07Bookmark fold

<main class="stage">
  <label class="bookmark is-demo">
    <input type="checkbox" class="bookmark__input">
    <span class="bookmark__icon" aria-hidden="true">
      <span class="bookmark__ribbon"></span>
      <span class="bookmark__fold"></span>
      <span class="bookmark__fx" aria-hidden="true">
        <span class="bookmark__chip"></span>
        <span class="bookmark__chip"></span>
        <span class="bookmark__chip"></span>
        <span class="bookmark__chip"></span>
        <span class="bookmark__chip"></span>
        <span class="bookmark__chip"></span>
      </span>
    </span>
    <span class="bookmark__label">Save</span>
  </label>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-base;                             // 리본이 채워지는 시간
$easing: $ease-spring;                            // 스프링 이징
$color: $subject-cream;                           // 채워진 리본 색

// ── 데모 무대 ──────────────────────────────────────────
@include stage($stage-orange);

$shape: polygon(0 0, 100% 0, 100% 100%, 50% 76%, 0 100%);

.bookmark {
  display: inline-flex;
  align-items: center;
  gap: clamp(8px, 2.6vw, 12px);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;

  &__input { position: absolute; opacity: 0; width: 1px; height: 1px; }
  &__icon { position: relative; width: 24px; height: 30px; flex: none; }

  &__ribbon {
    position: absolute; inset: 0;
    clip-path: $shape;
    background: rgba(255, 247, 230, .3);
    &::after {
      content: "";
      position: absolute; inset: 0;
      clip-path: $shape;
      background: $color;
      opacity: 0;
      transform: scaleY(.35);
      transform-origin: top; // 규칙8: 리본 세로 채움 위에서
      transition: opacity $duration $easing, transform $duration $easing;
    }
  }
  &__fold {
    position: absolute; top: 0; right: 0; width: 8px; height: 8px;
    clip-path: polygon(100% 0, 0 0, 100% 100%);
    background: rgba(23, 20, 26, .35);
    transform: scale(0) rotate(-90deg);
    transform-origin: 100% 0; // 규칙8: 접힌 귀 꼭짓점 경첩
    opacity: 0;
    transition: opacity $duration $easing, transform $duration $easing;
  }

  // 한 겹: 물리 종잇조각(confetti) 파티클 — 접힌 귀(오른쪽 위 모서리)에서 발사. 좌표·페이드는 JS 가 계산한다.
  &__fx { position: absolute; top: 0; left: 100%; pointer-events: none; } // 귀 꼭짓점이 원점
  &__chip {
    position: absolute; top: 0; left: 0;
    width: 8px; height: 8px; margin: -4px 0 0 -4px;
    background: $color;
    clip-path: polygon(50% 0%, 100% 50%, 50% 100%, 0% 50%);
    opacity: 0;
    pointer-events: none;
    will-change: transform, opacity;
  }
  &__label { font-weight: 600; font-size: clamp(15px, 4.2vw, 18px); line-height: 1; font-family: inherit; color: $subject-ink; }  // AA: 주황 무대 위 글자 5.50:1

  &__input:checked ~ &__icon &__ribbon::after { opacity: 1; transform: scaleY(1); }
  &__input:checked ~ &__icon &__fold { opacity: 1; transform: scale(1) rotate(0deg); }

  &.is-demo &__icon &__ribbon::after { animation: ribbon-fill-loop $dur-loop $easing infinite; }
  &.is-demo &__icon &__fold { animation: fold-in-loop $dur-loop $easing infinite; }
}

@keyframes ribbon-fill-loop {
  0%, 20%  { opacity: 0; transform: scaleY(.35); }
  40%, 80% { opacity: 1; transform: scaleY(1); }
  100%     { opacity: 0; transform: scaleY(.35); }
}
@keyframes fold-in-loop {
  0%, 20%  { opacity: 0; transform: scale(0) rotate(-90deg); }
  40%, 80% { opacity: 1; transform: scale(1) rotate(0deg); }
  100%     { opacity: 0; transform: scale(0) rotate(-90deg); }
}

