'use strict';

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

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';
const h2Hosts = new Set();     // 已知需要 H2 的主机
const h2Sessions = new Map();  // H2 session 缓存

// ─── H2 session 管理 ────────────────────────────────────
function getOrCreateH2Session(host) {
  const existing = h2Sessions.get(host);
  if (existing && !existing.closed && !existing.destroyed) return existing;
  if (existing) { try { existing.close(); } catch (_) {} }

  const session = http2.connect(`https://${host}`);
  session.on('error', (err) => {
    log('warn', 'h2_session_error', { host, error: err.message });
    h2Sessions.delete(host);
    try { session.close(); } catch (_) {}
  });
  session.on('close', () => h2Sessions.delete(host));
  session.on('goaway', () => { h2Sessions.delete(host); try { session.close(); } catch (_) {} });
  session.setTimeout(IDLE_TIMEOUT, () => { session.close(); h2Sessions.delete(host); });
  h2Sessions.set(host, session);
  return session;
}

function waitForConnect(session) {
  if (session.connected) return Promise.resolve();
  return new Promise((resolve, reject) => {
    session.once('connect', resolve);
    session.once('error', reject);
    const t = setTimeout(() => reject(new Error('h2 connect timeout')), CONNECT_TIMEOUT);
    session.once('connect', () => clearTimeout(t));
  });
}

// ─── CONNECT 隧道 ────────────────────────────────────────
function connectViaProxy(proxyUrl, targetHost, targetPort) {
  return new Promise((resolve, reject) => {
    const proxy = new URL(proxyUrl);
    const conn = net.connect(parseInt(proxy.port || '80', 10), proxy.hostname, () => {
      const auth = proxy.username
        ? `Proxy-Authorization: Basic ${Buffer.from(`${decodeURIComponent(proxy.username)}:${decodeURIComponent(proxy.password || '')}`).toString('base64')}\r\n`
        : '';
      conn.write(`CONNECT ${targetHost}:${targetPort} HTTP/1.1\r\nHost: ${targetHost}:${targetPort}\r\n${auth}\r\n`);
    });
    conn.once('error', reject);
    conn.setTimeout(CONNECT_TIMEOUT, () => conn.destroy(new Error('CONNECT timeout')));
    let buf = '';
    conn.on('data', function onData(chunk) {
      buf += chunk.toString();
      const idx = buf.indexOf('\r\n\r\n');
      if (idx === -1) return;
      conn.removeListener('data', onData);
      const code = parseInt(buf.split(' ')[1], 10);
      if (code === 200) { conn.setTimeout(0); resolve(conn); }
      else { conn.destroy(); reject(new Error(`CONNECT ${code}`)); }
    });
  });
}

// ─── 收集请求体 ──────────────────────────────────────────
function collectBody(req) {
  return new Promise((resolve) => {
    const chunks = [];
    req.on('data', (c) => chunks.push(c));
    req.on('end', () => resolve(Buffer.concat(chunks)));
    req.on('error', () => resolve(Buffer.concat(chunks)));
  });
}

// ─── H1 代理 ─────────────────────────────────────────────
function sendViaH1(targetHost, method, path, reqHeaders, body, res) {
  return new Promise((resolve) => {
    const headers = { ...reqHeaders, host: targetHost };
    ['x-forwarded-host', 'connection', 'keep-alive', 'proxy-connection', 'transfer-encoding'].forEach(h => delete headers[h]);
    if (body.length > 0) headers['content-length'] = String(body.length);

    const opts = { hostname: targetHost, port: 443, path, method, headers, servername: targetHost, timeout: CONNECT_TIMEOUT };
    const startTime = Date.now();

    const finish = (requestOpts) => {
      const proxyReq = https.request(requestOpts);
      proxyReq.on('response', (proxyRes) => {
        log('info', 'proxy_response', { host: targetHost, status: proxyRes.statusCode, path, proto: 'h1' });
        const rh = { ...proxyRes.headers };
        delete rh['connection']; delete rh['keep-alive'];
        res.writeHead(proxyRes.statusCode, rh);
        proxyRes.pipe(res, { end: true });
        resolve('ok');
      });
      proxyReq.on('error', (err) => {
        if (err.message === 'socket hang up' && (Date.now() - startTime) < 2000) {
          log('info', 'h1_rejected_switching_to_h2', { host: targetHost });
          h2Hosts.add(targetHost);
          sendViaH2(targetHost, method, path, reqHeaders, body, res).then(() => resolve('h2'));
          return;
        }
        log('error', 'h1_error', { error: err.message, host: targetHost, path });
        if (!res.headersSent) { res.writeHead(502); res.end(JSON.stringify({ error: err.message })); }
        resolve('error');
      });
      proxyReq.on('timeout', () => proxyReq.destroy(new Error('timeout')));
      proxyReq.end(body);
    };

