import crypto from 'node:crypto';
import { spawnSync } from 'node:child_process';
import fs from 'node:fs';
import http from 'node:http';
import https from 'node:https';
import path from 'node:path';

const PORT = Number.parseInt(process.env.PORT || '8081', 10);
if (!Number.isInteger(PORT) || PORT <= 0) throw new Error(`Invalid PORT: ${process.env.PORT}`);

const APP_VERSION = String(process.env.APP_VERSION || 'v1').trim() || 'v1';
const BUILD_TIMESTAMP = String(process.env.BUILD_TIMESTAMP || '').trim() || undefined;
const STARTED_AT = new Date().toISOString();

const STATIC_DIR = process.env.STATIC_DIR || '/srv';
const BASIC_AUTH_FILE = process.env.BASIC_AUTH_FILE || '/tokens/frontend.json';
const API_READ_TOKEN_FILE = process.env.API_READ_TOKEN_FILE || '/tokens/read.json';
const API_UPSTREAM = process.env.API_UPSTREAM || process.env.API_URL || 'http://api:8787';
const BASIC_AUTH_MODE = String(process.env.BASIC_AUTH_MODE || 'on')
  .trim()
  .toLowerCase();
const BASIC_AUTH_ENABLED = !['off', 'false', '0', 'disabled', 'none'].includes(BASIC_AUTH_MODE);
const AUTH_USER_HEADER = String(process.env.AUTH_USER_HEADER || 'x-trade-user')
  .trim()
  .toLowerCase();
const AUTH_MODE = String(process.env.AUTH_MODE || 'session')
  .trim()
  .toLowerCase();
const HTPASSWD_FILE = String(process.env.HTPASSWD_FILE || '/auth/users').trim();
const AUTH_SESSION_SECRET_FILE = String(process.env.AUTH_SESSION_SECRET_FILE || '').trim() || null;
const AUTH_SESSION_COOKIE = String(process.env.AUTH_SESSION_COOKIE || 'trade_session')
  .trim()
  .toLowerCase();
const AUTH_SESSION_TTL_SECONDS = Number.parseInt(process.env.AUTH_SESSION_TTL_SECONDS || '43200', 10); // 12h

function readJson(filePath) {
  const raw = fs.readFileSync(filePath, 'utf8');
  return JSON.parse(raw);
}

function readText(filePath) {
  return fs.readFileSync(filePath, 'utf8');
}

function timingSafeEqualStr(a, b) {
  const aa = Buffer.from(String(a), 'utf8');
  const bb = Buffer.from(String(b), 'utf8');
  if (aa.length !== bb.length) return false;
  return crypto.timingSafeEqual(aa, bb);
}

function timingSafeEqualBuf(a, b) {
  if (!(a instanceof Uint8Array) || !(b instanceof Uint8Array)) return false;
  if (a.length !== b.length) return false;
  return crypto.timingSafeEqual(Buffer.from(a), Buffer.from(b));
}

function loadBasicAuth() {
  const j = readJson(BASIC_AUTH_FILE);
  const username = (j?.username || '').toString();
  const password = (j?.password || '').toString();
  if (!username || !password) throw new Error(`Invalid BASIC_AUTH_FILE: ${BASIC_AUTH_FILE}`);
  return { username, password };
}

function loadApiReadToken() {
  const j = readJson(API_READ_TOKEN_FILE);
  const token = (j?.token || '').toString();
  if (!token) throw new Error(`Invalid API_READ_TOKEN_FILE: ${API_READ_TOKEN_FILE}`);
  return token;
}

function send(res, status, headers, body) {
  res.statusCode = status;
  for (const [k, v] of Object.entries(headers || {})) res.setHeader(k, v);
  if (body == null) return void res.end();
  res.end(body);
}

function sendJson(res, status, body) {
  send(res, status, { 'content-type': 'application/json; charset=utf-8', 'cache-control': 'no-store' }, JSON.stringify(body));
}

