08줄이 넘치면 「+N」으로 접는 칩 입력

<main class="stage">
<div class="ov is-demo" id="ov">
  <div class="ov__viewport" id="ovViewport">
    <div class="ov__row" id="ovRow" role="list" aria-label="태그 목록, 좁아지면 접힘">
      <span class="ov__chip" role="listitem">기획</span>
      <span class="ov__chip" role="listitem">디자인</span>
      <span class="ov__chip" role="listitem">개발</span>
      <span class="ov__chip" role="listitem">QA</span>
      <span class="ov__chip" role="listitem">마케팅</span>
      <span class="ov__chip" role="listitem">영업</span>
      <span class="ov__badge" id="ovBadge" role="listitem">+0</span>
    </div>
  </div>
  <p class="ov__meta">폭 <b id="ovWidth">0</b>px · 접힌 태그 <b id="ovHidden">0</b>개</p>
  <p class="ov__sr" role="status" aria-live="polite" id="ovLive"></p>
</div>
</main>

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

// 계산 겹: relayout() 이 뷰포트 폭을 칩 누적 너비합 + 배지 예약폭과 매 프레임(리사이즈 중) 비교해
// 넘치는 지점부터 칩을 감추고 감춘 개수를 배지에 적는다. 뷰포트는 max-width 로 좁아졌다 넓어졌다 한다.
@include stage($stage-paper);

.ov { width: min(100%, 320px); display: flex; flex-direction: column; gap: $sp-2; }
.ov__viewport {
  max-width: 280px; overflow: hidden;
  transition: max-width $dur-enter $ease-spring;
  border: 1px solid rgba($subject-ink, .16); border-radius: $r-control;
  padding: $sp-2 $sp-3; cursor: pointer;
}
.ov__viewport--narrow { max-width: 130px; }

.ov__row { display: flex; flex-wrap: nowrap; align-items: center; gap: $sp-2; }
.ov__chip {
  flex: 0 0 auto;
  display: inline-flex; align-items: center; height: 24px; padding: 0 $sp-3;
  background: $subject-blue-deep; color: $subject-cream; border-radius: $r-pill;
  font-size: 12px; font-weight: 700; white-space: nowrap;
}
.ov__badge {
  flex: 0 0 auto;
  display: inline-flex; align-items: center; height: 24px; padding: 0 $sp-3;
  background: $subject-ink; color: $subject-cream; border-radius: $r-pill;
  font-size: 12px; font-weight: 700; white-space: nowrap;
  transform: scale(.4); opacity: 0;
  transition: transform $dur-quick $ease-spring, opacity $dur-quick $ease-out;
}
.ov__badge--show { transform: scale(1); opacity: 1; }

.ov__meta { margin: 0; font-size: 11px; color: rgba($subject-ink, .72); }
.ov__meta b { color: $subject-ink; font-weight: 700; }
.ov__sr {
  position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); margin: -1px; padding: 0; border: 0;
}

@media (max-width: 340px) {
  .ov { width: 100%; }
  .ov__viewport { max-width: 100%; }
  .ov__viewport--narrow { max-width: 130px; }
}

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

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);
}

.ov {
  width: min(100%, 320px);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.ov__viewport {
  max-width: 280px;
  overflow: hidden;
  transition: max-width 600ms cubic-bezier(0.2, 0.8, 0.2, 1);
  border: 1px solid rgba(23, 20, 26, 0.16);
  border-radius: 12px;
  padding: 8px 12px;
  cursor: pointer;
}

.ov__viewport--narrow {
  max-width: 130px;
}

.ov__row {
  display: flex;
  flex-wrap: nowrap;
  align-items: center;
  gap: 8px;
}

.ov__chip {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  height: 24px;
  padding: 0 12px;
  background: #0a4fe8;
  color: #fff7e6;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
  white-space: nowrap;
}

.ov__badge {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  height: 24px;
  padding: 0 12px;
  background: #17141a;
  color: #fff7e6;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
  white-space: nowrap;
  transform: scale(0.4);
  opacity: 0;
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1), opacity 220ms ease-out;
}

.ov__badge--show {
  transform: scale(1);
  opacity: 1;
}

.ov__meta {
  margin: 0;
  font-size: 11px;
  color: rgba(23, 20, 26, 0.72);
}

.ov__meta b {
  color: #17141a;
  font-weight: 700;
}

.ov__sr {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  margin: -1px;
  padding: 0;
  border: 0;
}

