09Export panel

<main class="stage">
<div class="ep is-demo" id="ep">
  <div class="ep__frame">
    <canvas class="ep__view" id="view" width="320" height="200" role="img" aria-label="Photo to export"></canvas>
  </div>
  <div class="ep__panel">
    <div class="ep__fmts" id="fmts">
      <span class="ep__ring" aria-hidden="true"></span>
      <button type="button" class="ep__f" data-m="image/jpeg" aria-pressed="true">JPG</button>
      <button type="button" class="ep__f" data-m="image/png" aria-pressed="false">PNG</button>
      <button type="button" class="ep__f" data-m="image/webp" aria-pressed="false">WEBP</button>
    </div>
    <div class="ep__q">
      <span class="ep__lab" id="qLab">Quality</span>
      <span class="ep__track" id="track" role="slider" tabindex="0" aria-labelledby="qLab" aria-valuemin="0.3" aria-valuemax="1" aria-valuenow="0.8"><span class="ep__thumb" id="thumb"></span></span>
    </div>
    <p class="ep__size">
      <span class="ep__lab">Estimated size</span>
      <span class="ep__num">
        <span class="ep__real" id="size">— KB</span>
        <span class="ep__demo ep__demo--a" aria-hidden="true">5.8 KB</span>
        <span class="ep__demo ep__demo--b" aria-hidden="true">12.4 KB</span>
        <span class="ep__demo ep__demo--c" aria-hidden="true">3.3 KB</span>
        <span class="ep__demo ep__demo--d" aria-hidden="true">2.4 KB</span>
      </span>
    </p>
    <button type="button" class="ep__go" id="goBtn"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" class="ep__ico" 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 0m-101.66 5.66a8 8 0 0 0 11.32 0l40-40a8 8 0 0 0-11.32-11.32L136 124.69V32a8 8 0 0 0-16 0v92.69L93.66 98.34a8 8 0 0 0-11.32 11.32Z"/></g></svg><span>Export</span></button>
    <p class="ep__done" id="done">File ready</p>
  </div>
</div>
</main>

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

// 내보내기 패널 — 용량은 canvas 2D 의 toBlob 이 실제로 만든 파일 길이다(짐작한 값이 아니다).
// 격자 미리보기(.is-demo)는 형식 테두리를 밀고 용량 칸 넷을 steps(1, end) 로 갈아 끼운다 —
// 글자는 보간할 수 없어 교차 페이드로 두면 두 숫자가 반투명하게 겹친 장면이 대표 이미지로 뽑힌다.

$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-ink;

@include stage($stage-paper);

.ep { display: flex; align-items: center; gap: $sp-3; width: 100%; max-width: 400px; justify-content: center; }
.ep__frame {
  flex: 0 0 auto; height: clamp(72px, 34vh, 116px); aspect-ratio: 16 / 10;
  border-radius: $r-sm; overflow: hidden; box-shadow: $shadow-raised;
}
.ep__view { display: block; width: 100%; height: 100%; }
.ep__panel { flex: 0 0 auto; display: flex; flex-direction: column; gap: $sp-2; width: 152px; }

.ep__fmts { position: relative; display: grid; grid-template-columns: repeat(3, 1fr); }
.ep__ring {
  position: absolute; top: 0; left: 0; width: calc(100% / 3); height: 100%;
  border: 2px solid $subject-blue; border-radius: $r-sm; pointer-events: none;
}
.ep__f {
  width: 100%; cursor: pointer; padding: $sp-1 0; border: 0; background: transparent; color: $color;
  font-family: ui-monospace, "Consolas", monospace; font-weight: 700;
  font-size: clamp(8px, 2.2vw, 10px); line-height: 1.3;
}
.ep__f:focus-visible { outline: 3px solid $subject-blue; outline-offset: 2px; }

.ep__q { display: flex; align-items: center; gap: $sp-2; }
.ep__lab { font-weight: 800; font-size: clamp(8px, 2.2vw, 10px); color: rgba(23, 20, 26, .72); }
.ep__track {
  position: relative; display: block; flex: 0 0 auto; width: 76px; height: 6px; cursor: pointer;
  border-radius: $r-pill; background: rgba(23, 20, 26, .18);
}
.ep__track[aria-disabled="true"] { opacity: .42; }
.ep__track:focus-visible { outline: 3px solid $subject-blue; outline-offset: 4px; }
.ep__thumb {
  position: absolute; top: 50%; left: 71.4%; width: 13px; height: 13px;
  border-radius: 50%; background: $subject-blue; box-shadow: $shadow-press;
  transform: translate(-50%, -50%);
}

