04Perimeter countdown — a button whose surrounding perimeter progress value depletes over a set duration

<main class="stage">
<div class="ctaprc is-demo" id="ctaprc">
  <div class="ctaprc__panel">
    <div class="ctaprc__wrap">
      <svg class="ctaprc__ring" viewBox="0 0 84 84" id="ctaprcSvg">
        <circle class="ctaprc__track" cx="42" cy="42" r="38"></circle>
        <circle class="ctaprc__bar" id="ctaprcBar" cx="42" cy="42" r="38"></circle>
      </svg>
      <button class="ctaprc__btn" id="ctaprcBtn" type="button">Next step</button>
    </div>
    <span class="ctaprc__hint">Click and it automatically moves to the next step after 1.5 seconds</span>
  </div>
</div>
</main>

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

// 계산 겹(둘레·dashoffset 산술)은 JS 에 있다 — 여기는 정적 배치만.
@include stage($stage-yellow);

.stage { position: relative; }

.ctaprc__panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-4;
  padding: $sp-5;
  border-radius: $r-card;
  background: $stage-paper;
}

.ctaprc__wrap {
  position: relative;
  width: 92px;
  height: 92px;
  display: grid;
  place-items: center;
}

.ctaprc__ring {
  position: absolute;
  inset: 0;
  width: 92px;
  height: 92px;
  transform: rotate(-90deg);
}

.ctaprc__track {
  fill: none;
  stroke: rgba($subject-ink, .12);
  stroke-width: 6;
}

.ctaprc__bar {
  fill: none;
  stroke: $subject-blue-deep;
  stroke-width: 6;
  stroke-linecap: round;
}

.ctaprc__btn {
  position: relative;
  border: 0;
  border-radius: $r-pill;
  background: $subject-blue-deep;
  color: $subject-cream;
  font-family: inherit;
  font-weight: 700;
  font-size: 12px;
  width: 68px;
  height: 68px;
  cursor: pointer;
}

.ctaprc__hint {
  color: rgba($subject-ink, .72);
  font-size: 12px;
  text-align: center;
}

@media (max-width: 340px) {
  .ctaprc__panel { padding: $sp-4; gap: $sp-3; }
  .ctaprc__wrap { width: 76px; height: 76px; }
  .ctaprc__ring { width: 76px; height: 76px; }
  .ctaprc__btn { width: 56px; height: 56px; font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .ctaprc__ring { 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: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.stage {
  position: relative;
}

.ctaprc__panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  padding: 20px;
  border-radius: 16px;
  background: #ffffff;
}

.ctaprc__wrap {
  position: relative;
  width: 92px;
  height: 92px;
  display: grid;
  place-items: center;
}

.ctaprc__ring {
  position: absolute;
  inset: 0;
  width: 92px;
  height: 92px;
  transform: rotate(-90deg);
}

.ctaprc__track {
  fill: none;
  stroke: rgba(23, 20, 26, 0.12);
  stroke-width: 6;
}

.ctaprc__bar {
  fill: none;
  stroke: #0a4fe8;
  stroke-width: 6;
  stroke-linecap: round;
}

.ctaprc__btn {
  position: relative;
  border: 0;
  border-radius: 999px;
  background: #0a4fe8;
  color: #fff7e6;
  font-family: inherit;
  font-weight: 700;
  font-size: 12px;
  width: 68px;
  height: 68px;
  cursor: pointer;
}

.ctaprc__hint {
  color: rgba(23, 20, 26, 0.72);
  font-size: 12px;
  text-align: center;
}

@media (max-width: 340px) {
  .ctaprc__panel {
    padding: 16px;
    gap: 12px;
  }
  .ctaprc__wrap {
    width: 76px;
    height: 76px;
  }
  .ctaprc__ring {
    width: 76px;
    height: 76px;
  }
  .ctaprc__btn {
    width: 56px;
    height: 56px;
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ctaprc__ring {
    transition: none !important;
  }
}

(function () {
  var root = document.getElementById('ctaprc');
  var btn = document.getElementById('ctaprcBtn');
  var bar = document.getElementById('ctaprcBar');

