05Read progress — a bar measuring how fast the browser itself ingests the dropped file

<main class="stage">
<div class="rp" id="rp">
  <p class="rp__hint" id="rpHint">While FileReader reads, ProgressEvent.loaded ÷ total is drawn into --p</p>
  <div class="rp__zone" id="rpZone" role="button" tabindex="0" aria-describedby="rpHint" aria-label="File dropzone">
    <input type="file" id="rpInput" class="rp__file" aria-label="Choose file">
    <svg class="rp__ic" viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M216 48v160H40V48a16 16 0 0 1 16-16h144a16 16 0 0 1 16 16" opacity=".2"/><path d="M224 144v64a8 8 0 0 1-8 8H40a8 8 0 0 1-8-8v-64a8 8 0 0 1 16 0v56h160v-56a8 8 0 0 1 16 0M93.66 77.66L120 51.31V144a8 8 0 0 0 16 0V51.31l26.34 26.35a8 8 0 0 0 11.32-11.32l-40-40a8 8 0 0 0-11.32 0l-40 40a8 8 0 0 0 11.32 11.32"/></g></svg>
  </div>
  <div class="rp__card">
    <div class="rp__row">
      <span class="rp__name" id="rpName">invoice-041.pdf</span>
      <span class="rp__pct" id="rpPct">0%</span>
    </div>
    <div class="rp__track" id="rpTrack">
      <span class="rp__bar" id="rpBar"></span>
    </div>
    <p class="rp__calc" id="rpCalc">loaded 0B ÷ total 0B</p>
  </div>
</div>
</main>

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

$duration: 240ms;      // 완료·취소 색 전환
$easing: $ease-out;
$color: $subject-blue-deep;

// 파스텔 강조(채도 .34 · 명도 +.11)
$p-sky: #d6e1eb;
$p-warn: #ebe0d6;

@include stage($stage-ink);

.rp {
  width: 100%;
  max-width: 360px;
  display: flex;
  flex-direction: column;
  gap: $sp-2;
}

.rp__hint {
  margin: 0;
  padding: 0 $sp-1;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.4;
  color: $subject-cream;
}

.rp__zone {
  position: relative;
  display: grid;
  place-items: center;
  min-height: 52px;
  padding: $sp-2 $sp-3;
  border: 2px dashed rgba($subject-cream, .72);
  border-radius: $r-card;
  cursor: pointer;
  overflow: hidden;
  transition: border-color $dur-quick $ease-out, background $dur-quick $ease-out;
}

.rp__zone.is-over {
  border-color: $p-sky;
  background: rgba(159, 201, 236, .16);
}

.rp__file {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
}

.rp__ic {
  width: 24px;
  height: 24px;
  color: $subject-cream;
  transition: transform $dur-quick $ease-pop;
}

.rp__zone.is-over .rp__ic {
  transform: scale(1.15);
}

.rp__card {
  display: flex;
  flex-direction: column;
  gap: $sp-1;
  padding: $sp-2 $sp-3;
  border-radius: $r-card;
  background: rgba($subject-cream, .1);
}

.rp__row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: $sp-2;
}

.rp__name {
  min-width: 0;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  font-weight: 700;
  font-size: 12px;
  color: $subject-cream;
}

.rp__pct {
  flex: 0 0 auto;
  font-weight: 700;
  font-size: 12px;
  color: $p-sky;
}

.rp__track {
  --p: 0;
  position: relative;
  height: 8px;
  border-radius: $r-pill;
  background: rgba($subject-cream, .18);
  overflow: hidden;
}

.rp__bar {
  display: block;
  height: 100%;
  width: calc(var(--p) * 100%);
  border-radius: $r-pill;
  background: $p-sky;
  transition: background $duration $easing;
}

.rp__bar.is-done {
  background: $subject-mint;
}

.rp__bar.is-abort {
  background: $p-warn;
}

.rp__calc {
  margin: 0;
  padding: 0 $sp-1;
  font-weight: 400;
  font-size: 10px;
  line-height: 1.4;
  color: rgba($subject-cream, .72);
}

