04Push fader slider

<svg width="0" height="0" style="position:absolute" aria-hidden="true">
  <defs>
    <symbol id="ico-faders" viewBox="0 0 256 256" fill="currentColor"><g><path d="M200 40v176H56V40Z" opacity=".2"/><path d="M136 120v96a8 8 0 0 1-16 0v-96a8 8 0 0 1 16 0m64 72a8 8 0 0 0-8 8v16a8 8 0 0 0 16 0v-16a8 8 0 0 0-8-8m24-32h-16V40a8 8 0 0 0-16 0v120h-16a8 8 0 0 0 0 16h48a8 8 0 0 0 0-16m-168 0a8 8 0 0 0-8 8v48a8 8 0 0 0 16 0v-48a8 8 0 0 0-8-8m24-32H64V40a8 8 0 0 0-16 0v88H32a8 8 0 0 0 0 16h48a8 8 0 0 0 0-16m72-48h-16V40a8 8 0 0 0-16 0v40h-16a8 8 0 0 0 0 16h48a8 8 0 0 0 0-16"/></g></symbol>
  </defs>
</svg>
<main class="stage">
<div class="pf is-demo" id="pf">
  <p class="pf__hint">
    <svg class="pf__ico" aria-hidden="true"><use href="#ico-faders"/></svg>
    <span>Slide it left and right</span>
  </p>
  <button class="pf__well" id="well" type="button" role="slider" tabindex="0"
          aria-label="Channel fader" aria-orientation="horizontal"
          aria-valuemin="0" aria-valuemax="10" aria-valuenow="5">
    <span class="pf__slot"></span>
    <span class="pf__capWrap" id="capWrap"><span class="pf__cap"><i class="pf__stripe"></i></span></span>
  </button>
  <div class="pf__scale" aria-hidden="true">
    <span class="pf__num">0</span><span class="pf__num">1</span><span class="pf__num">2</span><span class="pf__num">3</span><span class="pf__num">4</span><span class="pf__num">5</span><span class="pf__num">6</span><span class="pf__num">7</span><span class="pf__num">8</span><span class="pf__num">9</span><span class="pf__num">10</span>
  </div>
</div>
</main>

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

// 밀기 페이더 슬라이더 — 믹서 채널 페이더를 좌우로 민다. 끝에 닿으면 쿠션 이징($easing)으로
// 캡이 살짝 눌렸다(scaleX) 멈춘다. 값은 눈금 아래 숫자 0 부터 10 까지 + aria-valuenow 로 읽힌다.
// 재질감은 그라디언트 하이라이트와 inset 그림자로: 잉크 패널 위 크림빛 캡, 가운데 파란 줄.
// .is-demo 루프는 캡이 왼쪽 끝에서 오른쪽 끝으로 갔다 돌아오고 양 끝에서 눌린다(2초 한 바퀴).
// 사람이 포인터나 키로 만지면 JS 가 .is-demo 를 뗀다.

$duration: $dur-quick;
$easing: $ease-spring;
$color: $stage-paper;

@include stage($stage-paper);

.pf { display: flex; flex-direction: column; align-items: center; gap: $sp-3; width: 100%; max-width: 352px; }
.pf__hint {
  display: flex; align-items: center; gap: $sp-1; margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); color: $subject-ink;
}
.pf__ico { width: 16px; height: 16px; flex: 0 0 auto; color: $subject-blue; }

// 채널 패널 — 잉크 몸체에 위에서 비친 하이라이트 한 줄
.pf__well {
  position: relative; overflow: hidden; width: 100%; height: clamp(72px, 20vw, 88px);
  border: 0; border-radius: $r-card; padding: 0; cursor: grab; touch-action: none;
  background: linear-gradient(180deg, rgba($subject-cream, .16), rgba($subject-cream, 0) 42%), $subject-ink;
  box-shadow: $shadow-raised, inset 0 1px 0 rgba($subject-cream, .22), inset 0 -2px 0 rgba(0, 0, 0, .45);
}
.pf__well:focus-visible { outline: 2px solid $subject-blue; outline-offset: 2px; }
.pf__well:active { cursor: grabbing; }

// 홈이 팬 슬롯 — 페이더 캡이 다니는 길
.pf__slot {
  position: absolute; left: $sp-2; right: $sp-2; top: 50%; height: clamp(14px, 4vw, 18px);
  transform: translateY(-50%); border-radius: $r-pill;
  background: rgba(0, 0, 0, .5);
  box-shadow: inset 0 2px 4px rgba(0, 0, 0, .7), inset 0 -1px 0 rgba($subject-cream, .14);
}

