import { createHash, randomBytes } from 'crypto';

/**
 * Generate a cryptographically secure random string
 */
export function generateRandomString(length: number): string {
  const bytes = randomBytes(Math.ceil(length / 2));
  return bytes.toString('hex').slice(0, length);
}

/**
 * Create a code challenge for PKCE (Proof Key for Code Exchange)
 */
export async function createCodeChallenge(codeVerifier: string): Promise<string> {
  const hash = createHash('sha256');
  hash.update(codeVerifier);
  const digest = hash.digest();
  
  // Convert to base64url (URL-safe base64 without padding)
  return digest
    .toString('base64')
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
    .replace(/=/g, '');
}

/**
 * Parse cookies from cookie header string
 */
export function parseCookies(cookieHeader: string): Record<string, string> {
  const cookies: Record<string, string> = {};
  
  if (!cookieHeader) return cookies;
  
  cookieHeader.split(';').forEach(cookie => {
    const [name, ...rest] = cookie.trim().split('=');
    if (name && rest.length > 0) {
      cookies[name] = rest.join('=');
    }
  });
  
  return cookies;
}