06유효성 실패 시 링이 떨리며 조여드는 단계

<main class="stage">
<div class="er is-demo" id="er">
  <span class="er__glow" id="erGlow" aria-hidden="true"></span>
  <ol class="er__row" id="erRow" role="list" aria-label="필수 입력 단계">
    <li class="er__node" data-i="0"><span class="er__ring" id="ring0"></span><span class="er__circle is-active" id="n0">1</span><span class="er__label">이름</span></li>
    <li class="er__connector"></li>
    <li class="er__node" data-i="1"><span class="er__ring" id="ring1"></span><span class="er__circle" id="n1">2</span><span class="er__label">연락처</span></li>
    <li class="er__connector"></li>
    <li class="er__node" data-i="2"><span class="er__ring" id="ring2"></span><span class="er__circle" id="n2">3</span><span class="er__label">완료</span></li>
  </ol>
  <label class="er__field">
    <span class="er__fieldLabel">이름 (필수)</span>
    <input type="text" id="erInput" class="er__input" autocomplete="off">
  </label>
  <p class="er__status" id="erStatus" aria-live="assertive"></p>
  <div class="er__controls">
    <button type="button" class="er__btn er__btn--primary" id="erNext">다음</button>
  </div>
</div>
</main>

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

// 핵심: 오류가 난 노드의 x 오프셋은 감쇠 사인 AMP·exp(-STEP_ERROR_SHAKE_DECAY·t)·sin(FREQ·t) 로
// 매 프레임 계산하고, 링 반경은 같은 감쇠 값을 이용해 STEP_ERROR_RING_CONTRACT_PX 만큼 조여든다.

$duration: $dur-quick;
$easing: $ease-out;
$color: $stage-ink;

@include stage($stage-yellow);

.er {
  position: relative;
  display: grid;
  gap: $sp-3;
  justify-items: center;
  width: min(90vw, 280px);
}

.er__glow {
  position: absolute;
  inset: 0;
  border-radius: $r-sm;
  background: $error;
  opacity: 0;
  pointer-events: none;
  z-index: 0;
}

.er__row {
  position: relative;
  z-index: 1;
  display: flex;
  align-items: flex-start;
  list-style: none;
  padding: 0;
  margin: 0;
  width: 100%;
}

.er__node {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-1;
  flex: 0 0 auto;
}

.er__ring {
  position: absolute;
  top: -10px;
  left: 50%;
  width: 64px;
  height: 64px;
  margin-left: -32px;
  border-radius: 50%;
  border: 2px solid $error;
  opacity: 0;
  pointer-events: none;
}

.er__circle {
  position: relative;
  z-index: 1;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-size: 15px;
  font-weight: 700;
  color: $stage-ink;
  background: $stage-paper;
  border: 2px solid rgba(23, 20, 26, .2);
}

.er__circle.is-active { border-color: $subject-blue-deep; }
.er__circle.is-done { background: $stage-ink; color: $stage-yellow; border-color: $stage-ink; }
.er__circle.is-error { background: $error-soft; border-color: $error; color: $error; }

.er__label { font-size: 9px; color: rgba(23, 20, 26, .7); font-weight: 600; }

.er__connector {
  flex: 1 1 auto;
  height: 3px;
  min-width: 18px;
  margin: 20px 4px 0;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .18);
}

.er__field {
  display: grid;
  gap: 4px;
  width: 100%;
  max-width: 220px;
}

.er__fieldLabel { font-size: 10px; font-weight: 600; color: rgba(23, 20, 26, .75); }

.er__input {
  border: 1px solid rgba(23, 20, 26, .3);
  border-radius: $r-sm;
  padding: $sp-2 $sp-3;
  font-size: 12px;
  background: $stage-paper;
  color: $stage-ink;
}

.er__status {
  margin: 0;
  min-height: 14px;
  font-size: 10px;
  font-weight: 700;
  color: $subject-orange-deep;
}

.er__controls { display: flex; gap: $sp-2; }

.er__btn {
  border: 1px solid rgba(23, 20, 26, .3);
  background: transparent;
  color: $stage-ink;
  border-radius: $r-control;
  padding: $sp-2 $sp-4;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
}

