05Thumbnail pop-in the instant the file finishes reading

<main class="stage">
<div class="tp is-demo" id="tpRoot" role="group" tabindex="0" aria-label="Image thumbnail upload">
  <label class="tp__drop" for="tpInput">
    <span class="tp__thumb" id="tpThumb" aria-hidden="true">
      <svg viewBox="0 0 256 256" width="22" height="22"><g fill="currentColor"><path d="M216 40H40a16 16 0 0 0-16 16v144a16 16 0 0 0 16 16h176a16 16 0 0 0 16-16V56a16 16 0 0 0-16-16m-72 88l-24-24-40 40h136Z" opacity=".2"/><path d="M216 40H40a16 16 0 0 0-16 16v144a16 16 0 0 0 16 16h176a16 16 0 0 0 16-16V56a16 16 0 0 0-16-16m0 16v102.75l-26.07-26.06a16 16 0 0 0-22.63 0l-20 20-44-44a16 16 0 0 0-22.63 0L40 149.37V56ZM40 172l52-52 76 76H40Zm176 28h-4.69l-40-40 20-20L216 164.69V200Z"/></g></svg>
    </span>
    <input class="tp__input" id="tpInput" type="file" accept="image/*">
    <span class="tp__hint">Click to choose an image</span>
  </label>
  <div class="tp__track">
    <span class="tp__fill" id="tpFill"></span>
  </div>
  <div class="tp__bar">
    <span class="tp__meta">FileReader · createObjectURL</span>
  </div>
</div>
</main>

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

// 썸네일 팝인(05) — 스케일 오버슈트는 토큰의 $ease-elastic(고무줄식 되돌아옴)을 그대로 쓴다.
// 실사용 경로는 .is-pop 클래스 전환(트랜지션)으로 같은 이징을 쓴다 — index.html 의 reader.onload 참고.

@include stage($stage-ink);

$tp-text: $subject-cream;
$tp-thumb: $subject-lilac;
$tp-fill: $subject-lilac;

$duration: $dur-loop;
$easing: $ease-elastic;
$color: $tp-thumb;

.tp {
  display: flex; flex-direction: column; gap: $sp-4;
  width: 100%; height: 100%; min-height: 164px;
  justify-content: center;
}
.tp:focus-visible { outline: 2px solid $tp-thumb; outline-offset: 2px; border-radius: $r-control; }

.tp__drop {
  display: flex; align-items: center; gap: $sp-3;
  cursor: pointer;
}

.tp__thumb {
  position: relative;
  flex: 0 0 auto;
  width: 48px; height: 48px;
  border-radius: $r-sm;
  background-color: rgba($tp-thumb, .16);
  background-size: cover; background-position: center;
  display: flex; align-items: center; justify-content: center;
  color: rgba($tp-thumb, .82);
  transform: scale(0);
  opacity: 0;
  transition: transform $dur-enter $ease-elastic, opacity $dur-quick $ease-out;
}
.tp__thumb.is-pop { transform: scale(1); opacity: 1; }

.tp__input {
  position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap;
}

.tp__hint {
  font-weight: 600; font-size: 11px; line-height: 1.3;
  color: rgba($tp-text, .82);
}

.tp__track {
  position: relative;
  height: $sp-2;
  border-radius: $r-pill;
  background: rgba($tp-text, .14);
  overflow: hidden;
}
.tp__fill {
  position: absolute; inset: 0;
  transform-origin: left center;
  transform: scaleX(0);
  border-radius: $r-pill;
  background: $tp-fill;
}

.tp__bar { display: flex; justify-content: flex-end; }
.tp__meta { font-weight: 500; font-size: 10px; color: rgba($tp-text, .6); }

// ── 데모 루프 — 팝인 뒤에야 바가 채워진다(신호 순서가 핵심) ──
@keyframes tpPop {
  0%, 8%  { opacity: 0; transform: scale(0); }
  14%     { opacity: 1; transform: scale(1.18); animation-timing-function: $ease-out; }
  20%     { transform: scale(1); }
  84%     { opacity: 1; transform: scale(1); }
  90%     { opacity: 0; transform: scale(.9); }
  100%    { opacity: 0; transform: scale(.9); }
}
@keyframes tpFillLoop {
  0%, 20% { transform: scaleX(0); }
  60%     { transform: scaleX(1); }
  84%     { transform: scaleX(1); }
  90%, 100% { transform: scaleX(0); }
}

