file-validator.interface.ts

/**
 * Interface describing FileValidators, which can be added to a {@link ParseFilePipe}.
 */
export abstract class FileValidator<TValidationOptions = Record<string, any>> {
  constructor(protected readonly validationOptions: TValidationOptions) {}

  /**
   * Indicates if this file should be considered valid, according to the options passed in the constructor.
   * @param file the file from the request object
   */
  abstract isValid(file?: any): boolean | Promise<boolean>;

  /**
   * Builds an error message in case the validation fails.
   * @param file the file from the request object
   */
  abstract buildErrorMessage(file: any): string;
}