02Skeleton Rows for the First List Load

<main class="stage">
<div class="skl is-demo" id="skl">
  <ul class="skl__list" id="sklList" aria-busy="true">
    <li class="skl__row" data-row="0">
      <span class="skl__bar" data-bar></span>
      <span class="skl__content" data-content hidden></span>
    </li>
    <li class="skl__row" data-row="1">
      <span class="skl__bar" data-bar></span>
      <span class="skl__content" data-content hidden></span>
    </li>
    <li class="skl__row" data-row="2">
      <span class="skl__bar" data-bar></span>
      <span class="skl__content" data-content hidden></span>
    </li>
    <li class="skl__row" data-row="3">
      <span class="skl__bar" data-bar></span>
      <span class="skl__content" data-content hidden></span>
    </li>
    <li class="skl__row" data-row="4">
      <span class="skl__bar" data-bar></span>
      <span class="skl__content" data-content hidden></span>
    </li>
  </ul>
  <button class="skl__reload" id="sklReload" type="button">Reload</button>
</div>
</main>

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

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

// 계산 겹: index.html 이 캔버스 measureText 로 잰 실제 글자 폭 비율을
// --bar-w 로 각 막대에 주입한다 — 막대 폭이 내용 길이를 미리 반영한다.
@include stage($stage-ink);

.skl {
  width: min(100%, 280px);
  display: flex;
  flex-direction: column;
  gap: $sp-3;
  align-items: center;
}

.skl__list {
  box-sizing: border-box;
  width: 100%;
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: $sp-2;
}

.skl__row {
  box-sizing: border-box;
  position: relative;
  height: 32px;
  padding: 0 $sp-3;
  border-radius: $r-sm;
  background: rgba(255, 255, 255, .06);
  display: flex;
  align-items: center;
}

.skl__bar {
  --bar-w: 60%;
  position: relative;
  overflow: hidden;
  display: block;
  width: var(--bar-w);
  height: 10px;
  border-radius: $r-xs;
  background: rgba(255, 255, 255, .14);

  &::after {
    content: "";
    position: absolute;
    inset: 0;
    background: linear-gradient(90deg, transparent, rgba($color, .5), transparent);
    transform: translateX(-140%);
    animation-name: sklShimmer;
    animation-duration: $duration;
    animation-timing-function: $easing;
    animation-iteration-count: infinite;
  }
}

.skl__content {
  color: $stage-paper;
  font-weight: 600;
  font-size: 12px;
}

.skl__row.is-loaded {
  .skl__bar { display: none; }

  .skl__content {
    animation-name: sklRowIn;
    animation-duration: $dur-base;
    animation-timing-function: $easing;
    animation-fill-mode: backwards;
  }
}

@keyframes sklShimmer {
  to { transform: translateX(140%); }
}

@keyframes sklRowIn {
  from { opacity: 0; transform: translateY($sp-2); }
  to { opacity: 1; transform: translateY(0); }
}

.skl__reload {
  box-sizing: border-box;
  border: 0;
  border-radius: $r-pill;
  padding: $sp-2 $sp-4;
  background: rgba(255, 255, 255, .1);
  color: $stage-paper;
  font-weight: 600;
  font-size: 12px;
  cursor: pointer;

  &:focus-visible {
    outline: 2px solid $color;
    outline-offset: 2px;
  }
}

@media (max-width: 340px) {
  .skl { gap: $sp-2; }
  .skl__list { gap: $sp-1; }
  .skl__row { height: 20px; padding: 0 $sp-1; }
  .skl__content { font-size: 11px; }
  .skl__reload { padding: $sp-1 $sp-3; }
}

// reduce: 실사용 경로 적용 — 스침·등장 트윈만 멈춘다. 로딩 완료 상태 자체는 그대로 보인다
@media (prefers-reduced-motion: reduce) {
  .skl__bar::after { animation: none; opacity: .5; transform: translateX(0); }
  .skl__row.is-loaded .skl__content { animation: 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);
}

.skl {
  width: min(100%, 280px);
  display: flex;
  flex-direction: column;
  gap: 12px;
  align-items: center;
}

.skl__list {
  box-sizing: border-box;
  width: 100%;
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.skl__row {
  box-sizing: border-box;
  position: relative;
  height: 32px;
  padding: 0 12px;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.06);
  display: flex;
  align-items: center;
}

.skl__bar {
  --bar-w: 60%;
  position: relative;
  overflow: hidden;
  display: block;
  width: var(--bar-w);
  height: 10px;
  border-radius: 4px;
  background: rgba(255, 255, 255, 0.14);
}
.skl__bar::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg, transparent, rgba(76, 212, 166, 0.5), transparent);
  transform: translateX(-140%);
  animation-name: sklShimmer;
  animation-duration: 220ms;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

.skl__content {
  color: #ffffff;
  font-weight: 600;
  font-size: 12px;
}

.skl__row.is-loaded .skl__bar {
  display: none;
}
.skl__row.is-loaded .skl__content {
  animation-name: sklRowIn;
  animation-duration: 300ms;
  animation-timing-function: ease-out;
  animation-fill-mode: backwards;
}