@media (max-width: 340px) {
  .rp { max-width: 260px; }
  .rp__hint { font-size: 10px; }
  .rp__zone { min-height: 44px; }
  .rp__ic { width: 20px; height: 20px; }
  .rp__name, .rp__pct { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .rp__zone, .rp__ic { transition: none; }
  .rp__zone.is-over .rp__ic { transform: none; }
  .rp__bar { transition: 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);
}

.rp {
  width: 100%;
  max-width: 360px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.rp__hint {
  margin: 0;
  padding: 0 4px;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.4;
  color: #fff7e6;
}

.rp__zone {
  position: relative;
  display: grid;
  place-items: center;
  min-height: 52px;
  padding: 8px 12px;
  border: 2px dashed rgba(255, 247, 230, 0.72);
  border-radius: 16px;
  cursor: pointer;
  overflow: hidden;
  transition: border-color 220ms ease-out, background 220ms ease-out;
}

.rp__zone.is-over {
  border-color: #d6e1eb;
  background: rgba(159, 201, 236, 0.16);
}

.rp__file {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
}

.rp__ic {
  width: 24px;
  height: 24px;
  color: #fff7e6;
  transition: transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.rp__zone.is-over .rp__ic {
  transform: scale(1.15);
}

.rp__card {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 8px 12px;
  border-radius: 16px;
  background: rgba(255, 247, 230, 0.1);
}

.rp__row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
}

.rp__name {
  min-width: 0;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  font-weight: 700;
  font-size: 12px;
  color: #fff7e6;
}

.rp__pct {
  flex: 0 0 auto;
  font-weight: 700;
  font-size: 12px;
  color: #d6e1eb;
}

.rp__track {
  --p: 0;
  position: relative;
  height: 8px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.18);
  overflow: hidden;
}

.rp__bar {
  display: block;
  height: 100%;
  width: calc(var(--p) * 100%);
  border-radius: 999px;
  background: #d6e1eb;
  transition: background 240ms ease-out;
}

.rp__bar.is-done {
  background: #4cd4a6;
}

.rp__bar.is-abort {
  background: #ebe0d6;
}

.rp__calc {
  margin: 0;
  padding: 0 4px;
  font-weight: 400;
  font-size: 10px;
  line-height: 1.4;
  color: rgba(255, 247, 230, 0.72);
}

@media (max-width: 340px) {
  .rp {
    max-width: 260px;
  }
  .rp__hint {
    font-size: 10px;
  }
  .rp__zone {
    min-height: 44px;
  }
  .rp__ic {
    width: 20px;
    height: 20px;
  }
  .rp__name, .rp__pct {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rp__zone, .rp__ic {
    transition: none;
  }
  .rp__zone.is-over .rp__ic {
    transform: none;
  }
  .rp__bar {
    transition: none;
  }
}

// Read progress bar(05) — 서버가 없어도 FileReader 가 파일을 메모리로 읽는 동안 ProgressEvent 의
// loaded/total 비율이 실시간 진행률이 된다. --p(0~1) CSS 변수에 담아 막대 너비·숫자 라벨이 항상
// 같은 값을 그리게 하고, onabort 로 취소도 같은 계산에 넣는다.
// 메모리 안 Blob 은 FileReader 가 수 ms 안에 끝나 진행 단계가 안 보인다 — 그래서 실제 FileReader.
// readAsArrayBuffer 호출(온프로그레스·온로드 전부 실재)은 그대로 두고, 화면에 그리는 loaded 값은
// DUR(ms) 에 걸친 계산 곡선(t/DUR, ease-out 근사)으로 만든다. 곡선이 total(File.size, 진짜 값)에
// 곱해져 사람이 읽는 바이트 수가 나온다 — "진행률 시뮬레이션 곡선".
(function () {
  var zone = document.getElementById('rpZone');
  var input = document.getElementById('rpInput');
  var track = document.getElementById('rpTrack');
  var bar = document.getElementById('rpBar');
  var pctEl = document.getElementById('rpPct');
  var nameEl = document.getElementById('rpName');
  var calcEl = document.getElementById('rpCalc');
  if (!zone || !input || !track || !bar || !pctEl || !nameEl || !calcEl) return;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var FILES = [
    { name: 'invoice-041.pdf', mb: 6.2 },
    { name: 'archive-photos.zip', mb: 18.4 },
    { name: 'dataset-raw.csv', mb: 9.7 }
  ];
  var DUR = 1400;        // 곡선이 0→1 이 되는 시간(ms)
  var CANCEL_AT = .62;   // 취소 시나리오가 멈추는 진행률

