01Route progress bar that crosses the top of the screen

<main class="stage">
  <section class="rp is-demo" id="rp" aria-label="Route progress bar preview">
    <div class="rp__bar">
      <span class="rp__fill" id="rp-fill" role="progressbar" aria-valuenow="0" aria-valuemin="0" aria-valuemax="100" aria-label="Loading progress for the next screen"></span>
    </div>
    <nav class="rp__tabs" aria-label="Screen navigation">
      <button class="rp__tab is-current" type="button" aria-current="page">
        <span class="rp__pill" aria-hidden="true"></span><span class="rp__label">Home</span>
      </button>
      <button class="rp__tab" type="button">
        <span class="rp__pill" aria-hidden="true"></span><span class="rp__label">Posts</span>
      </button>
      <button class="rp__tab" type="button">
        <span class="rp__pill" aria-hidden="true"></span><span class="rp__label">About</span>
      </button>
    </nav>
    <div class="rp__view" id="rp-view" aria-busy="false">
      <p class="rp__head" id="rp-head">Home</p>
      <p class="rp__wait">Preparing the next screen</p>
      <p class="rp__text">The screen you are on stays put; only the next one is fetched.</p>
    </div>
  </section>
</main>

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

// 상단 라우트 진행 바 — 링크를 누르면 화면 맨 위 띠가 가짜 fetch 진행만큼 scaleX 로 자란다
$duration: $dur-quick;
$easing: $ease-spring;
$color: $subject-blue;

@include stage($stage-ink);

$panel: color.mix($subject-cream, $stage-ink, 8%);
$line: rgba(255, 247, 230, .16);

.rp {
  box-sizing: border-box;
  display: grid;
  width: min(300px, 88vw);
  overflow: hidden;
  border: 1px solid $line;
  border-radius: $r-card;
  background: $panel;
  color: $subject-cream;
}
.rp * { box-sizing: border-box; }

// ── 화면 맨 위 진행 띠 ──
// 트랙은 늘 자리에 있고 채움만 scaleX 로 자란다. 폭(width)이 아니라 transform 이라 레이아웃을 다시 계산하지 않는다
.rp__bar { height: 4px; background: rgba(255, 247, 230, .12); }
.rp__fill {
  display: block;
  height: 100%;
  background: $color;
  transform: scaleX(0);
  transform-origin: left center; // 규칙8: 루트 진행띠 좌측 채움
  transition: transform $duration $easing;
}
// 100% 뒤 페이드는 실제 클릭 경로(.is-done)에서만. 격자 루프는 사라지는 장면을 재현하지 않는다
.rp.is-done .rp__fill { opacity: 0; transition: opacity $dur-base linear 180ms; }

// ── 링크 세 개 ──
// 균등 칸은 grid 로 짠다 (flex 1 1 0 + scaleX 조합은 인디케이터 오탐을 부른다)
.rp__tabs {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: $sp-1;
  padding: $sp-3 $sp-3 $sp-2;
}
.rp__tab {
  position: relative;
  margin: 0;
  padding: $sp-2 $sp-1;
  border: 0;
  border-radius: $r-pill;
  background: none;
  color: $subject-cream;
  font-family: inherit;
  font-size: 12px;
  font-weight: 700;
  line-height: 1;
  cursor: pointer;
}
.rp__tab:focus-visible { outline: 2px solid $color; outline-offset: 2px; }
.rp__pill {
  position: absolute;
  inset: 0;
  border-radius: $r-pill;
  background: rgba(255, 247, 230, .14);
  opacity: 0;
}
.rp__tab.is-current .rp__pill { opacity: 1; }
.rp__label { position: relative; }

// ── 본문: 기다리는 동안에도 자리와 글자가 그대로 남는다 ──
.rp__view {
  display: grid;
  gap: $sp-2;
  padding: 0 $sp-3 $sp-3;
}
.rp__head {
  margin: 0;
  font-size: 15px;
  font-weight: 800;
  line-height: 1.2;
}
// 안내 줄은 자리를 늘 차지하고 보임만 변한다 — 켜질 때 아래 글이 밀리지 않는다
.rp__wait {
  margin: 0;
  color: $color;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.2;
  opacity: 0;
}
.rp__text {
  margin: 0;
  color: rgba(255, 247, 230, .66);
  font-size: 12px;
  font-weight: 500;
  line-height: 1.5;
}
// 정적(손으로 조작) 경로 — aria-busy 가 켜지면 안내가 뜨고 본문이 옅어진다
.rp__view[aria-busy="true"] .rp__wait { opacity: 1; }
.rp__view[aria-busy="true"] .rp__text { opacity: .45; }

