06Indeterminate bar

<main class="stage">
  <div class="track" role="progressbar" aria-label="Loading">
    <span class="seg seg--a is-demo"></span>
    <span class="seg seg--b is-demo"></span>
  </div>
  <p class="cap">Loading</p>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: 1.6s;                                  // 긴 조각 하나가 지나가는 시간
$easing: cubic-bezier(.4, 0, .2, 1);
$color: $subject-ink;                             // 조각 색

@include stage($stage-yellow);

// 진행률을 모르므로 aria-valuenow 를 주지 않는다 (ARIA 명세: 불확정 progressbar 는 값 속성을 뺀다)
.track {
  position: relative;
  width: clamp(200px, 58vw, 280px);
  height: 8px;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .12);
  overflow: hidden;
}
.seg {
  position: absolute;
  inset: 0;                                       // 폭을 꽉 채운 뒤 transform 으로만 밀고 줄인다 (width 는 건드리지 않는다)
  border-radius: inherit;
  background: $color;
  transform-origin: left center; // 규칙8: 좌변 기준 이동·신축
}
// 짧은 바 하나가 오가는 대신, 길이가 다른 두 조각이 시간차를 두고 서로 겹쳐 지나간다 (머티리얼 디자인 방식)
.seg--a.is-demo { animation: seg-a $duration $easing infinite; }
.seg--b.is-demo { animation: seg-b $duration $easing infinite; animation-delay: $duration * .35; }

@keyframes seg-a {
  0%   { transform: translateX(-100%) scaleX(.15); }
  55%  { transform: translateX(30%)   scaleX(.7); }
  100% { transform: translateX(120%)  scaleX(.15); }
}
@keyframes seg-b {
  0%   { transform: translateX(-140%) scaleX(.1); }
  60%  { transform: translateX(10%)   scaleX(.4); }
  100% { transform: translateX(120%)  scaleX(.1); }
}

.cap {
  margin: 14px 0 0;
  color: rgba(23, 20, 26, .75);
  font: 600 clamp(12px, 3.2vw, 14px)/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

@media (prefers-reduced-motion: reduce) {
  .seg.is-demo { animation: none; transform: translateX(0) scaleX(.4); opacity: .7; }
}

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);
}

.track {
  position: relative;
  width: clamp(200px, 58vw, 280px);
  height: 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.12);
  overflow: hidden;
}

.seg {
  position: absolute;
  inset: 0;
  border-radius: inherit;
  background: #17141a;
  transform-origin: left center;
}

.seg--a.is-demo {
  animation: seg-a 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
}

.seg--b.is-demo {
  animation: seg-b 1.6s cubic-bezier(0.4, 0, 0.2, 1) infinite;
  animation-delay: 0.56s;
}

@keyframes seg-a {
  0% {
    transform: translateX(-100%) scaleX(0.15);
  }
  55% {
    transform: translateX(30%) scaleX(0.7);
  }
  100% {
    transform: translateX(120%) scaleX(0.15);
  }
}
@keyframes seg-b {
  0% {
    transform: translateX(-140%) scaleX(0.1);
  }
  60% {
    transform: translateX(10%) scaleX(0.4);
  }
  100% {
    transform: translateX(120%) scaleX(0.1);
  }
}
.cap {
  margin: 14px 0 0;
  color: rgba(23, 20, 26, 0.75);
  font: 600 clamp(12px, 3.2vw, 14px)/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

@media (prefers-reduced-motion: reduce) {
  .seg.is-demo {
    animation: none;
    transform: translateX(0) scaleX(0.4);
    opacity: 0.7;
  }
}

import type { CSSProperties } from "react";
import styles from "./IndeterminateBar.module.scss";

export type IndeterminateBarProps = {
  duration?: number;
  easing?: string;
  color?: string;
  /** 진행률을 모르므로 값이 아니라 상태만 알린다 */
  label?: string;
};

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

export default function IndeterminateBar({
  duration = 1600,
  easing = "cubic-bezier(.4,0,.2,1)",
  color = "#17141a",
  label = "Loading",
}: IndeterminateBarProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <div className={styles.track} style={vars} role="progressbar" aria-label={label}>
      <span className={`${styles.seg} ${styles.a}`} />
      <span className={`${styles.seg} ${styles.b}`} />
    </div>
  );
}