04수량 탄성 범프 — 늘어난 값만큼 커졌다가 되돌아오는 수량 숫자

<main class="stage">
<div class="cqbe is-demo" id="cqbe">
  <div class="cqbe__row">
    <span class="cqbe__name">캔버스 백</span>
    <div class="cqbe__stepper">
      <button class="cqbe__btn" id="cqbeMinus" type="button" aria-label="수량 줄이기">-</button>
      <span class="cqbe__badge">
        <span class="cqbe__ripple" id="cqbeRipple"></span>
        <span class="cqbe__qty" id="cqbeQty">1</span>
      </span>
      <button class="cqbe__btn" id="cqbePlus" type="button" aria-label="수량 늘리기">+</button>
    </div>
  </div>
</div>
</main>

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

// 계산 겹: 값이 바뀐 시각부터 지난 시간에 감쇠 사인파(elasticPulse(), index.html)를 매 프레임
// 계산해 scale 에 대입한다 — 고정 keyframes 곡선이 아니라 변경 시각 기준으로 다시 푼다.

$duration: $dur-quick;
$easing: $ease-pop;
$color: $subject-blue-deep;

@include stage($stage-paper);

.stage { position: relative; }

.cqbe {
  width: min(220px, 68vw);
}

.cqbe__row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: $sp-4;
  border-radius: $r-card;
  background: rgba(23, 20, 26, .06);
  transform-origin: center;
  will-change: transform;
}

.cqbe__name {
  color: $subject-ink;
  font-weight: 700;
  font-size: 14px;
}

.cqbe__stepper {
  display: flex;
  align-items: center;
  gap: $sp-3;
}

.cqbe__btn {
  width: 28px;
  height: 28px;
  border: 0;
  border-radius: $r-pill;
  background: $color;
  color: $subject-cream;
  font-family: inherit;
  font-weight: 700;
  font-size: 16px;
  line-height: 1;
  display: grid;
  place-items: center;
  cursor: pointer;
}

.cqbe__badge {
  position: relative;
  width: 40px;
  height: 40px;
  display: grid;
  place-items: center;
}

.cqbe__ripple {
  position: absolute;
  left: 50%;
  top: 50%;
  width: 40px;
  height: 40px;
  border-radius: $r-pill;
  background: $color;
  opacity: 0;
  transform: translate(-50%, -50%) scale(.4);
  transform-origin: center;
  pointer-events: none;
}

.cqbe__qty {
  position: relative;
  min-width: 20px;
  text-align: center;
  color: $subject-ink;
  font-weight: 700;
  font-size: 18px;
  display: inline-block;
  transform-origin: center;
}

@media (max-width: 340px) {
  .cqbe__row { padding: $sp-3; }
  .cqbe__btn { width: 24px; height: 24px; font-size: 14px; }
}

@media (prefers-reduced-motion: reduce) {
  .cqbe__qty { transition: none !important; }
}

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);
}

.stage {
  position: relative;
}

.cqbe {
  width: min(220px, 68vw);
}

.cqbe__row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px;
  border-radius: 16px;
  background: rgba(23, 20, 26, 0.06);
  transform-origin: center;
  will-change: transform;
}

.cqbe__name {
  color: #17141a;
  font-weight: 700;
  font-size: 14px;
}

.cqbe__stepper {
  display: flex;
  align-items: center;
  gap: 12px;
}

.cqbe__btn {
  width: 28px;
  height: 28px;
  border: 0;
  border-radius: 999px;
  background: #0a4fe8;
  color: #fff7e6;
  font-family: inherit;
  font-weight: 700;
  font-size: 16px;
  line-height: 1;
  display: grid;
  place-items: center;
  cursor: pointer;
}

.cqbe__badge {
  position: relative;
  width: 40px;
  height: 40px;
  display: grid;
  place-items: center;
}

.cqbe__ripple {
  position: absolute;
  left: 50%;
  top: 50%;
  width: 40px;
  height: 40px;
  border-radius: 999px;
  background: #0a4fe8;
  opacity: 0;
  transform: translate(-50%, -50%) scale(0.4);
  transform-origin: center;
  pointer-events: none;
}

.cqbe__qty {
  position: relative;
  min-width: 20px;
  text-align: center;
  color: #17141a;
  font-weight: 700;
  font-size: 18px;
  display: inline-block;
  transform-origin: center;
}