// 캡 래퍼는 슬롯 전체 폭. translateX 의 % 기준을 슬롯 폭으로 잡기 위해 분리했다
.pf__capWrap {
  position: absolute; left: $sp-2; right: $sp-2; top: $sp-1; bottom: $sp-1;
  transform: translateX(calc(var(--x, 0px)));
}
.pf__cap {
  position: absolute; left: 0; top: 0; width: 48px; height: 100%;
  border-radius: $r-control;
  background:
    linear-gradient(90deg, rgba($subject-ink, .38) 0 4px, rgba($subject-ink, 0) 4px 10px),
    linear-gradient(180deg, rgba($stage-paper, 1) 0 18%, rgba($subject-ink, .22) 52%, rgba($stage-paper, .92) 100%);
  box-shadow: 0 6px 10px rgba(0, 0, 0, .5), inset 0 1px 0 rgba(255, 255, 255, .9), inset 0 -2px 0 rgba(0, 0, 0, .25);
  transition: transform $duration $easing;
}
// 캡은 스스로 완결한 요소라 눌림(scaleX)도 자기 중심에서 일어난다
.pf__cap.is-press { transform: scaleX(.82); }
.pf__stripe {
  position: absolute; left: 10px; right: 10px; top: 50%; height: 4px;
  transform: translateY(-50%); border-radius: $r-pill;
  background: $subject-blue; box-shadow: inset 0 1px 0 rgba($subject-cream, .55), 0 1px 2px rgba(0, 0, 0, .4);
}

// 눈금 아래 숫자 — 값은 여기에도 표시된다(색만이 아니라 숫자로)
.pf__scale { display: flex; width: 100%; padding: 0 $sp-2; box-sizing: border-box; }
.pf__num {
  flex: 1; text-align: center; margin: 0; border-radius: $r-xs;
  font-weight: 700; font-size: clamp(9px, 2.4vw, 11px); line-height: 1.6; color: rgba($subject-ink, .78);
}
.pf__num.is-on { font-weight: 800; color: $subject-ink; box-shadow: inset 0 -2px 0 $subject-blue; }

// ── 미리보기 루프(2초 한 바퀴) ─────────────────────────────────────
// 이동(래퍼)과 쿠션 눌림(캡)을 분리: 래퍼를 scaleX 하면 끝에 있는 캡이 중심쪽으로 밀려
// 눌림이 아니라 옆걸음처럼 보인다. 낱개 속성으로 쓴다(단축은 delay 를 0 으로 리셋한다).
.pf.is-demo .pf__capWrap {
  animation-name: pfTravel; animation-duration: $dur-loop;
  animation-timing-function: $easing; animation-iteration-count: infinite;
}
.pf.is-demo .pf__cap {
  animation-name: pfCushion; animation-duration: $dur-loop;
  animation-timing-function: $easing; animation-iteration-count: infinite;
}
@keyframes pfTravel {
  0%   { transform: translateX(0); }
  5%   { transform: translateX(0); }
  44%  { transform: translateX(calc(100% - 48px)); }
  55%  { transform: translateX(calc(100% - 48px)); }
  89%  { transform: translateX(0); }
  100% { transform: translateX(0); }
}
@keyframes pfCushion {
  0%   { transform: scaleX(1); }
  3%   { transform: scaleX(.82); }
  9%   { transform: scaleX(1); }
  44%  { transform: scaleX(1); }
  48%  { transform: scaleX(.82); }
  54%  { transform: scaleX(1); }
  89%  { transform: scaleX(1); }
  93%  { transform: scaleX(.82); }
  97%  { transform: scaleX(1); }
  100% { transform: scaleX(1); }
}

@media (max-width: 340px) {
  .pf { gap: $sp-2; }
  .pf__well { height: 64px; }
  .pf__slot { height: 12px; }
}

// reduce 에서는 루프를 끄고 가운데 값의 정적 한 장으로 둔다
@media (prefers-reduced-motion: reduce) {
  .pf.is-demo .pf__capWrap { animation: none !important; }
  .pf.is-demo .pf__cap { animation: none !important; }
  .pf__cap { 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);
}