// ── 격자 미리보기 전용 2초 루프 ──
// 0 → 88% 까지만 채우고 그대로 둔다. 완료·퇴장은 재현하지 않는다(대표 이미지가 빈 띠가 된다)
// 처음 상태로는 88% 지점에서 한 프레임에 컷으로 돌아온다(24프레임의 마지막 샘플은 95.8%)
@keyframes rp-trickle {
  0% { transform: scaleX(0); animation-timing-function: steps(1, end); }
  8% { transform: scaleX(.12); }
  26% { transform: scaleX(.38); }
  48% { transform: scaleX(.66); }
  70% { transform: scaleX(.88); }
  80% { transform: scaleX(.88); animation-timing-function: steps(1, end); }
  88%, 100% { transform: scaleX(0); }
}
@keyframes rp-pill-home {
  0%, 7% { opacity: 1; }
  8%, 87% { opacity: 0; }
  88%, 100% { opacity: 1; }
}
@keyframes rp-pill-list {
  0%, 7% { opacity: 0; }
  8%, 87% { opacity: 1; }
  88%, 100% { opacity: 0; }
}
// 복귀는 셋으로 나눠 흘린다 — 누르는 순간(8%)이 가장 크게 변한 장면으로 남아야 대표 이미지가 산다
@keyframes rp-wait {
  0%, 7% { opacity: 0; }
  8%, 77% { opacity: 1; }
  78%, 100% { opacity: 0; }
}
@keyframes rp-text {
  0%, 7% { opacity: 1; }
  8%, 83% { opacity: .45; }
  84%, 100% { opacity: 1; }
}

.rp.is-demo {
  .rp__fill {
    animation-name: rp-trickle;
    animation-duration: $dur-loop;
    animation-timing-function: $easing;
    animation-iteration-count: infinite;
  }
  .rp__tab:nth-child(1) .rp__pill { animation-name: rp-pill-home; }
  .rp__tab:nth-child(2) .rp__pill { animation-name: rp-pill-list; }
  .rp__wait { animation-name: rp-wait; }
  .rp__text { animation-name: rp-text; }
  .rp__pill,
  .rp__wait,
  .rp__text {
    animation-duration: $dur-loop;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
}

@media (max-width: 340px) {
  .rp__tabs { padding: $sp-2; }
  .rp__tab { padding: $sp-1; font-size: 11px; }
  .rp__view { gap: $sp-1; padding: 0 $sp-2 $sp-2; }
  .rp__head { font-size: 13px; }
  .rp__wait { font-size: 10px; }
  .rp__text { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .rp.is-demo .rp__fill,
  .rp.is-demo .rp__pill,
  .rp.is-demo .rp__wait,
  .rp.is-demo .rp__text { animation: none !important; transition: none !important; }
  // 움직임만 끄고 "기다리는 중" 이라는 결과 상태는 남긴다
  .rp.is-demo .rp__fill { transform: scaleX(.88) !important; }
  .rp.is-demo .rp__tab:nth-child(1) .rp__pill { opacity: 0 !important; }
  .rp.is-demo .rp__tab:nth-child(2) .rp__pill { opacity: 1 !important; }
  .rp.is-demo .rp__wait { opacity: 1 !important; }
  .rp.is-demo .rp__text { opacity: .45 !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);
}

.rp {
  box-sizing: border-box;
  display: grid;
  width: min(300px, 88vw);
  overflow: hidden;
  border: 1px solid rgba(255, 247, 230, 0.16);
  border-radius: 16px;
  background: rgb(16.2980392157%, 14.9647058824%, 16.5960784314%);
  color: #fff7e6;
}

.rp * {
  box-sizing: border-box;
}

.rp__bar {
  height: 4px;
  background: rgba(255, 247, 230, 0.12);
}

.rp__fill {
  display: block;
  height: 100%;
  background: #2f6df6;
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.rp.is-done .rp__fill {
  opacity: 0;
  transition: opacity 300ms linear 180ms;
}

.rp__tabs {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 4px;
  padding: 12px 12px 8px;
}

.rp__tab {
  position: relative;
  margin: 0;
  padding: 8px 4px;
  border: 0;
  border-radius: 999px;
  background: none;
  color: #fff7e6;
  font-family: inherit;
  font-size: 12px;
  font-weight: 700;
  line-height: 1;
  cursor: pointer;
}

