02Tabs that swap the same example per language

<main class="stage">
  <div class="lts is-demo" id="root">
    <div class="pane">
      <div class="pane__head">
        <div class="tabs" role="tablist" aria-label="Select language" id="tablist">
          <button class="tab" role="tab" id="tabCss" aria-selected="true" aria-controls="panelCss" data-lang="css" type="button">CSS</button>
          <button class="tab" role="tab" id="tabScss" aria-selected="false" aria-controls="panelScss" tabindex="-1" data-lang="scss" type="button">SCSS</button>
          <button class="tab" role="tab" id="tabTw" aria-selected="false" aria-controls="panelTw" tabindex="-1" data-lang="tailwind" type="button">Tailwind</button>
          <span class="tabs__indicator" id="indicator" aria-hidden="true"></span>
        </div>
      </div>
      <div class="pane__body">
        <pre class="panel" id="panelCss" role="tabpanel" aria-labelledby="tabCss"><code><span class="k">.btn</span> {
  <span class="k">display</span>: <span class="s">flex</span>;
  <span class="k">align-items</span>: <span class="s">center</span>;
  <span class="k">gap</span>: <span class="n">8px</span>;
  <span class="k">padding</span>: <span class="n">8px</span> <span class="n">16px</span>;
}</code></pre>
        <pre class="panel" id="panelScss" role="tabpanel" aria-labelledby="tabScss" hidden><code><span class="k">.btn</span> {
  <span class="k">display</span>: <span class="s">flex</span>;
  <span class="k">gap</span>: <span class="n">8px</span>;
  <span class="k">&amp;:hover</span> { <span class="k">opacity</span>: <span class="n">.8</span>; }
}</code></pre>
        <pre class="panel" id="panelTw" role="tabpanel" aria-labelledby="tabTw" hidden><code><span class="c">&lt;button class="</span>
  <span class="s">flex items-center gap-2</span>
  <span class="s">px-4 py-2 rounded-xl</span>
<span class="c">"&gt;</span>
  Copy
<span class="c">&lt;/button&gt;</span></code></pre>
      </div>
    </div>
  </div>
</main>

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

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

$syn-key: $stage-orange;
$syn-str: $stage-yellow;
$syn-num: $subject-sky;
$syn-dim: rgba($subject-cream, .72);
$syn-txt: $subject-cream;

@include stage($stage-yellow);

.lts {
  position: relative;
}

.pane {
  box-sizing: border-box;
  width: 288px;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  background: $stage-ink;
  color: $subject-cream;
}

.pane__head {
  box-sizing: border-box;
  display: flex;
  align-items: center;
  gap: $sp-2;
  height: 28px;
  padding: 0 $sp-2;
  background: rgba(255, 247, 230, .06);
  border-bottom: 1px solid rgba(255, 247, 230, .12);
}

.tabs {
  position: relative;
  display: flex;
  align-items: stretch;
  height: 100%;
}
.tab {
  flex: 0 0 auto;
  box-sizing: border-box;
  height: 100%;
  padding: 0 $sp-3;
  border: 0;
  background: transparent;
  color: $syn-dim;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-size: 11px;
  font-weight: 700;
  cursor: pointer;
  transition: color $duration $easing;
}
.tab:focus-visible { outline: 2px solid $color; outline-offset: -2px; }
.tab[aria-selected="true"] { color: $subject-cream; }

.tabs__indicator {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 1px;
  height: 2px;
  border-radius: $r-xs;
  background: $color;
  transform-origin: left center; // 규칙8: 탭 언더라인 왼쪽 기준
  transform: translateX(0) scaleX(1);
  transition: transform $duration $easing;
}

.pane__body {
  position: relative;
  box-sizing: border-box;
  height: 132px;
  padding: $sp-3;
  font-family: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  font-size: 11px;
  line-height: 18px;
}
.panel {
  position: absolute;
  inset: $sp-3;
  margin: 0;
  font: inherit;
  white-space: pre;
  opacity: 1;
}
.panel[hidden] { display: block; opacity: 0; }
.k { color: $syn-key; }
.s { color: $syn-str; }
.n { color: $syn-num; }
.c { color: $syn-dim; }

// ── 자동 루프 (2s) ────────────────────────────────────
// 인디케이터는 부드럽게 미끄러지고, 코드 본문 세 겹은 steps(1,end) 컷으로 갈아 끼운다
.lts.is-demo .tabs__indicator {
  animation-name: lts-indicator;
  animation-duration: $dur-loop;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
.lts.is-demo #tabCss,
.lts.is-demo #tabScss,
.lts.is-demo #tabTw {
  animation-duration: $dur-loop;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.lts.is-demo #tabCss { animation-name: lts-tab-css; }
.lts.is-demo #tabScss { animation-name: lts-tab-scss; }
.lts.is-demo #tabTw { animation-name: lts-tab-tw; }
.lts.is-demo #panelCss,
.lts.is-demo #panelScss,
.lts.is-demo #panelTw {
  animation-duration: $dur-loop;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
  display: block;
}
.lts.is-demo #panelCss { animation-name: lts-panel-css; }
.lts.is-demo #panelScss { animation-name: lts-panel-scss; }
.lts.is-demo #panelTw { animation-name: lts-panel-tw; }