// ── 접근성 ──────────────────────────────────────────
@media (prefers-reduced-motion: reduce) {
  .bookmark__ribbon::after, .bookmark__fold { transition: opacity 1ms; }
  .bookmark.is-demo .bookmark__icon .bookmark__ribbon::after,
  .bookmark.is-demo .bookmark__icon .bookmark__fold { animation: none !important; opacity: 1; transform: none; }
  .bookmark__chip { display: none; } // 파티클 버스트는 꺼짐 — 기본 상태 전환만
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.bookmark {
  display: inline-flex;
  align-items: center;
  gap: clamp(8px, 2.6vw, 12px);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}
.bookmark__input {
  position: absolute;
  opacity: 0;
  width: 1px;
  height: 1px;
}
.bookmark__icon {
  position: relative;
  width: 24px;
  height: 30px;
  flex: none;
}
.bookmark__ribbon {
  position: absolute;
  inset: 0;
  clip-path: polygon(0 0, 100% 0, 100% 100%, 50% 76%, 0 100%);
  background: rgba(255, 247, 230, 0.3);
}
.bookmark__ribbon::after {
  content: "";
  position: absolute;
  inset: 0;
  clip-path: polygon(0 0, 100% 0, 100% 100%, 50% 76%, 0 100%);
  background: #fff7e6;
  opacity: 0;
  transform: scaleY(0.35);
  transform-origin: top;
  transition: opacity 300ms cubic-bezier(0.2, 0.8, 0.2, 1), transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}
.bookmark__fold {
  position: absolute;
  top: 0;
  right: 0;
  width: 8px;
  height: 8px;
  clip-path: polygon(100% 0, 0 0, 100% 100%);
  background: rgba(23, 20, 26, 0.35);
  transform: scale(0) rotate(-90deg);
  transform-origin: 100% 0;
  opacity: 0;
  transition: opacity 300ms cubic-bezier(0.2, 0.8, 0.2, 1), transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}
.bookmark__fx {
  position: absolute;
  top: 0;
  left: 100%;
  pointer-events: none;
}
.bookmark__chip {
  position: absolute;
  top: 0;
  left: 0;
  width: 8px;
  height: 8px;
  margin: -4px 0 0 -4px;
  background: #fff7e6;
  clip-path: polygon(50% 0%, 100% 50%, 50% 100%, 0% 50%);
  opacity: 0;
  pointer-events: none;
  will-change: transform, opacity;
}
.bookmark__label {
  font-weight: 600;
  font-size: clamp(15px, 4.2vw, 18px);
  line-height: 1;
  font-family: inherit;
  color: #17141a;
}
.bookmark__input:checked ~ .bookmark__icon .bookmark__ribbon::after {
  opacity: 1;
  transform: scaleY(1);
}
.bookmark__input:checked ~ .bookmark__icon .bookmark__fold {
  opacity: 1;
  transform: scale(1) rotate(0deg);
}
.bookmark.is-demo .bookmark__icon .bookmark__ribbon::after {
  animation: ribbon-fill-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}
.bookmark.is-demo .bookmark__icon .bookmark__fold {
  animation: fold-in-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes ribbon-fill-loop {
  0%, 20% {
    opacity: 0;
    transform: scaleY(0.35);
  }
  40%, 80% {
    opacity: 1;
    transform: scaleY(1);
  }
  100% {
    opacity: 0;
    transform: scaleY(0.35);
  }
}
@keyframes fold-in-loop {
  0%, 20% {
    opacity: 0;
    transform: scale(0) rotate(-90deg);
  }
  40%, 80% {
    opacity: 1;
    transform: scale(1) rotate(0deg);
  }
  100% {
    opacity: 0;
    transform: scale(0) rotate(-90deg);
  }
}
@media (prefers-reduced-motion: reduce) {
  .bookmark__ribbon::after, .bookmark__fold {
    transition: opacity 1ms;
  }
  .bookmark.is-demo .bookmark__icon .bookmark__ribbon::after,
  .bookmark.is-demo .bookmark__icon .bookmark__fold {
    animation: none !important;
    opacity: 1;
    transform: none;
  }
  .bookmark__chip {
    display: none;
  }
}

