02通貨を変えると記号と金額が同時に変わる

<main class="stage">
  <div class="cs is-demo" data-cur="usd">
    <div class="cs__left">
      <p class="cs__plan">スタンダードプラン</p>
      <div class="cs__priceline" aria-live="polite">
        <span class="cs__face" data-cur="usd"><span class="cs__sym">$</span><span class="cs__amt">29</span><span class="cs__unit">/ 月</span></span>
        <span class="cs__face" data-cur="krw"><span class="cs__sym">₩</span><span class="cs__amt">39,000</span><span class="cs__unit">/ 月</span></span>
        <span class="cs__face" data-cur="jpy"><span class="cs__sym">¥</span><span class="cs__amt">4,400</span><span class="cs__unit">/ 月</span></span>
        <span class="cs__face" data-cur="eur"><span class="cs__sym">€</span><span class="cs__amt">27</span><span class="cs__unit">/ 月</span></span>
      </div>
      <p class="cs__note">税別</p>
    </div>
    <div class="cs__pick">
      <button class="cs__trig" type="button" id="cs-trig" aria-expanded="false" aria-haspopup="listbox" aria-label="通貨を選ぶ">
        <span class="cs__code" id="cs-code">USD</span>
        <span class="cs__tsym" id="cs-tsym">$</span>
        <span class="cs__caret" aria-hidden="true"><svg viewBox="0 0 256 256" width="14" height="14"><g fill="currentColor"><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"/></g></svg></span>
      </button>
      <div class="cs__pop">
        <span class="cs__hl" aria-hidden="true"></span>
        <ul class="cs__list" role="listbox" aria-label="通貨を選ぶ">
          <li class="cs__opt" role="option" aria-selected="true" tabindex="0" data-cur="usd" data-code="USD" data-sym="$"><span class="cs__dot" aria-hidden="true"></span><span class="cs__oc">USD</span><span class="cs__os">$</span></li>
          <li class="cs__opt" role="option" aria-selected="false" tabindex="0" data-cur="krw" data-code="KRW" data-sym="₩"><span class="cs__dot" aria-hidden="true"></span><span class="cs__oc">KRW</span><span class="cs__os">₩</span></li>
          <li class="cs__opt" role="option" aria-selected="false" tabindex="0" data-cur="jpy" data-code="JPY" data-sym="¥"><span class="cs__dot" aria-hidden="true"></span><span class="cs__oc">JPY</span><span class="cs__os">¥</span></li>
          <li class="cs__opt" role="option" aria-selected="false" tabindex="0" data-cur="eur" data-code="EUR" data-sym="€"><span class="cs__dot" aria-hidden="true"></span><span class="cs__oc">EUR</span><span class="cs__os">€</span></li>
        </ul>
      </div>
    </div>
  </div>
</main>

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

$duration: $dur-quick;
$easing: $ease-spring;
$color: $subject-mint;

@include stage($stage-ink);

.cs {
  --row: 22px;          // 목록 한 줄 높이 — 표시 띠가 한 칸씩 미끄러지는 거리이기도 하다
  box-sizing: border-box;
  width: min(400px, 88vw);
  display: flex;
  align-items: flex-start;
  gap: $sp-3;
  padding: $sp-4;
  // 절대배치 목록이 아래로 내려오는 만큼 자리를 미리 비워 둔다 —
  // 절대배치는 부모 높이에서 빠지는데 scrollHeight 는 실제 크기로 잡혀 320px 렌더가 넘친다
  padding-bottom: $sp-12 + $sp-2;
  border: 2px solid rgba(255, 255, 255, .12);
  border-radius: $r-card;
  background: rgba(255, 255, 255, .06);
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $subject-cream;
}

.cs__left {
  flex: 1 1 auto;
  min-width: 0;
}
.cs__plan {
  margin: 0;
  font-size: 12px;
  line-height: 18px;
  font-weight: 700;
  letter-spacing: .04em;
  opacity: .72;
}

