'use strict';
/**
 * NetOps To-Do — innebygd autentisering (valgfri, AUTH_MODE=app).
 *
 * Passord hashes med scrypt (Node-kjerne, ingen avhengigheter). Sesjoner er
 * en signert, langlevd cookie: `base64url(user).exp.HMAC-SHA256` — ingen
 * server-side sesjonslager nødvendig, og en restart logger ingen ut så lenge
 * hemmeligheten overlever (env eller persistert fil).
 *
 * Brukere lagres i data/auth.json: { "<user>": { password: "scrypt$..", updated } }
 */

const fs = require('fs');
const path = require('path');
const crypto = require('crypto');

function hashPassword(password) {
  const salt = crypto.randomBytes(16);
  const hash = crypto.scryptSync(String(password), salt, 64);
  return `scrypt$${salt.toString('hex')}$${hash.toString('hex')}`;
}

function verifyPassword(password, stored) {
  if (typeof stored !== 'string') return false;
  const [alg, saltHex, hashHex] = stored.split('$');
  if (alg !== 'scrypt' || !saltHex || !hashHex) return false;
  let expected, actual;
  try {
    expected = Buffer.from(hashHex, 'hex');
    actual = crypto.scryptSync(String(password), Buffer.from(saltHex, 'hex'), expected.length);
  } catch { return false; }
  return expected.length === actual.length && crypto.timingSafeEqual(actual, expected);
}

class Auth {
  constructor(dataDir, { ttlDays = 30, secret = process.env.AUTH_SECRET || '' } = {}) {
    this.dataDir = dataDir;
    this.usersFile = path.join(dataDir, 'auth.json');
    this.secretFile = path.join(dataDir, 'auth.secret');
    this.ttlMs = Math.max(1, ttlDays) * 86400000;
    this.users = {};
    this.secret = secret;
  }

  load() {
    fs.mkdirSync(this.dataDir, { recursive: true });
    try {
      const d = JSON.parse(fs.readFileSync(this.usersFile, 'utf8'));
      if (d && typeof d === 'object' && !Array.isArray(d)) this.users = d;
    } catch { /* ingen brukere ennå */ }

    // Hemmelighet: env > persistert fil > nygenerert (persistert).
    if (!this.secret) {
      try { this.secret = fs.readFileSync(this.secretFile, 'utf8').trim(); } catch { /* genereres under */ }
    }
    if (!this.secret) {
      this.secret = crypto.randomBytes(32).toString('hex');
      try { fs.writeFileSync(this.secretFile, this.secret, { mode: 0o600 }); }
      catch (e) { console.error('Kunne ikke lagre auth.secret:', e.message); }
    }
  }

  _save() {
    const tmp = this.usersFile + '.tmp';
    fs.writeFileSync(tmp, JSON.stringify(this.users, null, 2) + '\n', { mode: 0o600 });
    fs.renameSync(tmp, this.usersFile);
  }

  hasPassword(user) { return !!(user && this.users[user] && this.users[user].password); }
  anyPassword() { return Object.values(this.users).some(u => u && u.password); }

  setPassword(user, password) {
    if (!user) throw new Error('Mangler bruker');
    if (typeof password !== 'string' || password.length < 6) throw new Error('Passord må være minst 6 tegn');
    this.users[user] = { ...(this.users[user] || {}), password: hashPassword(password), updated: new Date().toISOString() };
    this._save();
  }

  verify(user, password) {
    const u = this.users[user];
    return !!(u && u.password && verifyPassword(password, u.password));
  }

  // Signert sesjons-token. user → "<b64url(user)>.<exp>.<hmac>"
  makeToken(user) {
    const payload = `${Buffer.from(String(user)).toString('base64url')}.${Date.now() + this.ttlMs}`;
    const sig = crypto.createHmac('sha256', this.secret).update(payload).digest('base64url');
    return `${payload}.${sig}`;
  }

  verifyToken(token) {
    if (typeof token !== 'string') return null;
    const parts = token.split('.');
    if (parts.length !== 3) return null;
    const payload = `${parts[0]}.${parts[1]}`;
    const expected = crypto.createHmac('sha256', this.secret).update(payload).digest('base64url');
    const a = Buffer.from(parts[2]);
    const b = Buffer.from(expected);
    if (a.length !== b.length || !crypto.timingSafeEqual(a, b)) return null;
    const exp = Number(parts[1]);
    if (!exp || Date.now() > exp) return null;
    try { return Buffer.from(parts[0], 'base64url').toString('utf8') || null; }
    catch { return null; }
  }

  ttlSeconds() { return Math.floor(this.ttlMs / 1000); }
}

module.exports = { Auth, hashPassword, verifyPassword };