@media (max-width: 340px) {
  .ov {
    width: 100%;
  }
  .ov__viewport {
    max-width: 100%;
  }
  .ov__viewport--narrow {
    max-width: 130px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ov__viewport {
    transition: none;
  }
  .ov__badge {
    transition: none;
  }
}

(function () {
  var BADGE_RESERVE = 34; // 계산 겹 상수: 배지 자리 예약폭(px) — 실측 렌더폭 기준 어림
  var GAP = 8;
  var WIDE_MS = 900, NARROW_MS = 900, PAUSE_MS = 500;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var root = document.getElementById('ov');
  var viewport = document.getElementById('ovViewport');
  var row = document.getElementById('ovRow');
  var badge = document.getElementById('ovBadge');
  var widthEl = document.getElementById('ovWidth');
  var hiddenEl = document.getElementById('ovHidden');
  var live = document.getElementById('ovLive');

  function human() { if (root.classList.contains('is-demo')) root.classList.remove('is-demo'); }

  // 계산 겹: 뷰포트 폭을 칩들의 누적 너비합과 계속 비교해, 다음 칩(+배지 자리)이 넘치는 지점부터 감춘다.
  function relayout() {
    var chips = Array.prototype.slice.call(row.querySelectorAll('.ov__chip'));
    var containerWidth = viewport.getBoundingClientRect().width;
    var sum = 0, shown = 0;
    for (var i = 0; i < chips.length; i++) {
      chips[i].style.display = '';
    }
    for (i = 0; i < chips.length; i++) {
      var w = chips[i].getBoundingClientRect().width;
      var addGap = shown > 0 ? GAP : 0;
      var withThis = sum + addGap + w;
      var remaining = chips.length - (i + 1);
      var reserve = remaining > 0 ? GAP + BADGE_RESERVE : 0;
      if (withThis + reserve <= containerWidth) { sum = withThis; shown++; }
      else { break; }
    }
    for (var j = shown; j < chips.length; j++) { chips[j].style.display = 'none'; }
    var hidden = chips.length - shown;
    if (hidden > 0) {
      badge.textContent = '+' + hidden;
      badge.classList.add('ov__badge--show');
    } else {
      badge.classList.remove('ov__badge--show');
    }
    widthEl.textContent = Math.round(containerWidth);
    hiddenEl.textContent = hidden;
    live.textContent = hidden > 0 ? hidden + '개 태그 접힘' : '전체 표시';
  }

  var ro = window.ResizeObserver ? new ResizeObserver(function () { relayout(); }) : null;
  if (ro) ro.observe(viewport);

  var timer = 0, rafId = 0;
  function schedule(fn, ms) { timer = window.setTimeout(fn, ms); }

  function pollDuring(ms, cb) {
    var t0 = null;
    function step(ts) {
      if (!root.classList.contains('is-demo')) return;
      if (t0 === null) t0 = ts;
      relayout();
      if (ts - t0 < ms) { rafId = requestAnimationFrame(step); } else { relayout(); cb(); }
    }
    rafId = requestAnimationFrame(step);
  }

  function loop() {
    if (!root.classList.contains('is-demo')) return;
    viewport.classList.add('ov__viewport--narrow');
    pollDuring(NARROW_MS, function () {
      schedule(function () {
        if (!root.classList.contains('is-demo')) return;
        viewport.classList.remove('ov__viewport--narrow');
        pollDuring(WIDE_MS, function () { schedule(loop, PAUSE_MS); });
      }, PAUSE_MS);
    });
  }

  viewport.addEventListener('click', function () { human(); viewport.classList.toggle('ov__viewport--narrow'); relayout(); });
  window.addEventListener('resize', relayout);

  relayout();
  if (!reduce) {
    schedule(loop, 300);
  } else {
    root.classList.remove('is-demo');
  }
})();

// TagOverflowRowCollapse — vanilla 판(run/397/demo/08-tag-input-overflow-row-collapse/index.html) 의 React 포트.
// 계산 겹(뷰포트 폭 대 칩 누적 너비합 + 배지 예약폭 비교)은 vanilla 와 같은 값.
import { useEffect, useRef, useState } from "react";
import styles from "./TagOverflowRowCollapse.module.scss";

