06Chapter marker seek bar

<main class="stage">
  <figure class="pl is-demo" id="pl">
    <div class="pl__screen">
      <div class="pl__stripes" aria-hidden="true"></div>
      <div class="pl__world" aria-hidden="true"><span class="pl__sun"></span><span class="pl__hill pl__hill--a"></span><span class="pl__hill pl__hill--b"></span></div>
      <span class="pl__clock" id="clock">0:08</span>
      <span class="pl__badge">3:00</span>
      <div class="nm">
        <div class="nm__list" id="nm">
          <b class="nm__i">1 · Intro</b>
          <b class="nm__i">2 · Setup</b>
          <b class="nm__i">3 · Example</b>
          <b class="nm__i">4 · Recap</b>
        </div>
      </div>
    </div>
    <div class="sk__row">
      <span class="sk__t"><b id="t-now">0:08</b> / 3:00</span>
      <div class="sk" id="sk" role="slider" tabindex="0" aria-label="Seek position" aria-valuemin="0" aria-valuemax="180" aria-valuenow="8" aria-valuetext="Intro chapter, 0:08">
        <div class="ch" id="ch">
          <span class="ch__seg" style="--s:0;--e:.1333;--k:7.5"><i class="ch__fill"></i></span>
          <span class="ch__seg" style="--s:.1333;--e:.4;--k:3.75"><i class="ch__fill"></i></span>
          <span class="ch__seg" style="--s:.4;--e:.7778;--k:2.647"><i class="ch__fill"></i></span>
          <span class="ch__seg ch__seg--end" style="--s:.7778;--e:1;--k:4.5"><i class="ch__fill"></i></span>
          <span class="ch__head" aria-hidden="true"><i class="ch__dot"></i></span>
        </div>
      </div>
    </div>
  </figure>
</main>

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

// --p 는 등록된 사용자 지정 속성 — 키프레임에서 보간된다 (미등록이면 steps 처럼 튄다)
@property --p { syntax: "<number>"; inherits: true; initial-value: 0.0444; }

$duration: $dur-quick;
$easing: $ease-spring;
$color: $subject-blue;

@include stage($stage-yellow);

.pl {
  box-sizing: border-box;
  width: min(392px, 92vw);
  margin: 0;
  border-radius: $r-card;
  background: $stage-paper;
  box-shadow: $shadow-raised;
  overflow: hidden;
}
.pl__screen {
  position: relative;
  height: clamp(76px, 22vw, 108px);
  overflow: hidden;
  background: linear-gradient(180deg, rgba(47, 109, 246, .34), rgba(255, 247, 230, .96));
}
.pl__stripes {
  position: absolute; inset: 0 -72px;
  background: repeating-linear-gradient(90deg, rgba(23, 20, 26, .13) 0 12px, transparent 12px 32px);
  animation-name: pl-pan;
  animation-duration: $dur-loop;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}
@keyframes pl-pan { from { transform: translateX(0); } to { transform: translateX(-64px); } }
.pl__world { position: absolute; inset: 0; }
.pl__sun {
  position: absolute; right: 16%; top: 10%;
  width: 22px; height: 22px; border-radius: 50%;
  background: rgba(255, 210, 63, .95);
  box-shadow: 0 0 0 8px rgba(255, 210, 63, .25);
}
.pl__hill { position: absolute; bottom: -46%; height: 82%; border-radius: 50%; }
.pl__hill--a { left: -14%; width: 72%; background: rgba(23, 20, 26, .15); }
.pl__hill--b { right: -18%; width: 62%; background: rgba(23, 20, 26, .09); }
.pl__clock, .pl__badge {
  position: absolute; top: $sp-2;
  padding: $sp-1 $sp-2;
  border-radius: $r-xs;
  background: rgba(23, 20, 26, .62);
  font-family: ui-monospace, "Cascadia Mono", Menlo, Consolas, monospace;
  font-size: 10px; line-height: 14px; font-weight: 700;
}
.pl__clock { left: $sp-2; color: #fff; }
.pl__badge { right: $sp-2; color: rgba(255, 255, 255, .85); }

// ── 챕터 이름 — 한 줄짜리 창으로 4줄을 굴린다. 교체는 steps(1,end) 로 한 프레임 컷 ──
.nm {
  position: absolute; left: $sp-2; bottom: $sp-2;
  height: 20px;
  padding-left: $sp-2; padding-right: $sp-2;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .74);
  overflow: hidden;
}
.nm__list { translate: 0 calc(var(--i, 0) * -20px); }
.nm__i {
  display: block;
  height: 20px;
  color: #fff;
  font-size: 11px; line-height: 20px; font-weight: 700;
  white-space: nowrap;
}