.ep__size { display: flex; align-items: baseline; gap: $sp-2; margin: 0; }
.ep__num { position: relative; font-family: ui-monospace, "Consolas", monospace; font-weight: 700;
  font-size: clamp(9px, 2.4vw, 11px); color: $color; }
.ep__demo { display: none; position: absolute; left: 0; top: 0; white-space: nowrap; }

.ep__go {
  display: inline-flex; align-items: center; justify-content: center; gap: $sp-1; width: 100%;
  cursor: pointer; border: 0; background: $subject-ink; color: $subject-cream;
  border-radius: $r-control; font-family: inherit; font-weight: 800; line-height: 1.3;
  font-size: clamp(8px, 2.2vw, 10px); padding: $sp-1 $sp-2;
}
.ep__go:focus-visible { outline: 3px solid $subject-blue; outline-offset: 2px; }
.ep__ico { width: 12px; height: 12px; flex: 0 0 auto; }
.ep__done { margin: 0; font-weight: 700; font-size: clamp(8px, 2.1vw, 10px); color: $subject-blue; }

// ── 미리보기 루프: JPG → PNG → WEBP 순으로 형식을 돌고, WEBP 에서 품질을 0.8 에서 0.5 로 내린다.
//    복귀는 86% 에 끝난다. 24장 표본의 마지막 장이 2초의 95.8% 지점이라 그 뒤는 안 찍힌다
.ep.is-demo .ep__ring {
  animation-name: epRing; animation-duration: $duration;
  animation-timing-function: $easing; animation-iteration-count: infinite;
}
@keyframes epRing {
  0%, 24% { transform: translateX(0); }
  26%, 48% { transform: translateX(100%); }
  50%, 84% { transform: translateX(200%); }
  86%, 100% { transform: translateX(0); }
}
.ep.is-demo .ep__thumb {
  animation-name: epThumb; animation-duration: $duration;
  animation-timing-function: $easing; animation-iteration-count: infinite;
}
@keyframes epThumb {
  0%, 66% { transform: translate(-50%, -50%); }
  70%, 84% { transform: translate(-50%, -50%) translateX(-33px); }
  86%, 100% { transform: translate(-50%, -50%); }
}
.ep.is-demo .ep__real { color: transparent; }
.ep.is-demo .ep__demo {
  display: block;
  animation-duration: $duration;
  animation-timing-function: steps(1, end); animation-iteration-count: infinite;
}
.ep.is-demo .ep__demo--a { animation-name: epSizeA; }
.ep.is-demo .ep__demo--b { animation-name: epSizeB; }
.ep.is-demo .ep__demo--c { animation-name: epSizeC; }
.ep.is-demo .ep__demo--d { animation-name: epSizeD; }
@keyframes epSizeA { 0%, 25% { opacity: 1; } 26%, 85% { opacity: 0; } 86%, 100% { opacity: 1; } }
@keyframes epSizeB { 0%, 25% { opacity: 0; } 26%, 49% { opacity: 1; } 50%, 100% { opacity: 0; } }
@keyframes epSizeC { 0%, 49% { opacity: 0; } 50%, 69% { opacity: 1; } 70%, 100% { opacity: 0; } }
@keyframes epSizeD { 0%, 69% { opacity: 0; } 70%, 85% { opacity: 1; } 86%, 100% { opacity: 0; } }
// 내보내기 단추는 자기 중심에서 눌린다 — 원점을 모서리에 두면 눌리는 게 아니라 옆으로 밀려 보인다
.ep.is-demo .ep__go {
  animation-name: epPress; animation-duration: $duration;
  animation-timing-function: $ease-pop; animation-iteration-count: infinite;
}
@keyframes epPress {
  0%, 20% { transform: scale(1); }
  24% { transform: scale(0.93); }
  30%, 44% { transform: scale(1); }
  48% { transform: scale(0.93); }
  54%, 100% { transform: scale(1); }
}