@media (max-width: 340px) {
  .cqbe__row {
    padding: 12px;
  }
  .cqbe__btn {
    width: 24px;
    height: 24px;
    font-size: 14px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cqbe__qty {
    transition: none !important;
  }
}

(function () {
  var root = document.getElementById('cqbe');
  var qtyEl = document.getElementById('cqbeQty');
  var minusBtn = document.getElementById('cqbeMinus');
  var plusBtn = document.getElementById('cqbePlus');

  // 계산 겹: 값이 바뀐 순간부터 지난 시간(t)에 감쇠 사인파(elasticPulse())를 매 프레임 계산해
  // scale 에 대입한다 — CSS keyframes 의 고정 퍼센트 곡선이 아니라 값 변경 시각을 기준으로 다시 푼다.
  var AMPLITUDE = 0.3;
  var FREQ = 18;
  var DECAY = 9;
  function elasticPulse(tSec) {
    if (tSec <= 0) { return 1; }
    return 1 + AMPLITUDE * Math.sin(tSec * FREQ) * Math.exp(-DECAY * tSec);
  }

  // 계산 겹 2: 범프와 별도로, 배지 둘레의 번짐(ripple)은 ease-out 곡선으로 반지름을 키우고
  // 동시에 옅어지게 계산한다 — 하나의 진행값(p)에서 scale·opacity 둘을 같이 뽑는다(depth-scale 항목과 같은 패턴, 다른 대상).
  function easeOutCubic(p) { return 1 - Math.pow(1 - p, 3); }
  var rippleEl = document.getElementById('cqbeRipple');
  function applyRipple(tSec) {
    var p = Math.min(1, Math.max(0, tSec / 0.5));
    var eased = easeOutCubic(p);
    var s = 0.4 + eased * 2.1;
    var op = (1 - eased) * 0.4;
    rippleEl.style.transform = 'translate(-50%, -50%) scale(' + s.toFixed(3) + ')';
    rippleEl.style.opacity = op.toFixed(3);
  }

  var qty = 1;
  var pulseStart = null;
  var raf = null;

  var rowEl = root.querySelector('.cqbe__row');

  function frame(now) {
    var t = (now - pulseStart) / 1000;
    var scale = elasticPulse(t);
    rowEl.style.transform = 'scale(' + scale.toFixed(4) + ')';
    qtyEl.style.transform = 'scale(' + scale.toFixed(4) + ')';
    applyRipple(t);
    if (t < 0.5) {
      raf = requestAnimationFrame(frame);
    } else {
      rowEl.style.transform = 'scale(1)';
      qtyEl.style.transform = 'scale(1)';
      rippleEl.style.opacity = '0';
      raf = null;
    }
  }

  function bump() {
    if (raf) { cancelAnimationFrame(raf); }
    pulseStart = performance.now();
    raf = requestAnimationFrame(frame);
  }

  function setQty(n) {
    qty = Math.max(1, Math.min(9, n));
    qtyEl.textContent = String(qty);
    bump();
  }

  minusBtn.addEventListener('click', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    setQty(qty - 1);
  });
  plusBtn.addEventListener('click', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    setQty(qty + 1);
  });

  var autoplayTimer = null;
  var dir = 1;
  function stopAutoplay() {
    if (autoplayTimer) { clearInterval(autoplayTimer); autoplayTimer = null; }
  }
  function autoplayTick() {
    if (qty >= 5) { dir = -1; }
    if (qty <= 1) { dir = 1; }
    setQty(qty + dir);
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) {
    autoplayTimer = setInterval(autoplayTick, 700);
  }
})();

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

export type CartDrawerQtyBumpElasticProps = {
  duration?: number;
  color?: string;
};

// 계산 겹: 값이 바뀐 순간부터 지난 시간(t)에 감쇠 사인파(elasticPulse())를 매 프레임 계산해
// scale 에 대입한다 — CSS keyframes 의 고정 퍼센트 곡선이 아니라 값 변경 시각을 기준으로 다시 푼다.
const AMPLITUDE = 0.3;
const FREQ = 18;
const DECAY = 9;
function elasticPulse(tSec: number): number {
  if (tSec <= 0) return 1;
  return 1 + AMPLITUDE * Math.sin(tSec * FREQ) * Math.exp(-DECAY * tSec);
}

