08로딩 중 라벨 문구가 단계별로 바뀌는 버튼

<main class="stage">
<div class="scene is-demo" id="scene">
  <button class="btn" id="btn" type="button">
    <span class="btnContent">
      <span class="btnLabel" id="label">Submit</span>
      <span class="btnSteps" id="steps" aria-hidden="true">
        <span class="btnStepsTrack" id="track">
          <span class="btnStep" id="step0">Preparing</span>
          <span class="btnStep" id="step1">Uploading</span>
          <span class="btnStep" id="step2">Verifying</span>
          <span class="btnStep" id="step3">Done</span>
        </span>
      </span>
    </span>
  </button>
  <span class="visuallyHidden" id="status" role="status" aria-live="polite"></span>
</div>
</main>

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

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

// 계산 겹: index.html 의 measureOffsets() 가 각 단계 문구의 offsetTop 을 실측해 슬라이드
// 목표값으로 쓴다 — 줄 높이를 짐작한 고정 px 가 아니다.
@include stage($stage-paper);

.scene {
  display: grid;
  place-items: center;
}

.btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 44px;
  padding: 0 $sp-5;
  border: none;
  border-radius: $r-control;
  background: $color;
  color: $subject-cream;
  font-weight: 600;
  font-size: 14px;
  line-height: 1;
  box-shadow: $shadow-press;
  cursor: pointer;

  &:focus-visible { outline: 2px solid $subject-blue-deep; outline-offset: 3px; }
  &:disabled { cursor: default; }
}

.btnContent {
  position: relative;
  display: inline-block;
  min-width: 76px;
  height: 18px;
  overflow: hidden;
}

.btnLabel {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  white-space: nowrap;
}

.btnSteps {
  position: absolute;
  inset: 0;
  opacity: 0;
  overflow: hidden;
}

.btnStepsTrack {
  display: flex;
  flex-direction: column;
}

.btnStep {
  height: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  white-space: nowrap;
}

.visuallyHidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

@media (max-width: 340px) {
  .btn { height: 40px; padding: 0 $sp-4; font-size: 13px; }
  .btnContent { min-width: 66px; }
}

@media (prefers-reduced-motion: reduce) {
  // 실사용 경로 적용 — index.html 의 runReduced() 가 슬라이드 트윈 없이 단계마다 즉시 이동한다.
  // scss 만: 남은 트랜지션을 전부 끈다.
  * { 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);
}

.scene {
  display: grid;
  place-items: center;
}

.btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 44px;
  padding: 0 20px;
  border: none;
  border-radius: 12px;
  background: #0a4fe8;
  color: #fff7e6;
  font-weight: 600;
  font-size: 14px;
  line-height: 1;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  cursor: pointer;
}
.btn:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 3px;
}
.btn:disabled {
  cursor: default;
}

.btnContent {
  position: relative;
  display: inline-block;
  min-width: 76px;
  height: 18px;
  overflow: hidden;
}

.btnLabel {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  white-space: nowrap;
}

.btnSteps {
  position: absolute;
  inset: 0;
  opacity: 0;
  overflow: hidden;
}

.btnStepsTrack {
  display: flex;
  flex-direction: column;
}

.btnStep {
  height: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  white-space: nowrap;
}

.visuallyHidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

@media (max-width: 340px) {
  .btn {
    height: 40px;
    padding: 0 16px;
    font-size: 13px;
  }
  .btnContent {
    min-width: 66px;
  }
}
@media (prefers-reduced-motion: reduce) {
  * {
    transition: none !important;
  }
}

(function () {
  var STEP_INTERVAL_MS = 450;
  var STEP_ANIM_MS = 220;
  var FADE_MS = 160;
  var DONE_HOLD_MS = 400;
  var GAP_MS = 460;
  var START_DELAY_MS = 200;
  var STEP_LABELS = ['Preparing', 'Uploading', 'Verifying', 'Done'];
  var STEP_STATUS = ['준비하는 중', '올리는 중', '확인하는 중', '완료'];

  var scene = document.getElementById('scene');
  var btn = document.getElementById('btn');
  var label = document.getElementById('label');
  var steps = document.getElementById('steps');
  var track = document.getElementById('track');
  var status = document.getElementById('status');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var stepEls = [document.getElementById('step0'), document.getElementById('step1'), document.getElementById('step2'), document.getElementById('step3')];
  var gen = 0;
  var timers = [];

  function human() {
    if (scene.classList.contains('is-demo')) {
      scene.classList.remove('is-demo');
      timers.forEach(function (t) { clearTimeout(t); });
      timers = [];
    }
  }

  function easeInOutQuad(p) { return p < .5 ? 2 * p * p : 1 - Math.pow(-2 * p + 2, 2) / 2; }