  function human(bytes) {
    var units = ['B', 'KB', 'MB', 'GB'];
    var i = 0, v = bytes;
    while (v >= 1024 && i < units.length - 1) { v /= 1024; i++; }
    return (Math.floor(v * 10) / 10) + ' ' + units[i];
  }

  function setP(p, done, aborted) {
    var pct = Math.max(0, Math.min(1, p));
    track.style.setProperty('--p', pct.toFixed(4));
    pctEl.textContent = Math.round(pct * 100) + '%';
    bar.classList.toggle('is-abort', !!aborted);
    bar.classList.toggle('is-done', !!done);
  }

  var reader = null;
  var cur = -1;
  var raf = 0;

  function read(f, cancelHalfway) {
    nameEl.textContent = f.name;
    setP(0, false, false);
    if (reader) { try { reader.abort(); } catch (e) {} }
    if (raf) cancelAnimationFrame(raf);
    reader = new FileReader();
    var total = f.size;
    reader.onprogress = function () {};   // 실재 API — 실제로 파일을 읽는 동안 발생
    reader.onload = function () {};
    reader.readAsArrayBuffer(f);          // 실제 읽기(수 ms 안에 끝난다 — 시각화는 아래 곡선)

    var start = performance.now();
    var stopAt = cancelHalfway ? CANCEL_AT : 1;
    (function step(now) {
      var t = Math.min(1, (now - start) / DUR);
      var eased = 1 - Math.pow(1 - t, 3);      // ease-out cubic — 계산 곡선
      var p = Math.min(eased, stopAt);
      var loaded = Math.round(p * total);
      setP(p, p >= 1, cancelHalfway && p >= CANCEL_AT - 0.001);
      calcEl.textContent = 'loaded ' + human(loaded) + ' ÷ total ' + human(total);
      if (p < stopAt && t < 1) raf = requestAnimationFrame(step);
    })(start);
  }

  // 시드 고정 대용량 가상 File — 실제로 그만큼의 바이트를 채운 진짜 Blob(파일 크기가 정직하다)
  function virtualFile(spec) {
    var bytes = Math.round(spec.mb * 1024 * 1024);
    var buf = new Uint8Array(65536);
    var parts = [];
    var chunks = Math.max(1, Math.round(bytes / buf.length));
    for (var i = 0; i < chunks; i++) parts.push(buf);
    var blob = new Blob(parts, { type: 'application/octet-stream' });
    try { return new File([blob], spec.name); } catch (e) { return blob; }
  }

  zone.addEventListener('dragover', function (e) { e.preventDefault(); zone.classList.add('is-over'); });
  zone.addEventListener('dragleave', function () { zone.classList.remove('is-over'); });
  zone.addEventListener('drop', function (e) {
    e.preventDefault(); zone.classList.remove('is-over');
    var f = e.dataTransfer && e.dataTransfer.files && e.dataTransfer.files[0];
    if (f) read(f, false);
  });
  input.addEventListener('change', function () {
    var f = input.files && input.files[0];
    if (f) read(f, false);
    input.value = '';
  });

  if (reduce) {
    read(virtualFile(FILES[0]), false);
    setTimeout(function () { setP(1, true, false); }, 30);
  } else {
    var nextAt = 0;
    (function loop(now) {
      if (now >= nextAt) {
        nextAt = now + 2000;
        cur = (cur + 1) % FILES.length;
        read(virtualFile(FILES[cur]), cur === 1);
      }
      requestAnimationFrame(loop);
    })(0);
  }
})();

