04Before-and-after wipe

<main class="stage">
  <div class="bw is-demo">
    <div class="bw__scroller">
      <div class="bw__pad">
        <div class="bw__frame">
          <div class="bw__layer bw__layer--after" aria-hidden="true">
            <span class="bw__bar bw__bar--a"></span>
            <span class="bw__bar bw__bar--b"></span>
            <span class="bw__bar bw__bar--c"></span>
            <span class="bw__dot"></span>
          </div>
          <div class="bw__layer bw__layer--before" aria-hidden="true">
            <span class="bw__bar bw__bar--a"></span>
            <span class="bw__bar bw__bar--b"></span>
            <span class="bw__bar bw__bar--c"></span>
            <span class="bw__dot"></span>
          </div>
          <div class="bw__handle" aria-hidden="true">
            <svg viewBox="0 0 256 256" width="16" height="16" aria-hidden="true"><g fill="currentColor"><path d="M208 80v96H48V80Z" opacity=".2"/><path d="m213.66 181.66l-32 32a8 8 0 0 1-11.32-11.32L188.69 184H48a8 8 0 0 1 0-16h140.69l-18.35-18.34a8 8 0 0 1 11.32-11.32l32 32a8 8 0 0 1 0 11.32m-139.32-64a8 8 0 0 0 11.32-11.32L67.31 88H208a8 8 0 0 0 0-16H67.31l18.35-18.34a8 8 0 0 0-11.32-11.32l-32 32a8 8 0 0 0 0 11.32Z"/></g></svg>
          </div>
        </div>
        <p class="bw__tags"><span class="bw__tag bw__tag--old">Before</span><span class="bw__tag">After</span></p>
      </div>
    </div>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: 1s;          // alternate 라 한 바퀴는 2s
// 미리보기 곡선은 가운데가 가장 빠르다 — 대표 이미지(가장 크게 변한 장)가
// 반쯤 걷힌 장면으로 뽑혀야 전과 후가 한 장에 같이 보인다. 실제 스크롤 판은 linear
$easing: cubic-bezier(.65, 0, .35, 1);
$color: $subject-blue;

@include stage($stage-paper);

.bw {
  --h: clamp(148px, 58vh, 176px);
  --fw: min(272px, 82vw);
  width: min(360px, 92vw);
}

.bw__scroller {
  height: var(--h);
  overflow-y: auto;
  scrollbar-width: none;
  &::-webkit-scrollbar { display: none; }
}

.bw__pad {
  display: grid;
  justify-items: center;
  gap: $sp-2;
  // 상자가 처음에는 화면 밖에 있어야 뷰 타임라인의 entry 구간이 실제로 지나간다
  padding: calc(var(--h) * .95) 0 calc(var(--h) * .6);
}

// ⚠ 뷰 타임라인의 이름은 **관찰 대상**(이 상자)에 붙인다. 안쪽 층에서 view() 를 그냥 쓰면
// 이 상자의 overflow: hidden 이 스크롤포트로 잡혀 진행률이 0 에서 멈춘다 (실측)
.bw__frame {
  view-timeline-name: --bw-view;
  view-timeline-axis: block;
  position: relative;
  width: var(--fw);
  height: 104px;
  overflow: hidden;
  border-radius: $r-card;
}

.bw__layer {
  position: absolute;
  inset: 0;
  display: grid;
  align-content: center;
  gap: $sp-2;
  padding: $sp-4;
}

.bw__layer--after { background: #eef3ff; }
.bw__layer--after .bw__bar--a { background: $color; }
.bw__layer--after .bw__bar--b { background: $subject-mint; }
.bw__layer--after .bw__bar--c { background: $subject-lilac; }
.bw__layer--after .bw__dot { background: $stage-orange; }

// ── 실제 동작: 위층만 오른쪽부터 잘려 나간다.
//    inset() 의 오른쪽 값이 0 → 100% 로 자라면 아래층이 그만큼 드러난다 ──
.bw__layer--before {
  background: #e7e5ea;
  clip-path: inset(0 0 0 0);
  animation-name: bw-cut;
  animation-duration: 1s;
  animation-timing-function: linear;
  animation-fill-mode: both;
  animation-timeline: --bw-view;
}
.bw__layer--before .bw__bar--a,
.bw__layer--before .bw__bar--b,
.bw__layer--before .bw__bar--c { background: #b6b2bd; }
.bw__layer--before .bw__dot { background: #8d8895; }