  // 계산 겹: 각 단계 문구의 오프셋을 짐작하지 않고 offsetTop 으로 실측한다 — 트랙 안에서
  // 앞선 문구들이 쌓인 실제 높이만큼만 밀어 올리므로 줄 높이가 달라져도 어긋나지 않는다.
  function measureOffsets() {
    return stepEls.map(function (el) { return el.offsetTop; });
  }

  function fade(el, from, to, ms, myGen, onDone) {
    var start = null;
    function step(now) {
      if (myGen !== gen) return;
      if (start === null) start = now;
      var p = Math.min(1, (now - start) / ms);
      el.style.opacity = String(from + (to - from) * easeInOutQuad(p));
      if (p < 1) requestAnimationFrame(step); else if (onDone) onDone();
    }
    requestAnimationFrame(step);
  }

  function slideTo(myGen, fromY, toY, ms, onDone) {
    var start = null;
    function step(now) {
      if (myGen !== gen) return;
      if (start === null) start = now;
      var p = easeInOutQuad(Math.min(1, (now - start) / ms));
      var y = fromY + (toY - fromY) * p;
      track.style.transform = 'translateY(' + (-y).toFixed(2) + 'px)';
      if (p < 1) requestAnimationFrame(step); else onDone();
    }
    requestAnimationFrame(step);
  }

  function runAnimated() {
    gen++;
    var myGen = gen;
    var offsets = measureOffsets();
    btn.disabled = true;
    btn.setAttribute('aria-busy', 'true');
    status.textContent = STEP_STATUS[0];
    track.style.transform = 'translateY(0px)';
    fade(label, 1, 0, FADE_MS, myGen);
    fade(steps, 0, 1, FADE_MS, myGen);

    function advance(i) {
      if (i >= offsets.length) {
        timers.push(setTimeout(function () {
          fade(steps, 1, 0, FADE_MS, myGen);
          fade(label, 0, 1, FADE_MS, myGen, function () {
            btn.disabled = false;
            btn.removeAttribute('aria-busy');
            label.textContent = 'Submit';
            status.textContent = '';
          });
        }, DONE_HOLD_MS));
        return;
      }
      status.textContent = STEP_STATUS[i];
      timers.push(setTimeout(function () {
        if (i + 1 < offsets.length) {
          slideTo(myGen, offsets[i], offsets[i + 1], STEP_ANIM_MS, function () { advance(i + 1); });
        } else {
          advance(i + 1);
        }
      }, STEP_INTERVAL_MS));
    }
    advance(0);
  }

  function runReduced() {
    gen++;
    var myGen = gen;
    var offsets = measureOffsets();
    btn.disabled = true;
    btn.setAttribute('aria-busy', 'true');
    label.style.opacity = '0';
    steps.style.opacity = '1';
    var i = 0;
    function tick() {
      if (myGen !== gen) return;
      status.textContent = STEP_STATUS[i];
      track.style.transform = 'translateY(' + (-offsets[i]).toFixed(2) + 'px)';
      if (i < offsets.length - 1) {
        i++;
        timers.push(setTimeout(tick, STEP_INTERVAL_MS));
      } else {
        timers.push(setTimeout(function () {
          steps.style.opacity = '0';
          label.style.opacity = '1';
          label.textContent = 'Submit';
          btn.disabled = false;
          btn.removeAttribute('aria-busy');
          status.textContent = '';
        }, DONE_HOLD_MS));
      }
    }
    tick();
  }

  btn.addEventListener('click', function () {
    if (btn.disabled) return;
    human();
    if (reduce) runReduced(); else runAnimated();
  });