.er__btn--primary { background: $subject-blue-deep; border-color: $subject-blue-deep; color: $stage-paper; }

.er__btn:focus-visible, .er__input:focus-visible {
  outline: 2px solid $subject-blue-deep;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .er { gap: $sp-1; }
  .er__circle { width: 36px; height: 36px; font-size: 13px; }
  .er__ring { width: 48px; height: 48px; margin-left: -24px; top: -6px; }
  .er__connector { margin-top: 16px; }
  .er__field { gap: 0; }
  .er__input { padding: $sp-1 $sp-3; }
}

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

.er {
  position: relative;
  display: grid;
  gap: 12px;
  justify-items: center;
  width: min(90vw, 280px);
}

.er__glow {
  position: absolute;
  inset: 0;
  border-radius: 8px;
  background: #c2361a;
  opacity: 0;
  pointer-events: none;
  z-index: 0;
}

.er__row {
  position: relative;
  z-index: 1;
  display: flex;
  align-items: flex-start;
  list-style: none;
  padding: 0;
  margin: 0;
  width: 100%;
}

.er__node {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  flex: 0 0 auto;
}

.er__ring {
  position: absolute;
  top: -10px;
  left: 50%;
  width: 64px;
  height: 64px;
  margin-left: -32px;
  border-radius: 50%;
  border: 2px solid #c2361a;
  opacity: 0;
  pointer-events: none;
}

.er__circle {
  position: relative;
  z-index: 1;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-size: 15px;
  font-weight: 700;
  color: #17141a;
  background: #ffffff;
  border: 2px solid rgba(23, 20, 26, 0.2);
}

.er__circle.is-active {
  border-color: #0a4fe8;
}

.er__circle.is-done {
  background: #17141a;
  color: #ffd23f;
  border-color: #17141a;
}

.er__circle.is-error {
  background: #ffe0d8;
  border-color: #c2361a;
  color: #c2361a;
}

.er__label {
  font-size: 9px;
  color: rgba(23, 20, 26, 0.7);
  font-weight: 600;
}

.er__connector {
  flex: 1 1 auto;
  height: 3px;
  min-width: 18px;
  margin: 20px 4px 0;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.18);
}

.er__field {
  display: grid;
  gap: 4px;
  width: 100%;
  max-width: 220px;
}

.er__fieldLabel {
  font-size: 10px;
  font-weight: 600;
  color: rgba(23, 20, 26, 0.75);
}

.er__input {
  border: 1px solid rgba(23, 20, 26, 0.3);
  border-radius: 8px;
  padding: 8px 12px;
  font-size: 12px;
  background: #ffffff;
  color: #17141a;
}

.er__status {
  margin: 0;
  min-height: 14px;
  font-size: 10px;
  font-weight: 700;
  color: #c93000;
}

.er__controls {
  display: flex;
  gap: 8px;
}

.er__btn {
  border: 1px solid rgba(23, 20, 26, 0.3);
  background: transparent;
  color: #17141a;
  border-radius: 12px;
  padding: 8px 16px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
}

.er__btn--primary {
  background: #0a4fe8;
  border-color: #0a4fe8;
  color: #ffffff;
}

.er__btn:focus-visible, .er__input:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .er {
    gap: 4px;
  }
  .er__circle {
    width: 36px;
    height: 36px;
    font-size: 13px;
  }
  .er__ring {
    width: 48px;
    height: 48px;
    margin-left: -24px;
    top: -6px;
  }
  .er__connector {
    margin-top: 16px;
  }
  .er__field {
    gap: 0;
  }
  .er__input {
    padding: 4px 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .er__circle {
    transition: none;
  }
}

