02日付グループの値で折りたたまれるヘッダーリスト

<main class="stage">
  <div class="gh is-demo" id="gh">
    <section class="gh__group">
      <button class="gh__header" id="ghHeaderToday" type="button" aria-expanded="true" aria-controls="ghListToday">
        <svg class="gh__caret" id="ghCaretToday" viewBox="0 0 256 256" aria-hidden="true" focusable="false">
          <path d="m208 96l-80 80l-80-80Z" opacity=".2"/>
          <path d="M215.39 92.94A8 8 0 0 0 208 88H48a8 8 0 0 0-5.66 13.66l80 80a8 8 0 0 0 11.32 0l80-80a8 8 0 0 0 1.73-8.72M128 164.69L67.31 104h121.38Z"/>
        </svg>
        <span class="gh__headerLabel">今日 · <span id="ghCountToday">3</span></span>
      </button>
      <ul class="gh__list" id="ghListToday" role="list"></ul>
    </section>
    <section class="gh__group">
      <button class="gh__header" id="ghHeaderYesterday" type="button" aria-expanded="true" aria-controls="ghListYesterday">
        <svg class="gh__caret" id="ghCaretYesterday" viewBox="0 0 256 256" aria-hidden="true" focusable="false">
          <path d="m208 96l-80 80l-80-80Z" opacity=".2"/>
          <path d="M215.39 92.94A8 8 0 0 0 208 88H48a8 8 0 0 0-5.66 13.66l80 80a8 8 0 0 0 11.32 0l80-80a8 8 0 0 0 1.73-8.72M128 164.69L67.31 104h121.38Z"/>
        </svg>
        <span class="gh__headerLabel">昨日 · <span id="ghCountYesterday">2</span></span>
      </button>
      <ul class="gh__list" id="ghListYesterday" role="list"></ul>
    </section>
  </div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 계산 겹: index.html setGroup() 이 항목마다 실제 높이(getBoundingClientRect)를 재서
// dataset 에 저장해두고, 순번 x NOTIF_GROUP_COLLAPSE_DELAY_MS 를 transitionDelay 로 걸어
// 위→아래(펼 때는 아래→위) 순서로 접히는 계단식 흐름을 만든다.
.stage { @include stage($stage-yellow); }

.gh {
  width: min(100%, 300px);
  display: flex;
  flex-direction: column;
  gap: $sp-4;
}

.gh__group { display: flex; flex-direction: column; gap: $sp-2; }

.gh__header {
  display: flex;
  align-items: center;
  gap: $sp-2;
  border: none;
  background: transparent;
  padding: $sp-1 0;
  cursor: pointer;
  color: $subject-ink;
}

.gh__caret {
  width: 16px;
  height: 16px;
  color: $subject-ink;
  transition: transform $dur-base $ease-spring;
  transform-origin: center;
}
.gh__header[aria-expanded="false"] .gh__caret { transform: rotate(-90deg); }

.gh__headerLabel { font-size: 13px; font-weight: 700; }

.gh__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: $sp-1;
}

.gh__item {
  overflow: hidden;
  border-radius: $r-sm;
  background: $subject-ink;
  color: $subject-cream;
  font-size: 12px;
  padding: 0 $sp-3;
  display: flex;
  align-items: center;
  box-sizing: border-box;
  transition: height $dur-base $ease-spring, opacity $dur-base $ease-spring;
}

@media (max-width: 340px) {
  .gh { width: 100%; }
}

@media (prefers-reduced-motion: reduce) {
  .gh__item { transition: none; }
  .gh__caret { transition: none; }
}

.stage html, .stage body {
  margin: 0;
  overflow: hidden;
}
.stage .stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.gh {
  width: min(100%, 300px);
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.gh__group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.gh__header {
  display: flex;
  align-items: center;
  gap: 8px;
  border: none;
  background: transparent;
  padding: 4px 0;
  cursor: pointer;
  color: #17141a;
}

.gh__caret {
  width: 16px;
  height: 16px;
  color: #17141a;
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
  transform-origin: center;
}