// 금액 얼굴 넷을 같은 자리에 겹쳐 둔다 — 자리를 옮기지 않아야 컷이 깔끔하다
.cs__priceline {
  position: relative;
  height: 40px;
  margin-top: $sp-2;
  transform-origin: left center; // 규칙8: 왼쪽 정렬 금액 — 정렬 변을 고정해야 팝이 자리를 안 흔든다
}
.cs__face {
  position: absolute;
  left: 0;
  top: 0;
  display: flex;
  align-items: baseline;
  gap: $sp-1;
  white-space: nowrap;
  opacity: 0;
}
.cs__sym,
.cs__amt {
  color: $color;
  font-size: 30px;
  line-height: 40px;
  font-weight: 800;
}
.cs__unit {
  font-size: 12px;
  line-height: 18px;
  font-weight: 700;
  opacity: .7;
}
.cs__note {
  margin: $sp-1 0 0;
  font-size: 11px;
  line-height: 16px;
  font-weight: 600;
  opacity: .55;
}

.cs__pick {
  position: relative;
  flex: 0 0 auto;
  width: 96px;
}
.cs__trig {
  box-sizing: border-box;
  display: flex;
  align-items: center;
  gap: $sp-1;
  width: 100%;
  margin: 0;
  padding: $sp-1 $sp-2;
  border: 2px solid rgba(255, 255, 255, .22);
  border-radius: $r-control;
  background: rgba(255, 255, 255, .04);
  color: $subject-cream;
  font-family: inherit;
  font-size: 12px;
  line-height: 18px;
  font-weight: 700;
  cursor: pointer;
}
.cs__trig:focus-visible { outline: 2px solid $color; outline-offset: 2px; }
.cs__tsym { color: $color; }
.cs__caret {
  margin-left: auto;
  display: inline-flex;
  opacity: .6;
}
.cs__caret svg { display: block; }

// 목록은 띄워 두되(레이아웃을 밀지 않는다) 뿌리의 padding-bottom 이 그 높이를 미리 잡아 둔다
.cs__pop {
  position: absolute;
  left: 0;
  right: 0;
  top: calc(100% + 4px);
  box-sizing: border-box;
  padding: $sp-1 0;
  border: 2px solid rgba(255, 255, 255, .16);
  border-radius: $r-control;
  background: $subject-ink;
  box-shadow: $shadow-raised;
  transform-origin: top center; // 규칙8: 트리거 아래 변에서 펼침
  transform: scaleY(.5) translateY(-8px);
  opacity: 0;
  visibility: hidden;
}
.cs__hl {
  position: absolute;
  left: 4px;
  right: 4px;
  top: 4px;
  height: var(--row);
  border-radius: $r-sm;
  background: rgba(255, 255, 255, .1);
}
.cs__list {
  position: relative;
  margin: 0;
  padding: 0;
  list-style: none;
}
.cs__opt {
  display: flex;
  align-items: center;
  gap: $sp-2;
  height: var(--row);
  padding: 0 $sp-2;
  font-size: 11px;
  line-height: 16px;
  font-weight: 700;
  cursor: pointer;
}
.cs__opt:focus-visible { outline: 2px solid $color; outline-offset: -2px; }
.cs__dot {
  flex: 0 0 auto;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: $color;
  opacity: 0;
}
.cs__os { margin-left: auto; color: $color; }

// ── 사람이 만진 뒤(정적 경로) — 상태는 aria-expanded · aria-selected · data-cur 에만 있다 ──
.cs__trig[aria-expanded="true"] ~ .cs__pop {
  transform: none;
  opacity: 1;
  visibility: visible;
}
.cs__opt[aria-selected="true"] .cs__dot { opacity: 1; }
.cs:not(.is-demo)[data-cur="usd"] .cs__face[data-cur="usd"],
.cs:not(.is-demo)[data-cur="krw"] .cs__face[data-cur="krw"],
.cs:not(.is-demo)[data-cur="jpy"] .cs__face[data-cur="jpy"],
.cs:not(.is-demo)[data-cur="eur"] .cs__face[data-cur="eur"] { opacity: 1; }
.cs:not(.is-demo)[data-cur="krw"] .cs__hl { transform: translateY(var(--row)); }
.cs:not(.is-demo)[data-cur="jpy"] .cs__hl { transform: translateY(calc(var(--row) * 2)); }
.cs:not(.is-demo)[data-cur="eur"] .cs__hl { transform: translateY(calc(var(--row) * 3)); }