@media (max-width: 340px) {
  .ep { gap: $sp-2; }
  .ep__panel { width: 132px; }
  .ep__track { width: 60px; }
}

@media (prefers-reduced-motion: reduce) {
  .ep.is-demo .ep__ring,
  .ep.is-demo .ep__thumb,
  .ep.is-demo .ep__demo,
  .ep.is-demo .ep__go { animation: none !important; }
  // 움직임 없이 WEBP 를 고른 상태로 세운다
  .ep.is-demo .ep__ring { transform: translateX(200%) !important; }
  .ep.is-demo .ep__demo--a,
  .ep.is-demo .ep__demo--b,
  .ep.is-demo .ep__demo--d { opacity: 0 !important; }
  .ep.is-demo .ep__demo--c { opacity: 1 !important; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.ep {
  display: flex;
  align-items: center;
  gap: 12px;
  width: 100%;
  max-width: 400px;
  justify-content: center;
}

.ep__frame {
  flex: 0 0 auto;
  height: clamp(72px, 34vh, 116px);
  aspect-ratio: 16/10;
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

.ep__view {
  display: block;
  width: 100%;
  height: 100%;
}

.ep__panel {
  flex: 0 0 auto;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 152px;
}

.ep__fmts {
  position: relative;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
}

.ep__ring {
  position: absolute;
  top: 0;
  left: 0;
  width: 33.3333333333%;
  height: 100%;
  border: 2px solid #2f6df6;
  border-radius: 8px;
  pointer-events: none;
}

.ep__f {
  width: 100%;
  cursor: pointer;
  padding: 4px 0;
  border: 0;
  background: transparent;
  color: #17141a;
  font-family: ui-monospace, "Consolas", monospace;
  font-weight: 700;
  font-size: clamp(8px, 2.2vw, 10px);
  line-height: 1.3;
}

.ep__f:focus-visible {
  outline: 3px solid #2f6df6;
  outline-offset: 2px;
}

.ep__q {
  display: flex;
  align-items: center;
  gap: 8px;
}

.ep__lab {
  font-weight: 800;
  font-size: clamp(8px, 2.2vw, 10px);
  color: rgba(23, 20, 26, 0.72);
}

.ep__track {
  position: relative;
  display: block;
  flex: 0 0 auto;
  width: 76px;
  height: 6px;
  cursor: pointer;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.18);
}

.ep__track[aria-disabled=true] {
  opacity: 0.42;
}

.ep__track:focus-visible {
  outline: 3px solid #2f6df6;
  outline-offset: 4px;
}

.ep__thumb {
  position: absolute;
  top: 50%;
  left: 71.4%;
  width: 13px;
  height: 13px;
  border-radius: 50%;
  background: #2f6df6;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  transform: translate(-50%, -50%);
}

.ep__size {
  display: flex;
  align-items: baseline;
  gap: 8px;
  margin: 0;
}

.ep__num {
  position: relative;
  font-family: ui-monospace, "Consolas", monospace;
  font-weight: 700;
  font-size: clamp(9px, 2.4vw, 11px);
  color: #17141a;
}

.ep__demo {
  display: none;
  position: absolute;
  left: 0;
  top: 0;
  white-space: nowrap;
}

.ep__go {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
  width: 100%;
  cursor: pointer;
  border: 0;
  background: #17141a;
  color: #fff7e6;
  border-radius: 12px;
  font-family: inherit;
  font-weight: 800;
  line-height: 1.3;
  font-size: clamp(8px, 2.2vw, 10px);
  padding: 4px 8px;
}

.ep__go:focus-visible {
  outline: 3px solid #2f6df6;
  outline-offset: 2px;
}

.ep__ico {
  width: 12px;
  height: 12px;
  flex: 0 0 auto;
}

.ep__done {
  margin: 0;
  font-weight: 700;
  font-size: clamp(8px, 2.1vw, 10px);
  color: #2f6df6;
}

.ep.is-demo .ep__ring {
  animation-name: epRing;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@keyframes epRing {
  0%, 24% {
    transform: translateX(0);
  }
  26%, 48% {
    transform: translateX(100%);
  }
  50%, 84% {
    transform: translateX(200%);
  }
  86%, 100% {
    transform: translateX(0);
  }
}
.ep.is-demo .ep__thumb {
  animation-name: epThumb;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@keyframes epThumb {
  0%, 66% {
    transform: translate(-50%, -50%);
  }
  70%, 84% {
    transform: translate(-50%, -50%) translateX(-33px);
  }
  86%, 100% {
    transform: translate(-50%, -50%);
  }
}
.ep.is-demo .ep__real {
  color: transparent;
}

