04버퍼된 만큼 채워지는 파형

<main class="stage">
<div class="waveWrap is-demo" id="waveWrap" role="progressbar" aria-label="오디오 버퍼 진행률" aria-valuemin="0" aria-valuemax="100" aria-valuenow="0">
  <div class="bars" id="bars"></div>
  <div class="film" id="film"></div>
</div>
<button class="skipBtn" id="skipBtn" type="button">버퍼된 곳까지 건너뛰기</button>
</main>

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

// 변수 3개
$duration: $dur-loop;
$easing: $ease-out;
$color: $subject-blue;

// 계산 겹: index.html 의 bezier() 가 WAVEFORM_FILL_EASE 문자열을 실제 3차 베지어 곡선으로 풀어
// 진행률(t)을 채움 비율로 바꾸고, 그 비율의 경계 막대에만 sin() 범프를 얹어 "채워지는 순간"을 표시한다.
@include stage($stage-paper);

.waveWrap {
  position: relative;
  width: 280px;
  height: 100px;
}

.bars {
  display: flex;
  align-items: flex-end;
  gap: 4px;
  height: 100%;
}

.bar {
  --h: 20px;
  --bump: 0px;
  display: block;
  width: 8px;
  border-radius: $r-xs;
  background: $color;
  // 막대는 바닥에서 자라는 파형 계기라 origin 을 bottom 으로 둔다
  transform-origin: bottom;
  height: calc(var(--h) + var(--bump));
}

.film {
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba($stage-paper, .92), rgba($stage-paper, .8));
  mask-image: linear-gradient(to right, transparent var(--buffer-pct), #000 var(--buffer-pct));
  -webkit-mask-image: linear-gradient(to right, transparent var(--buffer-pct), #000 var(--buffer-pct));
}

.skipBtn {
  appearance: none;
  border: none;
  margin-top: $sp-3;
  border-radius: $r-pill;
  padding: $sp-1 $sp-3;
  font-size: 11px;
  font-weight: 600;
  color: $subject-cream;
  background: $subject-ink;
  cursor: pointer;

  &:focus-visible { outline: 2px solid $subject-blue-deep; outline-offset: 2px; }
}

@media (max-width: 340px) {
  .waveWrap { width: 220px; height: 76px; }
  .bar { width: 6px; }
  .skipBtn { font-size: 10px; }
}

// reduce: 실사용 경로 적용 — 채움 이징(진행) 자체는 JS 가 멈춘 채 한 값으로 그리므로 scss 는 덧붙일 전환이 없다
@media (prefers-reduced-motion: reduce) {
  .bar { transition: none; }
}

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);
}

.waveWrap {
  position: relative;
  width: 280px;
  height: 100px;
}

.bars {
  display: flex;
  align-items: flex-end;
  gap: 4px;
  height: 100%;
}

.bar {
  --h: 20px;
  --bump: 0px;
  display: block;
  width: 8px;
  border-radius: 4px;
  background: #2f6df6;
  transform-origin: bottom;
  height: calc(var(--h) + var(--bump));
}

.film {
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.92), rgba(255, 255, 255, 0.8));
  mask-image: linear-gradient(to right, transparent var(--buffer-pct), #000 var(--buffer-pct));
  -webkit-mask-image: linear-gradient(to right, transparent var(--buffer-pct), #000 var(--buffer-pct));
}

.skipBtn {
  appearance: none;
  border: none;
  margin-top: 12px;
  border-radius: 999px;
  padding: 4px 12px;
  font-size: 11px;
  font-weight: 600;
  color: #fff7e6;
  background: #17141a;
  cursor: pointer;
}
.skipBtn:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .waveWrap {
    width: 220px;
    height: 76px;
  }
  .bar {
    width: 6px;
  }
  .skipBtn {
    font-size: 10px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .bar {
    transition: none;
  }
}

(function () {
  var WAVEFORM_FILL_EASE = 'linear'; // 훅 — 변형이 cubic-bezier(.22,1,.36,1) 로 바꾸는 값
  var BAR_COUNT = 22;
  var LOOP_MS = 2000;
  var TICK_MS = 70;
  var BUMP_PX = 10; // 버퍼 경계 막대가 채워지는 순간 살짝 솟는 최대 높이