function basicAuthRequired(res) {
  res.setHeader('www-authenticate', 'Basic realm="trade"');
  send(res, 401, { 'content-type': 'text/plain; charset=utf-8' }, 'unauthorized');
}

function unauthorized(res) {
  sendJson(res, 401, { ok: false, error: 'unauthorized' });
}

function isAuthorized(req, creds) {
  const auth = req.headers.authorization || '';
  const m = String(auth).match(/^Basic\s+(.+)$/i);
  if (!m?.[1]) return false;
  let decoded;
  try {
    decoded = Buffer.from(m[1], 'base64').toString('utf8');
  } catch {
    return false;
  }
  const idx = decoded.indexOf(':');
  if (idx < 0) return false;
  const u = decoded.slice(0, idx);
  const p = decoded.slice(idx + 1);
  return timingSafeEqualStr(u, creds.username) && timingSafeEqualStr(p, creds.password);
}

const MIME = {
  '.html': 'text/html; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.js': 'application/javascript; charset=utf-8',
  '.mjs': 'application/javascript; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.gif': 'image/gif',
  '.ico': 'image/x-icon',
  '.txt': 'text/plain; charset=utf-8',
  '.map': 'application/json; charset=utf-8',
};

function contentTypeFor(filePath) {
  return MIME[path.extname(filePath).toLowerCase()] || 'application/octet-stream';
}

function safePathFromUrlPath(urlPath) {
  const decoded = decodeURIComponent(urlPath);
  const cleaned = decoded.replace(/\0/g, '');
  // strip leading slash so join() doesn't ignore STATIC_DIR
  const rel = cleaned.replace(/^\/+/, '');
  const normalized = path.normalize(rel);
  // prevent traversal
  if (normalized.startsWith('..') || path.isAbsolute(normalized)) return null;
  return normalized;
}

function serveStatic(req, res) {
  if (req.method !== 'GET' && req.method !== 'HEAD') {
    send(res, 405, { 'content-type': 'text/plain; charset=utf-8' }, 'method_not_allowed');
    return;
  }

  const url = new URL(req.url || '/', `http://${req.headers.host || 'localhost'}`);
  const rel = safePathFromUrlPath(url.pathname);
  if (rel == null) {
    send(res, 400, { 'content-type': 'text/plain; charset=utf-8' }, 'bad_request');
    return;
  }

  const root = path.resolve(STATIC_DIR);
  const fileCandidate = path.resolve(root, rel);
  if (!fileCandidate.startsWith(root)) {
    send(res, 400, { 'content-type': 'text/plain; charset=utf-8' }, 'bad_request');
    return;
  }

  const trySend = (filePath) => {
    try {
      const st = fs.statSync(filePath);
      if (st.isDirectory()) return trySend(path.join(filePath, 'index.html'));
      res.statusCode = 200;
      res.setHeader('content-type', contentTypeFor(filePath));
      res.setHeader('cache-control', filePath.endsWith('index.html') ? 'no-cache' : 'public, max-age=31536000');
      if (req.method === 'HEAD') return void res.end();
      fs.createReadStream(filePath).pipe(res);
      return true;
    } catch {
      return false;
    }
  };

  // exact file, otherwise SPA fallback
  if (trySend(fileCandidate)) return;
  const indexPath = path.join(root, 'index.html');
  if (trySend(indexPath)) return;

  send(res, 404, { 'content-type': 'text/plain; charset=utf-8' }, 'not_found');
}

function stripHopByHopHeaders(headers) {
  const hop = new Set([
    'connection',
    'keep-alive',
    'proxy-authenticate',
    'proxy-authorization',
    'te',
    'trailer',
    'transfer-encoding',
    'upgrade',
  ]);
  const out = {};
  for (const [k, v] of Object.entries(headers || {})) {
    if (hop.has(k.toLowerCase())) continue;
    out[k] = v;
  }
  return out;
}