.ep.is-demo .ep__demo {
  display: block;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

.ep.is-demo .ep__demo--a {
  animation-name: epSizeA;
}

.ep.is-demo .ep__demo--b {
  animation-name: epSizeB;
}

.ep.is-demo .ep__demo--c {
  animation-name: epSizeC;
}

.ep.is-demo .ep__demo--d {
  animation-name: epSizeD;
}

@keyframes epSizeA {
  0%, 25% {
    opacity: 1;
  }
  26%, 85% {
    opacity: 0;
  }
  86%, 100% {
    opacity: 1;
  }
}
@keyframes epSizeB {
  0%, 25% {
    opacity: 0;
  }
  26%, 49% {
    opacity: 1;
  }
  50%, 100% {
    opacity: 0;
  }
}
@keyframes epSizeC {
  0%, 49% {
    opacity: 0;
  }
  50%, 69% {
    opacity: 1;
  }
  70%, 100% {
    opacity: 0;
  }
}
@keyframes epSizeD {
  0%, 69% {
    opacity: 0;
  }
  70%, 85% {
    opacity: 1;
  }
  86%, 100% {
    opacity: 0;
  }
}
.ep.is-demo .ep__go {
  animation-name: epPress;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 1.4, 0.4, 1);
  animation-iteration-count: infinite;
}

@keyframes epPress {
  0%, 20% {
    transform: scale(1);
  }
  24% {
    transform: scale(0.93);
  }
  30%, 44% {
    transform: scale(1);
  }
  48% {
    transform: scale(0.93);
  }
  54%, 100% {
    transform: scale(1);
  }
}
@media (max-width: 340px) {
  .ep {
    gap: 8px;
  }
  .ep__panel {
    width: 132px;
  }
  .ep__track {
    width: 60px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ep.is-demo .ep__ring,
  .ep.is-demo .ep__thumb,
  .ep.is-demo .ep__demo,
  .ep.is-demo .ep__go {
    animation: none !important;
  }
  .ep.is-demo .ep__ring {
    transform: translateX(200%) !important;
  }
  .ep.is-demo .ep__demo--a,
  .ep.is-demo .ep__demo--b,
  .ep.is-demo .ep__demo--d {
    opacity: 0 !important;
  }
  .ep.is-demo .ep__demo--c {
    opacity: 1 !important;
  }
}

var ep = document.getElementById('ep');
var view = document.getElementById('view');
var track = document.getElementById('track');
var thumb = document.getElementById('thumb');
var sizeEl = document.getElementById('size');
var doneEl = document.getElementById('done');
var ring = document.querySelector('.ep__ring');
var formats = document.querySelectorAll('.ep__f');
var mime = 'image/jpeg', quality = 0.8;

// 가짜 사진 — 외부 파일 없이 그라디언트와 도형으로 합성한다. 필터·히스토그램이 보이도록 대비를 세게 준다
function paintPhoto(c, w, h) {
  var sky = c.createLinearGradient(0, 0, 0, h);
  sky.addColorStop(0, '#2f6df6'); sky.addColorStop(0.55, '#ff9ebb'); sky.addColorStop(1, '#ffd23f');
  c.fillStyle = sky; c.fillRect(0, 0, w, h);
  c.fillStyle = '#fff7e6';
  c.beginPath(); c.arc(w * 0.74, h * 0.28, h * 0.13, 0, Math.PI * 2); c.fill();
  // 곧은 수평선 하나 — 기울기 보정이 눈에 보이려면 비교할 직선이 있어야 한다
  c.fillStyle = 'rgba(23, 20, 26, 0.5)'; c.fillRect(0, Math.round(h * 0.66), w, 2);
  c.fillStyle = '#17141a';
  c.beginPath(); c.moveTo(0, h); c.lineTo(w * 0.34, h * 0.36); c.lineTo(w * 0.62, h); c.closePath(); c.fill();
  c.fillStyle = '#c2361a';
  c.beginPath(); c.moveTo(w * 0.46, h); c.lineTo(w * 0.78, h * 0.52); c.lineTo(w, h); c.closePath(); c.fill();
  for (var i = 0; i < 6; i++) { c.fillStyle = i % 2 ? '#fff7e6' : '#17141a'; c.fillRect(w * (0.08 + i * 0.07), h * (0.14 + (i % 3) * 0.06), 7, 7); }
}

