05Live validity value toggle — each time a digit value fills in, the whole number's validity value is recalculated and the display value changes

<main class="stage">
<div class="cl is-demo" id="cl">
  <label class="cl__field">
    <input class="cl__input" id="clInput" type="text" inputmode="numeric" autocomplete="off" spellcheck="false" maxlength="16" value="">
    <span class="cl__badge" id="clBadge">
      <svg viewBox="0 0 20 20" width="14" height="14" aria-hidden="true">
        <path id="clCheck" d="M4 10.5l3.5 3.5L16 5.5" fill="none" stroke="currentColor" stroke-width="2.6" stroke-linecap="round" stroke-linejoin="round" pathLength="1" stroke-dasharray="1" stroke-dashoffset="1"/>
      </svg>
    </span>
  </label>
  <div class="cl__sum" id="clSum">Weighted sum value 0</div>
</div>
</main>

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

// 계산 겹: 자리별 가중 합(룬 체크섬)을 매 입력마다 다시 계산해 유효성 값을 판정한다(index.html).
@include stage($stage-ink);

.cl {
  width: 100%;
  max-width: 300px;
  display: grid;
  gap: $sp-3;
}

.cl__field {
  position: relative;
  display: block;
}

.cl__input {
  width: 100%;
  box-sizing: border-box;
  padding: $sp-3 $sp-10 $sp-3 $sp-4;
  border-radius: $r-control;
  border: 0;
  background: $subject-cream;
  color: $subject-ink;
  font-family: "SFMono-Regular", Consolas, monospace;
  font-weight: 600;
  font-size: 16px;
  letter-spacing: .05em;

  &:focus { outline: 2px solid $subject-blue-light; outline-offset: 2px; }
}

.cl__badge {
  position: absolute;
  right: $sp-3;
  top: 50%;
  transform: translateY(-50%) scale(.6);
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: rgba($subject-ink, .14);
  color: transparent;
  display: grid;
  place-items: center;
  opacity: .5;
  transition: transform $dur-quick $ease-spring, background-color $dur-quick $ease-out, color $dur-quick $ease-out, opacity $dur-quick $ease-out;

  #clCheck { transition: stroke-dashoffset $dur-enter $ease-out; }
}

.cl__badge--on {
  background: $tick-up;
  color: $subject-ink;
  opacity: 1;
  transform: translateY(-50%) scale(1);

  #clCheck { stroke-dashoffset: 0; }
}

.cl__sum {
  color: rgba($subject-cream, .72);
  font-weight: 600;
  font-size: 13px;
  font-family: "SFMono-Regular", Consolas, monospace;
}

@media (max-width: 340px) {
  .cl__input { padding: $sp-2 $sp-8 $sp-2 $sp-3; font-size: 14px; }
}

@media (prefers-reduced-motion: reduce) {
  .cl__badge, .cl__badge #clCheck { transition: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.cl {
  width: 100%;
  max-width: 300px;
  display: grid;
  gap: 12px;
}

.cl__field {
  position: relative;
  display: block;
}

.cl__input {
  width: 100%;
  box-sizing: border-box;
  padding: 12px 40px 12px 16px;
  border-radius: 12px;
  border: 0;
  background: #fff7e6;
  color: #17141a;
  font-family: "SFMono-Regular", Consolas, monospace;
  font-weight: 600;
  font-size: 16px;
  letter-spacing: 0.05em;
}
.cl__input:focus {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.cl__badge {
  position: absolute;
  right: 12px;
  top: 50%;
  transform: translateY(-50%) scale(0.6);
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: rgba(23, 20, 26, 0.14);
  color: transparent;
  display: grid;
  place-items: center;
  opacity: 0.5;
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1), background-color 220ms ease-out, color 220ms ease-out, opacity 220ms ease-out;
}
.cl__badge #clCheck {
  transition: stroke-dashoffset 600ms ease-out;
}

.cl__badge--on {
  background: #3ddc97;
  color: #17141a;
  opacity: 1;
  transform: translateY(-50%) scale(1);
}
.cl__badge--on #clCheck {
  stroke-dashoffset: 0;
}

.cl__sum {
  color: rgba(255, 247, 230, 0.72);
  font-weight: 600;
  font-size: 13px;
  font-family: "SFMono-Regular", Consolas, monospace;
}

@media (max-width: 340px) {
  .cl__input {
    padding: 8px 32px 8px 12px;
    font-size: 14px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cl__badge, .cl__badge #clCheck {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('cl');
  var input = document.getElementById('clInput');
  var badge = document.getElementById('clBadge');
  var sumLabel = document.getElementById('clSum');