.pf {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  width: 100%;
  max-width: 352px;
}

.pf__hint {
  display: flex;
  align-items: center;
  gap: 4px;
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  color: #17141a;
}

.pf__ico {
  width: 16px;
  height: 16px;
  flex: 0 0 auto;
  color: #2f6df6;
}

.pf__well {
  position: relative;
  overflow: hidden;
  width: 100%;
  height: clamp(72px, 20vw, 88px);
  border: 0;
  border-radius: 16px;
  padding: 0;
  cursor: grab;
  touch-action: none;
  background: linear-gradient(180deg, rgba(255, 247, 230, 0.16), rgba(255, 247, 230, 0) 42%), #17141a;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32), inset 0 1px 0 rgba(255, 247, 230, 0.22), inset 0 -2px 0 rgba(0, 0, 0, 0.45);
}

.pf__well:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 2px;
}

.pf__well:active {
  cursor: grabbing;
}

.pf__slot {
  position: absolute;
  left: 8px;
  right: 8px;
  top: 50%;
  height: clamp(14px, 4vw, 18px);
  transform: translateY(-50%);
  border-radius: 999px;
  background: rgba(0, 0, 0, 0.5);
  box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.7), inset 0 -1px 0 rgba(255, 247, 230, 0.14);
}

.pf__capWrap {
  position: absolute;
  left: 8px;
  right: 8px;
  top: 4px;
  bottom: 4px;
  transform: translateX(calc(var(--x, 0px)));
}

.pf__cap {
  position: absolute;
  left: 0;
  top: 0;
  width: 48px;
  height: 100%;
  border-radius: 12px;
  background: linear-gradient(90deg, rgba(23, 20, 26, 0.38) 0 4px, rgba(23, 20, 26, 0) 4px 10px), linear-gradient(180deg, white 0 18%, rgba(23, 20, 26, 0.22) 52%, rgba(255, 255, 255, 0.92) 100%);
  box-shadow: 0 6px 10px rgba(0, 0, 0, 0.5), inset 0 1px 0 rgba(255, 255, 255, 0.9), inset 0 -2px 0 rgba(0, 0, 0, 0.25);
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.pf__cap.is-press {
  transform: scaleX(0.82);
}

.pf__stripe {
  position: absolute;
  left: 10px;
  right: 10px;
  top: 50%;
  height: 4px;
  transform: translateY(-50%);
  border-radius: 999px;
  background: #2f6df6;
  box-shadow: inset 0 1px 0 rgba(255, 247, 230, 0.55), 0 1px 2px rgba(0, 0, 0, 0.4);
}

.pf__scale {
  display: flex;
  width: 100%;
  padding: 0 8px;
  box-sizing: border-box;
}

.pf__num {
  flex: 1;
  text-align: center;
  margin: 0;
  border-radius: 4px;
  font-weight: 700;
  font-size: clamp(9px, 2.4vw, 11px);
  line-height: 1.6;
  color: rgba(23, 20, 26, 0.78);
}

.pf__num.is-on {
  font-weight: 800;
  color: #17141a;
  box-shadow: inset 0 -2px 0 #2f6df6;
}

.pf.is-demo .pf__capWrap {
  animation-name: pfTravel;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

.pf.is-demo .pf__cap {
  animation-name: pfCushion;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@keyframes pfTravel {
  0% {
    transform: translateX(0);
  }
  5% {
    transform: translateX(0);
  }
  44% {
    transform: translateX(calc(100% - 48px));
  }
  55% {
    transform: translateX(calc(100% - 48px));
  }
  89% {
    transform: translateX(0);
  }
  100% {
    transform: translateX(0);
  }
}
@keyframes pfCushion {
  0% {
    transform: scaleX(1);
  }
  3% {
    transform: scaleX(0.82);
  }
  9% {
    transform: scaleX(1);
  }
  44% {
    transform: scaleX(1);
  }
  48% {
    transform: scaleX(0.82);
  }
  54% {
    transform: scaleX(1);
  }
  89% {
    transform: scaleX(1);
  }
  93% {
    transform: scaleX(0.82);
  }
  97% {
    transform: scaleX(1);
  }
  100% {
    transform: scaleX(1);
  }
}
@media (max-width: 340px) {
  .pf {
    gap: 8px;
  }
  .pf__well {
    height: 64px;
  }
  .pf__slot {
    height: 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .pf.is-demo .pf__capWrap {
    animation: none !important;
  }
  .pf.is-demo .pf__cap {
    animation: none !important;
  }
  .pf__cap {
    transition: none !important;
  }
}