.sk__row {
  display: flex; align-items: center; gap: $sp-3;
  padding: $sp-3;
}
.sk__t {
  flex: 0 0 auto;
  color: rgba(23, 20, 26, .72);
  font-family: ui-monospace, "Cascadia Mono", Menlo, Consolas, monospace;
  font-size: 11px; line-height: 14px; font-weight: 600;
}

.sk {
  position: relative;
  display: flex; align-items: center;
  flex: 1 1 auto;
  box-sizing: border-box;
  height: 36px;
  padding-left: $sp-2; padding-right: $sp-2;
  cursor: pointer;
  touch-action: none;
}
.sk:focus-visible { outline: 2px solid $color; outline-offset: 2px; border-radius: $r-sm; }

// 구간은 % 로 자리를 잡는다 — 틈을 margin-right 로 깎아도 경계 좌표가 안 밀려 재생 머리와 딱 맞는다
.ch {
  --p: 0.0444;
  position: relative;
  flex: 1 1 auto;
  height: 12px;
}
.ch__seg {
  position: absolute; top: 0; bottom: 0;
  left: calc(var(--s) * 100%);
  right: calc(100% - var(--e) * 100%);
  margin-right: $sp-1;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .16);
  overflow: hidden;
}
.ch__seg--end { margin-right: 0; }
.ch__seg:hover { background: rgba(23, 20, 26, .26); }
.ch__fill {
  position: absolute; inset: 0;
  display: block;
  border-radius: $r-pill;
  background: $color;
  transform-origin: left center; // 규칙8: 좌변서 차오름
  // 구간 안 진행률 = (p − 시작) × 1/(끝−시작), 0~1 로 잘라낸다
  transform: scaleX(clamp(0, calc((var(--p) - var(--s)) * var(--k)), 1));
}
.ch__head {
  position: absolute; top: -6px; bottom: -6px;
  left: calc(var(--p) * 100%);
  width: 4px;
  border-radius: $r-pill;
  background: $subject-ink;
  transform: translateX(-50%);
  pointer-events: none;
}
.ch__dot {
  position: absolute; left: 50%; top: -4px;
  width: 12px; height: 12px;
  border-radius: 50%;
  background: $stage-paper;
  box-shadow: 0 2px 6px rgba(23, 20, 26, .45);
  transform: translateX(-50%);
}

// ── 자동 루프: 재생 머리가 바를 지나며 구간을 차례로 채우고, 경계를 넘을 때마다 이름이 갈린다 ──
.pl.is-demo .ch {
  animation-name: ch-p;
  animation-duration: $dur-loop;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}
@keyframes ch-p {
  0%   { --p: 0.0444; }
  80%  { --p: 0.94; }
  86%  { --p: 0.94; }
  87%  { --p: 0.0444; }
  100% { --p: 0.0444; }
}
.pl.is-demo .nm__list {
  animation-name: nm-roll, nm-rise;
  animation-duration: $dur-loop, $dur-loop;
  animation-timing-function: steps(1, end), $easing;
  animation-iteration-count: infinite, infinite;
}
// 경계 시각: --p 가 .1333 / .4 / .7778 을 지나는 순간 (7.9% · 31.8% · 65.5%), 복귀는 87%
@keyframes nm-roll {
  0%     { translate: 0 0; }
  7.9%   { translate: 0 -20px; }
  31.8%  { translate: 0 -40px; }
  65.5%  { translate: 0 -60px; }
  87%    { translate: 0 0; }
  100%   { translate: 0 0; }
}
@keyframes nm-rise {
  0%     { transform: translateY(0); }
  7.8%   { transform: translateY(0); }
  7.9%   { transform: translateY(4px); }
  15.9%  { transform: translateY(0); }
  31.7%  { transform: translateY(0); }
  31.8%  { transform: translateY(4px); }
  39.8%  { transform: translateY(0); }
  65.4%  { transform: translateY(0); }
  65.5%  { transform: translateY(4px); }
  73.5%  { transform: translateY(0); }
  86.9%  { transform: translateY(0); }
  87%    { transform: translateY(4px); }
  95%    { transform: translateY(0); }
  100%   { transform: translateY(0); }
}

@media (max-width: 340px) {
  .sk__row { gap: $sp-2; padding: $sp-2; }
  .sk { height: 32px; }
  .nm { bottom: $sp-1; }
}

@media (prefers-reduced-motion: reduce) {
  .pl.is-demo .ch, .pl.is-demo .nm__list, .pl__stripes { animation: none !important; }
  .ch__fill, .ch__head { transition: none; }
}