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

const BADGE_RESERVE = 34; // 계산 겹 상수: 배지 자리 예약폭(px)
const GAP = 8;
const WORDS = ["기획", "디자인", "개발", "QA", "마케팅", "영업"];
const WIDE_MS = 900, NARROW_MS = 900, PAUSE_MS = 500;

export default function TagOverflowRowCollapse() {
  const viewportRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const rowRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const isDemoRef = useRef(true) as unknown as Box<boolean>;
  const timerRef = useRef(0) as unknown as Box<number>;
  const rafRef = useRef(0) as unknown as Box<number>;

  const [isDemo, setIsDemo] = useState(true);
  const [narrow, setNarrow] = useState(false);
  const [width, setWidth] = useState(0);
  const [hidden, setHidden] = useState(0);
  const [visibleCount, setVisibleCount] = useState(WORDS.length);
  const [live, setLive] = useState("");

  function human() {
    if (isDemoRef.current) { isDemoRef.current = false; setIsDemo(false); }
  }

  function relayout() {
    const viewport = viewportRef.current;
    const row = rowRef.current;
    if (!viewport || !row) return;
    const chips = Array.prototype.slice.call(row.querySelectorAll("[data-chip]")) as HTMLElement[];
    const containerWidth = viewport.getBoundingClientRect().width;
    let sum = 0, shown = 0;
    for (let i = 0; i < chips.length; i++) {
      const w = chips[i].getBoundingClientRect().width;
      const addGap = shown > 0 ? GAP : 0;
      const withThis = sum + addGap + w;
      const remaining = chips.length - (i + 1);
      const reserve = remaining > 0 ? GAP + BADGE_RESERVE : 0;
      if (withThis + reserve <= containerWidth) { sum = withThis; shown++; } else break;
    }
    setVisibleCount(shown);
    setWidth(Math.round(containerWidth));
    setHidden(chips.length - shown);
    setLive(chips.length - shown > 0 ? (chips.length - shown) + "개 태그 접힘" : "전체 표시");
  }

  useEffect(() => {
    relayout();
    const ro = window.ResizeObserver ? new ResizeObserver(() => relayout()) : null;
    if (ro && viewportRef.current) ro.observe(viewportRef.current);
    window.addEventListener("resize", relayout);
    return () => { if (ro) ro.disconnect(); window.removeEventListener("resize", relayout); };
  }, [narrow]);

  useEffect(() => {
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    function pollDuring(ms: number, cb: () => void) {
      let t0 = 0;
      function step(ts: number) {
        if (!isDemoRef.current) return;
        if (!t0) t0 = ts;
        relayout();
        if (ts - t0 < ms) { rafRef.current = requestAnimationFrame(step); } else { relayout(); cb(); }
      }
      rafRef.current = requestAnimationFrame(step);
    }

    function loop() {
      if (!isDemoRef.current) return;
      setNarrow(true);
      pollDuring(NARROW_MS, () => {
        timerRef.current = window.setTimeout(() => {
          if (!isDemoRef.current) return;
          setNarrow(false);
          pollDuring(WIDE_MS, () => { timerRef.current = window.setTimeout(loop, PAUSE_MS); });
        }, PAUSE_MS);
      });
    }

    if (!reduce) {
      timerRef.current = window.setTimeout(loop, 300);
    } else {
      isDemoRef.current = false;
      setIsDemo(false);
    }
    return () => { window.clearTimeout(timerRef.current); cancelAnimationFrame(rafRef.current); };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  function onClick() {
    human();
    setNarrow((n) => !n);
  }

  return (
    <main className={styles.stage}>
      <div className={styles.ov + " " + (isDemo ? styles.isDemo : "")}>
        <div
          className={styles.viewport + " " + (narrow ? styles.viewportNarrow : "")}
          ref={viewportRef} onClick={onClick}
        >
          <div className={styles.row} ref={rowRef} role="list" aria-label="태그 목록, 좁아지면 접힘">
            {WORDS.map((w, i) => (
              <span key={w + i} data-chip className={styles.chip + " " + (i >= visibleCount ? styles.chipHidden : "")} role="listitem">{w}</span>
            ))}
            <span className={styles.badge + " " + (hidden > 0 ? styles.badgeShow : "")} role="listitem">{"+" + hidden}</span>
          </div>
        </div>
        <p className={styles.meta}>폭 <b>{width}</b>px · 접힌 태그 <b>{hidden}</b>개</p>
        <p className={styles.sr} role="status">{live}</p>
      </div>
    </main>
  );
}