// 용량은 짐작하지 않는다 — 실제로 파일을 만들어 보고 그 길이를 읽는다.
// PNG 는 무손실이라 quality 인자를 아예 무시한다. 이 사진 320x200 기준 실측:
// JPG 0.8 은 5.8 KB, PNG 는 12.4 KB, WEBP 0.8 은 3.3 KB, WEBP 0.5 는 2.4 KB
// 고른 형식을 브라우저가 모르면 규격상 조용히 PNG 가 나온다 — image/webp 는 Safari 에 아직 없다
// (caniuse 81.11%). blob.type 을 견줘 다르면 실제로 나온 형식을 같이 적는다
function label(blob) {
  if (!blob) { return '— KB'; }
  return (blob.size / 1024).toFixed(1) + ' KB' + (blob.type === mime ? '' : ' · ' + blob.type);
}

function estimate() {
  view.toBlob(function (blob) { sizeEl.textContent = label(blob); }, mime, quality);
}

function refresh() {
  thumb.style.left = ((quality - 0.3) / 0.7 * 100) + '%';
  track.setAttribute('aria-valuenow', quality.toFixed(2));
  track.setAttribute('aria-valuetext', quality.toFixed(2));
  track.setAttribute('aria-disabled', mime === 'image/png' ? 'true' : 'false');
  estimate();
}

for (var i = 0; i < formats.length; i++) {
  (function (index) {
    formats[index].addEventListener('click', function () {
      mime = formats[index].getAttribute('data-m');
      for (var j = 0; j < formats.length; j++) { formats[j].setAttribute('aria-pressed', j === index ? 'true' : 'false'); }
      ring.style.transform = 'translateX(' + index * 100 + '%)';
      ep.classList.remove('is-demo');
      doneEl.hidden = true;
      refresh();
    });
  })(i);
}

function setQuality(next) {
  quality = Math.max(0.3, Math.min(1, Math.round(next * 100) / 100));
  ep.classList.remove('is-demo');
  doneEl.hidden = true;
  refresh();
}
function fromPointer(e) {
  var r = track.getBoundingClientRect();
  setQuality((e.clientX - r.left) / r.width * 0.7 + 0.3);
}
track.addEventListener('pointerdown', function (e) { track.setPointerCapture(e.pointerId); fromPointer(e); });
track.addEventListener('pointermove', function (e) { if (e.buttons) { fromPointer(e); } });
// 화살표 0.05, Shift 와 함께면 0.2
track.addEventListener('keydown', function (e) {
  var step = e.shiftKey ? 0.2 : 0.05;
  if (e.key === 'ArrowLeft' || e.key === 'ArrowDown') { e.preventDefault(); setQuality(quality - step); }
  else if (e.key === 'ArrowRight' || e.key === 'ArrowUp') { e.preventDefault(); setQuality(quality + step); }
});

// 데모에서는 내려받기 대신 만들어진 파일의 길이만 보여준다
document.getElementById('goBtn').addEventListener('click', function () {
  ep.classList.remove('is-demo');
  view.toBlob(function (blob) {
    sizeEl.textContent = label(blob);
    doneEl.hidden = false;
  }, mime, quality);
});

doneEl.hidden = true;
paintPhoto(view.getContext('2d'), view.width, view.height);
refresh();

// ExportPanel — vanilla 판(run/295/demo/09-image-edit-export-panel/index.html) 의 React 포트.
// 용량은 짐작하지 않는다 — canvas 2D 의 toBlob 이 실제로 만든 파일 길이를 KB 로 읽는다(내려받지는 않는다).
// 격자 미리보기(.isDemo)는 형식 테두리를 밀고 용량 칸 넷을 steps(1, end) 로 갈아 끼운다.
// 값·수치는 vanilla 와 같다.
import { useCallback, useEffect, useRef, useState } from "react";
import type { CSSProperties, PointerEvent as ReactPointerEvent } from "react";
import styles from "./ExportPanel.module.scss";