function readHeader(req, name) {
  const v = req.headers[String(name).toLowerCase()];
  return Array.isArray(v) ? v[0] : v;
}

function readCookie(req, name) {
  const raw = typeof req.headers.cookie === 'string' ? req.headers.cookie : '';
  if (!raw) return null;
  const needle = `${name}=`;
  for (const part of raw.split(';')) {
    const t = part.trim();
    if (!t.startsWith(needle)) continue;
    return t.slice(needle.length) || null;
  }
  return null;
}

function resolveAuthUser(req) {
  const user = readHeader(req, AUTH_USER_HEADER) || readHeader(req, 'x-webauth-user');
  const value = typeof user === 'string' ? user.trim() : '';
  return value || null;
}

function isHttpsRequest(req) {
  const xf = readHeader(req, 'x-forwarded-proto');
  if (typeof xf === 'string' && xf.toLowerCase() === 'https') return true;
  return Boolean(req.socket && req.socket.encrypted);
}

function base64urlEncode(buf) {
  return Buffer.from(buf)
    .toString('base64')
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
    .replace(/=+$/g, '');
}

function base64urlDecode(str) {
  const cleaned = String(str).replace(/-/g, '+').replace(/_/g, '/');
  const pad = cleaned.length % 4 === 0 ? '' : '='.repeat(4 - (cleaned.length % 4));
  return Buffer.from(cleaned + pad, 'base64');
}

function loadSessionSecret() {
  if (process.env.AUTH_SESSION_SECRET && String(process.env.AUTH_SESSION_SECRET).trim()) {
    return Buffer.from(String(process.env.AUTH_SESSION_SECRET).trim(), 'utf8');
  }
  if (AUTH_SESSION_SECRET_FILE) {
    try {
      const txt = readText(AUTH_SESSION_SECRET_FILE).trim();
      if (txt) return Buffer.from(txt, 'utf8');
    } catch {
      // ignore
    }
  }
  return crypto.randomBytes(32);
}

const SESSION_SECRET = loadSessionSecret();

function signSessionPayload(payloadB64) {
  return crypto.createHmac('sha256', SESSION_SECRET).update(payloadB64).digest();
}

function makeSessionCookieValue(username) {
  const now = Math.floor(Date.now() / 1000);
  const exp = now + (Number.isFinite(AUTH_SESSION_TTL_SECONDS) && AUTH_SESSION_TTL_SECONDS > 0 ? AUTH_SESSION_TTL_SECONDS : 43200);
  const payload = JSON.stringify({ u: String(username), exp });
  const payloadB64 = base64urlEncode(Buffer.from(payload, 'utf8'));
  const sigB64 = base64urlEncode(signSessionPayload(payloadB64));
  return `${payloadB64}.${sigB64}`;
}

function getSessionUser(req) {
  const raw = readCookie(req, AUTH_SESSION_COOKIE);
  if (!raw) return null;
  const parts = raw.split('.');
  if (parts.length !== 2) return null;
  const [payloadB64, sigB64] = parts;
  if (!payloadB64 || !sigB64) return null;

  let payload;
  try {
    payload = JSON.parse(base64urlDecode(payloadB64).toString('utf8'));
  } catch {
    return null;
  }
  const u = typeof payload?.u === 'string' ? payload.u.trim() : '';
  const exp = Number(payload?.exp);
  if (!u || !Number.isFinite(exp)) return null;
  const now = Math.floor(Date.now() / 1000);
  if (now >= exp) return null;

  const expected = signSessionPayload(payloadB64);
  let got;
  try {
    got = base64urlDecode(sigB64);
  } catch {
    return null;
  }
  if (!timingSafeEqualBuf(expected, got)) return null;

  return u;
}

function resolveAuthenticatedUser(req) {
  const sessionUser = getSessionUser(req);
  if (sessionUser) return sessionUser;
  const headerUser = resolveAuthUser(req);
  if (headerUser) return headerUser;
  if (AUTH_MODE === 'off' || AUTH_MODE === 'none' || AUTH_MODE === 'disabled') return 'anonymous';
  return null;
}