@property --p {
  syntax: "<number>";
  inherits: true;
  initial-value: 0.0444;
}
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);
}

.pl {
  box-sizing: border-box;
  width: min(392px, 92vw);
  margin: 0;
  border-radius: 16px;
  background: #ffffff;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  overflow: hidden;
}

.pl__screen {
  position: relative;
  height: clamp(76px, 22vw, 108px);
  overflow: hidden;
  background: linear-gradient(180deg, rgba(47, 109, 246, 0.34), rgba(255, 247, 230, 0.96));
}

.pl__stripes {
  position: absolute;
  inset: 0 -72px;
  background: repeating-linear-gradient(90deg, rgba(23, 20, 26, 0.13) 0 12px, transparent 12px 32px);
  animation-name: pl-pan;
  animation-duration: 2s;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}

@keyframes pl-pan {
  from {
    transform: translateX(0);
  }
  to {
    transform: translateX(-64px);
  }
}
.pl__world {
  position: absolute;
  inset: 0;
}

.pl__sun {
  position: absolute;
  right: 16%;
  top: 10%;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: rgba(255, 210, 63, 0.95);
  box-shadow: 0 0 0 8px rgba(255, 210, 63, 0.25);
}

.pl__hill {
  position: absolute;
  bottom: -46%;
  height: 82%;
  border-radius: 50%;
}

.pl__hill--a {
  left: -14%;
  width: 72%;
  background: rgba(23, 20, 26, 0.15);
}

.pl__hill--b {
  right: -18%;
  width: 62%;
  background: rgba(23, 20, 26, 0.09);
}

.pl__clock, .pl__badge {
  position: absolute;
  top: 8px;
  padding: 4px 8px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.62);
  font-family: ui-monospace, "Cascadia Mono", Menlo, Consolas, monospace;
  font-size: 10px;
  line-height: 14px;
  font-weight: 700;
}

.pl__clock {
  left: 8px;
  color: #fff;
}

.pl__badge {
  right: 8px;
  color: rgba(255, 255, 255, 0.85);
}

.nm {
  position: absolute;
  left: 8px;
  bottom: 8px;
  height: 20px;
  padding-left: 8px;
  padding-right: 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.74);
  overflow: hidden;
}

.nm__list {
  translate: 0 calc(var(--i, 0) * -20px);
}

.nm__i {
  display: block;
  height: 20px;
  color: #fff;
  font-size: 11px;
  line-height: 20px;
  font-weight: 700;
  white-space: nowrap;
}

.sk__row {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px;
}

.sk__t {
  flex: 0 0 auto;
  color: rgba(23, 20, 26, 0.72);
  font-family: ui-monospace, "Cascadia Mono", Menlo, Consolas, monospace;
  font-size: 11px;
  line-height: 14px;
  font-weight: 600;
}

.sk {
  position: relative;
  display: flex;
  align-items: center;
  flex: 1 1 auto;
  box-sizing: border-box;
  height: 36px;
  padding-left: 8px;
  padding-right: 8px;
  cursor: pointer;
  touch-action: none;
}

.sk:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 2px;
  border-radius: 8px;
}

.ch {
  --p: 0.0444;
  position: relative;
  flex: 1 1 auto;
  height: 12px;
}

.ch__seg {
  position: absolute;
  top: 0;
  bottom: 0;
  left: calc(var(--s) * 100%);
  right: calc(100% - var(--e) * 100%);
  margin-right: 4px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.16);
  overflow: hidden;
}

.ch__seg--end {
  margin-right: 0;
}

.ch__seg:hover {
  background: rgba(23, 20, 26, 0.26);
}

.ch__fill {
  position: absolute;
  inset: 0;
  display: block;
  border-radius: 999px;
  background: #2f6df6;
  transform-origin: left center;
  transform: scaleX(clamp(0, (var(--p) - var(--s)) * var(--k), 1));
}

.ch__head {
  position: absolute;
  top: -6px;
  bottom: -6px;
  left: calc(var(--p) * 100%);
  width: 4px;
  border-radius: 999px;
  background: #17141a;
  transform: translateX(-50%);
  pointer-events: none;
}

.ch__dot {
  position: absolute;
  left: 50%;
  top: -4px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: #ffffff;
  box-shadow: 0 2px 6px rgba(23, 20, 26, 0.45);
  transform: translateX(-50%);
}

.pl.is-demo .ch {
  animation-name: ch-p;
  animation-duration: 2s;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}

