID(), structured_marker: marker() },
  }));
  return server;
}

export default async function handler(req, res) {
  res.setHeader('Cache-Control', 'no-store');
  if (req.method !== 'POST') {
    res.setHeader('Allow', 'POST');
    res.statusCode = 405;
    res.end(JSON.stringify({ jsonrpc: '2.0', error: { code: -32000, message: 'Use Streamable HTTP POST at /api/mcp' }, id: null }));
    return;
  }
  const server = createServer();
  const transport = new StreamableHTTPServerTransport({ sessionIdGenerator: undefined, enableJsonResponse: true });
  res.on('close', () => {
    void transport.close().catch(() => {});
    void server.close().catch(() => {});
  });
  try {
    await server.connect(transport);
    await transport.handleRequest(req, res, req.body);
  } catch (error) {
    console.error('MCP request failed:', error.message);
    if (!res.headersSent) {
      res.statusCode = 500;
      res.end(JSON.stringify({ jsonrpc: '2.0', error: { code: -32603, message: 'MCP request failed' }, id: null }));
    }
  }
}