06Video card — a card that derives playback from viewport ratio and scrub position from scroll

<main class="stage">
<section class="panel">
  <p class="hint" id="hint">Try scrolling the card — it recalculates the ready-rate from the actual portion inside the viewport, and skips the preview frame by that ratio.</p>
  <div class="scrollStage" id="scrollStage">
    <div class="scrollSpacer" aria-hidden="true"></div>
    <article class="card" id="card">
      <canvas class="thumb" id="thumb" width="240" height="135" aria-hidden="true"></canvas>
      <button class="playBtn" id="playBtn" type="button" aria-label="Play case video preview">
        <svg class="playIcon" xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 256 256"><g fill="currentColor"><path d="M228.23 134.69L84.15 222.81A8 8 0 0 1 72 216.12V39.88a8 8 0 0 1 12.15-6.69l144.08 88.12a7.82 7.82 0 0 1 0 13.38" opacity=".2"/><path d="M232.4 114.49L88.32 26.35a16 16 0 0 0-16.2-.3A15.86 15.86 0 0 0 64 39.87v176.26A15.94 15.94 0 0 0 80 232a16.07 16.07 0 0 0 8.36-2.35l144.04-88.14a15.81 15.81 0 0 0 0-27ZM80 215.94V40l143.83 88Z"/></g></svg>
      </button>
      <p class="readyLabel" id="readyLabel">Ready 0%</p>
    </article>
    <div class="scrollSpacer" aria-hidden="true"></div>
  </div>
</section>
</main>

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

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

@include stage($stage-yellow);

.panel {
  width: 100%;
  max-width: 320px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-2;
  text-align: center;
}

.hint {
  margin: 0;
  color: rgba($subject-ink, .72);
  font-weight: 400;
  font-size: 10px;
  line-height: 1.35;
}

.scrollStage {
  position: relative;
  width: 100%;
  height: 168px;
  overflow-y: auto;
  overscroll-behavior: contain;
  border-radius: $r-card;
  background: rgba($subject-ink, .06);
}

.scrollSpacer {
  height: 130px;
}

.card {
  position: relative;
  margin: 0 $sp-3;
  padding: $sp-2;
  border-radius: $r-control;
  background: $subject-ink;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-1;
}

.thumb {
  width: 100%;
  height: auto;
  border-radius: $r-sm;
  display: block;
}

.playBtn {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) scale(.86);
  transform-origin: center;
  width: 40px;
  height: 40px;
  border-radius: $r-pill;
  border: 0;
  display: grid;
  place-items: center;
  background: rgba($subject-cream, .22);
  color: $subject-cream;
  opacity: .72;
  cursor: not-allowed;
  transition: transform $duration $easing, opacity $duration $easing, background $duration $easing;

  &.playBtn--ready {
    opacity: 1;
    cursor: pointer;
    background: $color;
    transform: translate(-50%, -50%) scale(1);
  }

  &.playBtn--pressed {
    transform: translate(-50%, -50%) scale(.9);
  }

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

.playIcon {
  width: 18px;
  height: 18px;
}

.readyLabel {
  margin: 0;
  color: $subject-cream;
  font-weight: 600;
  font-size: 10px;
  font-variant-numeric: tabular-nums;
}

@media (max-width: 340px) {
  .panel { max-width: 280px; gap: $sp-1; }
  .scrollStage { height: 108px; }
  .scrollSpacer { height: 80px; }
  .hint { font-size: 8px; line-height: 1.25; }
  .readyLabel { font-size: 9px; }
  .playBtn { width: 32px; height: 32px; }
  .playIcon { width: 14px; height: 14px; }
}

@media (prefers-reduced-motion: reduce) {
  .playBtn {
    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);
}

.panel {
  width: 100%;
  max-width: 320px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  text-align: center;
}

.hint {
  margin: 0;
  color: rgba(23, 20, 26, 0.72);
  font-weight: 400;
  font-size: 10px;
  line-height: 1.35;
}

.scrollStage {
  position: relative;
  width: 100%;
  height: 168px;
  overflow-y: auto;
  overscroll-behavior: contain;
  border-radius: 16px;
  background: rgba(23, 20, 26, 0.06);
}