(function () {
  var STEP_ERROR_SHAKE_DECAY = 5.5;
  var STEP_ERROR_SHAKE_FREQ = 26;
  var STEP_ERROR_SHAKE_AMPLITUDE_PX = 6;
  var STEP_ERROR_RING_CONTRACT_PX = 6;
  var SHAKE_DURATION_S = 0.6;
  var STEP_COUNT = 3;
  var RING_BASE_PX = 64;
  var NEIGHBOR_SHAKE_RATIO = 0.3; // 인접 노드 미세 흔들림 — 같은 감쇠 함수의 축소판

  var root = document.getElementById('er');
  var glow = document.getElementById('erGlow');
  var input = document.getElementById('erInput');
  var status = document.getElementById('erStatus');
  var nextBtn = document.getElementById('erNext');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var circles = [0, 1, 2].map(function (i) { return document.getElementById('n' + i); });
  var rings = [0, 1, 2].map(function (i) { return document.getElementById('ring' + i); });

  var current = 0;
  var errorAt = null;

  function clamp(v, lo, hi) { return Math.max(lo, Math.min(hi, v)); }

  function render() {
    circles.forEach(function (el, i) {
      el.classList.toggle('is-active', i === current);
      el.classList.toggle('is-done', i < current);
    });
  }

  function clearShakeVisuals() {
    circles[current].style.transform = '';
    rings[current].style.boxShadow = 'none';
    glow.style.opacity = '0';
    [current - 1, current + 1].forEach(function (idx) {
      if (idx >= 0 && idx < STEP_COUNT) circles[idx].style.transform = '';
    });
  }

  function triggerError() {
    errorAt = performance.now();
    status.textContent = '이름을 입력해야 다음 단계로 갈 수 있습니다';
    if (reduce) {
      circles[current].classList.add('is-error');
      rings[current].classList.add('is-error');
    }
  }

  function advance() {
    if (current === 0 && input.value.trim() === '') { triggerError(); return; }
    circles[current].classList.remove('is-error');
    rings[current].classList.remove('is-error');
    current = clamp(current + 1, 0, STEP_COUNT - 1);
    status.textContent = current === STEP_COUNT - 1 ? '입력 완료' : '';
    render();
  }

  nextBtn.addEventListener('click', function () { root.classList.remove('is-demo'); advance(); });
  input.addEventListener('input', function () {
    if (input.value.trim() !== '') { errorAt = null; circles[0].classList.remove('is-error'); rings[0].classList.remove('is-error'); status.textContent = ''; clearShakeVisuals(); }
  });

  var startTime = null;
  var phase = 0;
  function tick(now) {
    if (startTime === null) startTime = now;
    var t = (now - startTime) / 1000 % 2;
    if (root.classList.contains('is-demo')) {
      if (t < 0.05 && phase !== 0) phase = 0;
      if (phase === 0 && t > 0.20) { triggerError(); phase = 1; }
      if (phase === 1 && t > 1.10) { input.value = ''; errorAt = null; circles[0].classList.remove('is-error'); rings[0].classList.remove('is-error'); triggerError(); phase = 2; }
    }
    if (!reduce && errorAt !== null) {
      var tt = (now - errorAt) / 1000;
      if (tt <= SHAKE_DURATION_S) {
        var envelope = Math.exp(-STEP_ERROR_SHAKE_DECAY * tt);
        var x = STEP_ERROR_SHAKE_AMPLITUDE_PX * envelope * Math.sin(STEP_ERROR_SHAKE_FREQ * tt);
        circles[current].style.transform = 'translateX(' + x.toFixed(2) + 'px)';
        circles[current].classList.add('is-error');
        var contract = STEP_ERROR_RING_CONTRACT_PX * (1 - envelope);
        var ringSize = RING_BASE_PX - contract;
        rings[current].style.width = ringSize.toFixed(1) + 'px';
        rings[current].style.height = ringSize.toFixed(1) + 'px';
        rings[current].style.marginLeft = (-ringSize / 2).toFixed(1) + 'px';
        rings[current].style.opacity = String(envelope);
        rings[current].style.boxShadow = '0 0 ' + (envelope * 22).toFixed(1) + 'px ' + (envelope * 8).toFixed(1) + 'px rgba(194, 54, 26, ' + (envelope * 0.55).toFixed(2) + ')';
        rings[current].classList.add('is-error');
        glow.style.opacity = (envelope * 0.4).toFixed(2);
        [current - 1, current + 1].forEach(function (idx) {
          if (idx >= 0 && idx < STEP_COUNT) circles[idx].style.transform = 'translateX(' + (x * NEIGHBOR_SHAKE_RATIO).toFixed(2) + 'px)';
        });
      } else {
        clearShakeVisuals();
      }
    }
    requestAnimationFrame(tick);
  }

  render();
  requestAnimationFrame(tick);
})();

