'use strict';
const httpProxy = require('/proxy/node_modules/http-proxy');
const http = require('http');

const N8N_PORT = parseInt(process.env.N8N_PORT || '5200');
const PROXY_PORT = 5678;
const USER = process.env.NGINX_USER;
const PASS = process.env.NGINX_PASSWORD;
const WEBHOOK_RE = /^\/webhook(-test)?\//;

// Rate limiter: max 10 failed attempts per IP within 15 minutes → block for 15 minutes
const MAX_FAILURES = 10;
const WINDOW_MS = 15 * 60 * 1000;
const BLOCK_MS = 15 * 60 * 1000;
const failures = new Map(); // ip → { count, windowStart, blockedUntil }

function getClientIp(req) {
  const forwarded = req.headers['x-forwarded-for'];
  return (forwarded ? forwarded.split(',')[0] : req.socket.remoteAddress).trim();
}

function isBlocked(ip) {
  const entry = failures.get(ip);
  if (!entry) return false;
  if (entry.blockedUntil && Date.now() < entry.blockedUntil) return true;
  // Block expired — reset
  if (entry.blockedUntil) failures.delete(ip);
  return false;
}

function recordFailure(ip) {
  const now = Date.now();
  const entry = failures.get(ip) || { count: 0, windowStart: now, blockedUntil: null };
  // Reset window if it has expired
  if (now - entry.windowStart > WINDOW_MS) {
    entry.count = 0;
    entry.windowStart = now;
  }
  entry.count += 1;
  if (entry.count >= MAX_FAILURES) {
    entry.blockedUntil = now + BLOCK_MS;
    console.warn(`[rate-limit] Blocked ${ip} after ${entry.count} failed attempts`);
  }
  failures.set(ip, entry);
}

function clearFailures(ip) {
  failures.delete(ip);
}

// Purge stale entries every 30 minutes to prevent memory growth
setInterval(() => {
  const now = Date.now();
  for (const [ip, entry] of failures) {
    const expired = entry.blockedUntil
      ? now > entry.blockedUntil
      : now - entry.windowStart > WINDOW_MS;
    if (expired) failures.delete(ip);
  }
}, 30 * 60 * 1000);

const proxy = httpProxy.createProxyServer({
  target: `http://127.0.0.1:${N8N_PORT}`,
  ws: true,
});

proxy.on('error', (err, req, res) => {
  if (res && res.writeHead) {
    res.writeHead(502);
    res.end('n8n starting up, please refresh in a moment');
  }
});

function isAuthorized(req) {
  if (WEBHOOK_RE.test(req.url)) return true;
  const auth = req.headers['authorization'];
  if (!auth || !auth.startsWith('Basic ')) return false;
  const decoded = Buffer.from(auth.slice(6), 'base64').toString();
  const colon = decoded.indexOf(':');
  const user = decoded.slice(0, colon);
  const pass = decoded.slice(colon + 1);
  return user === USER && pass === PASS;
}

const server = http.createServer((req, res) => {
  // Webhooks always pass through
  if (WEBHOOK_RE.test(req.url)) {
    delete req.headers['x-forwarded-for'];
    return proxy.web(req, res);
  }

  const ip = getClientIp(req);

  if (isBlocked(ip)) {
    res.writeHead(429, { 'Content-Type': 'text/plain', 'Retry-After': '900' });
    res.end('Too many failed attempts. Try again in 15 minutes.');
    return;
  }

  if (isAuthorized(req)) {
    clearFailures(ip);
    delete req.headers['x-forwarded-for'];
    proxy.web(req, res);
  } else {
    // Only count as a brute-force attempt when credentials were actually provided
    // but wrong. Unauthenticated requests (no Authorization header) are just the
    // browser loading the page for the first time — counting them would block users
    // before the Basic Auth dialog ever appears (browsers make ~20 parallel requests).
    const hasCredentials = req.headers['authorization'] && req.headers['authorization'].startsWith('Basic ');
    if (hasCredentials) recordFailure(ip);
    res.writeHead(401, {
      'WWW-Authenticate': 'Basic realm="n8n"',
      'Content-Type': 'text/plain',
    });
    res.end('Unauthorized');
  }
});

server.on('upgrade', (req, socket, head) => {
  if (WEBHOOK_RE.test(req.url) || isAuthorized(req)) {
    delete req.headers['x-forwarded-for'];
    proxy.ws(req, socket, head);
  } else {
    socket.destroy();
  }
});

server.listen(PROXY_PORT, () => {
  console.log(`Auth proxy ready on :${PROXY_PORT} → n8n on :${N8N_PORT}`);
});