'use strict';

const http = require('http');
const https = require('https');
const http2 = require('http2');
const tls = require('tls');
const net = require('net');

// ─── 配置 ───────────────────────────────────────────────
const UPSTREAM_HOST = process.env.UPSTREAM_HOST || 'api.anthropic.com';
const LISTEN_PORT = parseInt(process.env.PROXY_PORT || '3456', 10);
const LISTEN_HOST = process.env.PROXY_HOST || '127.0.0.1';
const UPSTREAM_PROXY = process.env.UPSTREAM_PROXY || '';
const CONNECT_TIMEOUT = parseInt(process.env.CONNECT_TIMEOUT || '30000', 10);
const IDLE_TIMEOUT = parseInt(process.env.IDLE_TIMEOUT || '600000', 10);

// ─── 日志 ───────────────────────────────────────────────
const log = (level, msg, extra = {}) => {
  const entry = { time: new Date().toISOString(), level, msg, ...extra };
  process.stderr.write(JSON.stringify(entry) + '\n');
};

const HEALTH_PATH = '/__health';

// ─── HTTP/2 会话缓存 ─────────────────────────────────────
// 按 host 缓存 h2 session，避免每个请求都建新连接
const h2Sessions = new Map();

function getH2Session(host) {
  const existing = h2Sessions.get(host);
  if (existing && !existing.closed && !existing.destroyed) {
    return existing;
  }
  const session = http2.connect(`https://${host}`, {
    // 不设置自定义 TLS 选项 → 用 Node.js 默认 TLS stack
  });
  session.on('error', (err) => {
    log('warn', 'h2 session error', { host, error: err.message });
    h2Sessions.delete(host);
  });
  session.on('close', () => {
    h2Sessions.delete(host);
  });
  // 空闲超时自动关闭
  session.setTimeout(IDLE_TIMEOUT, () => {
    session.close();
    h2Sessions.delete(host);
  });
  h2Sessions.set(host, session);
  return session;
}

// ─── 通过 HTTP 代理建立 CONNECT 隧道 ──────────────────────
function connectViaProxy(proxyUrl, targetHost, targetPort) {
  return new Promise((resolve, reject) => {
    const proxy = new URL(proxyUrl);
    const proxyPort = parseInt(proxy.port || '80', 10);

    const conn = net.connect(proxyPort, proxy.hostname, () => {
      const connectReq =
        `CONNECT ${targetHost}:${targetPort} HTTP/1.1\r\n` +
        `Host: ${targetHost}:${targetPort}\r\n`;

      const auth = proxy.username
        ? `Proxy-Authorization: Basic ${Buffer.from(
            `${decodeURIComponent(proxy.username)}:${decodeURIComponent(proxy.password || '')}`
          ).toString('base64')}\r\n`
        : '';

      conn.write(connectReq + auth + '\r\n');
    });

    conn.once('error', reject);
    conn.setTimeout(CONNECT_TIMEOUT, () => {
      conn.destroy(new Error('proxy CONNECT timeout'));
    });

    let buf = '';
    const onData = (chunk) => {
      buf += chunk.toString();
      const idx = buf.indexOf('\r\n\r\n');
      if (idx === -1) return;

      conn.removeListener('data', onData);
      const statusLine = buf.slice(0, buf.indexOf('\r\n'));
      const statusCode = parseInt(statusLine.split(' ')[1], 10);

      if (statusCode === 200) {
        conn.setTimeout(0);
        const remainder = buf.slice(idx + 4);
        if (remainder.length > 0) {
          conn.unshift(Buffer.from(remainder));
        }
        resolve(conn);
      } else {
        conn.destroy();
        reject(new Error(`proxy CONNECT failed: ${statusLine}`));
      }
    };
    conn.on('data', onData);
  });
}

