/**
 * Google ile Giriş — backend doğrulama (ek bağımlılık yok).
 * GIS ID-token akışı: frontend Google'dan ID token alır, buraya gönderir;
 * biz oauth2.googleapis.com/tokeninfo ile doğrular, aud=GOOGLE_CLIENT_ID +
 * email_verified kontrol eder, HMAC imzalı kısa bir uygulama token'ı veririz.
 * Admin: ADMIN_EMAILS listesindeki e-postalar.
 */

import crypto from 'node:crypto';
import https from 'node:https';

const CLIENT_ID = () => process.env.GOOGLE_CLIENT_ID || null;
const AUTH_SECRET = () => {
  const configured = process.env.AUTH_SECRET || process.env.GOOGLE_CLIENT_ID;
  if (configured) return configured;
  if (process.env.NODE_ENV === 'production') throw new Error('Üretimde AUTH_SECRET zorunludur.');
  return 'ihaleist-dev-secret';
};
const TOKEN_TTL_SEC = 30 * 24 * 60 * 60; // 30 gün

export function adminEmails() {
  return (process.env.ADMIN_EMAILS || '')
    .split(',')
    .map((e) => e.trim().toLowerCase())
    .filter(Boolean);
}
export function isAdminEmail(email) {
  return adminEmails().includes(String(email || '').toLowerCase());
}

// --- Uygulama token'ı (HMAC imzalı, kompakt) ---
function b64url(buf) {
  return Buffer.from(buf).toString('base64').replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
}
function b64urlJson(obj) {
  return b64url(JSON.stringify(obj));
}
export function signToken(payload) {
  const body = { ...payload, exp: Math.floor(Date.now() / 1000) + TOKEN_TTL_SEC };
  const data = b64urlJson(body);
  const sig = b64url(crypto.createHmac('sha256', AUTH_SECRET()).update(data).digest());
  return `${data}.${sig}`;
}
export function verifyToken(token) {
  if (!token || typeof token !== 'string' || !token.includes('.')) return null;
  const [data, sig] = token.split('.');
  const expected = b64url(crypto.createHmac('sha256', AUTH_SECRET()).update(data).digest());
  if (
    sig.length !== expected.length ||
    !crypto.timingSafeEqual(Buffer.from(sig), Buffer.from(expected))
  ) {
    return null;
  }
  try {
    const body = JSON.parse(Buffer.from(data.replace(/-/g, '+').replace(/_/g, '/'), 'base64').toString());
    if (body.exp && body.exp < Math.floor(Date.now() / 1000)) return null;
    return body;
  } catch {
    return null;
  }
}

// --- Google ID token doğrulama (tokeninfo) ---
function fetchJson(url) {
  return new Promise((resolve, reject) => {
    https
      .get(url, { timeout: 15000 }, (res) => {
        const chunks = [];
        res.on('data', (c) => chunks.push(c));
        res.on('end', () => {
          const text = Buffer.concat(chunks).toString('utf8');
          if (res.statusCode !== 200) return reject(new Error(`tokeninfo HTTP ${res.statusCode}`));
          try {
            resolve(JSON.parse(text));
          } catch {
            reject(new Error('tokeninfo geçersiz JSON'));
          }
        });
      })
      .on('timeout', function () {
        this.destroy(new Error('tokeninfo zaman aşımı'));
      })
      .on('error', reject);
  });
}

export async function loginWithGoogle(credential) {
  const clientId = CLIENT_ID();
  if (!clientId) throw new Error('Google girişi kapalı (GOOGLE_CLIENT_ID yok)');
  if (!credential) throw new Error('credential yok');
  const p = await fetchJson(
    `https://oauth2.googleapis.com/tokeninfo?id_token=${encodeURIComponent(credential)}`,
  );
  if (p.aud !== clientId) throw new Error('aud eşleşmiyor');
  if (p.email_verified !== 'true' && p.email_verified !== true) throw new Error('e-posta doğrulanmamış');
  const email = String(p.email).toLowerCase();
  const isAdmin = isAdminEmail(email);
  const user = {
    email,
    name: p.name || p.given_name || email.split('@')[0],
    picture: p.picture || null,
    isAdmin,
    roles: isAdmin ? ['USER', 'ADMIN'] : ['USER'],
  };
  const token = signToken({ email: user.email, name: user.name, isAdmin });
  return { token, user };
}

export function userFromAuthHeader(authHeader) {
  const m = /^Bearer\s+(.+)$/i.exec(authHeader || '');
  if (!m) return null;
  const claims = verifyToken(m[1]);
  if (!claims) return null;
  return {
    email: claims.email,
    name: claims.name,
    isAdmin: Boolean(claims.isAdmin),
    roles: claims.isAdmin ? ['USER', 'ADMIN'] : ['USER'],
  };
}