  // reduce: 실사용 경로 적용 — runReduced() 는 슬라이드 트윈 없이 단계마다 즉시 위치를 바꾼다.
  // 아래 자동 루프는 시연 게이트만 — reduce 에서는 돌지 않는다.
  function cycle() {
    if (!scene.classList.contains('is-demo')) return;
    runAnimated();
    var total = STEP_INTERVAL_MS * STEP_LABELS.length + STEP_ANIM_MS * (STEP_LABELS.length - 1) + DONE_HOLD_MS + FADE_MS;
    timers.push(setTimeout(function () {
      timers.push(setTimeout(cycle, GAP_MS));
    }, total));
  }

  if (!reduce) {
    timers.push(setTimeout(cycle, START_DELAY_MS));
  }
})();

import { useEffect, useRef } from 'react';
import styles from './ButtonLoadingMultiStepSequence.module.scss';

const STEP_INTERVAL_MS = 450;
const STEP_ANIM_MS = 220;
const FADE_MS = 160;
const DONE_HOLD_MS = 400;
const GAP_MS = 460;
const START_DELAY_MS = 200;
const STEP_LABELS = ['Preparing', 'Uploading', 'Verifying', 'Done'];
const STEP_STATUS = ['준비하는 중', '올리는 중', '확인하는 중', '완료'];

export default function ButtonLoadingMultiStepSequence() {
  const sceneRef = useRef<HTMLDivElement>(null);
  const btnRef = useRef<HTMLButtonElement>(null);
  const labelRef = useRef<HTMLSpanElement>(null);
  const stepsRef = useRef<HTMLSpanElement>(null);
  const trackRef = useRef<HTMLSpanElement>(null);
  const step0Ref = useRef<HTMLSpanElement>(null);
  const step1Ref = useRef<HTMLSpanElement>(null);
  const step2Ref = useRef<HTMLSpanElement>(null);
  const step3Ref = useRef<HTMLSpanElement>(null);
  const statusRef = useRef<HTMLSpanElement>(null);

  useEffect(() => {
    const scene = sceneRef.current;
    const btn = btnRef.current;
    const label = labelRef.current;
    const steps = stepsRef.current;
    const track = trackRef.current;
    const step0 = step0Ref.current;
    const step1 = step1Ref.current;
    const step2 = step2Ref.current;
    const step3 = step3Ref.current;
    const status = statusRef.current;
    if (!scene || !btn || !label || !steps || !track || !step0 || !step1 || !step2 || !step3 || !status) return undefined;
    const stepEls = [step0, step1, step2, step3];
    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

    let gen = 0;
    let timers: number[] = [];

    function human() {
      if (scene!.classList.contains(styles['is-demo'])) {
        scene!.classList.remove(styles['is-demo']);
        timers.forEach((t) => window.clearTimeout(t));
        timers = [];
      }
    }

    function easeInOutQuad(p: number) { return p < .5 ? 2 * p * p : 1 - Math.pow(-2 * p + 2, 2) / 2; }

    // 계산 겹: 각 단계 문구의 오프셋을 짐작하지 않고 offsetTop 으로 실측한다 — 트랙 안에서
    // 앞선 문구들이 쌓인 실제 높이만큼만 밀어 올리므로 줄 높이가 달라져도 어긋나지 않는다.
    function measureOffsets() {
      return stepEls.map((el) => el.offsetTop);
    }

    function fade(el: HTMLElement, from: number, to: number, ms: number, myGen: number, onDone?: () => void) {
      let start: number | null = null;
      function step(now: number) {
        if (myGen !== gen) return;
        if (start === null) start = now;
        const p = Math.min(1, (now - start) / ms);
        el.style.opacity = String(from + (to - from) * easeInOutQuad(p));
        if (p < 1) requestAnimationFrame(step); else if (onDone) onDone();
      }
      requestAnimationFrame(step);
    }

    function slideTo(myGen: number, fromY: number, toY: number, ms: number, onDone: () => void) {
      let start: number | null = null;
      function step(now: number) {
        if (myGen !== gen) return;
        if (start === null) start = now;
        const p = easeInOutQuad(Math.min(1, (now - start) / ms));
        const y = fromY + (toY - fromY) * p;
        track!.style.transform = 'translateY(' + (-y).toFixed(2) + 'px)';
        if (p < 1) requestAnimationFrame(step); else onDone();
      }
      requestAnimationFrame(step);
    }