// ─── TLS + ALPN 探测：判断上游支持 h2 还是 http/1.1 ─────────
const alpnCache = new Map();

function probeALPN(host) {
  const cached = alpnCache.get(host);
  if (cached) return Promise.resolve(cached);

  return new Promise((resolve) => {
    const socket = tls.connect(443, host, {
      ALPNProtocols: ['h2', 'http/1.1'],
      servername: host,
      timeout: 5000,
    });
    socket.once('secureConnect', () => {
      const proto = socket.alpnProtocol || 'http/1.1';
      alpnCache.set(host, proto);
      socket.destroy();
      resolve(proto);
    });
    socket.once('error', () => {
      alpnCache.set(host, 'http/1.1');
      socket.destroy();
      resolve('http/1.1');
    });
    socket.once('timeout', () => {
      alpnCache.set(host, 'http/1.1');
      socket.destroy();
      resolve('http/1.1');
    });
  });
}

// ─── HTTP/2 代理请求 ─────────────────────────────────────
function proxyViaH2(targetHost, req, res) {
  const session = getH2Session(targetHost);

  // 构建 h2 请求头
  const headers = { ...req.headers };
  headers[':method'] = req.method;
  headers[':path'] = req.url;
  headers[':authority'] = targetHost;
  headers[':scheme'] = 'https';
  // 移除 HTTP/1.1 专用头
  delete headers['host'];
  delete headers['connection'];
  delete headers['keep-alive'];
  delete headers['proxy-connection'];
  delete headers['transfer-encoding'];
  delete headers['x-forwarded-host'];

  const h2Req = session.request(headers);

  h2Req.on('response', (h2Headers) => {
    const status = h2Headers[':status'] || 502;
    // 过滤 h2 伪头
    const respHeaders = {};
    for (const [k, v] of Object.entries(h2Headers)) {
      if (!k.startsWith(':')) {
        respHeaders[k] = v;
      }
    }
    res.writeHead(status, respHeaders);
    h2Req.pipe(res, { end: true });
  });

  h2Req.on('error', (err) => {
    log('error', 'h2 upstream error', { error: err.message, host: targetHost, path: req.url });
    // h2 session 可能坏了，清理缓存
    h2Sessions.delete(targetHost);
    if (!res.headersSent) {
      res.writeHead(502, { 'content-type': 'application/json' });
      res.end(JSON.stringify({ error: 'h2_upstream_error', message: err.message }));
    }
  });

  h2Req.setTimeout(CONNECT_TIMEOUT, () => {
    h2Req.close();
  });

  req.on('close', () => {
    if (!h2Req.destroyed) h2Req.close();
  });

  req.pipe(h2Req, { end: true });
}

// ─── HTTP/1.1 代理请求 ────────────────────────────────────
async function proxyViaH1(targetHost, req, res) {
  const headers = { ...req.headers };
  headers.host = targetHost;
  delete headers['x-forwarded-host'];
  delete headers['connection'];
  delete headers['keep-alive'];
  delete headers['proxy-connection'];
  delete headers['transfer-encoding'];

  const opts = {
    hostname: targetHost,
    port: 443,
    path: req.url,
    method: req.method,
    headers,
    servername: targetHost,
    timeout: CONNECT_TIMEOUT,
  };

  let proxyReq;

  if (UPSTREAM_PROXY) {
    try {
      const socket = await connectViaProxy(UPSTREAM_PROXY, targetHost, 443);
      opts.socket = socket;
      opts.agent = false;
      proxyReq = https.request(opts);
    } catch (err) {
      log('error', 'proxy tunnel failed', { error: err.message, host: targetHost });
      if (!res.headersSent) {
        res.writeHead(502, { 'content-type': 'application/json' });
        res.end(JSON.stringify({ error: 'proxy_tunnel_error', message: err.message }));
      }
      return;
    }
  } else {
    proxyReq = https.request(opts);
  }

  proxyReq.on('response', (proxyRes) => {
    const responseHeaders = { ...proxyRes.headers };
    delete responseHeaders['connection'];
    delete responseHeaders['keep-alive'];
    delete responseHeaders['transfer-encoding'];