.scrollSpacer {
  height: 130px;
}

.card {
  position: relative;
  margin: 0 12px;
  padding: 8px;
  border-radius: 12px;
  background: #17141a;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

.thumb {
  width: 100%;
  height: auto;
  border-radius: 8px;
  display: block;
}

.playBtn {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%) scale(0.86);
  transform-origin: center;
  width: 40px;
  height: 40px;
  border-radius: 999px;
  border: 0;
  display: grid;
  place-items: center;
  background: rgba(255, 247, 230, 0.22);
  color: #fff7e6;
  opacity: 0.72;
  cursor: not-allowed;
  transition: transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1), opacity 220ms cubic-bezier(0.2, 1.4, 0.4, 1), background 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}
.playBtn.playBtn--ready {
  opacity: 1;
  cursor: pointer;
  background: #2f6df6;
  transform: translate(-50%, -50%) scale(1);
}
.playBtn.playBtn--pressed {
  transform: translate(-50%, -50%) scale(0.9);
}
.playBtn:focus-visible {
  outline: 2px solid #fff7e6;
  outline-offset: 2px;
}

.playIcon {
  width: 18px;
  height: 18px;
}

.readyLabel {
  margin: 0;
  color: #fff7e6;
  font-weight: 600;
  font-size: 10px;
  font-variant-numeric: tabular-nums;
}

@media (max-width: 340px) {
  .panel {
    max-width: 280px;
    gap: 4px;
  }
  .scrollStage {
    height: 108px;
  }
  .scrollSpacer {
    height: 80px;
  }
  .hint {
    font-size: 8px;
    line-height: 1.25;
  }
  .readyLabel {
    font-size: 9px;
  }
  .playBtn {
    width: 32px;
    height: 32px;
  }
  .playIcon {
    width: 14px;
    height: 14px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .playBtn {
    transition: none;
  }
}

// 영상 카드(06) — 실제 스크롤 컨테이너 안에서 카드가 뷰포트에 걸친 비율을 IntersectionObserver 로
// 실측해 Ready (%)을 매번 다시 구하고, 그 비율로 미리보기 프레임 인덱스를 정해 캔버스에 다시 그린다
// (계산 한 겹). 진짜 영상 파일은 없다 — 프레임은 mulberry32 시드 난수로 매번 다시 그리는 절차적 패턴이다.
(function () {
  var scrollStage = document.getElementById('scrollStage');
  var card = document.getElementById('card');
  var thumb = document.getElementById('thumb');
  var playBtn = document.getElementById('playBtn');
  var readyLabel = document.getElementById('readyLabel');
  if (!scrollStage || !card || !thumb || !playBtn || !readyLabel) return;
  var ctx = thumb.getContext('2d');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var FRAME_COUNT = 12;
  var READY_THRESHOLD = 0.62;
  var lastFrame = -1;

  function mulberry32(a) {
    return function () {
      a |= 0; a = (a + 0x6D2B79F5) | 0;
      var t = Math.imul(a ^ (a >>> 15), 1 | a);
      t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
      return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
    };
  }

  function drawFrame(frameIndex) {
    if (!ctx) return;
    var rnd = mulberry32(frameIndex * 7919 + 11);
    var w = thumb.width, h = thumb.height;
    var cols = 8, rows = 5;
    var cw = w / cols, ch = h / rows;
    for (var r = 0; r < rows; r++) {
      for (var c = 0; c < cols; c++) {
        var v = rnd();
        var lightness = 22 + v * 34;
        var hue = 214 + rnd() * 18;
        ctx.fillStyle = 'hsl(' + hue.toFixed(0) + ', 38%, ' + lightness.toFixed(0) + '%)';
        ctx.fillRect(c * cw, r * ch, cw + 1, ch + 1);
      }
    }
    ctx.fillStyle = 'rgba(255,255,255,.06)';
    for (var i = 0; i < 3; i++) {
      var bx = rnd() * w, by = rnd() * h, br = 8 + rnd() * 18;
      ctx.beginPath();
      ctx.arc(bx, by, br, 0, Math.PI * 2);
      ctx.fill();
    }
  }