.is-demo .tp__thumb {
  animation-name: tpPop;
  animation-duration: $duration;
  animation-timing-function: $ease-elastic;
  animation-iteration-count: infinite;
}
.is-demo .tp__fill {
  animation-name: tpFillLoop;
  animation-duration: $duration;
  animation-timing-function: $ease-out;
  animation-iteration-count: infinite;
}

@media (max-width: 340px) {
  .tp__thumb { width: 40px; height: 40px; }
}

@media (prefers-reduced-motion: reduce) {
  .is-demo .tp__thumb, .is-demo .tp__fill { animation: none !important; }
  .is-demo .tp__thumb { opacity: 1 !important; transform: scale(1) !important; }
  .is-demo .tp__fill { transform: scaleX(.7) !important; }
}

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);
}

.tp {
  display: flex;
  flex-direction: column;
  gap: 16px;
  width: 100%;
  height: 100%;
  min-height: 164px;
  justify-content: center;
}

.tp:focus-visible {
  outline: 2px solid #b9a0ff;
  outline-offset: 2px;
  border-radius: 12px;
}

.tp__drop {
  display: flex;
  align-items: center;
  gap: 12px;
  cursor: pointer;
}

.tp__thumb {
  position: relative;
  flex: 0 0 auto;
  width: 48px;
  height: 48px;
  border-radius: 8px;
  background-color: rgba(185, 160, 255, 0.16);
  background-size: cover;
  background-position: center;
  display: flex;
  align-items: center;
  justify-content: center;
  color: rgba(185, 160, 255, 0.82);
  transform: scale(0);
  opacity: 0;
  transition: transform 600ms cubic-bezier(0.34, 1.56, 0.64, 1), opacity 220ms ease-out;
}

.tp__thumb.is-pop {
  transform: scale(1);
  opacity: 1;
}

.tp__input {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

.tp__hint {
  font-weight: 600;
  font-size: 11px;
  line-height: 1.3;
  color: rgba(255, 247, 230, 0.82);
}

.tp__track {
  position: relative;
  height: 8px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.14);
  overflow: hidden;
}

.tp__fill {
  position: absolute;
  inset: 0;
  transform-origin: left center;
  transform: scaleX(0);
  border-radius: 999px;
  background: #b9a0ff;
}

.tp__bar {
  display: flex;
  justify-content: flex-end;
}

.tp__meta {
  font-weight: 500;
  font-size: 10px;
  color: rgba(255, 247, 230, 0.6);
}

@keyframes tpPop {
  0%, 8% {
    opacity: 0;
    transform: scale(0);
  }
  14% {
    opacity: 1;
    transform: scale(1.18);
    animation-timing-function: ease-out;
  }
  20% {
    transform: scale(1);
  }
  84% {
    opacity: 1;
    transform: scale(1);
  }
  90% {
    opacity: 0;
    transform: scale(0.9);
  }
  100% {
    opacity: 0;
    transform: scale(0.9);
  }
}
@keyframes tpFillLoop {
  0%, 20% {
    transform: scaleX(0);
  }
  60% {
    transform: scaleX(1);
  }
  84% {
    transform: scaleX(1);
  }
  90%, 100% {
    transform: scaleX(0);
  }
}
.is-demo .tp__thumb {
  animation-name: tpPop;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.34, 1.56, 0.64, 1);
  animation-iteration-count: infinite;
}

.is-demo .tp__fill {
  animation-name: tpFillLoop;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

@media (max-width: 340px) {
  .tp__thumb {
    width: 40px;
    height: 40px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .is-demo .tp__thumb, .is-demo .tp__fill {
    animation: none !important;
  }
  .is-demo .tp__thumb {
    opacity: 1 !important;
    transform: scale(1) !important;
  }
  .is-demo .tp__fill {
    transform: scaleX(0.7) !important;
  }
}

// 썸네일 팝인 — FileReader 가 dataURL 을 다 읽는 순간(onload)을 신호로 삼아
// 썸네일이 0에서 오버슈트로 커지고, 그 아래 진행 바는 그제서야 채워지기 시작한다.
(function () {
  var root  = document.getElementById('tpRoot');
  var input = document.getElementById('tpInput');
  var thumb = document.getElementById('tpThumb');
  var fill  = document.getElementById('tpFill');
  if (!root || !input || !thumb || !fill) return;

  function fillTo(pct, dur) {
    var t0 = performance.now();
    function step(now) {
      var k = Math.min(1, (now - t0) / dur);
      fill.style.transform = 'scaleX(' + (pct * k / 100) + ')';
      if (k < 1) requestAnimationFrame(step);
    }
    requestAnimationFrame(step);
  }

  input.addEventListener('change', function (e) {
    var file = e.target.files && e.target.files[0];
    if (!file) return;
    root.classList.remove('is-demo');
    var reader = new FileReader();
    reader.onload = function () {
      thumb.style.backgroundImage = 'url(' + reader.result + ')';
      thumb.classList.add('is-pop');
      fillTo(100, 900);
    };
    reader.readAsDataURL(file);
    // 더 빠른 미리보기가 필요하면 createObjectURL 로도 즉시 참조를 만들 수 있다(여기선 즉시 해제).
    var objUrl = URL.createObjectURL(file);
    URL.revokeObjectURL(objUrl);
  });
})();