@keyframes sklShimmer {
  to {
    transform: translateX(140%);
  }
}
@keyframes sklRowIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}
.skl__reload {
  box-sizing: border-box;
  border: 0;
  border-radius: 999px;
  padding: 8px 16px;
  background: rgba(255, 255, 255, 0.1);
  color: #ffffff;
  font-weight: 600;
  font-size: 12px;
  cursor: pointer;
}
.skl__reload:focus-visible {
  outline: 2px solid #4cd4a6;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .skl {
    gap: 8px;
  }
  .skl__list {
    gap: 4px;
  }
  .skl__row {
    height: 20px;
    padding: 0 4px;
  }
  .skl__content {
    font-size: 11px;
  }
  .skl__reload {
    padding: 4px 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .skl__bar::after {
    animation: none;
    opacity: 0.5;
    transform: translateX(0);
  }
  .skl__row.is-loaded .skl__content {
    animation: none;
  }
}

(function () {
  var ROWS = [
    'H1 growth report summary',
    'New signup trend graph',
    'Top-selling items this quarter',
    'Customer satisfaction survey results',
    'Low-stock item alert'
  ];
  var CYCLE_MS = 2000; // 캡처 창(2초)의 배수 — 스켈레톤/로딩완료 상태를 오가는 한 사이클
  var LOAD_POINT = 0.45; // 사이클 중 로딩 완료로 전환되는 지점
  var RESET_POINT = 0.96; // 이 지점부터 다시 스켈레톤으로
  var ENTER_STAGGER_MS = 70; // 행마다 등장 지연 간격
  var MIN_BAR_PCT = 32; // 막대 폭 하한(%)
  var TICK_MS = 50;

  var root = document.getElementById('skl');
  var list = document.getElementById('sklList');
  var reloadBtn = document.getElementById('sklReload');
  var rows = Array.prototype.slice.call(list.querySelectorAll('.skl__row'));

  // 계산 겹: 각 행이 로딩 완료 후 실제로 보여줄 글자의 캔버스 실측 폭을 재서
  // 스켈레톤 막대 폭을 그 비율로 정한다 — 고정폭이 아니라 내용 길이를 미리 반영한다.
  function measureBarWidths() {
    var canvas = document.createElement('canvas');
    var ctx = canvas.getContext('2d');
    ctx.font = '600 13px -apple-system, "Segoe UI", "Noto Sans KR", sans-serif';
    var widths = ROWS.map(function (text) { return ctx.measureText(text).width; });
    var maxW = Math.max.apply(null, widths);
    return widths.map(function (w) {
      var pct = (w / maxW) * 100;
      return Math.max(MIN_BAR_PCT, Math.round(pct));
    });
  }

  var barPct = measureBarWidths();
  rows.forEach(function (row, i) {
    var bar = row.querySelector('[data-bar]');
    var content = row.querySelector('[data-content]');
    bar.style.setProperty('--bar-w', barPct[i] + '%');
    content.textContent = ROWS[i];
  });

  function setLoaded(loaded) {
    rows.forEach(function (row, i) {
      var content = row.querySelector('[data-content]');
      if (loaded) {
        row.classList.add('is-loaded');
        content.hidden = false;
        row.style.animationDelay = (i * ENTER_STAGGER_MS) + 'ms';
      } else {
        row.classList.remove('is-loaded');
        content.hidden = true;
        row.style.animationDelay = '';
      }
    });
    list.setAttribute('aria-busy', loaded ? 'false' : 'true');
  }

  function human() {
    if (root.classList.contains('is-demo')) {
      root.classList.remove('is-demo');
      if (timer) { window.clearInterval(timer); timer = null; }
    }
  }

  reloadBtn.addEventListener('click', function () {
    human();
    setLoaded(false);
    window.setTimeout(function () { setLoaded(true); }, 650);
  });

  var timer = null;
  var start = 0;
  var loadedState = false;

  function tick(elapsedMs) {
    var phase = (elapsedMs % CYCLE_MS) / CYCLE_MS;
    var wantLoaded = phase >= LOAD_POINT && phase < RESET_POINT;
    if (wantLoaded !== loadedState) {
      loadedState = wantLoaded;
      setLoaded(loadedState);
    }
  }

  function loop() {
    tick(performance.now() - start);
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) {
    setLoaded(false);
    start = performance.now();
    timer = window.setInterval(loop, TICK_MS);
  } else {
    // reduce: 실사용 경로 적용 — 스켈레톤 스침·등장 트윈 없이 로딩 완료 상태를 바로 보여준다
    setLoaded(true);
  }
})();

