// @ts-check
/**
 * Files without the local program: when Kokkoja is opened from a web
 * site, an image file comes from the browser's own file chooser, and
 * anything to be saved is a download.
 */

/**
 * Let the user choose an image file.
 * @returns {Promise<File | null>}  Null if none was chosen.
 */
export function pickImageFile() {
  return new Promise((resolve) => {
    const picker = document.createElement('input');
    picker.type = 'file';
    picker.accept = 'image/*';
    picker.addEventListener('change', () => resolve(picker.files?.[0] ?? null));
    picker.addEventListener('cancel', () => resolve(null));
    picker.click();
  });
}

/**
 * Give the user a file, through the browser's downloads.
 * @param {string} name
 * @param {Blob} content
 */
export function download(name, content) {
  const address = URL.createObjectURL(content);
  const link = document.createElement('a');
  link.href = address;
  link.download = name;
  document.body.append(link);
  link.click();
  link.remove();
  // The browser has begun the download; the address can go a moment later.
  setTimeout(() => URL.revokeObjectURL(address), 10000);
}