.cs:not(.is-demo) .cs__pop {
  transition-property: transform, opacity, visibility;
  transition-duration: $duration;
  transition-timing-function: $easing;
}
.cs:not(.is-demo) .cs__hl {
  transition-property: transform;
  transition-duration: $duration;
  transition-timing-function: $easing;
}

// ── 자동 루프(2초) — 목록은 열린 채로 머물고 선택만 20% 마다 컷으로 넘어간다. 닫힘은 재현하지 않는다 ──
.cs.is-demo .cs__pop {
  visibility: visible;
  animation-name: cs-open;
  animation-duration: $dur-loop;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
@keyframes cs-open {
  0%   { transform: scaleY(.5) translateY(-8px); opacity: 0; }
  10%  { transform: none; opacity: 1; }
  100% { transform: none; opacity: 1; }
}

// 표시 띠만 부드럽게 미끄러진다 — 컷 옆에 움직인 프레임을 채우는 몫
.cs.is-demo .cs__hl {
  animation-name: cs-hl;
  animation-duration: $dur-loop;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
@keyframes cs-hl {
  0%, 10%   { transform: translateY(0); }
  20%, 30%  { transform: translateY(var(--row)); }
  40%, 50%  { transform: translateY(calc(var(--row) * 2)); }
  60%, 70%  { transform: translateY(calc(var(--row) * 3)); }
  80%, 100% { transform: translateY(0); }
}

// 금액 얼굴과 표시 점은 같은 시계로 한 프레임에 끊는다 — 크로스페이드는 반투명 유령을 남긴다
.cs.is-demo .cs__face,
.cs.is-demo .cs__dot {
  animation-duration: $dur-loop;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.cs.is-demo .cs__face[data-cur="usd"],
.cs.is-demo .cs__opt[data-cur="usd"] .cs__dot { animation-name: cs-usd; }
.cs.is-demo .cs__face[data-cur="krw"],
.cs.is-demo .cs__opt[data-cur="krw"] .cs__dot { animation-name: cs-krw; }
.cs.is-demo .cs__face[data-cur="jpy"],
.cs.is-demo .cs__opt[data-cur="jpy"] .cs__dot { animation-name: cs-jpy; }
.cs.is-demo .cs__face[data-cur="eur"],
.cs.is-demo .cs__opt[data-cur="eur"] .cs__dot { animation-name: cs-eur; }
@keyframes cs-usd {
  0%   { opacity: 1; }
  20%  { opacity: 0; }
  80%  { opacity: 1; }
  100% { opacity: 1; }
}
@keyframes cs-krw {
  0%   { opacity: 0; }
  20%  { opacity: 1; }
  40%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes cs-jpy {
  0%   { opacity: 0; }
  40%  { opacity: 1; }
  60%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes cs-eur {
  0%   { opacity: 0; }
  60%  { opacity: 1; }
  80%  { opacity: 0; }
  100% { opacity: 0; }
}

// 금액이 갈릴 때마다 가격 줄이 한 번 눌렸다 편다
.cs.is-demo .cs__priceline {
  animation-name: cs-pop;
  animation-duration: $dur-loop;
  animation-timing-function: $ease-pop;
  animation-iteration-count: infinite;
}
@keyframes cs-pop {
  0%, 16%   { transform: scale(1); }
  22%       { transform: scale(1.06); }
  28%, 36%  { transform: scale(1); }
  42%       { transform: scale(1.06); }
  48%, 56%  { transform: scale(1); }
  62%       { transform: scale(1.06); }
  68%, 76%  { transform: scale(1); }
  82%       { transform: scale(1.06); }
  88%, 100% { transform: scale(1); }
}

