/** 
 * Add To Home Screen Chrome 68+ 
 * 
 * Changes to Add to Home Screen Behavior has the full details, including code samples you can use and more: 
 * https://developers.google.com/web/updates/2018/06/a2hs-updates
 * 
 * Credit: https://developers.google.com/web/updates/2018/07/nic68#a2hs
 * Add to home screen app criteria: https://developers.google.com/web/fundamentals/app-install-banners/#criteria
 */

/** 
 * If your site meets the add to home screen criteria, Chrome will no longer show the add to home screen banner.
 * Instead, you’re in control over when and how to prompt the user.
 *
 * To prompt the user, listen for the beforeinstallprompt event, then, save the event 
 * and add a button or other UI element to your app to indicate it can be installed.
 */
let installPromptEvent;

window.addEventListener('beforeinstallprompt', (event) => {
  // Prevent Chrome <= 67 from automatically showing the prompt
  event.preventDefault();
  // Stash the event so it can be triggered later.
  installPromptEvent = event;
  // Update the install UI to notify the user app can be installed
  document.querySelector('#install-button').disabled = false;
});

/**
 * When the user clicks the install button, call prompt() on the saved beforeinstallprompt event, 
 * Chrome then shows the add to home screen dialog.
 */
btnInstall.addEventListener('click', () => {
  // Update the install UI to remove the install button
  document.querySelector('#install-button').disabled = true;
  // Show the modal add to home screen dialog
  installPromptEvent.prompt();
  // Wait for the user to respond to the prompt
  installPromptEvent.userChoice.then(handleInstall);
});