.gh__header[aria-expanded=false] .gh__caret {
  transform: rotate(-90deg);
}

.gh__headerLabel {
  font-size: 13px;
  font-weight: 700;
}

.gh__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.gh__item {
  overflow: hidden;
  border-radius: 8px;
  background: #17141a;
  color: #fff7e6;
  font-size: 12px;
  padding: 0 12px;
  display: flex;
  align-items: center;
  box-sizing: border-box;
  transition: height 300ms cubic-bezier(0.2, 0.8, 0.2, 1), opacity 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

@media (max-width: 340px) {
  .gh {
    width: 100%;
  }
}
@media (prefers-reduced-motion: reduce) {
  .gh__item {
    transition: none;
  }
  .gh__caret {
    transition: none;
  }
}

(function () {
  "use strict";

  var NOTIF_GROUP_COLLAPSE_DELAY_MS = 80; // 항목마다 접히는 시작 시각이 이 값 x 순번만큼 밀린다

  var GROUPS = {
    today: ["決済が承認されました", "新しいコメントが付きました", "会議まであと10分です"],
    yesterday: ["アップロードが完了しました", "招待状が届きました"]
  };

  var root = document.getElementById("gh");
  var reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  var synthetic = false;
  function human() {
    if (synthetic) return;
    if (root.classList.contains("is-demo")) root.classList.remove("is-demo");
  }

  function buildList(key) {
    var ul = document.getElementById("ghList" + (key === "today" ? "Today" : "Yesterday"));
    GROUPS[key].forEach(function (name) {
      var li = document.createElement("li");
      li.className = "gh__item";
      li.setAttribute("role", "listitem");
      li.textContent = name;
      ul.appendChild(li);
    });
  }
  buildList("today");
  buildList("yesterday");

  var state = { today: true, yesterday: true };

  function groupEls(key) {
    var suffix = key === "today" ? "Today" : "Yesterday";
    return {
      header: document.getElementById("ghHeader" + suffix),
      caret: document.getElementById("ghCaret" + suffix),
      list: document.getElementById("ghList" + suffix)
    };
  }

  // 계산 겹: 항목마다 실제 높이를 getBoundingClientRect 로 재고, 순번(index) x
  // NOTIF_GROUP_COLLAPSE_DELAY_MS 를 transitionDelay 로 걸어 위에서 아래로(펼 때는 아래에서
  // 위로) 순서대로 접히고 펼쳐지는 계단식 흐름을 만든다.
  function setGroup(key, expand) {
    state[key] = expand;
    var els = groupEls(key);
    els.header.setAttribute("aria-expanded", expand ? "true" : "false");
    var items = Array.prototype.slice.call(els.list.children);
    var n = items.length;
    items.forEach(function (li, i) {
      var order = expand ? (n - 1 - i) : i;
      var delay = reduce ? 0 : order * NOTIF_GROUP_COLLAPSE_DELAY_MS;
      var h = li.dataset.h ? parseFloat(li.dataset.h) : null;
      if (h === null) {
        li.style.height = "auto";
        h = li.getBoundingClientRect().height;
        li.dataset.h = String(h);
      }
      li.style.transitionDelay = delay + "ms";
      if (expand) {
        li.style.height = "0px";
        li.style.opacity = "0";
        requestAnimationFrame(function () {
          li.style.height = h + "px";
          li.style.opacity = "1";
        });
      } else {
        li.style.height = h + "px";
        li.style.opacity = "1";
        requestAnimationFrame(function () {
          li.style.height = "0px";
          li.style.opacity = "0";
        });
      }
    });
  }

  function toggleGroup(key) {
    human();
    setGroup(key, !state[key]);
  }

  groupEls("today").header.addEventListener("click", function () { toggleGroup("today"); });
  groupEls("yesterday").header.addEventListener("click", function () { toggleGroup("yesterday"); });
  [groupEls("today").header, groupEls("yesterday").header].forEach(function (btn, i) {
    btn.addEventListener("keydown", function (e) {
      if (e.key === "Enter" || e.key === " ") {
        e.preventDefault();
        toggleGroup(i === 0 ? "today" : "yesterday");
      }
    });
  });