@keyframes ch-p {
  0% {
    --p: 0.0444;
  }
  80% {
    --p: 0.94;
  }
  86% {
    --p: 0.94;
  }
  87% {
    --p: 0.0444;
  }
  100% {
    --p: 0.0444;
  }
}
.pl.is-demo .nm__list {
  animation-name: nm-roll, nm-rise;
  animation-duration: 2s, 2s;
  animation-timing-function: steps(1, end), cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite, infinite;
}

@keyframes nm-roll {
  0% {
    translate: 0 0;
  }
  7.9% {
    translate: 0 -20px;
  }
  31.8% {
    translate: 0 -40px;
  }
  65.5% {
    translate: 0 -60px;
  }
  87% {
    translate: 0 0;
  }
  100% {
    translate: 0 0;
  }
}
@keyframes nm-rise {
  0% {
    transform: translateY(0);
  }
  7.8% {
    transform: translateY(0);
  }
  7.9% {
    transform: translateY(4px);
  }
  15.9% {
    transform: translateY(0);
  }
  31.7% {
    transform: translateY(0);
  }
  31.8% {
    transform: translateY(4px);
  }
  39.8% {
    transform: translateY(0);
  }
  65.4% {
    transform: translateY(0);
  }
  65.5% {
    transform: translateY(4px);
  }
  73.5% {
    transform: translateY(0);
  }
  86.9% {
    transform: translateY(0);
  }
  87% {
    transform: translateY(4px);
  }
  95% {
    transform: translateY(0);
  }
  100% {
    transform: translateY(0);
  }
}
@media (max-width: 340px) {
  .sk__row {
    gap: 8px;
    padding: 8px;
  }
  .sk {
    height: 32px;
  }
  .nm {
    bottom: 4px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .pl.is-demo .ch, .pl.is-demo .nm__list, .pl__stripes {
    animation: none !important;
  }
  .ch__fill, .ch__head {
    transition: none;
  }
}

// 실제 동작: chapter 눈금을 누르면 그 chapter 시작으로 건너뛰고, ←→ 5초 · Home/End 로도 움직인다.
var root = document.getElementById('pl'), sk = document.getElementById('sk'), ch = document.getElementById('ch'),
    nm = document.getElementById('nm'), clock = document.getElementById('clock'), now = document.getElementById('t-now');
var DUR = 180, CH = [[0, 'Intro'], [24, 'Setup'], [72, 'Example'], [140, 'Recap']], t = 8;
function fmt(s) { s = Math.floor(s); return Math.floor(s / 60) + ':' + ('0' + (s % 60)).slice(-2); }
function idx(s) { var i = 0, k; for (k = 0; k < CH.length; k++) { if (s >= CH[k][0]) i = k; } return i; }
function label() {
  var i = idx(t);
  clock.textContent = fmt(t);
  now.textContent = fmt(t);
  sk.setAttribute('aria-valuenow', Math.floor(t));
  sk.setAttribute('aria-valuetext', CH[i][1] + ' chapter, ' + fmt(t));
  return i;
}
function paint() {
  ch.style.setProperty('--p', (t / DUR).toFixed(4));
  nm.style.setProperty('--i', label());
}
// 자동 루프 중엔 CSS 가 --p 를 움직인다 — 글자는 그리기 직전(rAF)에 그 값을 읽어 같은 프레임에 맞춘다.
// setInterval 로 읽으면 프레임 사이에 값이 어긋나 시계가 Play 머리와 따로 논다 (실측 2026-09-12: 2:49 인데 머리는 Intro)
var prev = 0;
requestAnimationFrame(function tick(ms) {
  if (root.classList.contains('is-demo')) {
    var v = parseFloat(getComputedStyle(ch).getPropertyValue('--p'));
    if (v === v) { t = v * DUR; label(); }
  } else if (ms - prev > 80) {
    prev = ms; t = (t + .08) % DUR; paint();
  }
  requestAnimationFrame(tick);
});
function take() { root.classList.remove('is-demo'); }
[].forEach.call(ch.querySelectorAll('.ch__seg'), function (el, i) {
  el.addEventListener('click', function () { take(); t = CH[i][0]; paint(); sk.focus({ preventScroll: true }); });
});
sk.addEventListener('keydown', function (e) {
  var k = e.key;
  if (k === 'ArrowRight') { t = Math.min(DUR - 1, t + 5); }
  else if (k === 'ArrowLeft') { t = Math.max(0, t - 5); }
  else if (k === 'Home') { t = 0; }
  else if (k === 'End') { t = DUR - 1; }
  else { return; }
  take(); paint(); e.preventDefault();
});

import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./ChapterMarkers.module.scss";

export type Chapter = { at: number; name: string };

export type ChapterMarkersProps = {
  /** 더미 영상 길이(초) */
  total?: number;
  /** 시작 위치(초) */
  start?: number;
  /** 챕터 시작 시각과 이름 */
  chapters?: Chapter[];
  duration?: number;
  easing?: string;
  color?: string;
};

