02Doubling backoff wait — the time value left before the next try doubles with each failure

<main class="stage">
<div class="abt is-demo" id="abt">
  <div class="abt__card">
    <div class="abt__row">
      <span class="abt__label">Fail <b id="abtFails">0</b>times</span>
      <span class="abt__wait" id="abtWait">No wait</span>
    </div>
    <div class="abt__track"><div class="abt__fill" id="abtFill"></div></div>
    <button class="abt__btn" id="abtBtn" type="button">Login attempt</button>
  </div>
</div>
</main>

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

// 계산 겹: 대기초 = min(CAP, BACKOFF_BASE×2^실패횟수) — index.html 참조. 막대는 남은비율로 scaleX
@include stage($stage-orange);

.abt {
  width: 100%;
  max-width: 300px;
}

.abt__card {
  display: grid;
  gap: $sp-3;
}

.abt__row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  font: 600 13px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $subject-cream;
}

.abt__label b { font-size: 16px; font-variant-numeric: tabular-nums; }

.abt__wait {
  font-variant-numeric: tabular-nums;
  color: $subject-cream;
}

.abt__track {
  position: relative;
  height: $sp-3;
  border-radius: $r-sm;
  background: rgba(23, 20, 26, .28);
  overflow: hidden;
}

.abt__fill {
  position: absolute;
  inset: 0;
  border-radius: $r-sm;
  background: $stage-ink;
  transform: scaleX(0);
  transform-origin: right center;
}

.abt__btn {
  border: 0;
  border-radius: $r-control;
  padding: $sp-2 $sp-4;
  background: $stage-ink;
  color: $subject-cream;
  font: 700 14px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  cursor: pointer;
  transition: opacity $dur-instant $ease-out;

  &:disabled { opacity: .5; cursor: not-allowed; }
}

@media (max-width: 340px) {
  .abt { max-width: 220px; }
  .abt__row { font-size: 12px; }
}

@media (prefers-reduced-motion: reduce) {
  .abt__btn { transition: none; }
}

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);
}

.abt {
  width: 100%;
  max-width: 300px;
}

.abt__card {
  display: grid;
  gap: 12px;
}

.abt__row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  font: 600 13px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #fff7e6;
}

.abt__label b {
  font-size: 16px;
  font-variant-numeric: tabular-nums;
}

.abt__wait {
  font-variant-numeric: tabular-nums;
  color: #fff7e6;
}

.abt__track {
  position: relative;
  height: 12px;
  border-radius: 8px;
  background: rgba(23, 20, 26, 0.28);
  overflow: hidden;
}

.abt__fill {
  position: absolute;
  inset: 0;
  border-radius: 8px;
  background: #17141a;
  transform: scaleX(0);
  transform-origin: right center;
}

.abt__btn {
  border: 0;
  border-radius: 12px;
  padding: 8px 16px;
  background: #17141a;
  color: #fff7e6;
  font: 700 14px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  cursor: pointer;
  transition: opacity 140ms ease-out;
}
.abt__btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

@media (max-width: 340px) {
  .abt {
    max-width: 220px;
  }
  .abt__row {
    font-size: 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .abt__btn {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('abt');
  var btn = document.getElementById('abtBtn');
  var failsEl = document.getElementById('abtFails');
  var waitEl = document.getElementById('abtWait');
  var fill = document.getElementById('abtFill');

  // 상수: 지수 백오프 = BACKOFF_BASE_SEC × 2^실패횟수(sec), CAP_SEC 에서 증가를 멈춘다
  var BACKOFF_BASE_SEC = 1;
  var CAP_SEC = 16;
  var DEMO_TICK_MS = 90; // 데모 안에서 "1sec"를 표현하는 실제 ms(가속)

  var fails = 0;
  var locked = false;
  var rafId = null;

  function waitSecondsOf(n) {
    return Math.min(CAP_SEC, BACKOFF_BASE_SEC * Math.pow(2, n));
  }