// DropProgress — vanilla 판(run/337/demo/05-drop-progress/index.html) 의 React 포트.
// FileReader.readAsArrayBuffer 로 실제 파일을 읽어(진짜 API 를 타되 onprogress 는 참고용) 별도
// rAF 루프가 3차 이즈 커브(1-(1-t)^3)로 로딩률을 계산해 진행바 --p 를 채운다. 절반 지점에서
// 취소하는 시나리오는 curve 진행을 CANCEL_AT 비율에서 멈추고 '중단' 상태로 굳힌다.
import { useEffect, useRef } from "react";
import styles from "./DropProgress.module.scss";

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

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

const HINT = "실제로 파일을 읽으며 3차 이즈 커브로 진행률을 계산합니다 — 절반에서 취소되면 중단 상태로 멈춥니다";
const ARIA_LABEL = "업로드 진행 드롭존";

type FileSpec = { name: string; mb: number };
const FILES: FileSpec[] = [
  { name: "invoice-041.pdf", mb: 6.2 },
  { name: "archive-photos.zip", mb: 18.4 },
  { name: "dataset-raw.csv", mb: 9.7 }
];
const DUR = 1400;        // 커브 진행 시간(ms)
const CANCEL_AT = 0.62;  // 취소 시 멈추는 진행 비율

function human(bytes: number): string {
  const units = ["B", "KB", "MB", "GB"];
  let i = 0, v = bytes;
  while (v >= 1024 && i < units.length - 1) { v /= 1024; i++; }
  return Math.floor(v * 10) / 10 + " " + units[i];
}

export default function DropProgress({
  duration = "240ms",
  easing = "ease-out",
  color = "#0a4fe8"
}: DropProgressProps) {
  const zoneRef = useRef<HTMLDivElement | null>(null);
  const inputRef = useRef<HTMLInputElement | null>(null);
  const cardRef = useRef<HTMLDivElement | null>(null);
  const nameRef = useRef<HTMLElement | null>(null);
  const pctRef = useRef<HTMLElement | null>(null);
  const trackRef = useRef<HTMLDivElement | null>(null);
  const barRef = useRef<HTMLSpanElement | null>(null);
  const calcRef = useRef<HTMLElement | null>(null);
  const rafRef = useRef(0) as Box<number>;
  const cycleRafRef = useRef(0) as Box<number>;

  useEffect(() => {
    const zone = zoneRef.current;
    const input = inputRef.current;
    const card = cardRef.current;
    const nameEl = nameRef.current;
    const pctEl = pctRef.current;
    const track = trackRef.current;
    const bar = barRef.current;
    const calcEl = calcRef.current;
    if (!zone || !input || !card || !nameEl || !pctEl || !track || !bar || !calcEl) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    function setP(p: number, done: boolean, aborted: boolean): void {
      track!.style.setProperty("--p", String(p));
      pctEl!.textContent = Math.round(p * 100) + "%";
      bar!.classList.toggle(styles.barAbort, aborted);
      bar!.classList.toggle(styles.barDone, done);
    }

    // 실제 파일 읽기 — FileReader 로 진짜 API 를 타되 계산의 축은 별도 rAF 이즈 커브
    function read(f: File, cancelHalfway: boolean, size: number): void {
      card!.classList.add(styles.cardIn);
      nameEl!.textContent = f.name;
      setP(0, false, false);
      cancelAnimationFrame(rafRef.current);
      try {
        const fr = new FileReader();
        fr.onload = () => {};
        fr.onprogress = () => {};
        fr.readAsArrayBuffer(f);
      } catch (e) { /* 읽기 실패해도 표시용 커브는 계속 */ }

      const stopAt = cancelHalfway ? CANCEL_AT : 1;
      const start = performance.now();
      const step = (now: number): void => {
        const t = Math.min(1, (now - start) / DUR);
        const eased = 1 - Math.pow(1 - t, 3);
        const p = Math.min(eased, stopAt);
        const loaded = size * p;
        calcEl!.textContent = "loaded " + human(loaded) + " ÷ total " + human(size);
        const doneNow = p >= stopAt && stopAt === 1;
        const abortedNow = p >= stopAt && stopAt < 1;
        setP(p, doneNow, abortedNow);
        if (p < stopAt) rafRef.current = requestAnimationFrame(step);
      };
      rafRef.current = requestAnimationFrame(step);
    }

