#!/usr/bin/env node
'use strict';

const http = require('http');
const net = require('net');

const expectedHostname = (process.env.TPROXY_HOSTNAME || '').toLowerCase();
const upstreamHost = '127.0.0.1';
const upstreamPort = 8080;
const listenPort = 8088;

const page = '<!doctype html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><meta name="robots" content="noindex"><title>Proxy Edge</title><style>body{margin:0;background:#0b1220;color:#dce7f7;font:16px system-ui,sans-serif}main{max-width:720px;margin:16vh auto;padding:32px}h1{font-size:42px;margin:0 0 12px;color:#fff}p{line-height:1.6;color:#9eb2cc}.badge{display:inline-block;padding:6px 10px;border:1px solid #274262;border-radius:999px;color:#86b7ea;font-size:13px}</style></head><body><main><span class="badge">Proxy Edge</span><h1>Private edge transport</h1><p>This endpoint provides resilient transport and availability services for authorized clients.</p></main></body></html>';

function requestHostname(req) {
  return (req.headers.host || '').split(':', 1)[0].toLowerCase();
}

function acceptHost(req) {
  return expectedHostname !== '' && requestHostname(req) === expectedHostname;
}

function failMisdirected(response) {
  response.writeHead(421, {
    'content-type': 'text/plain; charset=utf-8',
    'x-content-type-options': 'nosniff',
    'referrer-policy': 'no-referrer',
  });
  response.end('misdirected request\n');
}

const server = http.createServer((req, res) => {
  if (!acceptHost(req)) {
    failMisdirected(res);
    return;
  }

  const requestUrl = new URL(req.url, 'http://localhost');
  const staticPath =
    requestUrl.pathname === '/' ||
    requestUrl.pathname === '/about' ||
    requestUrl.pathname === '/privacy';

  if (req.method === 'GET' && staticPath && requestUrl.search === '') {
    res.writeHead(200, {
      'content-type': 'text/html; charset=utf-8',
      'cache-control': 'public, max-age=300',
      'x-content-type-options': 'nosniff',
      'referrer-policy': 'no-referrer',
    });
    res.end(page);
    return;
  }

  const upstream = http.request(
    {
      host: upstreamHost,
      port: upstreamPort,
      method: req.method,
      path: req.url,
      headers: req.headers,
    },
    (upstreamResponse) => {
      const headers = { ...upstreamResponse.headers };
      headers['x-content-type-options'] = 'nosniff';
      headers['referrer-policy'] = 'no-referrer';
      res.writeHead(upstreamResponse.statusCode || 502, headers);
      upstreamResponse.pipe(res);
    },
  );

  upstream.on('error', (error) => {
    if (!res.headersSent) {
      res.writeHead(502, { 'content-type': 'text/plain; charset=utf-8' });
    }
    res.end('upstream unavailable\n');
    console.error(`relay error: ${error.message}`);
  });
  req.pipe(upstream);
});

server.on('upgrade', (req, clientSocket, head) => {
  if (!acceptHost(req)) {
    clientSocket.end(
      'HTTP/1.1 421 Misdirected Request\r\nConnection: close\r\n\r\n',
    );
    return;
  }

  const upstreamSocket = net.connect(upstreamPort, upstreamHost, () => {
    let requestHead = `${req.method} ${req.url} HTTP/${req.httpVersion}\r\n`;
    for (let index = 0; index < req.rawHeaders.length; index += 2) {
      requestHead += `${req.rawHeaders[index]}: ${req.rawHeaders[index + 1]}\r\n`;
    }
    upstreamSocket.write(`${requestHead}\r\n`);
    if (head.length > 0) upstreamSocket.write(head);
    upstreamSocket.pipe(clientSocket);
    clientSocket.pipe(upstreamSocket);
  });

  upstreamSocket.on('error', () => clientSocket.destroy());
  clientSocket.on('error', () => upstreamSocket.destroy());
});

server.headersTimeout = 10_000;
server.keepAliveTimeout = 90_000;
server.listen(listenPort, '0.0.0.0', () => {
  console.log(`ingress listening on :${listenPort} for ${expectedHostname}`);
});