// 계산 겹 2: 범프와 별도로, 배지 둘레의 번짐(ripple)은 ease-out 곡선으로 반지름을 키우고
// 동시에 옅어지게 계산한다 — 하나의 진행값(p)에서 scale·opacity 둘을 같이 뽑는다.
function easeOutCubic(p: number): number {
  return 1 - Math.pow(1 - p, 3);
}

export default function CartDrawerQtyBumpElastic({
  color = "#0a4fe8",
}: CartDrawerQtyBumpElasticProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const rowRef = useRef<HTMLDivElement | null>(null);
  const qtyRef = useRef<HTMLSpanElement | null>(null);
  const rippleRef = useRef<HTMLSpanElement | null>(null);
  const [qty, setQtyState] = useState(1);
  const qtyValRef = useRef(1);
  const rafRef = useRef<number | null>(null);
  const timerRef = useRef<ReturnType<typeof setInterval> | null>(null);

  useEffect(() => {
    function applyRipple(tSec: number) {
      const el = rippleRef.current;
      if (!el) return;
      const p = Math.min(1, Math.max(0, tSec / 0.5));
      const eased = easeOutCubic(p);
      const s = 0.4 + eased * 2.1;
      const op = (1 - eased) * 0.4;
      el.style.transform = `translate(-50%, -50%) scale(${s.toFixed(3)})`;
      el.style.opacity = op.toFixed(3);
    }

    function bump() {
      if (rafRef.current) cancelAnimationFrame(rafRef.current);
      const start = performance.now();
      function frame(now: number) {
        const t = (now - start) / 1000;
        const scale = elasticPulse(t);
        if (rowRef.current) rowRef.current.style.transform = `scale(${scale.toFixed(4)})`;
        if (qtyRef.current) qtyRef.current.style.transform = `scale(${scale.toFixed(4)})`;
        applyRipple(t);
        if (t < 0.5) {
          rafRef.current = requestAnimationFrame(frame);
        } else {
          if (rowRef.current) rowRef.current.style.transform = "scale(1)";
          if (qtyRef.current) qtyRef.current.style.transform = "scale(1)";
          if (rippleRef.current) rippleRef.current.style.opacity = "0";
          rafRef.current = null;
        }
      }
      rafRef.current = requestAnimationFrame(frame);
    }

    function setQty(n: number) {
      qtyValRef.current = Math.max(1, Math.min(9, n));
      setQtyState(qtyValRef.current);
      bump();
    }

    function stopAutoplay() {
      if (timerRef.current) {
        clearInterval(timerRef.current);
        timerRef.current = null;
      }
    }

    const onMinus = () => {
      rootRef.current?.classList.remove(styles.isDemo);
      stopAutoplay();
      setQty((qtyValRef.current ?? 1) - 1);
    };
    const onPlus = () => {
      rootRef.current?.classList.remove(styles.isDemo);
      stopAutoplay();
      setQty((qtyValRef.current ?? 1) + 1);
    };
    const minusEl = rootRef.current?.querySelector<HTMLButtonElement>(`.${styles.minus}`);
    const plusEl = rootRef.current?.querySelector<HTMLButtonElement>(`.${styles.plus}`);
    minusEl?.addEventListener("click", onMinus);
    plusEl?.addEventListener("click", onPlus);

    let dir = 1;
    function autoplayTick() {
      const cur = qtyValRef.current ?? 1;
      if (cur >= 5) dir = -1;
      if (cur <= 1) dir = 1;
      setQty(cur + dir);
    }

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) {
      timerRef.current = setInterval(autoplayTick, 700);
    }

    return () => {
      stopAutoplay();
      if (rafRef.current) cancelAnimationFrame(rafRef.current);
      minusEl?.removeEventListener("click", onMinus);
      plusEl?.removeEventListener("click", onPlus);
    };
  }, []);

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.isDemo}`} style={{ "--color": color } as CSSProperties}>
      <div ref={rowRef} className={styles.row}>
        <span className={styles.name}>캔버스 백</span>
        <div className={styles.stepper}>
          <button className={styles.minus} type="button" aria-label="수량 줄이기">-</button>
          <span className={styles.badge}>
            <span ref={rippleRef} className={styles.ripple} />
            <span ref={qtyRef} className={styles.qty}>{qty}</span>
          </span>
          <button className={styles.plus} type="button" aria-label="수량 늘리기">+</button>
        </div>
      </div>
    </div>
  );
}