import crypto from 'node:crypto';

// Ohne leicht verwechselbare Zeichen (0/O, 1/I/L).
const CODE_ALPHABET = 'ABCDEFGHJKMNPQRSTUVWXYZ23456789';

export function randomCode(length = 8) {
  const bytes = crypto.randomBytes(length);
  let out = '';
  for (let i = 0; i < length; i++) out += CODE_ALPHABET[bytes[i] % CODE_ALPHABET.length];
  return out;
}

export function normalizeCode(input) {
  return String(input ?? '')
    .toUpperCase()
    .replace(/[^A-Z0-9]/g, '');
}

export function formatCode(code) {
  return code.length === 8 ? `${code.slice(0, 4)}-${code.slice(4)}` : code;
}

export function randomToken() {
  return crypto.randomBytes(32).toString('base64url');
}

export function randomId() {
  return crypto.randomBytes(9).toString('base64url');
}

/** Alphanumerisches Passwort, sicher für Konsolenbefehle ohne Escaping. */
export function randomPassword(length = 16) {
  const alphabet = 'abcdefghijkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789';
  const bytes = crypto.randomBytes(length);
  let out = '';
  for (let i = 0; i < length; i++) out += alphabet[bytes[i] % alphabet.length];
  return out;
}

export function hashToken(token) {
  return crypto.createHash('sha256').update(String(token)).digest('hex');
}

export function safeEqual(a, b) {
  const ba = Buffer.from(String(a));
  const bb = Buffer.from(String(b));
  return ba.length === bb.length && crypto.timingSafeEqual(ba, bb);
}

/** Einfacher In-Memory-Ratenbegrenzer (Fenster pro Schlüssel). */
export function createRateLimiter({ windowMs, max }) {
  const hits = new Map();
  return function check(key) {
    const now = Date.now();
    const entry = hits.get(key);
    if (!entry || now - entry.start > windowMs) {
      hits.set(key, { start: now, count: 1 });
      return true;
    }
    entry.count += 1;
    if (hits.size > 10_000) {
      for (const [k, v] of hits) if (now - v.start > windowMs) hits.delete(k);
    }
    return entry.count <= max;
  };
}