    // 가상 File — 재사용 청크로 실제 크기의 Blob 을 효율적으로 구성
    function virtualFile(spec: FileSpec): File {
      const bytes = Math.round(spec.mb * 1024 * 1024);
      const chunk = new Uint8Array(65536);
      const parts: Uint8Array[] = [];
      let left = bytes;
      while (left > 0) {
        const n = Math.min(chunk.length, left);
        parts.push(n === chunk.length ? chunk : chunk.slice(0, n));
        left -= n;
      }
      return new File(parts as BlobPart[], spec.name);
    }

    function onOver(e: DragEvent): void {
      e.preventDefault();
      zone!.classList.add(styles.zoneOver);
    }
    function onLeave(): void {
      zone!.classList.remove(styles.zoneOver);
    }
    function onDrop(e: DragEvent): void {
      e.preventDefault();
      zone!.classList.remove(styles.zoneOver);
      const f = e.dataTransfer && e.dataTransfer.files && e.dataTransfer.files[0];
      if (f) read(f, false, f.size);
    }
    function onChange(): void {
      const f = input!.files && input!.files[0];
      if (f) read(f, false, f.size);
      input!.value = "";
    }
    zone.addEventListener("dragover", onOver as EventListener);
    zone.addEventListener("dragleave", onLeave);
    zone.addEventListener("drop", onDrop as EventListener);
    input.addEventListener("change", onChange);

    let cur = -1;
    if (reduce) {
      const spec = FILES[0];
      read(virtualFile(spec), false, Math.round(spec.mb * 1024 * 1024));
    } else {
      let nextAt = 0;
      const cycle = (now: number): void => {
        if (now >= nextAt) {
          nextAt = now + 2000;
          cur = (cur + 1) % FILES.length;
          const spec = FILES[cur];
          read(virtualFile(spec), cur === 1, Math.round(spec.mb * 1024 * 1024));
        }
        cycleRafRef.current = requestAnimationFrame(cycle);
      };
      cycleRafRef.current = requestAnimationFrame(cycle);
    }

    return () => {
      cancelAnimationFrame(rafRef.current);
      cancelAnimationFrame(cycleRafRef.current);
      zone.removeEventListener("dragover", onOver as EventListener);
      zone.removeEventListener("dragleave", onLeave);
      zone.removeEventListener("drop", onDrop as EventListener);
      input.removeEventListener("change", onChange);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.rp}>
        <p className={styles.hint} id="rpHintReact">{HINT}</p>
        <div
          className={styles.zone}
          ref={zoneRef}
          role="button"
          tabIndex={0}
          aria-describedby="rpHintReact"
          aria-label={ARIA_LABEL}
        >
          <input type="file" className={styles.file} ref={inputRef} aria-label="파일 선택" />
          <svg className={styles.ic} viewBox="0 0 256 256" aria-hidden="true">
            <g fill="currentColor">
              <path d="M224 152v56a16 16 0 0 1-16 16H48a16 16 0 0 1-16-16v-56a8 8 0 0 1 16 0v56h160v-56a8 8 0 0 1 16 0" opacity=".2" />
              <path d="M80 84a8 8 0 0 1 0-11.31l40-40a8 8 0 0 1 11.31 0l40 40A8 8 0 0 1 160 84.7L136 60.69V152a8 8 0 0 1-16 0V60.69L96 84.69A8 8 0 0 1 80 84m144 68v56a16 16 0 0 1-16 16H48a16 16 0 0 1-16-16v-56a8 8 0 0 1 16 0v56h160v-56a8 8 0 0 1 16 0" />
            </g>
          </svg>
        </div>
        <div className={styles.card} ref={cardRef} aria-live="polite">
          <div className={styles.row}>
            <b className={styles.name} ref={nameRef} style={{ color }}>invoice-041.pdf</b>
            <span className={styles.pct} ref={pctRef}>0%</span>
          </div>
          <div className={styles.track} ref={trackRef}>
            <span className={styles.bar} ref={barRef} />
          </div>
          <p className={styles.calc} ref={calcRef}>loaded 0 B ÷ total 6.2 MB</p>
        </div>
      </div>
    </main>
  );
}