  // 계산 겹: 자리별 가중 합(오른쪽부터 한 자리씩 건너 2배) — 룬 체크섬을 매 입력마다 다시 계산한다.
  function luhnSum(digits) {
    var sum = 0, dbl = false;
    for (var i = digits.length - 1; i >= 0; i--) {
      var d = digits.charCodeAt(i) - 48;
      if (dbl) { d *= 2; if (d > 9) d -= 9; }
      sum += d;
      dbl = !dbl;
    }
    return sum;
  }

  function paint(digits) {
    var sum = digits.length ? luhnSum(digits) : 0;
    var valid = digits.length >= 13 && sum % 10 === 0;
    sumLabel.textContent = 'Weighted sum value ' + sum;
    badge.classList.toggle('cl__badge--on', valid);
  }

  input.addEventListener('input', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    var digits = input.value.replace(/\D/g, '').slice(0, 16);
    input.value = digits;
    paint(digits);
  });

  // 자동 루프: 유효 번호를 한 자리씩 채웠다가, 마지막 자리를 잘못된 값으로 바꿔 무효 상태도 보여준다.
  var VALID = '9999999999999995';
  var INVALID = '9999999999999990';
  var SEQ = [];
  for (var i = 0; i <= VALID.length; i++) SEQ.push(VALID.slice(0, i));
  SEQ.push(INVALID);
  SEQ.push(VALID);
  for (var k = VALID.length - 1; k >= 0; k--) SEQ.push(VALID.slice(0, k));
  var si = 0;
  var autoTimer = null;
  function autoTick() {
    var digits = SEQ[si];
    input.value = digits;
    paint(digits);
    si = (si + 1) % SEQ.length;
  }
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoTimer = setInterval(autoTick, 180); autoTick(); }
  else { autoTick(); }
})();

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

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

const CHECK_PATH = "M4 10.5l3.5 3.5L16 5.5";

export default function LuhnLiveCheckmark() {
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement | null>;

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const input = root.querySelector(`.${styles.input}`) as HTMLInputElement | null;
    const badge = root.querySelector(`.${styles.badge}`) as HTMLElement | null;
    const sumLabel = root.querySelector(`.${styles.sum}`) as HTMLElement | null;
    if (!input || !badge || !sumLabel) return;

    // 계산 겹: 자리별 가중 합(오른쪽부터 한 자리씩 건너 2배) — 룬 체크섬을 매 입력마다 다시 계산한다.
    function luhnSum(digits: string) {
      let sum = 0, dbl = false;
      for (let i = digits.length - 1; i >= 0; i--) {
        let d = digits.charCodeAt(i) - 48;
        if (dbl) { d *= 2; if (d > 9) d -= 9; }
        sum += d;
        dbl = !dbl;
      }
      return sum;
    }

    function paint(digits: string) {
      const sum = digits.length ? luhnSum(digits) : 0;
      const valid = digits.length >= 13 && sum % 10 === 0;
      sumLabel!.textContent = "가중 합 값 " + sum;
      badge!.classList.toggle(styles["badge--on"], valid);
    }

    function onInput() {
      root!.classList.remove(styles["is-demo"]);
      stopAutoplay();
      const digits = input!.value.replace(/\D/g, "").slice(0, 16);
      input!.value = digits;
      paint(digits);
    }
    input.addEventListener("input", onInput);

    // 자동 루프: 유효 번호를 한 자리씩 채웠다가, 마지막 자리를 잘못된 값으로 바꿔 무효 상태도 보여준다.
    const VALID = "9999999999999995";
    const INVALID = "9999999999999990";
    const SEQ: string[] = [];
    for (let i = 0; i <= VALID.length; i++) SEQ.push(VALID.slice(0, i));
    SEQ.push(INVALID);
    SEQ.push(VALID);
    for (let k = VALID.length - 1; k >= 0; k--) SEQ.push(VALID.slice(0, k));
    let si = 0;
    let autoTimer: number | null = null;
    function autoTick() {
      const digits = SEQ[si];
      input!.value = digits;
      paint(digits);
      si = (si + 1) % SEQ.length;
    }
    function stopAutoplay() {
      if (autoTimer !== null) { window.clearInterval(autoTimer); autoTimer = null; }
    }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) { autoTimer = window.setInterval(autoTick, 180); autoTick(); }
    else { autoTick(); }

    return () => {
      stopAutoplay();
      input.removeEventListener("input", onInput);
    };
  }, []);

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.cl} ${styles["is-demo"]}`}>
      <label className={styles.field}>
        <input className={styles.input} type="text" inputMode="numeric" autoComplete="off" spellCheck={false} maxLength={16} defaultValue="" />
        <span className={styles.badge}>
          <svg viewBox="0 0 20 20" width="14" height="14" aria-hidden="true">
            <path className={styles.check} d={CHECK_PATH} fill="none" stroke="currentColor" strokeWidth={2.6} strokeLinecap="round" strokeLinejoin="round" pathLength={1} strokeDasharray={1} strokeDashoffset={1} />
          </svg>
        </span>
      </label>
      <div className={styles.sum}>가중 합 값 0</div>
    </div>
  );
}