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

.rp__pill {
  position: absolute;
  inset: 0;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.14);
  opacity: 0;
}

.rp__tab.is-current .rp__pill {
  opacity: 1;
}

.rp__label {
  position: relative;
}

.rp__view {
  display: grid;
  gap: 8px;
  padding: 0 12px 12px;
}

.rp__head {
  margin: 0;
  font-size: 15px;
  font-weight: 800;
  line-height: 1.2;
}

.rp__wait {
  margin: 0;
  color: #2f6df6;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.2;
  opacity: 0;
}

.rp__text {
  margin: 0;
  color: rgba(255, 247, 230, 0.66);
  font-size: 12px;
  font-weight: 500;
  line-height: 1.5;
}

.rp__view[aria-busy=true] .rp__wait {
  opacity: 1;
}

.rp__view[aria-busy=true] .rp__text {
  opacity: 0.45;
}

@keyframes rp-trickle {
  0% {
    transform: scaleX(0);
    animation-timing-function: steps(1, end);
  }
  8% {
    transform: scaleX(0.12);
  }
  26% {
    transform: scaleX(0.38);
  }
  48% {
    transform: scaleX(0.66);
  }
  70% {
    transform: scaleX(0.88);
  }
  80% {
    transform: scaleX(0.88);
    animation-timing-function: steps(1, end);
  }
  88%, 100% {
    transform: scaleX(0);
  }
}
@keyframes rp-pill-home {
  0%, 7% {
    opacity: 1;
  }
  8%, 87% {
    opacity: 0;
  }
  88%, 100% {
    opacity: 1;
  }
}
@keyframes rp-pill-list {
  0%, 7% {
    opacity: 0;
  }
  8%, 87% {
    opacity: 1;
  }
  88%, 100% {
    opacity: 0;
  }
}
@keyframes rp-wait {
  0%, 7% {
    opacity: 0;
  }
  8%, 77% {
    opacity: 1;
  }
  78%, 100% {
    opacity: 0;
  }
}
@keyframes rp-text {
  0%, 7% {
    opacity: 1;
  }
  8%, 83% {
    opacity: 0.45;
  }
  84%, 100% {
    opacity: 1;
  }
}
.rp.is-demo .rp__fill {
  animation-name: rp-trickle;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}
.rp.is-demo .rp__tab:nth-child(1) .rp__pill {
  animation-name: rp-pill-home;
}
.rp.is-demo .rp__tab:nth-child(2) .rp__pill {
  animation-name: rp-pill-list;
}
.rp.is-demo .rp__wait {
  animation-name: rp-wait;
}
.rp.is-demo .rp__text {
  animation-name: rp-text;
}
.rp.is-demo .rp__pill,
.rp.is-demo .rp__wait,
.rp.is-demo .rp__text {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

@media (max-width: 340px) {
  .rp__tabs {
    padding: 8px;
  }
  .rp__tab {
    padding: 4px;
    font-size: 11px;
  }
  .rp__view {
    gap: 4px;
    padding: 0 8px 8px;
  }
  .rp__head {
    font-size: 13px;
  }
  .rp__wait {
    font-size: 10px;
  }
  .rp__text {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rp.is-demo .rp__fill,
  .rp.is-demo .rp__pill,
  .rp.is-demo .rp__wait,
  .rp.is-demo .rp__text {
    animation: none !important;
    transition: none !important;
  }
  .rp.is-demo .rp__fill {
    transform: scaleX(0.88) !important;
  }
  .rp.is-demo .rp__tab:nth-child(1) .rp__pill {
    opacity: 0 !important;
  }
  .rp.is-demo .rp__tab:nth-child(2) .rp__pill {
    opacity: 1 !important;
  }
  .rp.is-demo .rp__wait {
    opacity: 1 !important;
  }
  .rp.is-demo .rp__text {
    opacity: 0.45 !important;
  }
}