  // 계산 겹: 반지름(r)으로 둘레(circumference = 2*PI*r)를 구하고, 남은 시간 비율(progress)을
  // stroke-dashoffset = circumference * (1 - progress) 산술로 매 프레임 다시 그린다.
  var R = 38;
  var CIRC = 2 * Math.PI * R;
  bar.style.strokeDasharray = CIRC.toFixed(2);
  var DURATION = 1500;
  var raf = null, startT = 0, running = false;

  function frame(now) {
    var t = now - startT;
    var progress = Math.min(1, t / DURATION);
    var offset = CIRC * (1 - progress);
    bar.style.strokeDashoffset = offset.toFixed(2);
    if (progress < 1) {
      raf = requestAnimationFrame(frame);
    } else {
      running = false; raf = null;
      btn.textContent = 'Completed';
      setTimeout(function () { btn.textContent = 'Next step'; bar.style.strokeDashoffset = CIRC.toFixed(2); }, 500);
    }
  }
  function startCountdown() {
    if (running) { return; }
    running = true;
    startT = performance.now();
    raf = requestAnimationFrame(frame);
  }

  function wireReal() {
    btn.addEventListener('click', function () { root.classList.remove('is-demo'); stopAutoplay(); startCountdown(); });
  }
  wireReal();
  bar.style.strokeDashoffset = CIRC.toFixed(2);

  var autoplayTimer = null;
  function stopAutoplay() { if (autoplayTimer) { clearInterval(autoplayTimer); autoplayTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { startCountdown(); autoplayTimer = setInterval(startCountdown, 2000); }
})();

import { useEffect, useRef } from "react";
import styles from "./CtaBtnProgressRingCountdown.module.scss";

export type CtaBtnProgressRingCountdownProps = {
  color?: string;
};

export default function CtaBtnProgressRingCountdown({
  color = "#0a4fe8",
}: CtaBtnProgressRingCountdownProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const btn = root.querySelector<HTMLButtonElement>(`.${styles.btn}`);
    const bar = root.querySelector<SVGCircleElement>(`.${styles.bar}`);
    if (!btn || !bar) return;

    // 계산 겹: 반지름(r)으로 둘레(circumference = 2*PI*r)를 구하고, 남은 시간 비율(progress)을
    // stroke-dashoffset = circumference * (1 - progress) 산술로 매 프레임 다시 그린다.
    const R = 38;
    const CIRC = 2 * Math.PI * R;
    bar.style.strokeDasharray = CIRC.toFixed(2);
    bar.style.strokeDashoffset = CIRC.toFixed(2);
    const DURATION = 1500;
    let raf: number | null = null;
    let startT = 0;
    let running = false;

    function frame(now: number) {
      const t = now - startT;
      const progress = Math.min(1, t / DURATION);
      const offset = CIRC * (1 - progress);
      bar!.style.strokeDashoffset = offset.toFixed(2);
      if (progress < 1) {
        raf = requestAnimationFrame(frame);
      } else {
        running = false; raf = null;
        btn!.textContent = "완료됨";
        window.setTimeout(() => { btn!.textContent = "다음 단계"; bar!.style.strokeDashoffset = CIRC.toFixed(2); }, 500);
      }
    }
    function startCountdown() {
      if (running) return;
      running = true;
      startT = performance.now();
      raf = requestAnimationFrame(frame);
    }

    function onClick() { stopAutoplay(); startCountdown(); }
    btn.addEventListener("click", onClick);

    let autoplayTimer: number | null = null;
    function stopAutoplay() { if (autoplayTimer !== null) { window.clearInterval(autoplayTimer); autoplayTimer = null; } }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) { startCountdown(); autoplayTimer = window.setInterval(startCountdown, 2000); }

    return () => {
      stopAutoplay();
      if (raf !== null) { cancelAnimationFrame(raf); }
      btn.removeEventListener("click", onClick);
    };
  }, []);

  return (
    <div ref={rootRef} className={styles.stage}>
      <div className={styles.panel}>
        <div className={styles.wrap}>
          <svg className={styles.ring} viewBox="0 0 84 84">
            <circle className={styles.track} cx={42} cy={42} r={38} />
            <circle className={styles.bar} cx={42} cy={42} r={38} style={{ stroke: color }} />
          </svg>
          <button className={styles.btn} type="button" style={{ background: color }}>다음 단계</button>
        </div>
        <span className={styles.hint}>클릭하면 1.5초 뒤 자동으로 다음 단계로 넘어갑니다</span>
      </div>
    </div>
  );
}