@media (max-width: 340px) {
  .cs {
    --row: 20px;
    gap: $sp-2;
    padding: $sp-3;
    padding-bottom: $sp-12 + $sp-2;
  }
  .cs__plan { font-size: 11px; line-height: 16px; }
  .cs__priceline { height: 30px; margin-top: $sp-1; }
  .cs__sym,
  .cs__amt { font-size: 21px; line-height: 30px; }
  .cs__pick { width: 88px; }
  .cs__trig { padding: $sp-1; font-size: 11px; line-height: 16px; }
}

@media (prefers-reduced-motion: reduce) {
  .cs.is-demo .cs__pop,
  .cs.is-demo .cs__hl,
  .cs.is-demo .cs__face,
  .cs.is-demo .cs__dot,
  .cs.is-demo .cs__priceline { animation: none !important; }
  .cs:not(.is-demo) .cs__pop,
  .cs:not(.is-demo) .cs__hl { transition: none !important; }
  .cs.is-demo .cs__pop { transform: none; opacity: 1; }
  .cs.is-demo .cs__face[data-cur="usd"] { opacity: 1; }
  .cs.is-demo .cs__opt[data-cur="usd"] .cs__dot { opacity: 1; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.cs {
  --row: 22px;
  box-sizing: border-box;
  width: min(400px, 88vw);
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 16px;
  padding-bottom: 56px;
  border: 2px solid rgba(255, 255, 255, 0.12);
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.06);
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #fff7e6;
}

.cs__left {
  flex: 1 1 auto;
  min-width: 0;
}

.cs__plan {
  margin: 0;
  font-size: 12px;
  line-height: 18px;
  font-weight: 700;
  letter-spacing: 0.04em;
  opacity: 0.72;
}

.cs__priceline {
  position: relative;
  height: 40px;
  margin-top: 8px;
  transform-origin: left center;
}

.cs__face {
  position: absolute;
  left: 0;
  top: 0;
  display: flex;
  align-items: baseline;
  gap: 4px;
  white-space: nowrap;
  opacity: 0;
}

.cs__sym,
.cs__amt {
  color: #4cd4a6;
  font-size: 30px;
  line-height: 40px;
  font-weight: 800;
}

.cs__unit {
  font-size: 12px;
  line-height: 18px;
  font-weight: 700;
  opacity: 0.7;
}

.cs__note {
  margin: 4px 0 0;
  font-size: 11px;
  line-height: 16px;
  font-weight: 600;
  opacity: 0.55;
}

.cs__pick {
  position: relative;
  flex: 0 0 auto;
  width: 96px;
}

.cs__trig {
  box-sizing: border-box;
  display: flex;
  align-items: center;
  gap: 4px;
  width: 100%;
  margin: 0;
  padding: 4px 8px;
  border: 2px solid rgba(255, 255, 255, 0.22);
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.04);
  color: #fff7e6;
  font-family: inherit;
  font-size: 12px;
  line-height: 18px;
  font-weight: 700;
  cursor: pointer;
}

.cs__trig:focus-visible {
  outline: 2px solid #4cd4a6;
  outline-offset: 2px;
}

.cs__tsym {
  color: #4cd4a6;
}

.cs__caret {
  margin-left: auto;
  display: inline-flex;
  opacity: 0.6;
}

.cs__caret svg {
  display: block;
}

.cs__pop {
  position: absolute;
  left: 0;
  right: 0;
  top: calc(100% + 4px);
  box-sizing: border-box;
  padding: 4px 0;
  border: 2px solid rgba(255, 255, 255, 0.16);
  border-radius: 12px;
  background: #17141a;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  transform-origin: top center;
  transform: scaleY(0.5) translateY(-8px);
  opacity: 0;
  visibility: hidden;
}

.cs__hl {
  position: absolute;
  left: 4px;
  right: 4px;
  top: 4px;
  height: var(--row);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.1);
}

.cs__list {
  position: relative;
  margin: 0;
  padding: 0;
  list-style: none;
}