(function () {
  var root = document.getElementById('pf');
  var well = document.getElementById('well');
  var wrap = document.getElementById('capWrap');
  var cap = wrap.querySelector('.pf__cap');
  var nums = [].slice.call(document.querySelectorAll('.pf__num'));
  var MIN = 0, MAX = 10;
  var value = 5;
  var lastPx = 0;
  var pressTimer = 0;

  function travel() { return Math.max(0, wrap.clientWidth - cap.offsetWidth); }
  function human() { root.classList.remove('is-demo'); }
  function cushion() {
    cap.classList.add('is-press');
    clearTimeout(pressTimer);
    pressTimer = setTimeout(function () { cap.classList.remove('is-press'); }, 180);
  }
  function apply(px) {
    wrap.style.setProperty('--x', px + 'px');
    lastPx = px;
    value = travel() > 0 ? Math.round(px / travel() * MAX) : 0;
    well.setAttribute('aria-valuenow', String(value));
    nums.forEach(function (n, i) { n.classList.toggle('is-on', i === value); });
  }
  apply(value / MAX * travel());

  var startX = 0, startPx = 0;
  well.addEventListener('pointerdown', function (e) {
    human();
    well.setPointerCapture(e.pointerId);
    startX = e.clientX;
    startPx = lastPx;
    e.preventDefault();
  });
  well.addEventListener('pointermove', function (e) {
    if (!well.hasPointerCapture(e.pointerId)) { return; }
    var t = travel();
    var px = Math.min(t, Math.max(0, startPx + (e.clientX - startX)));
    if ((px === 0 && lastPx > 0) || (px === t && lastPx < t)) { cushion(); }
    apply(px);
  });
  well.addEventListener('pointerup', function (e) {
    if (well.hasPointerCapture(e.pointerId)) { well.releasePointerCapture(e.pointerId); }
  });
  well.addEventListener('keydown', function (e) {
    var next = null;
    if (e.key === 'ArrowRight' || e.key === 'ArrowUp') { next = Math.min(MAX, value + 1); }
    else if (e.key === 'ArrowLeft' || e.key === 'ArrowDown') { next = Math.max(MIN, value - 1); }
    else if (e.key === 'Home') { next = MIN; }
    else if (e.key === 'End') { next = MAX; }
    if (next === null) { return; }
    e.preventDefault();
    human();
    if (next === MIN || next === MAX) { cushion(); }
    apply(next / MAX * travel());
  });
})();

// PushFader — vanilla 판(run/013/demo/04-skeuo-push-slider) 의 React 포트.
// 좌우 드래그·화살표로 캡을 밀고 끝에서 쿠션 눌림이 일어난다. 값·타이밍은 vanilla 와 같다.
// duration·easing·color 는 props 로 받아 CSS 변수로 들어간다(기본값은 vanilla 의 토큰값).
import { useEffect, useRef, useState } from "react";
import type { CSSProperties, PointerEvent as ReactPointerEvent } from "react";
import styles from "./PushFader.module.scss";

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

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type WrapRef = { current: HTMLSpanElement | null };
type DragState = { current: { startX: number; startPx: number; lastPx: number; active: boolean } };
type PtrEvt = ReactPointerEvent<HTMLButtonElement>;
type KeyEvt = { key: string; preventDefault(): void };

const MAX = 10;
const CAP_W = 48; // .cap 의 고정 폭(vanilla 와 같은 값)
const HINT = "좌우로 밀어 보세요";
const ARIA_LABEL = "채널 페이더";

export default function PushFader({
  duration = 220,
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#ffffff",
}: PushFaderProps) {
  const wrapRef = useRef(null) as WrapRef;
  const drag = useRef({ startX: 0, startPx: 0, lastPx: 0, active: false }) as DragState;
  const [demo, setDemo] = useState(true);
  const [value, setValue] = useState(5);
  const [press, setPress] = useState(false);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  function travelPx(): number {
    const wrap = wrapRef.current;
    return wrap ? Math.max(0, wrap.clientWidth - CAP_W) : 0;
  }
  function applyPx(px: number) {
    const wrap = wrapRef.current;
    if (wrap) { wrap.style.setProperty("--x", `${px}px`); }
    drag.current.lastPx = px;
    const t = travelPx();
    setValue(t > 0 ? Math.round((px / t) * MAX) : 0);
  }
  function cushion() {
    setPress(true);
    window.setTimeout(() => { setPress(false); }, 180);
  }

