// Manages run-comparison selection on the runs list.
// HTMX re-renders #runs-slot every 3s, so we keep state in a Set outside
// the polled region and re-apply checked state on every afterSwap.

(function () {
  const MAX = 2;
  const selected = new Set();

  const btn = document.getElementById('compare-btn');
  const countEl = document.getElementById('compare-count');
  const slot = document.getElementById('runs-slot');
  if (!btn || !countEl || !slot) return;

  function refreshButton() {
    const n = selected.size;
    countEl.textContent = `(${n}/${MAX})`;
    btn.disabled = n !== MAX;
  }

  function applyToDOM() {
    const checkboxes = slot.querySelectorAll('.compare-cb');
    // Drop any selected stems that are no longer in the DOM (run aged out of list)
    const present = new Set();
    checkboxes.forEach((cb) => present.add(cb.dataset.stem));
    for (const s of [...selected]) if (!present.has(s)) selected.delete(s);

    const atCap = selected.size >= MAX;
    checkboxes.forEach((cb) => {
      const stem = cb.dataset.stem;
      cb.checked = selected.has(stem);
      cb.disabled = atCap && !cb.checked;
    });
    refreshButton();
  }

  slot.addEventListener('change', (e) => {
    const cb = e.target;
    if (!cb.matches || !cb.matches('.compare-cb')) return;
    const stem = cb.dataset.stem;
    if (cb.checked) {
      if (selected.size >= MAX) {
        cb.checked = false;
        return;
      }
      selected.add(stem);
    } else {
      selected.delete(stem);
    }
    applyToDOM();
  });

  document.body.addEventListener('htmx:afterSwap', (e) => {
    if (e.target && e.target.id === 'runs-slot') applyToDOM();
  });

  btn.addEventListener('click', () => {
    if (selected.size !== MAX) return;
    const [a, b] = [...selected];
    const url = `/compare?a=${encodeURIComponent(a)}&b=${encodeURIComponent(b)}`;
    window.open(url, '_blank', 'noopener');
  });

  applyToDOM();
})();