// 한 겹: 종이 조각(confetti) 물리 파티클 — Save 체크 순간 접힌 귀(오른쪽 위 모서리)에서
// 다이아몬드 종잇조각이 흩어진다. 각 조각은 질량·감쇠(-k/m·v)·중력을 매 프레임 준암시 오일러
// 적분으로 받아 날아갔다 멈춘다. transform 은 JS 가 계산해 기입한다(키이프레임 아님).
(function () {
  var ps = [].slice.call(document.querySelectorAll('.bookmark__chip'));
  var reduce = matchMedia('(prefers-reduced-motion: reduce)').matches;
  var alive = false, raf = 0, last = 0;

  function fire() {
    if (reduce || !ps.length) return;
    var now = performance.now();
    for (var i = 0; i < ps.length; i++) {
      var m = .7 + Math.random() * .9;                          // 개별 질량 0.7~1.6
      var ang = -Math.PI / 4 + (Math.random() - .5) * 2.8;      // 바깥쪽(위·오른쪽) 부채꼴 ±80°
      var v0 = (110 + Math.random() * 80) * (1.15 - m * .2);    // 무거울수록 느게 출발
      ps[i]._p = { x: 0, y: 0, vx: Math.cos(ang) * v0, vy: Math.sin(ang) * v0,
        m: m, k: 3.2, g: 320, rot: (Math.random() - .5) * 40, spin: (Math.random() - .5) * 960,
        s: .4 + m * .3, born: now + i * 20, life: 700 + Math.random() * 300 };
    }
    if (!alive) { alive = true; last = now; raf = requestAnimationFrame(step); }
  }

  function step(t) {
    var dt = Math.min((t - last) / 1000, .05); last = t;        // 탭 복귀 시 폭주 방지 클램프
    var any = false;
    for (var i = 0; i < ps.length; i++) {
      var el = ps[i], p = el._p; if (!p) continue;
      var age = t - p.born;
      if (age < 0) { any = true; continue; }                     // 방출 전 지연(순차 분사)
      if (age >= p.life) { el.style.opacity = '0'; el._p = null; continue; } // 수명 끝 → 그 자리에 정지
      p.vx += (-p.k / p.m * p.vx) * dt;                          // 감쇠 가속도 = -k/m·v
      p.vy += (p.g - p.k / p.m * p.vy) * dt;                     // 중력 가속도 = g (질량 무관)
      p.x += p.vx * dt; p.y += p.vy * dt; p.rot += p.spin * dt;
      var o = age / p.life;                                      // 수명 후반 45%에서 페이드아웃
      el.style.opacity = o < .55 ? '1' : (1 - (o - .55) / .45).toFixed(3);
      el.style.transform = 'translate(' + p.x.toFixed(1) + 'px,' + p.y.toFixed(1) + 'px) rotate(' + p.rot.toFixed(1) + 'deg) scale(' + p.s.toFixed(3) + ')';
      any = true;
    }
    if (any) raf = requestAnimationFrame(step); else alive = false; // 전부 정지하면 루프 종료
  }

  // 트리거 1: 실제 클릭 — 체크되는 순간(Save 순간) 발사
  document.querySelectorAll('.bookmark').forEach(function (b) {
    var inp = b.querySelector('.bookmark__input');
    if (inp) inp.addEventListener('change', function () { b.classList.remove('is-demo'); if (inp.checked) fire(); });
    if (inp) inp.addEventListener('pointerdown', function () { b.classList.remove('is-demo'); });
  });
  // 트리거 2: 데모 루프 — 귀 접힘(2s 루프의 40% ≈ 800ms)에 맞춰 발사
  function demoShot() {
    document.querySelectorAll('.bookmark').forEach(function (b) {
      if (b.classList.contains('is-demo')) setTimeout(fire, 800);
    });
  }
  setInterval(demoShot, 2000);
  demoShot();
})();

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

export type BookmarkFoldProps = {
  duration?: number;
  easing?: string;
  color?: string;
  defaultSaved?: boolean;
  onChange?: (saved: boolean) => void;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

/** 종잇조각 1개의 물성 — 질량·감쇠·중력으로 날아갔다 멈춘다 (귀 꼭짓점 기준 바깥 부채꼴) */
type Particle = {
  x: number; y: number; vx: number; vy: number;
  m: number; k: number; g: number;
  rot: number; spin: number; s: number;
  born: number; life: number;
};

const CHIP_COUNT = 6;