  useEffect(() => {
    applyPx((5 / MAX) * travelPx());
  }, []);

  function onPointerDown(e: PtrEvt) {
    setDemo(false);
    drag.current = { startX: e.clientX, startPx: drag.current.lastPx, lastPx: drag.current.lastPx, active: true };
    e.currentTarget.setPointerCapture(e.pointerId);
    e.preventDefault();
  }
  function onPointerMove(e: PtrEvt) {
    if (!drag.current.active) { return; }
    const t = travelPx();
    const px = Math.min(t, Math.max(0, drag.current.startPx + (e.clientX - drag.current.startX)));
    if ((px === 0 && drag.current.lastPx > 0) || (px === t && drag.current.lastPx < t)) { cushion(); }
    applyPx(px);
  }
  function onPointerUp(e: PtrEvt) {
    if (!drag.current.active) { return; }
    drag.current.active = false;
    if (e.currentTarget.hasPointerCapture(e.pointerId)) { e.currentTarget.releasePointerCapture(e.pointerId); }
  }
  function onKeyDown(e: KeyEvt) {
    let next: number | null = null;
    if (e.key === "ArrowRight" || e.key === "ArrowUp") { next = Math.min(MAX, value + 1); }
    else if (e.key === "ArrowLeft" || e.key === "ArrowDown") { next = Math.max(0, value - 1); }
    else if (e.key === "Home") { next = 0; }
    else if (e.key === "End") { next = MAX; }
    if (next === null) { return; }
    e.preventDefault();
    setDemo(false);
    if (next === 0 || next === MAX) { cushion(); }
    applyPx((next / MAX) * travelPx());
  }

  const nums: number[] = [];
  for (let i = 0; i <= MAX; i++) { nums.push(i); }
  const cls = [styles.root, demo ? styles.isDemo : ""].filter(Boolean).join(" ");

  return (
    <main className={styles.stage}>
      <svg width="0" height="0" style={{ position: "absolute" }} aria-hidden="true">
        <defs>
          <symbol id="ico-faders" viewBox="0 0 256 256" fill="currentColor"><g><path d="M200 40v176H56V40Z" opacity=".2"/><path d="M136 120v96a8 8 0 0 1-16 0v-96a8 8 0 0 1 16 0m64 72a8 8 0 0 0-8 8v16a8 8 0 0 0 16 0v-16a8 8 0 0 0-8-8m24-32h-16V40a8 8 0 0 0-16 0v120h-16a8 8 0 0 0 0 16h48a8 8 0 0 0 0-16m-168 0a8 8 0 0 0-8 8v48a8 8 0 0 0 16 0v-48a8 8 0 0 0-8-8m24-32H64V40a8 8 0 0 0-16 0v88H32a8 8 0 0 0 0 16h48a8 8 0 0 0 0-16m72-48h-16V40a8 8 0 0 0-16 0v40h-16a8 8 0 0 0 0 16h48a8 8 0 0 0 0-16"/></g></symbol>
        </defs>
      </svg>
      <div className={cls} style={vars}>
        <p className={styles.hint}>
          <svg className={styles.ico} aria-hidden="true"><use href="#ico-faders" /></svg>
          <span>{HINT}</span>
        </p>
        <button
          className={styles.well}
          type="button"
          role="slider"
          tabIndex={0}
          aria-label={ARIA_LABEL}
          aria-orientation="horizontal"
          aria-valuemin={0}
          aria-valuemax={MAX}
          aria-valuenow={value}
          onPointerDown={onPointerDown}
          onPointerMove={onPointerMove}
          onPointerUp={onPointerUp}
          onKeyDown={onKeyDown}
        >
          <span className={styles.slot} />
          <span className={styles.capWrap} ref={wrapRef}>
            <span className={press ? `${styles.cap} ${styles.press}` : styles.cap}>
              <i className={styles.stripe} />
            </span>
          </span>
        </button>
        <div className={styles.scale} aria-hidden="true">
          {nums.map((n) => (
            <span key={n} className={n === value ? `${styles.num} ${styles.on}` : styles.num}>{n}</span>
          ))}
        </div>
      </div>
    </main>
  );
}