const PBKDF2_ITERATIONS = 100000;
const SALT_LENGTH = 16;

export async function hashPassword(password: string): Promise<string> {
  const salt = new Uint8Array(SALT_LENGTH);
  crypto.getRandomValues(salt);

  const keyMaterial = await crypto.subtle.importKey(
    'raw',
    encoder.encode(password),
    'PBKDF2',
    false,
    ['deriveBits']
  );

  const derivedBits = await crypto.subtle.deriveBits(
    { name: 'PBKDF2', salt: salt, iterations: PBKDF2_ITERATIONS, hash: 'SHA-256' },
    keyMaterial,
    256
  );
  // ... returns `pbkdf2:${iterations}:${salt}:${hash}`
}

export async function generateAccessToken(
  env: Env,
  config: Config,
  payload: AccessTokenPayload
): Promise<string> {
  const privateKey = await getPrivateKey(env);

  const jwt = await new jose.SignJWT(payload)
    .setProtectedHeader({ alg: 'RS256', typ: 'at+jwt', kid: 'idpflare-key-1' })
    .setIssuer(config.urls.issuer)
    .setIssuedAt()
    .setExpirationTime(`${config.session.accessTokenDurationSeconds}s`)
    .setJti(crypto.randomUUID())
    .sign(privateKey);
  return jwt;
}

export async function encrypt(plaintext: string, keyHex: string): Promise<string> {
  const key = await crypto.subtle.importKey(
    'raw', hexToBytes(keyHex), 'AES-GCM', false, ['encrypt']
  );

  const iv = new Uint8Array(12);  // 96-bit IV
  crypto.getRandomValues(iv);

  const ciphertext = await crypto.subtle.encrypt(
    { name: 'AES-GCM', iv }, key, encoder.encode(plaintext)
  );

  // Returns `${ivHex}:${ciphertextHex}`
}

const encryptedSecret = await encrypt(secret, env.ENCRYPTION_KEY);
const encryptedBackupCodes = await encrypt(JSON.stringify(backupCodes), env.ENCRYPTION_KEY);

async function generateTOTP(secret: string, timestamp?: number): Promise<string> {
  const time = timestamp || Math.floor(Date.now() / 1000);
  const counter = Math.floor(time / 30); // 30-second period

  const key = base32Decode(secret);
  const counterBytes = intToBytes(counter);

  const hmac = await hmacSha1(key, counterBytes);

  // Dynamic truncation per RFC 6238
  const offset = hmac[hmac.length - 1] & 0x0f;
  // ... 6-digit code
}

export function generateCsrfToken(): string {
  const bytes = new Uint8Array(32);
  crypto.getRandomValues(bytes);
  return btoa(String.fromCharCode(...bytes))
    .replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
}

export function isSafeExternalUrl(url: string): boolean {
  // Only allow HTTPS
  if (parsed.protocol !== 'https:') return false;

  // Block localhost and loopback
  if (hostname === 'localhost' || hostname === '127.0.0.1' || hostname === '::1') return false;

  // Block cloud metadata endpoints
  const blockedHosts = [
    '169.254.169.254', // AWS/GCP
    'metadata.google.internal',
    // ...
  ];

  // Block private IP ranges (RFC 1918)
  // 10.x.x.x, 172.16.x.x-172.31.x.x, 192.168.x.x
  // ...
}

// Email validation
export function isValidEmail(email: string): boolean {
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  return emailRegex.test(email);
}

// Length limits
export const INPUT_LIMITS = {
  EMAIL_MAX_LENGTH: 254,
  PASSWORD_MAX_LENGTH: 128,
  NAME_MAX_LENGTH: 100,
  // ...
};

// XSS prevention
export function escapeHtml(unsafe: string): string {
  return unsafe
    .replace(/&/g, "&")
    .replace(//g, ">")
    .replace(/"/g, """)
    .replace(/'/g, "'");
}