// Screen wake lock and fullscreen helpers.

export function createWakeLock() {
  let sentinel = null;
  let pending = false;
  let wanted = false;

  async function acquire() {
    if (!('wakeLock' in navigator) || sentinel || pending || document.visibilityState !== 'visible') return;
    pending = true;
    try {
      sentinel = await navigator.wakeLock.request('screen');
      sentinel.addEventListener('release', () => {
        sentinel = null;
      });
      if (!wanted) release();
    } catch {
      /* denied, insecure context or low battery: no big deal */
    } finally {
      pending = false;
    }
  }

  function release() {
    const s = sentinel;
    sentinel = null;
    s?.release().catch(() => {});
  }

  // The lock is dropped automatically when the page is hidden.
  document.addEventListener('visibilitychange', () => {
    if (wanted && document.visibilityState === 'visible') acquire();
  });

  return {
    set(on) {
      if (on === wanted) return;
      wanted = on;
      if (on) acquire();
      else release();
    },
  };
}

export const fullscreenSupported = () => !!(document.fullscreenEnabled || document.webkitFullscreenEnabled);
export const isFullscreen = () => !!(document.fullscreenElement || document.webkitFullscreenElement);

export async function toggleFullscreen() {
  try {
    if (isFullscreen()) {
      await (document.exitFullscreen || document.webkitExitFullscreen).call(document);
    } else {
      const el = document.documentElement;
      if (el.requestFullscreen) await el.requestFullscreen({ navigationUI: 'hide' });
      else el.webkitRequestFullscreen?.();
    }
  } catch {
    /* user agent refused */
  }
}

export function onFullscreenChange(fn) {
  document.addEventListener('fullscreenchange', fn);
  document.addEventListener('webkitfullscreenchange', fn);
}