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

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Format = { mime: string; name: string };
// ambient 타입에 KeyboardEvent 가 없다 — 화살표 조작에 쓰는 것만 지역 타입으로 선언한다
type KeyEvt = { key: string; shiftKey: boolean; preventDefault(): void };

const FORMATS: Format[] = [
  { mime: "image/jpeg", name: "JPG" },
  { mime: "image/png", name: "PNG" },
  { mime: "image/webp", name: "WEBP" },
];
const EMPTY = "— KB";

// 가짜 사진 — 외부 파일 없이 그라디언트와 도형으로 합성한다. 필터·히스토그램이 보이도록 대비를 세게 준다
function paintPhoto(c: CanvasRenderingContext2D, w: number, h: number): void {
  const sky = c.createLinearGradient(0, 0, 0, h);
  sky.addColorStop(0, "#2f6df6");
  sky.addColorStop(0.55, "#ff9ebb");
  sky.addColorStop(1, "#ffd23f");
  c.fillStyle = sky;
  c.fillRect(0, 0, w, h);
  c.fillStyle = "#fff7e6";
  c.beginPath();
  c.arc(w * 0.74, h * 0.28, h * 0.13, 0, Math.PI * 2);
  c.fill();
  // 곧은 수평선 하나 — 기울기 보정이 눈에 보이려면 비교할 직선이 있어야 한다
  c.fillStyle = "rgba(23, 20, 26, 0.5)";
  c.fillRect(0, Math.round(h * 0.66), w, 2);
  c.fillStyle = "#17141a";
  c.beginPath();
  c.moveTo(0, h);
  c.lineTo(w * 0.34, h * 0.36);
  c.lineTo(w * 0.62, h);
  c.closePath();
  c.fill();
  c.fillStyle = "#c2361a";
  c.beginPath();
  c.moveTo(w * 0.46, h);
  c.lineTo(w * 0.78, h * 0.52);
  c.lineTo(w, h);
  c.closePath();
  c.fill();
  for (let i = 0; i < 6; i++) {
    c.fillStyle = i % 2 ? "#fff7e6" : "#17141a";
    c.fillRect(w * (0.08 + i * 0.07), h * (0.14 + (i % 3) * 0.06), 7, 7);
  }
}

export default function ExportPanel({
  duration = 2000,
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#17141a",
}: ExportPanelProps) {
  const viewRef = useRef<HTMLCanvasElement | null>(null);
  const trackRef = useRef<HTMLSpanElement | null>(null);
  const [demo, setDemo] = useState(true);
  const [picked, setPicked] = useState(0);
  const [quality, setQuality] = useState(0.8);
  const [sizeText, setSizeText] = useState(EMPTY);
  const [done, setDone] = useState(false);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  useEffect(() => {
    const view = viewRef.current;
    if (!view) return;
    const vctx = view.getContext("2d");
    if (vctx) paintPhoto(vctx, view.width, view.height);
  }, []);

  // 용량은 짐작하지 않는다 — 실제로 파일을 만들어 보고 그 길이를 읽는다.
  // PNG 는 무손실이라 quality 인자를 아예 무시한다. 이 사진 320x200 기준 실측:
  // JPG 0.8 은 5.8 KB, PNG 는 12.4 KB, WEBP 0.8 은 3.3 KB, WEBP 0.5 는 2.4 KB
  const estimate = useCallback((finish: boolean) => {
    const view = viewRef.current;
    if (!view) return;
    // 고른 형식을 브라우저가 모르면 규격상 조용히 PNG 가 나온다 — image/webp 는 Safari 에 아직 없다
    // (caniuse 81.11%). blob.type 을 견줘 다르면 실제로 나온 형식을 같이 적는다
    view.toBlob(
      (blob: Blob | null) => {
        const mime = FORMATS[picked].mime;
        setSizeText(blob
          ? (blob.size / 1024).toFixed(1) + " KB" + (blob.type === mime ? "" : " · " + blob.type)
          : EMPTY);
        if (finish) setDone(true);
      },
      FORMATS[picked].mime,
      quality
    );
  }, [picked, quality]);

  useEffect(() => {
    estimate(false);
  }, [estimate]);

