Function classifyFetchError

src/utils/urlUtils.ts:43–91

(err: unknown, url?: string)

 * Classify error type from fetch error.
 */
export function classifyFetchError(err: unknown, url?: string): UrlLoadError {
  if (err instanceof Error) {
    // AbortError from timeout
    if (err.name === 'AbortError') {
      return {
        type: 'timeout',
        message: 'Request timed out',
        details: `The request to ${url || 'the server'} took too long to respond.`,
        failedFile: url,
      };
    }

    // CORS errors typically appear as TypeError with network failure message
    if (err.name === 'TypeError' && (
      err.message.includes('Failed to fetch') ||
      err.message.includes('NetworkError') ||
      err.message.includes('CORS')
    )) {
      return {
        type: 'cors',
        message: 'Cross-origin request blocked',
        details: 'This URL does not allow cross-origin requests. The server needs to include CORS headers.',
        failedFile: url,
      };
    }

    // Generic network error
    if (err.name === 'TypeError') {
      return {
        type: 'network',
        message: 'Network error',
        details: err.message,
        failedFile: url,
      };
    }

    return {
      type: 'unknown',
      message: err.message,
      failedFile: url,
    };
  }

  return {
    type: 'unknown',
    message: String(err),
    failedFile: url,
  };
}

/**
 * Create a File object from fetched blob.