// 가짜 fetch 진행: 12 → 38 → 66 → 88 → 100. 그때마다 aria-valuenow 를 실제로 갱신한다.
var rp = document.getElementById('rp');
var rpFill = document.getElementById('rp-fill');
var rpView = document.getElementById('rp-view');
var rpHead = document.getElementById('rp-head');
var rpTabs = rp.querySelectorAll('.rp__tab');
var rpSteps = [12, 38, 66, 88, 100];
var rpTimer = 0;
function rpSet(v) {
  rpFill.style.transform = 'scaleX(' + v / 100 + ')';
  rpFill.setAttribute('aria-valuenow', String(v));
}
function rpGo(btn) {
  rp.classList.remove('is-demo');
  rp.classList.remove('is-done');
  clearInterval(rpTimer);
  for (var i = 0; i < rpTabs.length; i++) {
    var on = rpTabs[i] === btn;
    rpTabs[i].classList.toggle('is-current', on);
    if (on) rpTabs[i].setAttribute('aria-current', 'page');
    else rpTabs[i].removeAttribute('aria-current');
  }
  rpView.setAttribute('aria-busy', 'true');
  rpSet(0);
  var k = 0;
  rpTimer = setInterval(function () {
    rpSet(rpSteps[k]);
    k += 1;
    if (k < rpSteps.length) return;
    clearInterval(rpTimer);
    rpHead.textContent = btn.querySelector('.rp__label').textContent;
    rpView.setAttribute('aria-busy', 'false');
    // 완료 뒤 페이드는 실제 클릭 경로에서만 — 격자 루프는 재현하지 않는다
    rp.classList.add('is-done');
  }, 240);
}
for (var t = 0; t < rpTabs.length; t++) {
  rpTabs[t].addEventListener('click', function (e) { rpGo(e.currentTarget); });
}

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

export type RouteProgressBarProps = {
  /** 링크(탭) 라벨 — 누르면 가짜 fetch 진행이 시작된다 */
  links?: string[];
  bodyText?: string;
  waitLabel?: string;
  progressLabel?: string;
  navLabel?: string;
  groupLabel?: string;
  /** 격자 미리보기용 2초 자동 루프. 사람이 손대면 꺼진다 */
  demo?: boolean;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
// ambient 가 얇아 useRef 가 T | null 을 돌려준다 — 필요한 꼴만 로컬 타입으로 단언
type Box<T> = { current: T };

const DEFAULT_LINKS = ["Home", "Posts", "About"];
// 가짜 fetch 진행 — 마지막 100 뒤에만 띠가 사라진다
const STEPS = [12, 38, 66, 88, 100];

export default function RouteProgressBar({
  links = DEFAULT_LINKS,
  bodyText = "The screen you are on stays put; only the next one is fetched.",
  waitLabel = "Preparing the next screen",
  progressLabel = "Loading progress for the next screen",
  navLabel = "Screen navigation",
  groupLabel = "Route progress bar preview",
  demo = true,
  duration = 220,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
}: RouteProgressBarProps) {
  const [live, setLive] = useState(demo);
  const [current, setCurrent] = useState(0);
  const [head, setHead] = useState(links[0]);
  const [value, setValue] = useState(0);
  const [busy, setBusy] = useState(false);
  const [done, setDone] = useState(false);
  const timer = useRef<number>(0) as Box<number>;

  useEffect(() => () => clearInterval(timer.current), []);

  function go(i: number) {
    setLive(false);
    setDone(false);
    setBusy(true);
    setCurrent(i);
    setValue(0);
    clearInterval(timer.current);
    let k = 0;
    timer.current = window.setInterval(() => {
      setValue(STEPS[k]);
      k += 1;
      if (k < STEPS.length) return;
      clearInterval(timer.current);
      setHead(links[i]);
      setBusy(false);
      // 100% 뒤 페이드는 실제 클릭 경로에서만 — 미리보기 루프는 재현하지 않는다
      setDone(true);
    }, 240);
  }

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const cls = [styles.rp, live ? styles.isDemo : "", done ? styles.isDone : ""].filter(Boolean).join(" ");

  return (
    <section className={cls} style={vars} aria-label={groupLabel}>
      <div className={styles.bar}>
        <span
          className={styles.fill}
          role="progressbar"
          aria-valuenow={value}
          aria-valuemin={0}
          aria-valuemax={100}
          aria-label={progressLabel}
          style={{ transform: `scaleX(${value / 100})` }}
        />
      </div>
      <nav className={styles.tabs} aria-label={navLabel}>
        {links.map((l, i) => (
          <button
            className={[styles.tab, i === current ? styles.isCurrent : ""].filter(Boolean).join(" ")}
            type="button"
            key={l}
            aria-current={i === current ? "page" : undefined}
            onClick={() => go(i)}
          >
            <span className={styles.pill} aria-hidden="true" />
            <span className={styles.label}>{l}</span>
          </button>
        ))}
      </nav>
      <div className={styles.view} aria-busy={busy}>
        <p className={styles.head}>{head}</p>
        <p className={styles.wait}>{waitLabel}</p>
        <p className={styles.text}>{bodyText}</p>
      </div>
    </section>
  );
}