空状態の監視

<%# Empty-state demo: add/remove items and the empty placeholder toggles itself. The
    controller observes the list with a MutationObserver, toggles hidden on the
    list / empty targets at the 0 <-> 1+ boundary, and reflects data-empty / data-count.
    demo.js adds/removes <li> (standing in for Turbo Stream rows). This demo only styles
    it; the empty placeholder's copy is owned here. %>
<div
  class="empty-state-demo"
  data-controller="stimeo--empty-state"
  data-stimeo--empty-state-announce-value="true">
  <div class="empty-state-demo__bar">
    <button
      type="button"
      class="demo-trigger"
      data-empty-state-add
      data-item-label="<%= t("components.empty_state.demo.item") %>">
      <%= t("components.empty_state.demo.add") %>
    </button>
    <button type="button" class="demo-trigger" data-empty-state-clear>
      <%= t("components.empty_state.demo.clear") %>
    </button>
  </div>
  <ul class="empty-state-demo__list" data-stimeo--empty-state-target="list">
    <li><%= t("components.empty_state.demo.item") %> 1</li>
    <li><%= t("components.empty_state.demo.item") %> 2</li>
  </ul>
  <p class="empty-state-demo__empty" data-stimeo--empty-state-target="empty" hidden>
    <%= t("components.empty_state.demo.empty") %>
  </p>
</div>

/*
 * Presentation-only styles for the empty-state demo.
 * The library toggles `hidden` on the list / empty targets and reflects
 * data-empty / data-count; this CSS only lays out the list, items, and placeholder.
 */

.empty-state-demo {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  max-width: 28rem;
}

.empty-state-demo__bar {
  display: flex;
  gap: 0.5rem;
}

.empty-state-demo__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.empty-state-demo__list li {
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 0.375rem;
  background: var(--surface-subtle);
}

.empty-state-demo__empty {
  margin: 0;
  padding: 1.5rem;
  border: 1px dashed var(--border);
  border-radius: 0.5rem;
  text-align: center;
  color: var(--color-text-muted);
}

// Empty-state demo (consumer-side JS).
//
// The controller watches the list with a MutationObserver and toggles the empty
// placeholder on its own. This catalog has no Turbo Stream backend, so here the
// buttons add/remove <li> rows — exactly the kind of mutation Turbo Stream would
// make — and the controller reacts to them.
document.querySelectorAll(".empty-state-demo").forEach((root) => {
  const list = root.querySelector('[data-stimeo--empty-state-target="list"]');
  const add = root.querySelector("[data-empty-state-add]");
  const label = add?.dataset.itemLabel;
  if (!list) return;

  let count = list.children.length;

  add?.addEventListener("click", () => {
    const li = document.createElement("li");
    li.textContent = `${label ?? "Item"} ${(count += 1)}`;
    list.appendChild(li);
  });

  root.querySelector("[data-empty-state-clear]")?.addEventListener("click", () => {
    list.replaceChildren();
  });
});