/**
 * TenderRadar Authentication Utilities
 * Shared auth module for all app pages
 */

/**
 * Get JWT token from localStorage
 * @returns {string|null} JWT token or null if not found
 */
function getToken() {
  return localStorage.getItem('tenderradar_token');
}

/**
 * Set JWT token in localStorage
 * @param {string} token - JWT token to store
 */
function setToken(token) {
  localStorage.setItem('tenderradar_token', token);
}

/**
 * Clear JWT token from localStorage
 */
function clearToken() {
  localStorage.removeItem('tenderradar_token');
}

/**
 * Check if user is authenticated
 * @returns {boolean} true if token exists, false otherwise
 */
function isAuthenticated() {
  return !!getToken();
}

/**
 * Decode JWT payload (simple, does not verify signature)
 * @returns {object|null} Decoded payload or null if token invalid
 */
function getUserInfo() {
  const token = getToken();
  if (!token) return null;

  try {
    const parts = token.split('.');
    if (parts.length !== 3) return null;

    const payload = JSON.parse(atob(parts[1]));
    return payload;
  } catch (e) {
    console.error('Failed to decode token:', e);
    return null;
  }
}

/**
 * Redirect to login if not authenticated
 */
function requireAuth() {
  if (!isAuthenticated()) {
    window.location.href = '/login.html';
  }
}

/**
 * Fetch with automatic Authorization header
 * @param {string} url - API endpoint URL
 * @param {object} options - Fetch options
 * @returns {Promise<Response>} Fetch response
 */
async function fetchWithAuth(url, options = {}) {
  const token = getToken();
  
  const headers = {
    'Content-Type': 'application/json',
    ...options.headers
  };

  if (token) {
    headers['Authorization'] = `Bearer ${token}`;
  }

  return fetch(url, {
    ...options,
    headers
  });
}

/**
 * Logout user: clear token and redirect to login
 */
function logout() {
  clearToken();
  window.location.href = '/login.html';
}

// Export for use as ES module
if (typeof module !== 'undefined' && module.exports) {
  module.exports = {
    getToken,
    setToken,
    clearToken,
    isAuthenticated,
    getUserInfo,
    requireAuth,
    fetchWithAuth,
    logout
  };
}