import { openTab } from './lib/scaffold.mjs';

/**
 * Render on change: the editor draws what changed, not sixty pictures a second.
 *
 * This is the one thing the rest of the suite cannot see. `pixelAt` re-renders the stage on
 * demand, so every colour check would pass just as well on a screen that froze a minute ago –
 * only the drawn-frame counter tells the difference between "drawn" and "merely correct".
 *
 * The step runs last and leaves the editor as it found it.
 */
export async function renderOnChange(t) {
  const { check, sleep, evaluate, select, click, locate, play, stop, shot, waitUntil } = t;

  const stats = () => evaluate('__gm.renderStats()');
  /** Frames drawn over `ms` of doing nothing at all. */
  const drawnDuring = async (ms) => {
    const before = await stats();
    await sleep(ms);
    const after = await stats();
    return after.drawn - before.drawn;
  };
  /**
   * Waits for the trailing window of the last event to run out. Measuring without this counts the
   * frames the previous click is still entitled to and calls them a leak.
   *
   * The autosave is waited out first. It fires ~1 s after the last model change and paints the
   * status twice – `saving`, then `saved` – so an earlier step's last edit lands in this step's
   * quiet window and looks like a renderer that will not go to sleep. Those frames are earned:
   * the status text really did change. The step has to stop measuring before them, not call them
   * a leak.
   */
  const settle = async (timeoutMs = 5000) => {
    await waitUntil("!['dirty', 'saving'].includes(__gm.state.saveStatus)", {
      timeout: timeoutMs,
      label: 'the autosave finished',
    });
    for (let waited = 0; waited < timeoutMs; waited += 100) {
      if (!(await stats()).awake) return true;
      await sleep(100);
    }
    return false;
  };

  // 33a. A tab whose picture stands still: the scene viewport may wear a Time shader, and the
  // particles and animation previews are moving pictures by definition.
  await openTab(t, 'graph');
  await select(null);

  const quiet = await settle();
  const idle = await drawnDuring(700);
  check(
    'an editor nobody touches draws no frames at all',
    quiet && idle === 0,
    `settled=${quiet}, ${idle} frames drawn`,
  );

  // 33b. A model change that arrives without any input – no click, no key – still reaches the
  // screen. This is the wake-up that a strict dirty flag on the widgets would have missed.
  const beforeChange = (await stats()).drawn;
  await evaluate(`__gm.state.setNotice('render check', 'info')`);
  await sleep(150);
  const afterChange = (await stats()).drawn;
  check(
    'a change nobody clicked for is drawn anyway',
    afterChange > beforeChange,
    `${beforeChange} → ${afterChange}`,
  );

  // 33c. Input wakes it, and it goes back to sleep on its own afterwards.
  await settle();
  const beforeClick = (await stats()).drawn;
  const spot = await locate('Behavior');
  await click(spot.x, spot.y);
  const afterClick = (await stats()).drawn;
  check('a click draws again', afterClick > beforeClick, `${beforeClick} → ${afterClick}`);

  const settled = await settle();
  const backToSleep = await drawnDuring(700);
  check(
    'and it stops on its own once the click is dealt with',
    settled && backToSleep === 0,
    `settled=${settled}, ${backToSleep} frames`,
  );

  // 33d. While the game runs, the frame cannot come from an event: the world moves by itself.
  await play();
  const playing = await drawnDuring(600);
  const fps = await evaluate('__gm.fps()');
  check(
    'a running game keeps getting frames without being touched',
    playing > 10,
    `${playing} frames in 600 ms`,
  );
  check('and the fps readout keeps measuring them', typeof fps === 'number' && fps > 0, `fps=${fps}`);
  await shot('01-playing');
  await stop();

  // 33e. Stopping ends the reason to draw. Back off the scene tab first: a Time shader left on
  // screen by an earlier step is a legitimate reason to keep drawing, and would mask this check.
  await openTab(t, 'graph');
  const stopped = await settle();
  const afterStop = await drawnDuring(700);
  check(
    'stopping puts it back to sleep',
    stopped && afterStop === 0,
    `settled=${stopped}, ${afterStop} frames`,
  );

  await evaluate(`__gm.state.setNotice('', 'info')`);
  await sleep(200);
}