// UploadProgressThumbnailPop — vanilla 판(run/329/demo/05-upload-progress-thumbnail-pop/index.html) 의 React 포트.
// FileReader 가 dataURL 을 다 읽는 순간(onload)을 신호로 삼아 썸네일이 0에서 오버슈트로 커지고,
// 그 아래 진행 바는 그제서야 채워지기 시작한다.
import { useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./UploadProgressThumbnailPop.module.scss";

export type UploadProgressThumbnailPopProps = {
  duration?: string;
  easing?: string;
  color?: string;
  fillMs?: number; // 팝인 뒤 바가 채워지는 데 걸리는 시간(ms)
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type FileEvt = { target: { files: { length: number; 0?: File } | FileList | null } };

const HINT = "클릭해 이미지 선택";
const META = "FileReader · createObjectURL";

export default function UploadProgressThumbnailPop({
  duration = "2s",
  easing = "cubic-bezier(.34,1.56,.64,1)",
  color = "#b9a0ff",
  fillMs = 900
}: UploadProgressThumbnailPopProps) {
  const [demo, setDemo] = useState(true);
  const [popped, setPopped] = useState(false);
  const [bgUrl, setBgUrl] = useState("");
  const fillRef = useRef<HTMLSpanElement | null>(null);
  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  function fillTo(pct: number, dur: number): void {
    const t0 = performance.now();
    function step(now: number): void {
      const k = Math.min(1, (now - t0) / dur);
      if (fillRef.current) fillRef.current.style.transform = "scaleX(" + (pct * k / 100) + ")";
      if (k < 1) requestAnimationFrame(step);
    }
    requestAnimationFrame(step);
  }

  function onChange(e: FileEvt): void {
    const files = e.target.files as FileList | null;
    const file = files && files[0] ? files[0] : null;
    if (!file) return;
    setDemo(false);
    const reader = new FileReader();
    reader.onload = () => {
      setBgUrl(String(reader.result));
      setPopped(true);
      fillTo(100, fillMs);
    };
    reader.readAsDataURL(file);
    // 더 빠른 미리보기가 필요하면 createObjectURL 로도 즉시 참조를 만들 수 있다(여기선 즉시 해제).
    const objUrl = URL.createObjectURL(file);
    URL.revokeObjectURL(objUrl);
  }

  const rootCls = demo ? `${styles.tp} ${styles.isDemo}` : styles.tp;
  const thumbCls = popped ? `${styles.thumb} ${styles.isPop}` : styles.thumb;

  return (
    <main className={styles.stage}>
      <div className={rootCls} style={vars} role="group" tabIndex={0} aria-label="이미지 썸네일 업로드">
        <label className={styles.drop}>
          <span
            className={thumbCls}
            aria-hidden="true"
            style={bgUrl ? { backgroundImage: `url(${bgUrl})` } : undefined}
          >
            <svg viewBox="0 0 256 256" width="22" height="22"><g fill="currentColor"><path d="M216 40H40a16 16 0 0 0-16 16v144a16 16 0 0 0 16 16h176a16 16 0 0 0 16-16V56a16 16 0 0 0-16-16m-72 88l-24-24-40 40h136Z" opacity=".2"/><path d="M216 40H40a16 16 0 0 0-16 16v144a16 16 0 0 0 16 16h176a16 16 0 0 0 16-16V56a16 16 0 0 0-16-16m0 16v102.75l-26.07-26.06a16 16 0 0 0-22.63 0l-20 20-44-44a16 16 0 0 0-22.63 0L40 149.37V56ZM40 172l52-52 76 76H40Zm176 28h-4.69l-40-40 20-20L216 164.69V200Z"/></g></svg>
          </span>
          <input className={styles.input} type="file" accept="image/*" onChange={onChange} />
          <span className={styles.hint}>{HINT}</span>
        </label>
        <div className={styles.track}>
          <span className={styles.fill} ref={fillRef}></span>
        </div>
        <div className={styles.bar}>
          <span className={styles.meta}>{META}</span>
        </div>
      </div>
    </main>
  );
}