    res.writeHead(proxyRes.statusCode, responseHeaders);
    proxyRes.pipe(res, { end: true });

    proxyRes.on('error', (err) => {
      log('error', 'upstream response error', { error: err.message, host: targetHost });
      res.end();
    });
  });

  proxyReq.on('error', (err) => {
    log('error', 'h1 upstream error', { error: err.message, host: targetHost, path: req.url, method: req.method });
    if (!res.headersSent) {
      res.writeHead(502, { 'content-type': 'application/json' });
      res.end(JSON.stringify({ error: 'upstream_error', message: err.message }));
    }
  });

  proxyReq.on('timeout', () => {
    log('warn', 'upstream request timeout', { host: targetHost, path: req.url });
    proxyReq.destroy(new Error('upstream timeout'));
  });

  req.on('close', () => {
    if (!proxyReq.destroyed) proxyReq.destroy();
  });

  req.pipe(proxyReq, { end: true });
}

// ─── 代理请求入口 ─────────────────────────────────────────
async function proxyRequest(req, res) {
  const targetHost = req.headers['x-forwarded-host'] || UPSTREAM_HOST;

  log('info', 'proxy_request', { host: targetHost, method: req.method, path: req.url });

  // 探测上游支持的协议，选择 h2 或 h1
  const proto = await probeALPN(targetHost);

  if (proto === 'h2') {
    proxyViaH2(targetHost, req, res);
  } else {
    await proxyViaH1(targetHost, req, res);
  }
}

// ─── HTTP 服务器 ─────────────────────────────────────────
const server = http.createServer((req, res) => {
  if (req.url === HEALTH_PATH) {
    res.writeHead(200, { 'content-type': 'application/json' });
    res.end(JSON.stringify({
      status: 'ok',
      upstream: UPSTREAM_HOST,
      node: process.version,
      openssl: process.versions.openssl,
      uptime: process.uptime(),
      h2Sessions: h2Sessions.size,
      alpnCache: Object.fromEntries(alpnCache),
    }));
    return;
  }

  proxyRequest(req, res).catch((err) => {
    log('error', 'unhandled proxy error', { error: err.message });
    if (!res.headersSent) {
      res.writeHead(500, { 'content-type': 'application/json' });
      res.end(JSON.stringify({ error: 'internal_error' }));
    }
  });
});

server.timeout = 0;
server.keepAliveTimeout = IDLE_TIMEOUT;
server.headersTimeout = 60000;

server.listen(LISTEN_PORT, LISTEN_HOST, () => {
  log('info', 'node-tls-proxy started', {
    listen: `${LISTEN_HOST}:${LISTEN_PORT}`,
    upstream: `${UPSTREAM_HOST}:443`,
    proxy: UPSTREAM_PROXY || '(direct)',
    node: process.version,
    openssl: process.versions.openssl,
    features: ['dynamic-host', 'h2-auto', 'alpn-probe'],
  });
});

// ─── 优雅关闭 ─────────────────────────────────────────────
let shuttingDown = false;
function shutdown(signal) {
  if (shuttingDown) return;
  shuttingDown = true;
  log('info', `received ${signal}, shutting down`);
  // 关闭所有 h2 session
  for (const [host, session] of h2Sessions) {
    session.close();
  }
  h2Sessions.clear();
  server.close(() => {
    log('info', 'server closed');
    process.exit(0);
  });
  setTimeout(() => process.exit(1), 5000);
}
process.on('SIGTERM', () => shutdown('SIGTERM'));
process.on('SIGINT', () => shutdown('SIGINT'));

process.on('uncaughtException', (err) => {
  log('error', 'uncaught exception', { error: err.message, stack: err.stack });
});
process.on('unhandledRejection', (reason) => {
  log('error', 'unhandled rejection', { error: String(reason) });
});