  // 화면 폭이 바뀌면 줄바꿈 여부가 달라져 캐시해둔 실측 높이가 더는 맞지 않는다 — 지운다.
  window.addEventListener("resize", function () {
    Array.prototype.forEach.call(root.querySelectorAll(".gh__item"), function (li) {
      delete li.dataset.h;
    });
  });

  if (reduce) {
    setGroup("today", false);
  } else {
    var step = 0;
    function loop() {
      if (!root.classList.contains("is-demo")) return;
      synthetic = true;
      if (step === 0) setGroup("today", false);
      else if (step === 1) setGroup("today", true);
      else if (step === 2) setGroup("yesterday", false);
      else setGroup("yesterday", true);
      synthetic = false;
      step = (step + 1) % 4;
      window.setTimeout(loop, 1500);
    }
    window.setTimeout(loop, 500);
  }
})();

// NotifGroupHeaderCollapse — vanilla 판(run/405/demo/02-.../index.html) 의 React 포트.
// 계산 겹: 항목마다 실제 높이를 getBoundingClientRect 로 재고, 순번(index) x
// NOTIF_GROUP_COLLAPSE_DELAY_MS 를 transitionDelay 로 걸어 위에서 아래로(펼 때는 아래에서
// 위로) 순서대로 접히고 펼쳐지는 계단식 흐름을 만든다 — vanilla 와 동일 동작.
import { useEffect, useRef, useState } from "react";
import styles from "./NotifGroupHeaderCollapse.module.scss";

type Box<T> = { current: T };
type KeyEvt = { key: string; preventDefault(): void };
type GroupKey = "today" | "yesterday";

const NOTIF_GROUP_COLLAPSE_DELAY_MS = 80; // 항목마다 접히는 시작 시각이 이 값 x 순번만큼 밀린다

const GROUPS: { [k in GroupKey]: string[] } = {
  today: ["결제가 승인됐어요", "새 댓글이 달렸어요", "회의 10분 전이에요"],
  yesterday: ["업로드가 끝났어요", "초대장이 도착했어요"],
};

export default function NotifGroupHeaderCollapse() {
  const [isDemo, setIsDemo] = useState(true);
  const [expanded, setExpanded] = useState<{ [k in GroupKey]: boolean }>({ today: true, yesterday: true });

  const isDemoRef = useRef(true) as unknown as Box<boolean>;
  const synthRef = useRef(false) as unknown as Box<boolean>;
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const headerRef = {
    today: useRef(null) as unknown as Box<HTMLButtonElement>,
    yesterday: useRef(null) as unknown as Box<HTMLButtonElement>,
  };
  const listRef = {
    today: useRef(null) as unknown as Box<HTMLUListElement>,
    yesterday: useRef(null) as unknown as Box<HTMLUListElement>,
  };
  const stateRef = useRef({ today: true, yesterday: true }) as unknown as Box<{ [k in GroupKey]: boolean }>;
  const loopTimerRef = useRef(0) as unknown as Box<number>;
  const stepRef = useRef(0) as unknown as Box<number>;

  function human() {
    if (synthRef.current) return;
    if (isDemoRef.current) { isDemoRef.current = false; setIsDemo(false); }
  }

  function buildList(key: GroupKey) {
    const ul = listRef[key].current;
    if (!ul) return;
    ul.innerHTML = "";
    GROUPS[key].forEach((name) => {
      const li = document.createElement("li");
      li.className = styles.item;
      li.setAttribute("role", "listitem");
      li.textContent = name;
      ul.appendChild(li);
    });
  }

  function setGroup(key: GroupKey, expand: boolean, reduce: boolean) {
    stateRef.current[key] = expand;
    setExpanded((prev) => ({ ...prev, [key]: expand }));
    const list = listRef[key].current;
    if (!list) return;
    const items = Array.prototype.slice.call(list.children) as HTMLLIElement[];
    const n = items.length;
    items.forEach((li, i) => {
      const order = expand ? n - 1 - i : i;
      const delay = reduce ? 0 : order * NOTIF_GROUP_COLLAPSE_DELAY_MS;
      let h = li.dataset.h ? parseFloat(li.dataset.h) : null;
      if (h === null) {
        li.style.height = "auto";
        h = li.getBoundingClientRect().height;
        li.dataset.h = String(h);
      }
      li.style.transitionDelay = delay + "ms";
      if (expand) {
        li.style.height = "0px";
        li.style.opacity = "0";
        requestAnimationFrame(() => { li.style.height = h + "px"; li.style.opacity = "1"; });
      } else {
        li.style.height = h + "px";
        li.style.opacity = "1";
        requestAnimationFrame(() => { li.style.height = "0px"; li.style.opacity = "0"; });
      }
    });
  }