// StepErrorRingShake — vanilla 판(06-step-precision-error-ring-shake) 의 React 포트.
// 값 하나: 오류 발생 시점부터의 경과 tt 에 대해 감쇠 사인 envelope·x오프셋을 매 프레임 계산하고,
// 같은 envelope 로 링 반경을 STEP_ERROR_RING_CONTRACT_PX 만큼 조인다 — 흔들림과 조임이 한 값에서 나온다.
import { useEffect, useRef, useState } from "react";
import styles from "./StepErrorRingShake.module.scss";

type Box<T> = { current: T };

const STEP_ERROR_SHAKE_DECAY = 5.5;
const STEP_ERROR_SHAKE_FREQ = 26;
const STEP_ERROR_SHAKE_AMPLITUDE_PX = 6;
const STEP_ERROR_RING_CONTRACT_PX = 6;
const SHAKE_DURATION_S = 0.6;
const STEP_COUNT = 3;
const RING_BASE_PX = 64;
const NEIGHBOR_SHAKE_RATIO = 0.3; // 인접 노드 미세 흔들림 — 같은 감쇠 함수의 축소판
const LABELS = ["이름", "연락처", "완료"];

function clamp(v: number, lo: number, hi: number): number {
  return Math.max(lo, Math.min(hi, v));
}

export default function StepErrorRingShake() {
  const [current, setCurrent] = useState(0);
  const [errorIdx, setErrorIdx] = useState<number | null>(null);
  const [status, setStatus] = useState("");
  const [value, setValue] = useState("");
  const [reduce, setReduce] = useState(false);
  const currentRef = useRef<number>(0) as Box<number>;
  const errorAtRef = useRef<number | null>(null) as Box<number | null>;
  const errorIdxRef = useRef<number | null>(null) as Box<number | null>;
  const demoRef = useRef<boolean>(true) as Box<boolean>;
  const circleRefs = useRef<Array<HTMLSpanElement | null>>([null, null, null]) as Box<Array<HTMLSpanElement | null>>;
  const ringRefs = useRef<Array<HTMLSpanElement | null>>([null, null, null]) as Box<Array<HTMLSpanElement | null>>;
  const glowRef = useRef<HTMLSpanElement | null>(null);
  const frameRef = useRef<number>(0) as Box<number>;

  useEffect(() => {
    setReduce(window.matchMedia("(prefers-reduced-motion: reduce)").matches);
  }, []);

  function triggerError(): void {
    errorAtRef.current = performance.now();
    errorIdxRef.current = currentRef.current;
    setErrorIdx(currentRef.current);
    setStatus("이름을 입력해야 다음 단계로 갈 수 있습니다");
  }

  function clearError(): void {
    errorAtRef.current = null;
    errorIdxRef.current = null;
    setErrorIdx(null);
  }

  function advance(currentValue: string): void {
    if (currentRef.current === 0 && currentValue.trim() === "") { triggerError(); return; }
    clearError();
    const next = clamp(currentRef.current + 1, 0, STEP_COUNT - 1);
    currentRef.current = next;
    setCurrent(next);
    setStatus(next === STEP_COUNT - 1 ? "입력 완료" : "");
  }

  function stopDemo(): void { demoRef.current = false; }

  function onInputChange(v: string): void {
    setValue(v);
    if (v.trim() !== "") { clearError(); setStatus(""); }
  }