function clearSessionCookie(res, secure) {
  const parts = [`${AUTH_SESSION_COOKIE}=`, 'Path=/', 'Max-Age=0', 'HttpOnly', 'SameSite=Lax'];
  if (secure) parts.push('Secure');
  res.setHeader('set-cookie', parts.join('; '));
}

function setSessionCookie(res, secure, username) {
  const value = makeSessionCookieValue(username);
  const parts = [
    `${AUTH_SESSION_COOKIE}=${value}`,
    'Path=/',
    `Max-Age=${Number.isFinite(AUTH_SESSION_TTL_SECONDS) ? AUTH_SESSION_TTL_SECONDS : 43200}`,
    'HttpOnly',
    'SameSite=Lax',
  ];
  if (secure) parts.push('Secure');
  res.setHeader('set-cookie', parts.join('; '));
}

function verifyWithHtpasswd(username, password) {
  try {
    const r = spawnSync('htpasswd', ['-vb', HTPASSWD_FILE, String(username), String(password)], {
      stdio: 'ignore',
      timeout: 3000,
    });
    return r.status === 0;
  } catch {
    return false;
  }
}

function readBody(req, limitBytes = 1024 * 16) {
  return new Promise((resolve, reject) => {
    let total = 0;
    const chunks = [];
    req.on('data', (chunk) => {
      total += chunk.length;
      if (total > limitBytes) {
        reject(new Error('payload_too_large'));
        req.destroy();
        return;
      }
      chunks.push(chunk);
    });
    req.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
    req.on('error', reject);
  });
}

function proxyApi(req, res, apiReadToken) {
  const upstreamBase = new URL(API_UPSTREAM);
  const inUrl = new URL(req.url || '/', `http://${req.headers.host || 'localhost'}`);

  const prefix = '/api';
  const strippedPath = inUrl.pathname === prefix ? '/' : inUrl.pathname.startsWith(prefix + '/') ? inUrl.pathname.slice(prefix.length) : null;
  if (strippedPath == null) {
    send(res, 404, { 'content-type': 'text/plain; charset=utf-8' }, 'not_found');
    return;
  }

  const target = new URL(upstreamBase.toString());
  target.pathname = strippedPath || '/';
  target.search = inUrl.search;

  const isHttps = target.protocol === 'https:';
  const lib = isHttps ? https : http;

  const headers = stripHopByHopHeaders(req.headers);
  delete headers.authorization; // basic auth from client must not leak upstream
  headers.host = target.host;
  headers.authorization = `Bearer ${apiReadToken}`;

  const upstreamReq = lib.request(
    {
      protocol: target.protocol,
      hostname: target.hostname,
      port: target.port || (isHttps ? 443 : 80),
      method: req.method,
      path: target.pathname + target.search,
      headers,
    },
    (upstreamRes) => {
      const outHeaders = stripHopByHopHeaders(upstreamRes.headers);
      res.writeHead(upstreamRes.statusCode || 502, outHeaders);
      upstreamRes.pipe(res);
    }
  );

  upstreamReq.on('error', (err) => {
    if (!res.headersSent) {
      send(res, 502, { 'content-type': 'text/plain; charset=utf-8' }, `bad_gateway: ${err?.message || err}`);
    } else {
      res.destroy();
    }
  });

  req.pipe(upstreamReq);
}

async function handler(req, res) {
  if (req.method === 'GET' && (req.url === '/healthz' || req.url?.startsWith('/healthz?'))) {
    send(
      res,
      200,
      { 'content-type': 'application/json; charset=utf-8' },
      JSON.stringify({ ok: true, version: APP_VERSION, buildTimestamp: BUILD_TIMESTAMP, startedAt: STARTED_AT })
    );
    return;
  }

