/**
 * Custom type for file input element (`<input type="file" />`).
 */
type InputFile = HTMLInputElement & {
  capture?: boolean | string;
};

/**
 * Type of options for file input element (`<input type="file" />`) virtually
 * created to select files.
 */
export type Options = {
  /**
   * Defines accepted file types. It's a comma-separated list of file
   * extensions, mime-types or unique file type specifiers.
   *
   * https://developer.mozilla.org/docs/Web/HTML/Element/input/file#Unique_file_type_specifiers
   *
   * @example ```js
   * "image/*,video/*,.pdf,.doc,.docx,.xls"
   * ```
   */
  accept?: string;

  /**
   * Combined with `accept` property it specifies which camera to use for
   * capture of image or video. It was previously a Boolean value.
   */
  capture?: string | boolean;

  /**
   * Allow multiple files selection.
   */
  multiple?: boolean;
};

/**
 * Creates a virtual file input element (`<input type="file" />`) with options.
 * @param options
 */
const createInputFile = ({
  accept = '',
  capture = false,
  multiple = false,
}: Options = {}): InputFile => {
  const input = document.createElement('input') as InputFile;

  input.type = 'file';
  input.accept = accept;
  input.capture = capture;
  input.multiple = multiple;

  return input;
};

/**
 * Virtually creates a file input element (`<input type="file" />`), triggers it
 * and returns selected files.
 *
 * @example
 * selectFiles({ accept: 'image/*', multiple: true }).then(files => {
 *   // ...
 * });
 *
 * @param options
 */
const selectFiles = (options?: Options) =>
  new Promise<null | FileList>((resolve) => {
    const input = createInputFile(options);

    input.addEventListener('change', () => resolve(input.files || null));

    setTimeout(() => {
      const event = new MouseEvent('click');
      input.dispatchEvent(event);
    }, 0);
  });

export default selectFiles;