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

// TS7006 방지 — 'react' 의 이벤트 제네릭 대신 필요한 필드만 로컬로 선언한다
type KeyEvt = { key: string; preventDefault: () => void };

function fmt(s: number) {
  const n = Math.floor(s);
  return Math.floor(n / 60) + ":" + ("0" + (n % 60)).slice(-2);
}

function clamp01(v: number) {
  return Math.max(0, Math.min(1, v));
}

export default function ChapterMarkers({
  total = 180,
  start = 8,
  chapters = [
    { at: 0, name: "인트로" },
    { at: 24, name: "설치" },
    { at: 72, name: "예제" },
    { at: 140, name: "정리" },
  ],
  duration = 220,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
}: ChapterMarkersProps) {
  const [t, setT] = useState(start);
  const skRef = useRef<HTMLDivElement>(null);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  // 더미 재생 시계 — 바닐라의 rAF(실시간 1배) 를 setInterval(250ms, +0.25초) 로
  useEffect(() => {
    const id = setInterval(() => setT((p) => (p + 0.25) % total), 250);
    return () => clearInterval(id);
  }, [total]);

  // 구간은 % 로 자리를 잡는다 — s(시작) · e(끝) · k = 1/(e−s) 로 구간 안 진행률을 낸다
  const segs = chapters.map((c, i) => {
    const s = c.at / total;
    const e = (i + 1 < chapters.length ? chapters[i + 1].at : total) / total;
    return { at: c.at, name: c.name, s, e, k: 1 / (e - s) };
  });

  let i = 0;
  for (let k = 0; k < chapters.length; k++) if (t >= chapters[k].at) i = k;
  const p = t / total;
  const nameVars: NameVars = { "--i": String(i) };

  return (
    <figure className={styles.player} style={vars}>
      <div className={styles.screen}>
        <div className={styles.stripes} aria-hidden="true" />
        <div className={styles.world} aria-hidden="true">
          <span className={styles.sun} />
          <span className={`${styles.hill} ${styles.hillA}`} />
          <span className={`${styles.hill} ${styles.hillB}`} />
        </div>
        <span className={styles.clock}>{fmt(t)}</span>
        <span className={styles.badge}>{fmt(total)}</span>
        <div className={styles.nm}>
          <div className={styles.nmList} style={nameVars}>
            {chapters.map((c, k) => (
              <b key={c.at} className={styles.nmItem}>
                {k + 1} · {c.name}
              </b>
            ))}
          </div>
        </div>
      </div>

      <div className={styles.row}>
        <span className={styles.rowTime}>
          <b>{fmt(t)}</b> / {fmt(total)}
        </span>
        <div
          ref={skRef}
          className={styles.sk}
          role="slider"
          tabIndex={0}
          aria-label="재생 위치"
          aria-valuemin={0}
          aria-valuemax={total}
          aria-valuenow={Math.floor(t)}
          aria-valuetext={`${chapters[i].name} 챕터, ${fmt(t)}`}
          onKeyDown={(e: KeyEvt) => {
            if (e.key === "ArrowRight") { setT((v) => Math.min(total - 1, v + 5)); e.preventDefault(); }
            else if (e.key === "ArrowLeft") { setT((v) => Math.max(0, v - 5)); e.preventDefault(); }
            else if (e.key === "Home") { setT(0); e.preventDefault(); }
            else if (e.key === "End") { setT(total - 1); e.preventDefault(); }
          }}
        >
          <div className={styles.ch}>
            {segs.map((g, k) => (
              <span
                key={g.at}
                className={`${styles.seg} ${k === segs.length - 1 ? styles.segEnd : ""}`}
                style={{ left: `${(g.s * 100).toFixed(4)}%`, right: `${(100 - g.e * 100).toFixed(4)}%` }}
                onClick={() => {
                  setT(g.at);
                  skRef.current?.focus({ preventScroll: true });
                }}
              >
                <i
                  className={styles.segFill}
                  style={{ transform: `scaleX(${clamp01((p - g.s) * g.k).toFixed(4)})` }}
                />
              </span>
            ))}
            <span className={styles.head} style={{ left: `${(p * 100).toFixed(4)}%` }} aria-hidden="true">
              <i className={styles.dot} />
            </span>
          </div>
        </div>
      </div>
    </figure>
  );
}