/**
 * Normalizes a URL to ensure it has the correct /api prefix
 * This prevents double prefixing which causes API errors
 */
function normalizeApiUrl(url: string): string {
  // Remove any existing /api or api prefix
  const cleanPath = url.replace(/^\/?(api\/)+/, '');
  
  // Add a single /api prefix
  return `/api/${cleanPath.replace(/^\//, '')}`;
}

/**
 * Get the authentication token from cookies or localStorage
 */
function getAuthToken(): string | null {
  if (typeof document === 'undefined') return null; // Guard for SSR
  
  return document.cookie
    .split('; ')
    .find(row => row.startsWith('Authorization='))
    ?.split('=')[1] || localStorage.getItem('Authorization');
}

/**
 * Creates standard API request headers with authentication
 * 
 * @param token Optional auth token (fetched automatically if not provided)
 * @param customHeaders Additional headers to include
 * @returns Headers object ready for fetch requests
 */
function createApiHeaders(token?: string | null, customHeaders: Record<string, string> = {}): Headers {
  const headers = new Headers({
    'Content-Type': 'application/json',
    'accept': '*/*',  
    ...customHeaders
  });

  const authToken = token || getAuthToken();
  if (authToken) {
    headers.set('authorization', `Bearer ${authToken}`);
  }

  return headers;
}

/**
 * Simple client-side fetch function for making API calls with Authorization header.
 * Ensures all requests go through the Next.js API proxy.
 */
export async function clientFetch<T = any>(url: string, options: RequestInit = {}): Promise<T> {
  try {
    // Create headers with authentication
    const headers = createApiHeaders(null, options.headers as Record<string, string>);

    // Normalize URL to ensure it uses the Next.js API proxy  
    const fullUrl = normalizeApiUrl(url);
    
    const res = await fetch(fullUrl, {
      ...options,
      headers,
      credentials: 'include',
      mode: 'cors',
      referrerPolicy: 'strict-origin-when-cross-origin'
    });

    if (!res.ok) {
      const errorData = await res.json().catch(() => ({}));
      const errorMessage = errorData.message || errorData.error || `Request failed: ${res.status} ${res.statusText}`;
      throw new Error(errorMessage);
    }

    // Handle 204 No Content responses
    if (res.status === 204) {
      return {} as T;
    }

    return await res.json();
  } catch (error) {
    console.error(`Client fetch error at ${url}:`, error);
    throw error;
  }
}

/**
 * Get a cookie value by name
 */
export function getCookie(name: string): string | undefined {
  return document.cookie
    .split('; ')
    .find(row => row.startsWith(`${name}=`))
    ?.split('=')[1];
}