  function countdown(totalSec) {
    locked = true;
    btn.disabled = true;
    var start = null;
    var totalMs = totalSec * DEMO_TICK_MS;
    function frame(ts) {
      if (start === null) start = ts;
      var elapsed = ts - start;
      var left = Math.max(0, totalSec - elapsed / DEMO_TICK_MS);
      waitEl.textContent = 'Until next try ' + Math.ceil(left) + 'sec';
      fill.style.transform = 'scaleX(' + Math.max(0, left / totalSec) + ')';
      if (elapsed < totalMs) { rafId = requestAnimationFrame(frame); }
      else {
        waitEl.textContent = 'No wait';
        fill.style.transform = 'scaleX(0)';
        locked = false;
        btn.disabled = false;
      }
    }
    rafId = requestAnimationFrame(frame);
  }

  function fail() {
    if (locked) return;
    fails += 1;
    failsEl.textContent = String(fails);
    countdown(waitSecondsOf(fails));
  }

  function reset() {
    if (rafId) cancelAnimationFrame(rafId);
    fails = 0;
    locked = false;
    btn.disabled = false;
    failsEl.textContent = '0';
    waitEl.textContent = 'No wait';
    fill.style.transform = 'scaleX(0)';
  }

  btn.addEventListener('click', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    fail();
  });

  var autoTimer = null;
  var stage = 0;
  function autoTick() {
    if (locked) return;
    if (stage >= 4) { reset(); stage = 0; return; }
    fail();
    stage += 1;
  }
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoTimer = setInterval(autoTick, 260); }
})();

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

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

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

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const btn = root.querySelector(`.${styles.btn}`) as HTMLButtonElement | null;
    const failsEl = root.querySelector(`.${styles.fails}`) as HTMLElement | null;
    const waitEl = root.querySelector(`.${styles.wait}`) as HTMLElement | null;
    const fill = root.querySelector(`.${styles.fill}`) as HTMLElement | null;
    if (!btn || !failsEl || !waitEl || !fill) return;

    // 상수: 지수 백오프 = BACKOFF_BASE_SEC × 2^실패횟수(초), CAP_SEC 에서 증가를 멈춘다
    const BACKOFF_BASE_SEC = 1;
    const CAP_SEC = 16;
    const DEMO_TICK_MS = 90;

    let fails = 0;
    let locked = false;
    let rafId: number | null = null;

    function waitSecondsOf(n: number) {
      return Math.min(CAP_SEC, BACKOFF_BASE_SEC * Math.pow(2, n));
    }

    function countdown(totalSec: number) {
      locked = true;
      btn!.disabled = true;
      let start: number | null = null;
      const totalMs = totalSec * DEMO_TICK_MS;
      function frame(ts: number) {
        if (start === null) start = ts;
        const elapsed = ts - start;
        const left = Math.max(0, totalSec - elapsed / DEMO_TICK_MS);
        waitEl!.textContent = "다음 시도까지 " + Math.ceil(left) + "초";
        fill!.style.transform = "scaleX(" + Math.max(0, left / totalSec) + ")";
        if (elapsed < totalMs) { rafId = requestAnimationFrame(frame); }
        else {
          waitEl!.textContent = "대기 없음";
          fill!.style.transform = "scaleX(0)";
          locked = false;
          btn!.disabled = false;
        }
      }
      rafId = requestAnimationFrame(frame);
    }

    function fail() {
      if (locked) return;
      fails += 1;
      failsEl!.textContent = String(fails);
      countdown(waitSecondsOf(fails));
    }

    function reset() {
      if (rafId !== null) cancelAnimationFrame(rafId);
      fails = 0;
      locked = false;
      btn!.disabled = false;
      failsEl!.textContent = "0";
      waitEl!.textContent = "대기 없음";
      fill!.style.transform = "scaleX(0)";
    }

    function onClick() {
      root!.classList.remove(styles["is-demo"]);
      stopAutoplay();
      fail();
    }
    btn.addEventListener("click", onClick);

    let autoTimer: number | null = null;
    let stage = 0;
    function autoTick() {
      if (locked) return;
      if (stage >= 4) { reset(); stage = 0; return; }
      fail();
      stage += 1;
    }
    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, 260); }

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

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.abt} ${styles["is-demo"]}`}>
      <div className={styles.card}>
        <div className={styles.row}>
          <span className={styles.label}>실패 <b className={styles.fails}>0</b>회</span>
          <span className={styles.wait}>대기 없음</span>
        </div>
        <div className={styles.track}><div className={styles.fill} /></div>
        <button className={styles.btn} type="button">로그인 시도</button>
      </div>
    </div>
  );
}