  function onFormat(index: number): void {
    setPicked(index);
    setDemo(false);
    setDone(false);
  }

  const applyQuality = useCallback((next: number) => {
    setQuality(Math.max(0.3, Math.min(1, Math.round(next * 100) / 100)));
    setDemo(false);
    setDone(false);
  }, []);

  function fromPointer(event: ReactPointerEvent<HTMLSpanElement>): void {
    const track = trackRef.current;
    if (!track) return;
    const r = track.getBoundingClientRect();
    applyQuality(((event.clientX - r.left) / r.width) * 0.7 + 0.3);
  }

  function onTrackDown(event: ReactPointerEvent<HTMLSpanElement>): void {
    const track = trackRef.current;
    if (!track) return;
    track.setPointerCapture(event.pointerId);
    fromPointer(event);
  }

  function onTrackMove(event: ReactPointerEvent<HTMLSpanElement>): void {
    if (event.buttons) fromPointer(event);
  }

  // 화살표 0.05, Shift 와 함께면 0.2
  function onTrackKey(event: KeyEvt): void {
    const step = event.shiftKey ? 0.2 : 0.05;
    if (event.key === "ArrowLeft" || event.key === "ArrowDown") {
      event.preventDefault();
      applyQuality(quality - step);
    } else if (event.key === "ArrowRight" || event.key === "ArrowUp") {
      event.preventDefault();
      applyQuality(quality + step);
    }
  }

  // 데모에서는 내려받기 대신 만들어진 파일의 길이만 보여준다
  function onExport(): void {
    setDemo(false);
    estimate(true);
  }

  const cls = [styles.root, demo ? styles.isDemo : ""].filter(Boolean).join(" ");
  return (
    <main className={styles.stage}>
      <div className={cls} style={vars}>
        <div className={styles.frame}>
          <canvas className={styles.view} ref={viewRef} width={320} height={200} role="img" aria-label="내보낼 사진"></canvas>
        </div>
        <div className={styles.panel}>
          <div className={styles.fmts}>
            <span className={styles.ring} aria-hidden="true" style={{ transform: `translateX(${picked * 100}%)` }}></span>
            {FORMATS.map((format, index) => (
              <button
                key={format.mime}
                type="button"
                className={styles.fmt}
                aria-pressed={index === picked}
                onClick={() => onFormat(index)}
              >
                {format.name}
              </button>
            ))}
          </div>
          <div className={styles.q}>
            <span className={styles.lab} id="qLab">품질</span>
            <span
              className={styles.track}
              ref={trackRef}
              role="slider"
              tabIndex={0}
              aria-labelledby="qLab"
              aria-valuemin={0.3}
              aria-valuemax={1}
              aria-valuenow={quality.toFixed(2)}
              aria-valuetext={quality.toFixed(2)}
              aria-disabled={FORMATS[picked].mime === "image/png"}
              onPointerDown={onTrackDown}
              onPointerMove={onTrackMove}
              onKeyDown={onTrackKey}
            >
              <span className={styles.thumb} style={{ left: `${((quality - 0.3) / 0.7) * 100}%` }}></span>
            </span>
          </div>
          <p className={styles.size}>
            <span className={styles.lab}>예상 용량</span>
            <span className={styles.num}>
              <span className={styles.real}>{sizeText}</span>
              <span className={`${styles.demo} ${styles.demoA}`} aria-hidden="true">5.8 KB</span>
              <span className={`${styles.demo} ${styles.demoB}`} aria-hidden="true">12.4 KB</span>
              <span className={`${styles.demo} ${styles.demoC}`} aria-hidden="true">3.3 KB</span>
              <span className={`${styles.demo} ${styles.demoD}`} aria-hidden="true">2.4 KB</span>
            </span>
          </p>
          <button type="button" className={styles.go} onClick={onExport}>
            <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" className={styles.ico} 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 0m-101.66 5.66a8 8 0 0 0 11.32 0l40-40a8 8 0 0 0-11.32-11.32L136 124.69V32a8 8 0 0 0-16 0v92.69L93.66 98.34a8 8 0 0 0-11.32 11.32Z"/></g></svg>
            <span>내보내기</span>
          </button>
          <p className={styles.done} hidden={!done}>파일 준비 완료</p>
        </div>
      </div>
    </main>
  );
}