@keyframes bw-cut {
  from { clip-path: inset(0 0 0 0); }
  to   { clip-path: inset(0 100% 0 0); }
}

.bw__bar {
  height: 12px;
  border-radius: $r-pill;
}
.bw__bar--a { width: 64%; }
.bw__bar--b { width: 88%; }
.bw__bar--c { width: 46%; }

.bw__dot {
  position: absolute;
  top: $sp-4;
  right: $sp-4;
  width: 28px;
  height: 28px;
  border-radius: 50%;
}

// 손잡이는 잘린 경계에 붙어 같은 진행률로 움직인다
.bw__handle {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  display: grid;
  place-items: center;
  width: 4px;
  background: $subject-ink;
  color: $subject-ink;
  animation-name: bw-handle;
  animation-duration: 1s;
  animation-timing-function: linear;
  animation-fill-mode: both;
  animation-timeline: --bw-view;

  svg {
    padding: $sp-1;
    border-radius: 50%;
    background: $subject-ink;
    color: $subject-cream;
  }
}

@keyframes bw-handle {
  from { transform: translateX(calc(var(--fw) - 4px)); }
  to   { transform: translateX(0); }
}

.bw__tags {
  display: flex;
  gap: $sp-2;
  margin: 0;
}

.bw__tag {
  padding: $sp-1 $sp-2;
  border-radius: $r-pill;
  background: $color;
  color: #fff;
  font-size: 11px;
  line-height: 14px;
  font-weight: 700;
}
.bw__tag--old { background: #b6b2bd; }

// 미리보기 루프는 실제로 스크롤하지 않으니 위 여백을 줄여 상자를 화면 안에 둔다
.bw.is-demo .bw__pad { padding-top: calc(var(--h) * .1); }

// ── 격자 미리보기 루프 — 같은 두 애니메이션을 시간으로 되감는다 ──
.bw.is-demo .bw__layer--before,
.bw.is-demo .bw__handle {
  animation-duration: $duration;
  animation-timing-function: $easing;
  animation-direction: alternate;
  animation-iteration-count: infinite;
  animation-timeline: auto;
}

@media (prefers-reduced-motion: reduce) {
  .bw__layer--before { animation: none !important; clip-path: inset(0 50% 0 0); }
  .bw__handle { animation: none !important; transform: translateX(calc(var(--fw) * .5)); }
}

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

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

.bw {
  --h: clamp(148px, 58vh, 176px);
  --fw: min(272px, 82vw);
  width: min(360px, 92vw);
}

.bw__scroller {
  height: var(--h);
  overflow-y: auto;
  scrollbar-width: none;
}
.bw__scroller::-webkit-scrollbar {
  display: none;
}

.bw__pad {
  display: grid;
  justify-items: center;
  gap: 8px;
  padding: calc(var(--h) * 0.95) 0 calc(var(--h) * 0.6);
}

.bw__frame {
  view-timeline-name: --bw-view;
  view-timeline-axis: block;
  position: relative;
  width: var(--fw);
  height: 104px;
  overflow: hidden;
  border-radius: 16px;
}

.bw__layer {
  position: absolute;
  inset: 0;
  display: grid;
  align-content: center;
  gap: 8px;
  padding: 16px;
}

.bw__layer--after {
  background: #eef3ff;
}

.bw__layer--after .bw__bar--a {
  background: #2f6df6;
}

.bw__layer--after .bw__bar--b {
  background: #4cd4a6;
}

.bw__layer--after .bw__bar--c {
  background: #b9a0ff;
}

.bw__layer--after .bw__dot {
  background: #ff4d1f;
}

.bw__layer--before {
  background: #e7e5ea;
  clip-path: inset(0 0 0 0);
  animation-name: bw-cut;
  animation-duration: 1s;
  animation-timing-function: linear;
  animation-fill-mode: both;
  animation-timeline: --bw-view;
}

.bw__layer--before .bw__bar--a,
.bw__layer--before .bw__bar--b,
.bw__layer--before .bw__bar--c {
  background: #b6b2bd;
}

.bw__layer--before .bw__dot {
  background: #8d8895;
}

@keyframes bw-cut {
  from {
    clip-path: inset(0 0 0 0);
  }
  to {
    clip-path: inset(0 100% 0 0);
  }
}
.bw__bar {
  height: 12px;
  border-radius: 999px;
}

.bw__bar--a {
  width: 64%;
}

.bw__bar--b {
  width: 88%;
}

.bw__bar--c {
  width: 46%;
}

.bw__dot {
  position: absolute;
  top: 16px;
  right: 16px;
  width: 28px;
  height: 28px;
  border-radius: 50%;
}