  // 고정 패턴(사인 두 겹 합성) — Math.random 없이 매번 같은 파형을 만든다
  var HEIGHTS = [];
  for (var i = 0; i < BAR_COUNT; i++) {
    var v = 18 + 16 * Math.abs(Math.sin(i * 0.7)) + 8 * Math.abs(Math.sin(i * 1.9));
    HEIGHTS.push(Math.round(v));
  }

  var wrap = document.getElementById('waveWrap');
  var barsEl = document.getElementById('bars');
  var film = document.getElementById('film');
  var skipBtn = document.getElementById('skipBtn');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var bars = HEIGHTS.map(function (h, i) {
    var b = document.createElement('span');
    b.className = 'bar';
    b.style.setProperty('--h', h + 'px');
    barsEl.appendChild(b);
    return b;
  });

  // 3차 베지어 이징 평가기 — WAVEFORM_FILL_EASE 값을 실제 진행률 곡선에 반영한다
  function bezier(x1, y1, x2, y2) {
    function s(a, b) { return 3 * a * (1 - 3 * b + 3 * a) + 3 * b * b * (0); }
    function bx(t) { return 3 * (1 - t) * (1 - t) * t * x1 + 3 * (1 - t) * t * t * x2 + t * t * t; }
    function by(t) { return 3 * (1 - t) * (1 - t) * t * y1 + 3 * (1 - t) * t * t * y2 + t * t * t; }
    return function (x) {
      var t = x;
      for (var it = 0; it < 6; it++) {
        var cx = bx(t) - x;
        var d = 3 * (1 - t) * (1 - t) * x1 + 6 * (1 - t) * t * (x2 - x1) + 3 * t * t * (1 - x2);
        if (Math.abs(d) < 1e-6) break;
        t -= cx / d;
        t = Math.min(1, Math.max(0, t));
      }
      return by(t);
    };
  }

  function easeFn() {
    if (WAVEFORM_FILL_EASE === 'linear') return function (x) { return x; };
    var nums = WAVEFORM_FILL_EASE.replace('cubic-bezier(', '').replace(')', '').split(',').map(Number);
    return bezier(nums[0], nums[1], nums[2], nums[3]);
  }
  var ease = easeFn();

  function paint(pct) {
    var pctStr = (pct * 100).toFixed(1) + '%';
    film.style.setProperty('--buffer-pct', pctStr);
    wrap.setAttribute('aria-valuenow', String(Math.round(pct * 100)));
    var raw = pct * BAR_COUNT;
    var idx = Math.min(BAR_COUNT - 1, Math.floor(raw));
    var frac = raw - idx;
    bars.forEach(function (b, i) {
      var bump = i === idx ? Math.sin(frac * Math.PI) * BUMP_PX : 0;
      b.style.setProperty('--bump', bump.toFixed(1) + 'px');
    });
  }

  var manualPct = null;

  function tick(elapsedMs) {
    if (manualPct !== null) { paint(manualPct); return; }
    var t = (elapsedMs % LOOP_MS) / LOOP_MS;
    paint(ease(t));
  }

  var timer = null;
  var start = 0;
  function loop() { tick(performance.now() - start); }

  function human() {
    if (wrap.classList.contains('is-demo')) {
      wrap.classList.remove('is-demo');
      window.clearInterval(timer);
      timer = null;
    }
  }

  skipBtn.addEventListener('click', function () {
    human();
    manualPct = 1;
    paint(1);
  });

  if (!reduce) {
    start = performance.now();
    tick(0);
    timer = window.setInterval(loop, TICK_MS);
  } else {
    // reduce: 실사용 경로 — 채워지는 전환은 멈추고 버퍼 진행률을 고정된 한 장면으로만 보여준다
    paint(0.55);
  }
})();

import { useEffect, useRef } from 'react';
import type { CSSProperties } from 'react';
import styles from './BufferingWaveformFill.module.scss';

const WAVEFORM_FILL_EASE: string = 'linear'; // 훅 — 변형이 cubic-bezier(.22,1,.36,1) 로 바꾸는 값
const BAR_COUNT = 22;
const LOOP_MS = 2000;
const TICK_MS = 70;
const BUMP_PX = 10; // 버퍼 경계 막대가 채워지는 순간 살짝 솟는 최대 높이

// 고정 패턴(사인 두 겹 합성) — Math.random 없이 매번 같은 파형을 만든다
const HEIGHTS: number[] = [];
for (let i = 0; i < BAR_COUNT; i++) {
  const v = 18 + 16 * Math.abs(Math.sin(i * 0.7)) + 8 * Math.abs(Math.sin(i * 1.9));
  HEIGHTS.push(Math.round(v));
}