  function update(ratio) {
    var percent = Math.round(ratio * 100);
    readyLabel.textContent = 'Ready  ' + percent + '%';
    var frameIndex = Math.min(FRAME_COUNT - 1, Math.floor(ratio * (FRAME_COUNT - 1)));
    if (frameIndex !== lastFrame) {
      lastFrame = frameIndex;
      drawFrame(frameIndex);
    }
    if (ratio >= READY_THRESHOLD) {
      playBtn.classList.add('playBtn--ready');
      playBtn.disabled = false;
    } else {
      playBtn.classList.remove('playBtn--ready');
      playBtn.disabled = true;
    }
  }

  drawFrame(0);
  update(0);

  var io = new IntersectionObserver(function (entries) {
    var entry = entries[0];
    if (!entry) return;
    update(entry.intersectionRatio);
  }, {
    root: scrollStage,
    threshold: Array.from({ length: 51 }, function (_, i) { return i / 50; })
  });
  io.observe(card);

  playBtn.addEventListener('click', function () {
    if (playBtn.disabled) return;
    playBtn.classList.add('playBtn--pressed');
    setTimeout(function () { playBtn.classList.remove('playBtn--pressed'); }, 260);
  });

  if (!reduce) {
    var max = 0;
    requestAnimationFrame(function tick() {
      max = scrollStage.scrollHeight - scrollStage.clientHeight;
      var t = performance.now() / 1400;
      var wave = (Math.sin(t) + 1) / 2;
      scrollStage.scrollTop = wave * max;
      requestAnimationFrame(tick);
    });
  }
})();

// CaseVideoCard — vanilla 판(run/340/demo/06-case-video-card/index.html) 의 React 포트.
// 실제 스크롤 컨테이너 안에서 카드가 뷰포트에 걸친 비율을 IntersectionObserver 로 실측해
// 준비율(%)을 매번 다시 구하고, 그 비율로 미리보기 프레임 인덱스를 정해 캔버스에 다시 그린다.
// 진짜 영상 파일은 없다 — 프레임은 mulberry32 시드 난수로 매번 다시 그리는 절차적 패턴이다.
import { useEffect, useRef } from "react";
import styles from "./CaseVideoCard.module.scss";

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

const HINT = "카드를 스크롤해 보세요 — 실제 뷰포트에 걸친 비율만큼 준비율을 재계산하고, 그 비율만큼 미리보기 프레임을 넘깁니다";

const FRAME_COUNT = 12;
const READY_THRESHOLD = 0.62;

function mulberry32(a: number): () => number {
  return function () {
    a |= 0;
    a = (a + 0x6d2b79f5) | 0;
    let t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}

export default function CaseVideoCard({
  duration = "220ms",
  easing = "cubic-bezier(.2,1.4,.4,1)",
  color = "#2f6df6"
}: CaseVideoCardProps) {
  const scrollStageRef = useRef<HTMLDivElement | null>(null);
  const cardRef = useRef<HTMLElement | null>(null);
  const thumbRef = useRef<HTMLCanvasElement | null>(null);
  const playBtnRef = useRef<HTMLButtonElement | null>(null);
  const readyLabelRef = useRef<HTMLParagraphElement | null>(null);

  useEffect(() => {
    const scrollStage = scrollStageRef.current;
    const card = cardRef.current;
    const thumb = thumbRef.current;
    const playBtn = playBtnRef.current;
    const readyLabel = readyLabelRef.current;
    if (!scrollStage || !card || !thumb || !playBtn || !readyLabel) return;
    const ctx = thumb.getContext("2d");
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let lastFrame = -1;