// SkeletonList — vanilla 판(run/381/demo/02-skeleton-list/index.html)의 React 포트.
// 각 행이 로딩 완료 후 실제로 보여줄 글자의 캔버스 실측 폭을 재서 스켈레톤 막대 폭을
// 그 비율로 정한다 — 고정폭이 아니라 내용 길이를 미리 반영한다.
import { useEffect, useRef } from "react";
import type { CSSProperties } from "react";
import styles from "./SkeletonList.module.scss";

export type SkeletonListProps = {
  duration?: string;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

const ROWS = [
  "상반기 성장 보고서 요약",
  "신규 가입자 추이 그래프",
  "이번 분기 매출 상위 상품",
  "고객 만족도 조사 결과",
  "재고 부족 임박 품목 알림",
];

export default function SkeletonList({
  duration = "220ms", // vanilla $duration: $dur-quick
  easing = "ease-out", // vanilla $easing: $ease-out
  color = "#4cd4a6", // vanilla $color: $subject-mint
}: SkeletonListProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const list = root.querySelector<HTMLUListElement>('[data-role="list"]');
    const reloadBtn = root.querySelector<HTMLButtonElement>('[data-role="reload"]');
    if (!list || !reloadBtn) return;
    const rows = Array.prototype.slice.call(list.querySelectorAll("[data-row]")) as HTMLLIElement[];

    const CYCLE_MS = 2000; // 캡처 창(2초)의 배수 — 스켈레톤/로딩완료 상태를 오가는 한 사이클
    const LOAD_POINT = 0.45; // 사이클 중 로딩 완료로 전환되는 지점
    const RESET_POINT = 0.96; // 이 지점부터 다시 스켈레톤으로
    const ENTER_STAGGER_MS = 70; // 행마다 등장 지연 간격
    const MIN_BAR_PCT = 32; // 막대 폭 하한(%)
    const TICK_MS = 50;

    // 계산 겹: 각 행이 로딩 완료 후 실제로 보여줄 글자의 캔버스 실측 폭을 재서
    // 스켈레톤 막대 폭을 그 비율로 정한다 — 고정폭이 아니라 내용 길이를 미리 반영한다.
    function measureBarWidths(): number[] {
      const canvas = document.createElement("canvas");
      const ctx = canvas.getContext("2d")!;
      ctx.font = '600 13px -apple-system, "Segoe UI", "Noto Sans KR", sans-serif';
      const widths = ROWS.map((text) => ctx.measureText(text).width);
      const maxW = Math.max.apply(null, widths);
      return widths.map((w) => {
        const pct = (w / maxW) * 100;
        return Math.max(MIN_BAR_PCT, Math.round(pct));
      });
    }

    const barPct = measureBarWidths();
    rows.forEach((row, i) => {
      const bar = row.querySelector<HTMLSpanElement>("[data-bar]");
      const content = row.querySelector<HTMLSpanElement>("[data-content]");
      if (!bar || !content) return;
      bar.style.setProperty("--bar-w", barPct[i] + "%");
      content.textContent = ROWS[i];
    });

    function setLoaded(loaded: boolean): void {
      rows.forEach((row, i) => {
        const content = row.querySelector<HTMLSpanElement>("[data-content]");
        if (!content) return;
        if (loaded) {
          row.classList.add("is-loaded");
          content.hidden = false;
          row.style.animationDelay = i * ENTER_STAGGER_MS + "ms";
        } else {
          row.classList.remove("is-loaded");
          content.hidden = true;
          row.style.animationDelay = "";
        }
      });
      list!.setAttribute("aria-busy", loaded ? "false" : "true");
    }

    function human(): void {
      if (root!.classList.contains("is-demo")) {
        root!.classList.remove("is-demo");
        if (timer) {
          window.clearInterval(timer);
          timer = null;
        }
      }
    }

    function onReload(): void {
      human();
      setLoaded(false);
      window.setTimeout(() => {
        setLoaded(true);
      }, 650);
    }
    reloadBtn.addEventListener("click", onReload);

    let timer: number | null = null;
    let start = 0;
    let loadedState = false;

    function tick(elapsedMs: number): void {
      const phase = (elapsedMs % CYCLE_MS) / CYCLE_MS;
      const wantLoaded = phase >= LOAD_POINT && phase < RESET_POINT;
      if (wantLoaded !== loadedState) {
        loadedState = wantLoaded;
        setLoaded(loadedState);
      }
    }

    function loop(): void {
      tick(performance.now() - start);
    }

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) {
      setLoaded(false);
      start = performance.now();
      timer = window.setInterval(loop, TICK_MS);
    } else {
      // reduce: 실사용 경로 적용 — 스켈레톤 스침·등장 트윈 없이 로딩 완료 상태를 바로 보여준다
      setLoaded(true);
    }

    return () => {
      reloadBtn.removeEventListener("click", onReload);
      if (timer) {
        window.clearInterval(timer);
      }
    };
  }, []);

  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  return (
    <main className={styles.stage}>
      <div className={`${styles.skl} is-demo`} ref={rootRef} style={vars}>
        <ul className={styles.skl__list} data-role="list" aria-busy="true">
          {ROWS.map((_, i) => (
            <li className={styles.skl__row} data-row={i} key={i}>
              <span className={styles.skl__bar} data-bar />
              <span className={styles.skl__content} data-content hidden />
            </li>
          ))}
        </ul>
        <button type="button" className={styles.skl__reload} data-role="reload">
          다시 불러오기
        </button>
      </div>
    </main>
  );
}