.cs__opt {
  display: flex;
  align-items: center;
  gap: 8px;
  height: var(--row);
  padding: 0 8px;
  font-size: 11px;
  line-height: 16px;
  font-weight: 700;
  cursor: pointer;
}

.cs__opt:focus-visible {
  outline: 2px solid #4cd4a6;
  outline-offset: -2px;
}

.cs__dot {
  flex: 0 0 auto;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: #4cd4a6;
  opacity: 0;
}

.cs__os {
  margin-left: auto;
  color: #4cd4a6;
}

.cs__trig[aria-expanded=true] ~ .cs__pop {
  transform: none;
  opacity: 1;
  visibility: visible;
}

.cs__opt[aria-selected=true] .cs__dot {
  opacity: 1;
}

.cs:not(.is-demo)[data-cur=usd] .cs__face[data-cur=usd],
.cs:not(.is-demo)[data-cur=krw] .cs__face[data-cur=krw],
.cs:not(.is-demo)[data-cur=jpy] .cs__face[data-cur=jpy],
.cs:not(.is-demo)[data-cur=eur] .cs__face[data-cur=eur] {
  opacity: 1;
}

.cs:not(.is-demo)[data-cur=krw] .cs__hl {
  transform: translateY(var(--row));
}

.cs:not(.is-demo)[data-cur=jpy] .cs__hl {
  transform: translateY(calc(var(--row) * 2));
}

.cs:not(.is-demo)[data-cur=eur] .cs__hl {
  transform: translateY(calc(var(--row) * 3));
}

.cs:not(.is-demo) .cs__pop {
  transition-property: transform, opacity, visibility;
  transition-duration: 220ms;
  transition-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
}

.cs:not(.is-demo) .cs__hl {
  transition-property: transform;
  transition-duration: 220ms;
  transition-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
}

.cs.is-demo .cs__pop {
  visibility: visible;
  animation-name: cs-open;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@keyframes cs-open {
  0% {
    transform: scaleY(0.5) translateY(-8px);
    opacity: 0;
  }
  10% {
    transform: none;
    opacity: 1;
  }
  100% {
    transform: none;
    opacity: 1;
  }
}
.cs.is-demo .cs__hl {
  animation-name: cs-hl;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@keyframes cs-hl {
  0%, 10% {
    transform: translateY(0);
  }
  20%, 30% {
    transform: translateY(var(--row));
  }
  40%, 50% {
    transform: translateY(calc(var(--row) * 2));
  }
  60%, 70% {
    transform: translateY(calc(var(--row) * 3));
  }
  80%, 100% {
    transform: translateY(0);
  }
}
.cs.is-demo .cs__face,
.cs.is-demo .cs__dot {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

.cs.is-demo .cs__face[data-cur=usd],
.cs.is-demo .cs__opt[data-cur=usd] .cs__dot {
  animation-name: cs-usd;
}

.cs.is-demo .cs__face[data-cur=krw],
.cs.is-demo .cs__opt[data-cur=krw] .cs__dot {
  animation-name: cs-krw;
}

.cs.is-demo .cs__face[data-cur=jpy],
.cs.is-demo .cs__opt[data-cur=jpy] .cs__dot {
  animation-name: cs-jpy;
}

.cs.is-demo .cs__face[data-cur=eur],
.cs.is-demo .cs__opt[data-cur=eur] .cs__dot {
  animation-name: cs-eur;
}

@keyframes cs-usd {
  0% {
    opacity: 1;
  }
  20% {
    opacity: 0;
  }
  80% {
    opacity: 1;
  }
  100% {
    opacity: 1;
  }
}
@keyframes cs-krw {
  0% {
    opacity: 0;
  }
  20% {
    opacity: 1;
  }
  40% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes cs-jpy {
  0% {
    opacity: 0;
  }
  40% {
    opacity: 1;
  }
  60% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes cs-eur {
  0% {
    opacity: 0;
  }
  60% {
    opacity: 1;
  }
  80% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
.cs.is-demo .cs__priceline {
  animation-name: cs-pop;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 1.4, 0.4, 1);
  animation-iteration-count: infinite;
}