  useEffect(() => {
    let startTime = 0;
    let phase = 0;
    function clearShakeVisuals(eIdx: number): void {
      const circle = circleRefs.current[eIdx];
      if (circle) circle.style.transform = "";
      const ring = ringRefs.current[eIdx];
      if (ring) ring.style.boxShadow = "none";
      if (glowRef.current) glowRef.current.style.opacity = "0";
      [eIdx - 1, eIdx + 1].forEach((idx) => {
        if (idx >= 0 && idx < STEP_COUNT) {
          const neighbor = circleRefs.current[idx];
          if (neighbor) neighbor.style.transform = "";
        }
      });
    }
    function tick(now: number): void {
      if (startTime === 0) startTime = now;
      const t = ((now - startTime) / 1000) % 2;
      if (demoRef.current) {
        if (t < 0.05 && phase !== 0) phase = 0;
        if (phase === 0 && t > 0.20) { triggerError(); phase = 1; }
        if (phase === 1 && t > 1.10) { setValue(""); clearError(); triggerError(); phase = 2; }
      }
      const eIdx = errorIdxRef.current;
      if (!reduce && errorAtRef.current !== null && eIdx !== null) {
        const tt = (now - errorAtRef.current) / 1000;
        const circle = circleRefs.current[eIdx];
        const ring = ringRefs.current[eIdx];
        if (tt <= SHAKE_DURATION_S) {
          const envelope = Math.exp(-STEP_ERROR_SHAKE_DECAY * tt);
          const x = STEP_ERROR_SHAKE_AMPLITUDE_PX * envelope * Math.sin(STEP_ERROR_SHAKE_FREQ * tt);
          if (circle) circle.style.transform = "translateX(" + x.toFixed(2) + "px)";
          const contract = STEP_ERROR_RING_CONTRACT_PX * (1 - envelope);
          const ringSize = RING_BASE_PX - contract;
          if (ring) {
            ring.style.width = ringSize.toFixed(1) + "px";
            ring.style.height = ringSize.toFixed(1) + "px";
            ring.style.marginLeft = (-ringSize / 2).toFixed(1) + "px";
            ring.style.opacity = String(envelope);
            ring.style.boxShadow = "0 0 " + (envelope * 22).toFixed(1) + "px " + (envelope * 8).toFixed(1) + "px rgba(194, 54, 26, " + (envelope * 0.55).toFixed(2) + ")";
          }
          if (glowRef.current) glowRef.current.style.opacity = (envelope * 0.4).toFixed(2);
          [eIdx - 1, eIdx + 1].forEach((idx) => {
            if (idx >= 0 && idx < STEP_COUNT) {
              const neighbor = circleRefs.current[idx];
              if (neighbor) neighbor.style.transform = "translateX(" + (x * NEIGHBOR_SHAKE_RATIO).toFixed(2) + "px)";
            }
          });
        } else {
          clearShakeVisuals(eIdx);
        }
      }
      frameRef.current = requestAnimationFrame(tick);
    }
    frameRef.current = requestAnimationFrame(tick);
    return () => cancelAnimationFrame(frameRef.current);
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [reduce]);

  return (
    <main className={styles.stage}>
      <div className={styles.er}>
        <span className={styles.glow} ref={glowRef} aria-hidden="true" />
        <ol className={styles.row} role="list" aria-label="필수 입력 단계">
          {LABELS.map((label, i) => (
            <li key={label} style={{ display: "contents" }}>
              <div className={styles.node}>
                <span className={[styles.ring, errorIdx === i ? styles.ringError : ""].join(" ")} ref={(el: HTMLSpanElement | null) => { ringRefs.current[i] = el; }} />
                <span
                  className={[styles.circle, i === current ? styles.circleActive : "", i < current ? styles.circleDone : "", errorIdx === i ? styles.circleError : ""].join(" ")}
                  ref={(el: HTMLSpanElement | null) => { circleRefs.current[i] = el; }}
                >
                  {i + 1}
                </span>
                <span className={styles.label}>{label}</span>
              </div>
              {i < STEP_COUNT - 1 && <div className={styles.connector} />}
            </li>
          ))}
        </ol>
        <label className={styles.field}>
          <span className={styles.fieldLabel}>이름 (필수)</span>
          <input
            type="text"
            className={styles.input}
            autoComplete="off"
            value={value}
            onChange={(e: { target: { value: string } }) => onInputChange(e.target.value)}
          />
        </label>
        <p className={styles.status} aria-live="assertive">{status}</p>
        <div className={styles.controls}>
          <button
            type="button"
            className={[styles.btn, styles.btnPrimary].join(" ")}
            onClick={() => { stopDemo(); advance(value); }}
          >
            다음
          </button>
        </div>
      </div>
    </main>
  );
}