/** 질량-감쇠 물리 초기 상태. 감쇠 = -k/m·v, 중력 = g. 접힌 귀에서 위·오른쪽 부채꼴로 흩어진다. */
function spawn(now: number, i: number): Particle {
  const m = 0.7 + Math.random() * 0.9;                          // 개별 질량 0.7~1.6
  const ang = -Math.PI / 4 + (Math.random() - 0.5) * 2.8;       // 바깥쪽(위·오른쪽) 부채꼴 ±80°
  const v0 = (110 + Math.random() * 80) * (1.15 - m * 0.2);     // 무거울수록 느게 출발
  return {
    x: 0, y: 0,
    vx: Math.cos(ang) * v0, vy: Math.sin(ang) * v0,
    m, k: 3.2, g: 320,
    rot: (Math.random() - 0.5) * 40, spin: (Math.random() - 0.5) * 960,
    s: 0.4 + m * 0.3,
    born: now + i * 20, life: 700 + Math.random() * 300,        // 순차 분사 + 수명 랜덤
  };
}

export default function BookmarkFold({ duration = 300, easing = "cubic-bezier(.2,.8,.2,1)", color = "#fff7e6", defaultSaved = false, onChange }: BookmarkFoldProps) {
  const [saved, setSaved] = useState(defaultSaved);
  const [burstKey, setBurstKey] = useState(0);
  const iconRef = useRef<HTMLSpanElement>(null);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  const fire = useCallback(() => setBurstKey((k) => k + 1), []);

  // 준암시 오일러 적분 루프 — rAF 안에서 좌표를 계산해 transform 에 쓴다 (keyframes 하드코딩 아님)
  useEffect(() => {
    if (!burstKey) return;
    if (window.matchMedia("(prefers-reduced-motion: reduce)").matches) return;
    const icon = iconRef.current;
    if (!icon) return;
    const els = Array.from(icon.querySelectorAll<HTMLElement>(`.${styles.chip}`));
    if (!els.length) return;
    const now = performance.now();
    const ps: (Particle | null)[] = els.map((_, i) => spawn(now, i));
    let raf = 0, last = now;
    const step = (t: number) => {
      const dt = Math.min((t - last) / 1000, 0.05);            // 탭 복귀 시 폭주 방지 클램프
      last = t;
      let any = false;
      for (let i = 0; i < els.length; i++) {
        const el = els[i], p = ps[i]; if (!p) continue;
        const age = t - p.born;
        if (age < 0) { any = true; continue; }                  // 방출 전 지연
        if (age >= p.life) { el.style.opacity = "0"; ps[i] = null; continue; } // 수명 끝 → 정지
        p.vx += (-p.k / p.m * p.vx) * dt;                       // 감쇠 = -k/m·v
        p.vy += (p.g - p.k / p.m * p.vy) * dt;                  // 중력 + 감쇠
        p.x += p.vx * dt; p.y += p.vy * dt; p.rot += p.spin * dt;
        const o = age / p.life;
        el.style.opacity = o < 0.55 ? "1" : (1 - (o - 0.55) / 0.45).toFixed(3);
        el.style.transform =
          `translate(${p.x.toFixed(1)}px,${p.y.toFixed(1)}px) rotate(${p.rot.toFixed(1)}deg) scale(${p.s.toFixed(3)})`;
        any = true;
      }
      if (any) raf = requestAnimationFrame(step);               // 전부 정지하면 루프 종료
    };
    raf = requestAnimationFrame(step);
    return () => cancelAnimationFrame(raf);
  }, [burstKey]);

  return (
    <label className={styles.bookmark} style={vars}>
      <input
        type="checkbox"
        className={styles.input}
        checked={saved}
        onChange={(e: ChangeEvent<HTMLInputElement>) => { setSaved(e.target.checked); if (e.target.checked) fire(); onChange?.(e.target.checked); }}
      />
      <span className={styles.icon} aria-hidden="true" ref={iconRef}>
        <span className={styles.ribbon}>
          <span className={`${styles.ribbonFill} ${saved ? styles.isSaved : ""}`} />
        </span>
        <span className={`${styles.fold} ${saved ? styles.isSaved : ""}`} />
        <span className={styles.fx} aria-hidden="true">
          {Array.from({ length: CHIP_COUNT }, (_, i) => (
            <span key={`${burstKey}-${i}`} className={styles.chip} aria-hidden="true" />
          ))}
        </span>
      </span>
      <span className={styles.label}>저장</span>
    </label>
  );
}