09Pill loader button

<main class="stage is-demo">
  <button class="btn" type="button">
    <span class="btn__label">Send file</span>
    <span class="btn__loader" aria-hidden="true">
      <span class="btn__track"><span class="btn__bar"></span></span>
    </span>
  </button>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-loop;     // 2s — 기다림 한 주기
$easing: ease-in-out;
$color: $subject-blue;    // 버튼 색
$busy: #6f67b4;           // 기다리는 동안 잠기는 진한 색

@include stage($stage-ink);

.btn {
  box-sizing: border-box;
  position: relative;
  width: 240px;
  height: 64px;
  border: none;
  border-radius: $r-pill;
  background: $color;
  color: $subject-cream;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 700;
  font-size: 17px;
  cursor: pointer;
  transition: background-color $dur-quick $easing;
}

.btn__label {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
}

// 로더 — 라벨이 사라진 자리에 나타난다
.btn__loader {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  opacity: 0;
}
.btn__track {
  position: relative;
  width: 168px;                 // 버튼의 70%
  height: 8px;
  border-radius: $r-pill;
  background: rgba($subject-cream, .25);
  overflow: hidden;
}
.btn__bar {
  position: absolute;
  top: 0; bottom: 0;
  width: 60px;
  border-radius: $r-pill;
  background: $subject-cream;
  transform: translateX(-60px);
}

// 실사용: 보내는 동안 is-busy 클래스를 붙인다
.btn.is-busy { background: $busy; }
.btn.is-busy .btn__label   { opacity: 0; }
.btn.is-busy .btn__loader  { opacity: 1; }
.btn__label, .btn__loader  { transition: opacity $dur-quick $easing; }
.btn.is-busy .btn__bar     { animation: bar-run 1s $easing infinite; }

.btn:focus-visible { outline: 3px solid $stage-yellow; outline-offset: 4px; }

// 격자 미리보기: 라벨 사라짐 → 잠김 → 막대 두 번 왕복 → 복귀
.stage.is-demo .btn          { animation: busy-bg $duration $easing infinite; }
.stage.is-demo .btn__label   { animation: label-out $duration $easing infinite; }
.stage.is-demo .btn__loader  { animation: loader-in $duration $easing infinite; }
.stage.is-demo .btn__bar     { animation: bar-run 1s $easing infinite; }

@keyframes busy-bg {
  0%, 15%   { background: $color; }
  25%, 85%  { background: $busy; }
  95%,100%  { background: $color; }
}
@keyframes label-out {
  0%, 15%   { opacity: 1; }
  25%, 85%  { opacity: 0; }
  95%,100%  { opacity: 1; }
}
@keyframes loader-in {
  0%, 15%   { opacity: 0; }
  25%, 85%  { opacity: 1; }
  95%,100%  { opacity: 0; }
}
@keyframes bar-run {
  0%   { transform: translateX(-60px); }
  100% { transform: translateX(168px); }
}

@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .btn, .stage.is-demo .btn__label,
  .stage.is-demo .btn__loader, .stage.is-demo .btn__bar { animation: none; }
  .stage.is-demo .btn__bar { transform: translateX(54px); }   // 가운데 정지
}

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);
}

.btn {
  box-sizing: border-box;
  position: relative;
  width: 240px;
  height: 64px;
  border: none;
  border-radius: 999px;
  background: #2f6df6;
  color: #fff7e6;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 700;
  font-size: 17px;
  cursor: pointer;
  transition: background-color 220ms ease-in-out;
}

.btn__label {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
}

.btn__loader {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  opacity: 0;
}

.btn__track {
  position: relative;
  width: 168px;
  height: 8px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.25);
  overflow: hidden;
}

.btn__bar {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 60px;
  border-radius: 999px;
  background: #fff7e6;
  transform: translateX(-60px);
}

.btn.is-busy {
  background: #6f67b4;
}

.btn.is-busy .btn__label {
  opacity: 0;
}

.btn.is-busy .btn__loader {
  opacity: 1;
}

.btn__label, .btn__loader {
  transition: opacity 220ms ease-in-out;
}

.btn.is-busy .btn__bar {
  animation: bar-run 1s ease-in-out infinite;
}

.btn:focus-visible {
  outline: 3px solid #ffd23f;
  outline-offset: 4px;
}

.stage.is-demo .btn {
  animation: busy-bg 2s ease-in-out infinite;
}

.stage.is-demo .btn__label {
  animation: label-out 2s ease-in-out infinite;
}

.stage.is-demo .btn__loader {
  animation: loader-in 2s ease-in-out infinite;
}

.stage.is-demo .btn__bar {
  animation: bar-run 1s ease-in-out infinite;
}

@keyframes busy-bg {
  0%, 15% {
    background: #2f6df6;
  }
  25%, 85% {
    background: #6f67b4;
  }
  95%, 100% {
    background: #2f6df6;
  }
}
@keyframes label-out {
  0%, 15% {
    opacity: 1;
  }
  25%, 85% {
    opacity: 0;
  }
  95%, 100% {
    opacity: 1;
  }
}
@keyframes loader-in {
  0%, 15% {
    opacity: 0;
  }
  25%, 85% {
    opacity: 1;
  }
  95%, 100% {
    opacity: 0;
  }
}
@keyframes bar-run {
  0% {
    transform: translateX(-60px);
  }
  100% {
    transform: translateX(168px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .btn, .stage.is-demo .btn__label,
  .stage.is-demo .btn__loader, .stage.is-demo .btn__bar {
    animation: none;
  }
  .stage.is-demo .btn__bar {
    transform: translateX(54px);
  }
}

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

export type PillLoaderButtonProps = {
  duration?: number;
  easing?: string;
  color?: string;
  busyColor?: string;
  busy?: boolean;
  label?: string;
};

export default function PillLoaderButton({
  duration = 1000,
  easing = "ease-in-out",
  color = "#2f6df6",
  busyColor = "#3a2bb8",
  busy = false,
  label = "파일 보내기",
}: PillLoaderButtonProps) {
  const vars: CSSProperties = {
    "--duration": `${duration}ms`,
    "--easing": easing,
    "--color": color,
    "--busy": busyColor,
  } as CSSProperties;
  return (
    <button className={styles.btn} style={vars} data-busy={busy || undefined} type="button">
      <span className={styles.label}>{label}</span>
      <span className={styles.loader} aria-hidden="true">
        <span className={styles.track}><span className={styles.bar} /></span>
      </span>
    </button>
  );
}