/**
 * Shared proxy utilities for Cloudflare Pages Functions
 * Handles CORS, error responses, and Worker API forwarding
 */

export interface Env {
  WORKER_API_KEY: string;
  WORKER_API_URL: string;
  DB: D1Database;
}

export interface ErrorResponse {
  success: false;
  error: string;
  details?: any;
}

const CORS_HEADERS = {
  'Access-Control-Allow-Origin': 'https://hosting.anvil.it.com',
  'Access-Control-Allow-Methods': 'GET, POST, OPTIONS',
  'Access-Control-Allow-Headers': 'Content-Type',
} as const;

/**
 * Create CORS preflight response
 */
export function createCorsPreflightResponse(): Response {
  return new Response(null, {
    status: 204,
    headers: CORS_HEADERS,
  });
}

/**
 * Create error response with CORS headers
 */
export function createErrorResponse(
  error: string,
  status: number = 500,
  details?: any
): Response {
  const body: ErrorResponse = {
    success: false,
    error,
    ...(details && { details }),
  };

  return new Response(JSON.stringify(body), {
    status,
    headers: {
      ...CORS_HEADERS,
      'Content-Type': 'application/json',
    },
  });
}

/**
 * Proxy request to Worker API with authentication
 */
export async function proxyToWorker(
  env: Env,
  path: string,
  options: RequestInit = {}
): Promise<Response> {
  const workerUrl = `${env.WORKER_API_URL}${path}`;

  try {
    const response = await fetch(workerUrl, {
      ...options,
      headers: {
        ...options.headers,
        'X-API-Key': env.WORKER_API_KEY,
      },
    });

    // Clone response to add CORS headers
    const body = await response.text();
    return new Response(body, {
      status: response.status,
      statusText: response.statusText,
      headers: {
        ...CORS_HEADERS,
        'Content-Type': response.headers.get('Content-Type') || 'application/json',
      },
    });
  } catch (error) {
    console.error(`[Proxy] Failed to fetch ${workerUrl}:`, error);
    return createErrorResponse(
      'Failed to connect to API server',
      503,
      error instanceof Error ? error.message : String(error)
    );
  }
}

/**
 * Build query string from URL search params
 */
export function buildQueryString(searchParams: URLSearchParams): string {
  const params = searchParams.toString();
  return params ? `?${params}` : '';
}