// 3차 베지어 이징 평가기 — WAVEFORM_FILL_EASE 값을 실제 진행률 곡선에 반영한다
function bezier(x1: number, y1: number, x2: number, y2: number) {
  function bx(t: number) { return 3 * (1 - t) * (1 - t) * t * x1 + 3 * (1 - t) * t * t * x2 + t * t * t; }
  function by(t: number) { return 3 * (1 - t) * (1 - t) * t * y1 + 3 * (1 - t) * t * t * y2 + t * t * t; }
  return function (x: number) {
    let t = x;
    for (let it = 0; it < 6; it++) {
      const cx = bx(t) - x;
      const d = 3 * (1 - t) * (1 - t) * x1 + 6 * (1 - t) * t * (x2 - x1) + 3 * t * t * (1 - x2);
      if (Math.abs(d) < 1e-6) break;
      t -= cx / d;
      t = Math.min(1, Math.max(0, t));
    }
    return by(t);
  };
}

function easeFn(): (x: number) => number {
  if (WAVEFORM_FILL_EASE === 'linear') return (x: number) => x;
  const nums = WAVEFORM_FILL_EASE.replace('cubic-bezier(', '').replace(')', '').split(',').map(Number);
  return bezier(nums[0], nums[1], nums[2], nums[3]);
}

export default function BufferingWaveformFill() {
  const wrapRef = useRef<HTMLDivElement>(null);
  const filmRef = useRef<HTMLDivElement>(null);
  const skipBtnRef = useRef<HTMLButtonElement>(null);
  const barRefs = useRef<(HTMLSpanElement | null)[]>([]);

  useEffect(() => {
    const wrap = wrapRef.current;
    const film = filmRef.current;
    const skipBtn = skipBtnRef.current;
    const bars = barRefs.current;
    if (!wrap || !film || !skipBtn || !bars) return undefined;
    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    const ease = easeFn();

    function paint(pct: number) {
      if (!film || !wrap) return;
      const pctStr = (pct * 100).toFixed(1) + '%';
      film.style.setProperty('--buffer-pct', pctStr);
      wrap.setAttribute('aria-valuenow', String(Math.round(pct * 100)));
      const raw = pct * BAR_COUNT;
      const idx = Math.min(BAR_COUNT - 1, Math.floor(raw));
      const frac = raw - idx;
      bars!.forEach((b, i) => {
        if (!b) return;
        const bump = i === idx ? Math.sin(frac * Math.PI) * BUMP_PX : 0;
        b.style.setProperty('--bump', bump.toFixed(1) + 'px');
      });
    }

    let manualPct: number | null = null;

    function tick(elapsedMs: number) {
      if (manualPct !== null) { paint(manualPct); return; }
      const t = (elapsedMs % LOOP_MS) / LOOP_MS;
      paint(ease(t));
    }

    let timer: ReturnType<typeof window.setInterval> | null = null;
    let start = 0;
    function loop() {
      tick(performance.now() - start);
    }

    function human() {
      if (wrap && wrap.classList.contains(styles['is-demo'])) {
        wrap.classList.remove(styles['is-demo']);
        if (timer !== null) window.clearInterval(timer);
        timer = null;
      }
    }

    function onSkip() {
      human();
      manualPct = 1;
      paint(1);
    }
    skipBtn.addEventListener('click', onSkip);

    if (!reduce) {
      start = performance.now();
      tick(0);
      timer = window.setInterval(loop, TICK_MS);
    } else {
      // reduce: 실사용 경로 — 채워지는 전환은 멈추고 버퍼 진행률을 고정된 한 장면으로만 보여준다
      paint(0.55);
    }

    return () => {
      if (timer !== null) window.clearInterval(timer);
      skipBtn.removeEventListener('click', onSkip);
    };
  }, []);

  return (
    <>
      <div
        className={`${styles.waveWrap} ${styles['is-demo']}`}
        ref={wrapRef}
        role="progressbar"
        aria-label="오디오 버퍼 진행률"
        aria-valuemin={0}
        aria-valuemax={100}
        aria-valuenow={0}
      >
        <div className={styles.bars}>
          {HEIGHTS.map((h, i) => (
            <span
              key={i}
              className={styles.bar}
              ref={(el: HTMLSpanElement | null) => { if (barRefs.current) barRefs.current[i] = el; }}
              style={{ ['--h' as string]: h + 'px' } as CSSProperties}
            />
          ))}
        </div>
        <div className={styles.film} ref={filmRef} />
      </div>
      <button className={styles.skipBtn} ref={skipBtnRef} type="button">버퍼된 곳까지 건너뛰기</button>
    </>
  );
}