    if (UPSTREAM_PROXY) {
      connectViaProxy(UPSTREAM_PROXY, targetHost, 443)
        .then((socket) => { opts.socket = socket; opts.agent = false; finish(opts); })
        .catch((err) => { log('error', 'tunnel_failed', { error: err.message }); if (!res.headersSent) { res.writeHead(502); res.end('tunnel error'); } resolve('error'); });
    } else {
      finish(opts);
    }
  });
}

// ─── H2 代理 ─────────────────────────────────────────────
async function sendViaH2(targetHost, method, path, reqHeaders, body, res) {
  try {
    const session = getOrCreateH2Session(targetHost);
    await waitForConnect(session);

    const headers = {};
    const skip = new Set(['host','connection','keep-alive','proxy-connection','transfer-encoding','upgrade','x-forwarded-host','http2-settings']);
    for (const [k, v] of Object.entries(reqHeaders)) {
      if (!skip.has(k.toLowerCase())) headers[k] = v;
    }
    headers[':method'] = method;
    headers[':path'] = path;
    headers[':authority'] = targetHost;
    headers[':scheme'] = 'https';
    if (body.length > 0) headers['content-length'] = String(body.length);

    const stream = session.request(headers);
    let responded = false;

    stream.on('response', (h2h) => {
      responded = true;
      const status = h2h[':status'] || 502;
      const rh = {};
      for (const [k, v] of Object.entries(h2h)) { if (!k.startsWith(':')) rh[k] = v; }
      log('info', 'proxy_response', { host: targetHost, status, path, proto: 'h2' });
      res.writeHead(status, rh);
      stream.on('data', (c) => res.write(c));
      stream.on('end', () => res.end());
    });

    stream.on('error', (err) => {
      if (err.message && err.message.includes('NGHTTP2')) {
        h2Sessions.delete(targetHost);
        try { session.close(); } catch (_) {}
      }
      if (responded) { if (!res.writableEnded) res.end(); return; }
      log('error', 'h2_error', { error: err.message, host: targetHost, path });
      if (!res.headersSent) { res.writeHead(502); res.end(JSON.stringify({ error: err.message })); }
    });

    stream.on('close', () => {
      if (!responded && !res.headersSent) {
        log('warn', 'h2_no_response', { host: targetHost, path });
        res.writeHead(502); res.end('{"error":"h2_no_response"}');
      } else if (!res.writableEnded) { res.end(); }
    });

    stream.setTimeout(CONNECT_TIMEOUT, () => stream.close());
    stream.end(body);
  } catch (err) {
    log('error', 'h2_exception', { error: err.message, host: targetHost });
    h2Sessions.delete(targetHost);
    if (!res.headersSent) { res.writeHead(502); res.end(JSON.stringify({ error: err.message })); }
  }
}

// ─── 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 });

  const body = await collectBody(req);

  if (h2Hosts.has(targetHost)) {
    await sendViaH2(targetHost, req.method, req.url, req.headers, body, res);
  } else {
    await sendViaH1(targetHost, req.method, req.url, req.headers, body, 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', node: process.version, openssl: process.versions.openssl, uptime: process.uptime(), h2Hosts: [...h2Hosts] }));
    return;
  }
  proxyRequest(req, res).catch((err) => {
    log('error', 'unhandled', { error: err.message });
    if (!res.headersSent) { res.writeHead(500); res.end('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}`, node: process.version, openssl: process.versions.openssl });
});

let stopping = false;
function shutdown(sig) {
  if (stopping) return; stopping = true;
  for (const s of h2Sessions.values()) try { s.close(); } catch (_) {}
  h2Sessions.clear();
  server.close(() => process.exit(0));
  setTimeout(() => process.exit(1), 5000);
}
process.on('SIGTERM', () => shutdown('SIGTERM'));
process.on('SIGINT', () => shutdown('SIGINT'));
process.on('uncaughtException', (e) => log('error', 'uncaught', { error: e.message }));
process.on('unhandledRejection', (r) => log('error', 'rejection', { error: String(r) }));