07ラバーバンド境界

<main class="stage">
  <div class="rb is-demo" id="rb-root">
    <div class="rb__view" id="rb-view" tabindex="0" role="group" aria-label="お知らせリスト — 矢印キーで端を確認">
      <span class="rb__end rb__end--top" id="rb-top" aria-hidden="true">これより前のお知らせはありません</span>
      <div class="rb__inner" id="rb-inner">
        <div class="rb__row"><span class="rb__dot"></span><strong>10月メンテナンスのお知らせ</strong><time>10-02</time></div>
        <div class="rb__row"><span class="rb__dot rb__dot--pink"></span><strong>イベント当選者発表</strong><time>09-28</time></div>
        <div class="rb__row"><span class="rb__dot rb__dot--blue"></span><strong>新機能リリース</strong><time>09-21</time></div>
        <div class="rb__row"><span class="rb__dot rb__dot--lilac"></span><strong>休業日のお知らせ</strong><time>09-18</time></div>
        <div class="rb__row"><span class="rb__dot"></span><strong>利用規約改定</strong><time>09-10</time></div>
      </div>
      <span class="rb__end rb__end--bottom" id="rb-bottom" aria-hidden="true">最後のお知らせです</span>
    </div>
    <p class="rb__hint">端から先は引くほど抵抗が強くなり、指を離すとばねで戻ります</p>
  </div>
</main>

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

$duration: $dur-enter;
$easing: $ease-pop;
$color: $subject-ink;

@include stage($stage-yellow);

.rb { display: flex; flex-direction: column; align-items: center; gap: $sp-3; user-select: none; -webkit-user-select: none; }
.rb__view {
  position: relative;
  width: min(228px, 84vw);
  height: 132px;
  overflow: hidden;
  background: #fff;
  border-radius: $r-card;
  box-shadow: $shadow-press;
  touch-action: none;
  cursor: grab;
}
.rb__view:active { cursor: grabbing; }
.rb__view:focus-visible { outline: 3px solid rgba(23, 20, 26, .5); outline-offset: 2px; }
.rb__inner {
  transition: transform $duration $easing;
  will-change: transform;
}
.rb__row {
  box-sizing: border-box;
  display: flex;
  align-items: center;
  gap: $sp-2;
  height: 30px;
  padding: 0 $sp-3;
  border-bottom: 1px solid rgba(23, 20, 26, .07);
  background: #fff;
}
.rb__row strong { flex: 1; font-size: 12px; line-height: 14px; font-weight: 700; color: $subject-ink; }
.rb__row time { font-size: 10px; line-height: 12px; font-weight: 600; color: rgba(23, 20, 26, .72); }
.rb__dot { width: 7px; height: 7px; border-radius: 50%; background: $stage-orange; }
.rb__dot--pink { background: $subject-pink; }
.rb__dot--blue { background: $subject-blue; }
.rb__dot--lilac { background: $subject-lilac; }

.rb__end {
  position: absolute;
  left: 0; right: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 24px;
  background: $subject-ink;
  color: $subject-cream;
  font-size: 10px; line-height: 12px; font-weight: 700;
  opacity: 0;
  transform: translateY(-100%);
  transition: opacity $dur-quick steps(1, end);
  pointer-events: none;
}
.rb__end--top { top: 0; }
.rb__end--bottom { bottom: 0; transform: translateY(100%); }
.rb__end.is-on { opacity: 1; }

.rb__hint {
  margin: 0;
  font-size: 11px; line-height: 14px; font-weight: 600;
  color: rgba(23, 20, 26, .72);
}

// ── 자동 루프: 위 끝 당김(저항) → 튕겨 복귀 → 아래 끝 당김 → 복귀. 튕김은 ease-pop ──
.rb.is-demo .rb__inner { animation: rb-band $dur-loop infinite; }
@keyframes rb-band {
  0%, 8% { transform: translateY(0); }
  22% { transform: translateY(13px); }
  30% { transform: translateY(-5px); }
  36%, 46% { transform: translateY(0); }
  60% { transform: translateY(-13px); }
  68% { transform: translateY(5px); }
  74%, 100% { transform: translateY(0); }
}
.rb.is-demo .rb__end { transition: none; }
.rb.is-demo .rb__end--top { animation: rb-endt $dur-loop steps(1, end) infinite; }
.rb.is-demo .rb__end--bottom { animation: rb-endb $dur-loop steps(1, end) infinite; }
@keyframes rb-endt { 0%, 21% { opacity: 0; } 22%, 34% { opacity: 1; } 35%, 100% { opacity: 0; } }
@keyframes rb-endb { 0%, 59% { opacity: 0; } 60%, 72% { opacity: 1; } 73%, 100% { opacity: 0; } }

@media (prefers-reduced-motion: reduce) {
  .rb.is-demo .rb__inner,
  .rb.is-demo .rb__end { animation: none !important; }
  .rb__inner { transition: none; }
}