.bw__handle {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  display: grid;
  place-items: center;
  width: 4px;
  background: #17141a;
  color: #17141a;
  animation-name: bw-handle;
  animation-duration: 1s;
  animation-timing-function: linear;
  animation-fill-mode: both;
  animation-timeline: --bw-view;
}
.bw__handle svg {
  padding: 4px;
  border-radius: 50%;
  background: #17141a;
  color: #fff7e6;
}

@keyframes bw-handle {
  from {
    transform: translateX(calc(var(--fw) - 4px));
  }
  to {
    transform: translateX(0);
  }
}
.bw__tags {
  display: flex;
  gap: 8px;
  margin: 0;
}

.bw__tag {
  padding: 4px 8px;
  border-radius: 999px;
  background: #2f6df6;
  color: #fff;
  font-size: 11px;
  line-height: 14px;
  font-weight: 700;
}

.bw__tag--old {
  background: #b6b2bd;
}

.bw.is-demo .bw__pad {
  padding-top: calc(var(--h) * 0.1);
}

.bw.is-demo .bw__layer--before,
.bw.is-demo .bw__handle {
  animation-duration: 1s;
  animation-timing-function: cubic-bezier(0.65, 0, 0.35, 1);
  animation-direction: alternate;
  animation-iteration-count: infinite;
  animation-timeline: auto;
}

@media (prefers-reduced-motion: reduce) {
  .bw__layer--before {
    animation: none !important;
    clip-path: inset(0 50% 0 0);
  }
  .bw__handle {
    animation: none !important;
    transform: translateX(calc(var(--fw) * 0.5));
  }
}

// 실제 동작은 CSS 만: 위층의 clip-path 와 손잡이 위치를 animation-timeline: view() 가 함께 끌고 간다.
var r = document.querySelector('.bw');
var s = r.querySelector('.bw__scroller');
function stopDemo(){ r.classList.remove('is-demo'); }
r.addEventListener('pointerdown', stopDemo);
s.addEventListener('scroll', stopDemo, { passive: true });

import type { CSSProperties, ReactNode } from "react";
import styles from "./BeforeAfterWipe.module.scss";

export type BeforeAfterWipeProps = {
  beforeLabel?: string;
  afterLabel?: string;
  preview?: boolean;
  duration?: number;
  easing?: string;
  color?: string;
};

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

const IconArrows = (): ReactNode => (
  <svg viewBox="0 0 256 256" width="16" height="16" aria-hidden="true"><g fill="currentColor"><path d="M208 80v96H48V80Z" opacity=".2"/><path d="m213.66 181.66l-32 32a8 8 0 0 1-11.32-11.32L188.69 184H48a8 8 0 0 1 0-16h140.69l-18.35-18.34a8 8 0 0 1 11.32-11.32l32 32a8 8 0 0 1 0 11.32m-139.32-64a8 8 0 0 0 11.32-11.32L67.31 88H208a8 8 0 0 0 0-16H67.31l18.35-18.34a8 8 0 0 0-11.32-11.32l-32 32a8 8 0 0 0 0 11.32Z"/></g></svg>
);

const Layer = ({ kind }: { kind: string }): ReactNode => (
  <div className={`${styles.layer} ${styles[kind]}`} aria-hidden="true">
    <span className={`${styles.bar} ${styles.barA}`} />
    <span className={`${styles.bar} ${styles.barB}`} />
    <span className={`${styles.bar} ${styles.barC}`} />
    <span className={styles.dot} />
  </div>
);

export default function BeforeAfterWipe({
  beforeLabel = "Before",
  afterLabel = "After",
  preview = true,
  duration = 1000,
  easing = "cubic-bezier(.65, 0, .35, 1)",
  color = "#2f6df6",
}: BeforeAfterWipeProps): ReactNode {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const cls = preview ? `${styles.bw} ${styles.isDemo}` : styles.bw;

  return (
    <div className={cls} style={vars}>
      <div className={styles.scroller}>
        <div className={styles.pad}>
          <div className={styles.frame}>
            <Layer kind="after" />
            <Layer kind="before" />
            <div className={styles.handle} aria-hidden="true"><IconArrows /></div>
          </div>
          <p className={styles.tags}>
            <span className={`${styles.tag} ${styles.tagOld}`}>{beforeLabel}</span>
            <span className={styles.tag}>{afterLabel}</span>
          </p>
        </div>
      </div>
    </div>
  );
}