@keyframes cs-pop {
  0%, 16% {
    transform: scale(1);
  }
  22% {
    transform: scale(1.06);
  }
  28%, 36% {
    transform: scale(1);
  }
  42% {
    transform: scale(1.06);
  }
  48%, 56% {
    transform: scale(1);
  }
  62% {
    transform: scale(1.06);
  }
  68%, 76% {
    transform: scale(1);
  }
  82% {
    transform: scale(1.06);
  }
  88%, 100% {
    transform: scale(1);
  }
}
@media (max-width: 340px) {
  .cs {
    --row: 20px;
    gap: 8px;
    padding: 12px;
    padding-bottom: 56px;
  }
  .cs__plan {
    font-size: 11px;
    line-height: 16px;
  }
  .cs__priceline {
    height: 30px;
    margin-top: 4px;
  }
  .cs__sym,
  .cs__amt {
    font-size: 21px;
    line-height: 30px;
  }
  .cs__pick {
    width: 88px;
  }
  .cs__trig {
    padding: 4px;
    font-size: 11px;
    line-height: 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cs.is-demo .cs__pop,
  .cs.is-demo .cs__hl,
  .cs.is-demo .cs__face,
  .cs.is-demo .cs__dot,
  .cs.is-demo .cs__priceline {
    animation: none !important;
  }
  .cs:not(.is-demo) .cs__pop,
  .cs:not(.is-demo) .cs__hl {
    transition: none !important;
  }
  .cs.is-demo .cs__pop {
    transform: none;
    opacity: 1;
  }
  .cs.is-demo .cs__face[data-cur=usd] {
    opacity: 1;
  }
  .cs.is-demo .cs__opt[data-cur=usd] .cs__dot {
    opacity: 1;
  }
}

// 실제 동작: 트리거의 aria-expanded 로 목록을 열고 닫는다. 고르면 뿌리의 data-cur 가 바뀌고
// 그 값에 걸린 CSS 가 금액 얼굴과 표시 점을 한꺼번에 갈아 끼운다.
// JS 가 넣는 문자열은 라틴 코드와 통화 기호뿐 — 한국어를 만들지 않는다
var root = document.querySelector('.cs');
var trig = document.getElementById('cs-trig');
var code = document.getElementById('cs-code');
var tsym = document.getElementById('cs-tsym');
var opts = [].slice.call(document.querySelectorAll('.cs__opt'));
function open(on) { trig.setAttribute('aria-expanded', String(on)); }
function pick(li) {
  root.classList.remove('is-demo');
  root.setAttribute('data-cur', li.getAttribute('data-cur'));
  opts.forEach(function (o) { o.setAttribute('aria-selected', String(o === li)); });
  code.textContent = li.getAttribute('data-code');
  tsym.textContent = li.getAttribute('data-sym');
  open(false);
  trig.focus({ preventScroll: true });
}
trig.addEventListener('click', function () {
  root.classList.remove('is-demo');
  open(trig.getAttribute('aria-expanded') !== 'true');
});
opts.forEach(function (li) {
  li.addEventListener('click', function () { pick(li); });
  li.addEventListener('keydown', function (e) {
    if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); pick(li); }
  });
});
document.addEventListener('keydown', function (e) {
  if (e.key === 'Escape' && trig.getAttribute('aria-expanded') === 'true') {
    open(false);
    trig.focus({ preventScroll: true });
  }
});

import { useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./CurrencySwitch.module.scss";

export type Currency = { id: string; code: string; sym: string; amt: string };
export type CurrencySwitchProps = {
  planName?: string;
  note?: string;
  pickLabel?: string;
  unit?: string;
  items?: Currency[];
  duration?: number;
  easing?: string;
  color?: string;
};