    function drawFrame(frameIndex: number): void {
      if (!ctx) return;
      const rnd = mulberry32(frameIndex * 7919 + 11);
      const w = thumb!.width;
      const h = thumb!.height;
      const cols = 8;
      const rows = 5;
      const cw = w / cols;
      const ch = h / rows;
      for (let r = 0; r < rows; r++) {
        for (let c = 0; c < cols; c++) {
          const v = rnd();
          const lightness = 22 + v * 34;
          const hue = 214 + rnd() * 18;
          ctx.fillStyle = "hsl(" + hue.toFixed(0) + ", 38%, " + lightness.toFixed(0) + "%)";
          ctx.fillRect(c * cw, r * ch, cw + 1, ch + 1);
        }
      }
      ctx.fillStyle = "rgba(255,255,255,.06)";
      for (let i = 0; i < 3; i++) {
        const bx = rnd() * w;
        const by = rnd() * h;
        const br = 8 + rnd() * 18;
        ctx.beginPath();
        ctx.arc(bx, by, br, 0, Math.PI * 2);
        ctx.fill();
      }
    }

    function update(ratio: number): void {
      const percent = Math.round(ratio * 100);
      readyLabel!.textContent = "준비율 " + percent + "%";
      const frameIndex = Math.min(FRAME_COUNT - 1, Math.floor(ratio * (FRAME_COUNT - 1)));
      if (frameIndex !== lastFrame) {
        lastFrame = frameIndex;
        drawFrame(frameIndex);
      }
      if (ratio >= READY_THRESHOLD) {
        playBtn!.classList.add(styles.playBtnReady);
        playBtn!.disabled = false;
      } else {
        playBtn!.classList.remove(styles.playBtnReady);
        playBtn!.disabled = true;
      }
    }

    drawFrame(0);
    update(0);

    const io = new IntersectionObserver(
      (entries) => {
        const entry = entries[0];
        if (!entry) return;
        update(entry.intersectionRatio);
      },
      {
        root: scrollStage,
        threshold: Array.from({ length: 51 }, (_, i) => i / 50)
      }
    );
    io.observe(card);

    function onPlayClick(): void {
      if (playBtn!.disabled) return;
      playBtn!.classList.add(styles.playBtnPressed);
      window.setTimeout(() => playBtn!.classList.remove(styles.playBtnPressed), 260);
    }
    playBtn.addEventListener("click", onPlayClick);

    let raf = 0;
    if (!reduce) {
      const tick = () => {
        const max = scrollStage!.scrollHeight - scrollStage!.clientHeight;
        const t = performance.now() / 1400;
        const wave = (Math.sin(t) + 1) / 2;
        scrollStage!.scrollTop = wave * max;
        raf = requestAnimationFrame(tick);
      };
      raf = requestAnimationFrame(tick);
    }

    return () => {
      io.disconnect();
      playBtn.removeEventListener("click", onPlayClick);
      if (raf) cancelAnimationFrame(raf);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <section className={styles.panel}>
        <p className={styles.hint}>{HINT}</p>
        <div className={styles.scrollStage} ref={scrollStageRef}>
          <div className={styles.scrollSpacer} aria-hidden="true" />
          <article className={styles.card} ref={cardRef}>
            <canvas className={styles.thumb} ref={thumbRef} width={240} height={135} aria-hidden="true" />
            <button className={styles.playBtn} type="button" aria-label="사례 영상 미리보기 재생" ref={playBtnRef}>
              <svg className={styles.playIcon} xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 256 256">
                <g fill="currentColor">
                  <path d="M228.23 134.69L84.15 222.81A8 8 0 0 1 72 216.12V39.88a8 8 0 0 1 12.15-6.69l144.08 88.12a7.82 7.82 0 0 1 0 13.38" opacity=".2" />
                  <path d="M232.4 114.49L88.32 26.35a16 16 0 0 0-16.2-.3A15.86 15.86 0 0 0 64 39.87v176.26A15.94 15.94 0 0 0 80 232a16.07 16.07 0 0 0 8.36-2.35l144.04-88.14a15.81 15.81 0 0 0 0-27ZM80 215.94V40l143.83 88Z" />
                </g>
              </svg>
            </button>
            <p className={styles.readyLabel} ref={readyLabelRef}>준비율 0%</p>
          </article>
          <div className={styles.scrollSpacer} aria-hidden="true" />
        </div>
      </section>
    </main>
  );
}