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

.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);
}

.rb {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  user-select: none;
  -webkit-user-select: none;
}

.rb__view {
  position: relative;
  width: min(228px, 84vw);
  height: 132px;
  overflow: hidden;
  background: #fff;
  border-radius: 16px;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  touch-action: none;
  cursor: grab;
}

.rb__view:active {
  cursor: grabbing;
}

.rb__view:focus-visible {
  outline: 3px solid rgba(23, 20, 26, 0.5);
  outline-offset: 2px;
}

.rb__inner {
  transition: transform 600ms cubic-bezier(0.2, 1.4, 0.4, 1);
  will-change: transform;
}

.rb__row {
  box-sizing: border-box;
  display: flex;
  align-items: center;
  gap: 8px;
  height: 30px;
  padding: 0 12px;
  border-bottom: 1px solid rgba(23, 20, 26, 0.07);
  background: #fff;
}

.rb__row strong {
  flex: 1;
  font-size: 12px;
  line-height: 14px;
  font-weight: 700;
  color: #17141a;
}

.rb__row time {
  font-size: 10px;
  line-height: 12px;
  font-weight: 600;
  color: rgba(23, 20, 26, 0.72);
}

.rb__dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: #ff4d1f;
}

.rb__dot--pink {
  background: #ff9ebb;
}

.rb__dot--blue {
  background: #2f6df6;
}

.rb__dot--lilac {
  background: #b9a0ff;
}

.rb__end {
  position: absolute;
  left: 0;
  right: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 24px;
  background: #17141a;
  color: #fff7e6;
  font-size: 10px;
  line-height: 12px;
  font-weight: 700;
  opacity: 0;
  transform: translateY(-100%);
  transition: opacity 220ms steps(1, end);
  pointer-events: none;
}

.rb__end--top {
  top: 0;
}

.rb__end--bottom {
  bottom: 0;
  transform: translateY(100%);
}

.rb__end.is-on {
  opacity: 1;
}

.rb__hint {
  margin: 0;
  font-size: 11px;
  line-height: 14px;
  font-weight: 600;
  color: rgba(23, 20, 26, 0.72);
}

.rb.is-demo .rb__inner {
  animation: rb-band 2s infinite;
}

@keyframes rb-band {
  0%, 8% {
    transform: translateY(0);
  }
  22% {
    transform: translateY(13px);
  }
  30% {
    transform: translateY(-5px);
  }
  36%, 46% {
    transform: translateY(0);
  }
  60% {
    transform: translateY(-13px);
  }
  68% {
    transform: translateY(5px);
  }
  74%, 100% {
    transform: translateY(0);
  }
}
.rb.is-demo .rb__end {
  transition: none;
}

.rb.is-demo .rb__end--top {
  animation: rb-endt 2s steps(1, end) infinite;
}

.rb.is-demo .rb__end--bottom {
  animation: rb-endb 2s steps(1, end) infinite;
}

@keyframes rb-endt {
  0%, 21% {
    opacity: 0;
  }
  22%, 34% {
    opacity: 1;
  }
  35%, 100% {
    opacity: 0;
  }
}
@keyframes rb-endb {
  0%, 59% {
    opacity: 0;
  }
  60%, 72% {
    opacity: 1;
  }
  73%, 100% {
    opacity: 0;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rb.is-demo .rb__inner,
  .rb.is-demo .rb__end {
    animation: none !important;
  }
  .rb__inner {
    transition: none;
  }
}

// 실제 동작: 끝에서 더 당기면 점점 저항(거리/3)이 붙고, 떼면 탄력으로 복귀. 화살표 키도 같은 반발을 보여준다.
var root = document.getElementById('rb-root');
var view = document.getElementById('rb-view');
var inner = document.getElementById('rb-inner');
var topEnd = document.getElementById('rb-top');
var bottomEnd = document.getElementById('rb-bottom');
var y0 = 0, dragging = false, cur = 0;