  function toggleGroup(key: GroupKey) {
    human();
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    setGroup(key, !stateRef.current[key], reduce);
  }

  function onKeyDown(key: GroupKey, e: KeyEvt) {
    if (e.key === "Enter" || e.key === " ") {
      e.preventDefault();
      toggleGroup(key);
    }
  }

  useEffect(() => {
    buildList("today");
    buildList("yesterday");
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    function onResize() {
      const root = rootRef.current;
      if (!root) return;
      Array.prototype.forEach.call(root.querySelectorAll("li"), (li: HTMLLIElement) => { delete li.dataset.h; });
    }
    window.addEventListener("resize", onResize);

    if (reduce) {
      setGroup("today", false, true);
    } else {
      function loop() {
        if (!isDemoRef.current) return;
        synthRef.current = true;
        const step = stepRef.current;
        if (step === 0) setGroup("today", false, false);
        else if (step === 1) setGroup("today", true, false);
        else if (step === 2) setGroup("yesterday", false, false);
        else setGroup("yesterday", true, false);
        synthRef.current = false;
        stepRef.current = (step + 1) % 4;
        loopTimerRef.current = window.setTimeout(loop, 1500);
      }
      loopTimerRef.current = window.setTimeout(loop, 500);
    }

    return () => {
      window.removeEventListener("resize", onResize);
      window.clearTimeout(loopTimerRef.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.gh + " " + (isDemo ? styles.isDemo : "")} ref={rootRef}>
        <section className={styles.group}>
          <button className={styles.header} type="button" aria-expanded={expanded.today ? "true" : "false"}
                  aria-controls="ghListToday" ref={headerRef.today}
                  onClick={() => toggleGroup("today")} onKeyDown={(e: KeyEvt) => onKeyDown("today", e)}>
            <svg className={styles.caret} viewBox="0 0 256 256" aria-hidden="true" focusable="false">
              <path d="m208 96l-80 80l-80-80Z" opacity=".2" />
              <path d="M215.39 92.94A8 8 0 0 0 208 88H48a8 8 0 0 0-5.66 13.66l80 80a8 8 0 0 0 11.32 0l80-80a8 8 0 0 0 1.73-8.72M128 164.69L67.31 104h121.38Z" />
            </svg>
            <span className={styles.headerLabel}>오늘 · {GROUPS.today.length}</span>
          </button>
          <ul className={styles.list} id="ghListToday" role="list" ref={listRef.today} />
        </section>
        <section className={styles.group}>
          <button className={styles.header} type="button" aria-expanded={expanded.yesterday ? "true" : "false"}
                  aria-controls="ghListYesterday" ref={headerRef.yesterday}
                  onClick={() => toggleGroup("yesterday")} onKeyDown={(e: KeyEvt) => onKeyDown("yesterday", e)}>
            <svg className={styles.caret} viewBox="0 0 256 256" aria-hidden="true" focusable="false">
              <path d="m208 96l-80 80l-80-80Z" opacity=".2" />
              <path d="M215.39 92.94A8 8 0 0 0 208 88H48a8 8 0 0 0-5.66 13.66l80 80a8 8 0 0 0 11.32 0l80-80a8 8 0 0 0 1.73-8.72M128 164.69L67.31 104h121.38Z" />
            </svg>
            <span className={styles.headerLabel}>어제 · {GROUPS.yesterday.length}</span>
          </button>
          <ul className={styles.list} id="ghListYesterday" role="list" ref={listRef.yesterday} />
        </section>
      </div>
    </main>
  );
}