  const url = new URL(req.url || '/', `http://${req.headers.host || 'localhost'}`);
  if (req.method === 'GET' && url.pathname === '/whoami') {
    sendJson(res, 200, { ok: true, user: resolveAuthenticatedUser(req), mode: AUTH_MODE });
    return;
  }

  if (req.method === 'POST' && url.pathname === '/auth/login') {
    if (AUTH_MODE === 'off' || AUTH_MODE === 'none' || AUTH_MODE === 'disabled') {
      sendJson(res, 400, { ok: false, error: 'auth_disabled' });
      return;
    }

    const raw = await readBody(req);
    const ct = String(req.headers['content-type'] || '').toLowerCase();
    let username = '';
    let password = '';
    if (ct.includes('application/json')) {
      let json;
      try {
        json = JSON.parse(raw);
      } catch {
        sendJson(res, 400, { ok: false, error: 'bad_json' });
        return;
      }
      username = typeof json?.username === 'string' ? json.username.trim() : '';
      password = typeof json?.password === 'string' ? json.password : '';
    } else {
      const params = new URLSearchParams(raw);
      username = String(params.get('username') || '').trim();
      password = String(params.get('password') || '');
    }

    if (!username || !password || username.length > 64 || password.length > 200) {
      sendJson(res, 400, { ok: false, error: 'invalid_input' });
      return;
    }

    const ok = verifyWithHtpasswd(username, password);
    if (!ok) {
      unauthorized(res);
      return;
    }

    const secure = isHttpsRequest(req);
    setSessionCookie(res, secure, username);
    sendJson(res, 200, { ok: true, user: username });
    return;
  }

  if ((req.method === 'POST' || req.method === 'GET') && (url.pathname === '/auth/logout' || url.pathname === '/logout')) {
    clearSessionCookie(res, isHttpsRequest(req));
    if (req.method === 'GET') {
      res.statusCode = 302;
      res.setHeader('location', '/');
      res.end();
      return;
    }
    sendJson(res, 200, { ok: true });
    return;
  }

  if (BASIC_AUTH_ENABLED) {
    let creds;
    try {
      creds = loadBasicAuth();
    } catch (e) {
      send(res, 500, { 'content-type': 'text/plain; charset=utf-8' }, String(e?.message || e));
      return;
    }

    if (!isAuthorized(req, creds)) {
      basicAuthRequired(res);
      return;
    }
  }

  if (req.url?.startsWith('/api') && (req.url === '/api' || req.url.startsWith('/api/'))) {
    if (AUTH_MODE !== 'off' && AUTH_MODE !== 'none' && AUTH_MODE !== 'disabled') {
      const user = resolveAuthenticatedUser(req);
      if (!user) {
        unauthorized(res);
        return;
      }
    }

    let token;
    try {
      token = loadApiReadToken();
    } catch (e) {
      send(res, 500, { 'content-type': 'text/plain; charset=utf-8' }, String(e?.message || e));
      return;
    }
    proxyApi(req, res, token);
    return;
  }

  serveStatic(req, res);
}

const server = http.createServer((req, res) => {
  handler(req, res).catch((e) => {
    if (res.headersSent) {
      res.destroy();
      return;
    }
    send(res, 500, { 'content-type': 'text/plain; charset=utf-8' }, String(e?.message || e));
  });
});
server.listen(PORT, () => {
  console.log(
    JSON.stringify(
      {
        service: 'trade-frontend',
        port: PORT,
        staticDir: STATIC_DIR,
        apiUpstream: API_UPSTREAM,
        basicAuthFile: BASIC_AUTH_FILE,
        basicAuthMode: BASIC_AUTH_MODE,
        apiReadTokenFile: API_READ_TOKEN_FILE,
        authUserHeader: AUTH_USER_HEADER,
        authMode: AUTH_MODE,
        htpasswdFile: HTPASSWD_FILE,
      },
      null,
      2
    )
  );
});