function bounds() {
  return { top: 0, bottom: Math.max(0, inner.offsetHeight - view.clientHeight + 2) };
}
function paint(y) {
  var b = bounds();
  var yd = y;
  if (yd < b.top) yd = b.top + (yd - b.top) / 3;        // 위 끝: 거리의 1/3만 따라오는 저항
  if (yd > b.bottom) yd = b.bottom + (yd - b.bottom) / 3;
  cur = y;
  inner.style.transform = 'translateY(' + (-yd) + 'px)';
  topEnd.classList.toggle('is-on', y < -6);
  bottomEnd.classList.toggle('is-on', y > b.bottom + 6);
}
view.addEventListener('pointerdown', function (e) {
  root.classList.remove('is-demo');
  dragging = true; y0 = e.clientY + cur;
  view.setPointerCapture(e.pointerId);
  inner.style.transition = 'none';
  e.preventDefault();
});
view.addEventListener('pointermove', function (e) {
  if (!dragging) return;
  paint(y0 - e.clientY); // 손가락을 아래로 당기면 콘텐츠도 아래로 늘어난다
});
function drop() {
  if (!dragging) return;
  dragging = false;
  inner.style.transition = '';
  var b = bounds();
  paint(Math.max(b.top, Math.min(b.bottom, cur)));
}
view.addEventListener('pointerup', drop);
view.addEventListener('pointercancel', drop);
view.addEventListener('keydown', function (e) {
  var b = bounds();
  if (e.key === 'ArrowUp') { root.classList.remove('is-demo'); bounce(b.top - 26); e.preventDefault(); }
  else if (e.key === 'ArrowDown') { root.classList.remove('is-demo'); bounce(b.bottom + 26); e.preventDefault(); }
});
function bounce(y) {
  inner.style.transition = 'none';
  paint(y);
  window.setTimeout(function () {
    inner.style.transition = '';
    var b = bounds();
    paint(Math.max(b.top, Math.min(b.bottom, y)));
  }, 240);
}
paint(0);

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

export type RubberBandProps = {
  rows?: string[];
  topLabel?: string;
  bottomLabel?: string;
  duration?: number;
  easing?: string;
  color?: string;
};

type PEvt = { clientX: number; clientY: number; pointerId: number; preventDefault(): void; currentTarget: { setPointerCapture(id: number): void } };
type KeyEvt = { key: string; preventDefault(): void };
type Box<T> = { current: T };
type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

export default function RubberBand({
  rows = ["October maintenance", "Event winners announced", "New feature released", "Holiday notice", "Terms updated"],
  topLabel = "No earlier notices",
  bottomLabel = "This is the last notice",
  duration = 600,
  easing = "cubic-bezier(.2,1.4,.4,1)",
  color = "#17141a",
}: RubberBandProps) {
  const [y, setY] = useState(0);
  const [bounce, setBounce] = useState(false);
  const viewRef = useRef<HTMLDivElement>(null);
  const innerRef = useRef<HTMLDivElement>(null);
  const drag = useRef({ on: false, y0: 0 }) as Box<{ on: boolean; y0: number }>;
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  function bounds() {
    const v = viewRef.current, i = innerRef.current;
    const bottom = v && i ? Math.max(0, i.offsetHeight - v.clientHeight + 2) : 0;
    return { top: 0, bottom };
  }

  function display(yv: number) {
    const b = bounds();
    let yd = yv;
    if (yd < b.top) yd = b.top + (yd - b.top) / 3;
    if (yd > b.bottom) yd = b.bottom + (yd - b.bottom) / 3;
    return yd;
  }

  function onDown(e: PEvt) {
    drag.current = { on: true, y0: e.clientY + y };
    e.currentTarget.setPointerCapture(e.pointerId);
    setBounce(false);
    e.preventDefault();
  }
  function onMove(e: PEvt) {
    if (!drag.current.on) return;
    setY(drag.current.y0 - e.clientY);
  }
  function onUp() {
    if (!drag.current.on) return;
    drag.current.on = false;
    const b = bounds();
    setBounce(true);
    setY(Math.max(b.top, Math.min(b.bottom, y)));
  }

  function onKey(e: KeyEvt) {
    const b = bounds();
    if (e.key === "ArrowUp") { setBounce(false); setY(b.top - 26); window.setTimeout((): void => { setBounce(true); setY(0); }, 240); e.preventDefault(); }
    else if (e.key === "ArrowDown") { setBounce(false); setY(b.bottom + 26); window.setTimeout((): void => { setBounce(true); setY(b.bottom); }, 240); e.preventDefault(); }
  }

  return (
    <div className={styles.rb} style={vars}>
      <div
        ref={viewRef}
        className={styles.view}
        tabIndex={0}
        role="group"
        aria-label="Notice list — arrow keys check the ends"
        onPointerDown={onDown}
        onPointerMove={onMove}
        onPointerUp={onUp}
        onPointerCancel={onUp}
        onKeyDown={onKey}
      >
        <span className={y < -6 ? styles.endOn : styles.endTop} aria-hidden="true">{topLabel}</span>
        <div ref={innerRef} className={bounce ? styles.innerBounce : styles.inner} style={{ transform: `translateY(${-display(y)}px)` }}>
          {rows.map((r, i) => (
            <div key={r} className={styles.row}>
              <span className={i % 4 === 0 ? styles.dot : i % 4 === 1 ? styles.dotPink : i % 4 === 2 ? styles.dotBlue : styles.dotLilac} />
              <strong>{r}</strong>
              <time>{`10-0${(5 - i)}`}</time>
            </div>
          ))}
        </div>
        <span className={y > bounds().bottom + 6 ? styles.endOn : styles.endBottom} aria-hidden="true">{bottomLabel}</span>
      </div>
      <p className={styles.hint}>Past the end each pixel drags harder, and releasing springs it back</p>
    </div>
  );
}