// React 이벤트 타입은 import 하지 않는다 — 필요한 모양만 여기서 적는다
type KeyEvt = { key: string; preventDefault(): void };

type Vars = CSSProperties & {
  "--duration"?: string;
  "--easing"?: string;
  "--color"?: string;
};

const DEFAULT_ITEMS: Currency[] = [
  { id: "usd", code: "USD", sym: "$", amt: "29" },
  { id: "krw", code: "KRW", sym: "₩", amt: "39,000" },
  { id: "jpy", code: "JPY", sym: "¥", amt: "4,400" },
  { id: "eur", code: "EUR", sym: "€", amt: "27" },
];

export default function CurrencySwitch({
  planName = "Standard plan",
  note = "Tax not included",
  pickLabel = "Pick a currency",
  unit = "/ mo",
  items = DEFAULT_ITEMS,
  duration = 220,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#4cd4a6",
}: CurrencySwitchProps) {
  const [demo, setDemo] = useState(true);
  const [open, setOpen] = useState(false);
  const [cur, setCur] = useState(items[0].id);
  const trigRef = useRef<HTMLButtonElement>(null);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const now = items.find((c) => c.id === cur) || items[0];
  const at = Math.max(0, items.findIndex((c) => c.id === cur));

  function toggle() {
    setDemo(false);
    setOpen((v) => !v);
  }
  function pick(c: Currency) {
    setDemo(false);
    setCur(c.id);
    setOpen(false);
    trigRef.current?.focus({ preventScroll: true });
  }
  function onKey(e: KeyEvt) {
    if (e.key === "Escape" && open) {
      e.preventDefault();
      setOpen(false);
      trigRef.current?.focus({ preventScroll: true });
    }
  }

  return (
    <div
      className={`${styles.cs} ${demo ? styles.isDemo : ""}`}
      data-cur={cur}
      style={vars}
      onKeyDown={onKey}
    >
      <div className={styles.left}>
        <p className={styles.plan}>{planName}</p>
        <div className={styles.priceline} aria-live="polite">
          {items.map((c) => (
            <span key={c.id} className={styles.face} data-cur={c.id} data-on={!demo && c.id === cur ? "1" : "0"}>
              <span className={styles.sym}>{c.sym}</span>
              <span className={styles.amt}>{c.amt}</span>
              <span className={styles.unit}>{unit}</span>
            </span>
          ))}
        </div>
        <p className={styles.note}>{note}</p>
      </div>
      <div className={styles.pick}>
        <button
          ref={trigRef}
          className={styles.trig}
          type="button"
          aria-expanded={open}
          aria-haspopup="listbox"
          aria-label={pickLabel}
          onClick={toggle}
        >
          <span className={styles.code}>{now.code}</span>
          <span className={styles.tsym}>{now.sym}</span>
          <span className={styles.caret} aria-hidden="true">
            <svg viewBox="0 0 256 256" width="14" height="14">
              <g fill="currentColor">
                <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" />
              </g>
            </svg>
          </span>
        </button>
        <div className={styles.pop} data-open={open ? "1" : "0"}>
          {/* 표시 띠만 부드럽게 미끄러진다 — 컷 옆에서 움직인 프레임을 채우는 몫 */}
          <span className={styles.hl} style={{ transform: `translateY(calc(var(--row) * ${at}))` }} aria-hidden="true" />
          <ul className={styles.list} role="listbox" aria-label={pickLabel}>
            {items.map((c) => (
              <li
                key={c.id}
                className={styles.opt}
                role="option"
                aria-selected={!demo && c.id === cur}
                tabIndex={0}
                data-cur={c.id}
                onClick={() => pick(c)}
                onKeyDown={(e: KeyEvt) => {
                  if (e.key === "Enter" || e.key === " ") {
                    e.preventDefault();
                    pick(c);
                  }
                }}
              >
                <span className={styles.dot} data-on={!demo && c.id === cur ? "1" : "0"} aria-hidden="true" />
                <span className={styles.oc}>{c.code}</span>
                <span className={styles.os}>{c.sym}</span>
              </li>
            ))}
          </ul>
        </div>
      </div>
    </div>
  );
}