    function runAnimated() {
      gen++;
      const myGen = gen;
      const offsets = measureOffsets();
      btn!.disabled = true;
      btn!.setAttribute('aria-busy', 'true');
      status!.textContent = STEP_STATUS[0];
      track!.style.transform = 'translateY(0px)';
      fade(label!, 1, 0, FADE_MS, myGen);
      fade(steps!, 0, 1, FADE_MS, myGen);

      function advance(i: number) {
        if (i >= offsets.length) {
          timers.push(window.setTimeout(() => {
            fade(steps!, 1, 0, FADE_MS, myGen);
            fade(label!, 0, 1, FADE_MS, myGen, () => {
              btn!.disabled = false;
              btn!.removeAttribute('aria-busy');
              label!.textContent = 'Submit';
              status!.textContent = '';
            });
          }, DONE_HOLD_MS));
          return;
        }
        status!.textContent = STEP_STATUS[i];
        timers.push(window.setTimeout(() => {
          if (i + 1 < offsets.length) {
            slideTo(myGen, offsets[i], offsets[i + 1], STEP_ANIM_MS, () => { advance(i + 1); });
          } else {
            advance(i + 1);
          }
        }, STEP_INTERVAL_MS));
      }
      advance(0);
    }

    function runReduced() {
      gen++;
      const myGen = gen;
      const offsets = measureOffsets();
      btn!.disabled = true;
      btn!.setAttribute('aria-busy', 'true');
      label!.style.opacity = '0';
      steps!.style.opacity = '1';
      let i = 0;
      function tick() {
        if (myGen !== gen) return;
        status!.textContent = STEP_STATUS[i];
        track!.style.transform = 'translateY(' + (-offsets[i]).toFixed(2) + 'px)';
        if (i < offsets.length - 1) {
          i++;
          timers.push(window.setTimeout(tick, STEP_INTERVAL_MS));
        } else {
          timers.push(window.setTimeout(() => {
            steps!.style.opacity = '0';
            label!.style.opacity = '1';
            label!.textContent = 'Submit';
            btn!.disabled = false;
            btn!.removeAttribute('aria-busy');
            status!.textContent = '';
          }, DONE_HOLD_MS));
        }
      }
      tick();
    }

    function onClick() {
      if (btn!.disabled) return;
      human();
      if (reduce) runReduced(); else runAnimated();
    }
    btn.addEventListener('click', onClick);

    // reduce: 실사용 경로 적용 — runReduced() 는 슬라이드 트윈 없이 단계마다 즉시 위치를 바꾼다.
    // 아래 자동 루프는 시연 게이트만 — reduce 에서는 돌지 않는다.
    function cycle() {
      if (!scene!.classList.contains(styles['is-demo'])) return;
      runAnimated();
      const total = STEP_INTERVAL_MS * STEP_LABELS.length + STEP_ANIM_MS * (STEP_LABELS.length - 1) + DONE_HOLD_MS + FADE_MS;
      timers.push(window.setTimeout(() => {
        timers.push(window.setTimeout(cycle, GAP_MS));
      }, total));
    }

    if (!reduce) {
      timers.push(window.setTimeout(cycle, START_DELAY_MS));
    }

    return () => {
      btn.removeEventListener('click', onClick);
      timers.forEach((t) => window.clearTimeout(t));
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.scene + ' ' + styles['is-demo']} ref={sceneRef}>
        <button className={styles.btn} ref={btnRef} type="button">
          <span className={styles.btnContent}>
            <span className={styles.btnLabel} ref={labelRef}>Submit</span>
            <span className={styles.btnSteps} ref={stepsRef} aria-hidden="true">
              <span className={styles.btnStepsTrack} ref={trackRef}>
                <span className={styles.btnStep} ref={step0Ref}>Preparing</span>
                <span className={styles.btnStep} ref={step1Ref}>Uploading</span>
                <span className={styles.btnStep} ref={step2Ref}>Verifying</span>
                <span className={styles.btnStep} ref={step3Ref}>Done</span>
              </span>
            </span>
          </span>
        </button>
        <span className={styles.visuallyHidden} ref={statusRef} role="status" aria-live="polite" />
      </div>
    </main>
  );
}