// 폭·오프셋은 Playwright getBoundingClientRect 실측값(스크래치패드/261_tabmeasure.py):
// CSS 43.2px @0 · SCSS 49.38px @43.2 · Tailwind 67.05px @92.58 (기준폭 = CSS 43.2px)
@keyframes lts-indicator {
  0%   { transform: translateX(0) scaleX(1); }
  30%  { transform: translateX(43.2px) scaleX(1.14); }
  60%  { transform: translateX(92.58px) scaleX(1.55); }
  88%  { transform: translateX(0) scaleX(1); }
  100% { transform: translateX(0) scaleX(1); }
}
@keyframes lts-tab-css {
  0%   { color: $subject-cream; }
  30%  { color: $syn-dim; }
  88%  { color: $subject-cream; }
  100% { color: $subject-cream; }
}
@keyframes lts-tab-scss {
  0%   { color: $syn-dim; }
  30%  { color: $subject-cream; }
  60%  { color: $syn-dim; }
  100% { color: $syn-dim; }
}
@keyframes lts-tab-tw {
  0%   { color: $syn-dim; }
  60%  { color: $subject-cream; }
  88%  { color: $syn-dim; }
  100% { color: $syn-dim; }
}
@keyframes lts-panel-css {
  0%   { opacity: 1; }
  30%  { opacity: 0; }
  88%  { opacity: 1; }
  100% { opacity: 1; }
}
@keyframes lts-panel-scss {
  0%   { opacity: 0; }
  30%  { opacity: 1; }
  60%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes lts-panel-tw {
  0%   { opacity: 0; }
  60%  { opacity: 1; }
  88%  { opacity: 0; }
  100% { opacity: 0; }
}

@media (max-width: 340px) {
  .pane { width: 100%; }
  .pane__body { font-size: 10px; line-height: 16px; padding: $sp-2; height: 118px; }
  .panel { inset: $sp-2; }
}

@media (prefers-reduced-motion: reduce) {
  .lts.is-demo .tabs__indicator,
  .lts.is-demo #tabCss,
  .lts.is-demo #tabScss,
  .lts.is-demo #tabTw,
  .lts.is-demo #panelCss,
  .lts.is-demo #panelScss,
  .lts.is-demo #panelTw { animation: none !important; }
  .lts.is-demo #panelScss,
  .lts.is-demo #panelTw { opacity: 0; }
}

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);
}

.lts {
  position: relative;
}

.pane {
  box-sizing: border-box;
  width: 288px;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  background: #17141a;
  color: #fff7e6;
}

.pane__head {
  box-sizing: border-box;
  display: flex;
  align-items: center;
  gap: 8px;
  height: 28px;
  padding: 0 8px;
  background: rgba(255, 247, 230, 0.06);
  border-bottom: 1px solid rgba(255, 247, 230, 0.12);
}

.tabs {
  position: relative;
  display: flex;
  align-items: stretch;
  height: 100%;
}

.tab {
  flex: 0 0 auto;
  box-sizing: border-box;
  height: 100%;
  padding: 0 12px;
  border: 0;
  background: transparent;
  color: rgba(255, 247, 230, 0.72);
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-size: 11px;
  font-weight: 700;
  cursor: pointer;
  transition: color 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

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

.tab[aria-selected=true] {
  color: #fff7e6;
}

.tabs__indicator {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 1px;
  height: 2px;
  border-radius: 4px;
  background: #2f6df6;
  transform-origin: left center;
  transform: translateX(0) scaleX(1);
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.pane__body {
  position: relative;
  box-sizing: border-box;
  height: 132px;
  padding: 12px;
  font-family: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  font-size: 11px;
  line-height: 18px;
}

.panel {
  position: absolute;
  inset: 12px;
  margin: 0;
  font: inherit;
  white-space: pre;
  opacity: 1;
}

.panel[hidden] {
  display: block;
  opacity: 0;
}

.k {
  color: #ff4d1f;
}

.s {
  color: #ffd23f;
}

.n {
  color: #6ec8ff;
}

.c {
  color: rgba(255, 247, 230, 0.72);
}

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

.lts.is-demo #tabCss,
.lts.is-demo #tabScss,
.lts.is-demo #tabTw {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

.lts.is-demo #tabCss {
  animation-name: lts-tab-css;
}

.lts.is-demo #tabScss {
  animation-name: lts-tab-scss;
}

.lts.is-demo #tabTw {
  animation-name: lts-tab-tw;
}

.lts.is-demo #panelCss,
.lts.is-demo #panelScss,
.lts.is-demo #panelTw {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
  display: block;
}

.lts.is-demo #panelCss {
  animation-name: lts-panel-css;
}

.lts.is-demo #panelScss {
  animation-name: lts-panel-scss;
}

.lts.is-demo #panelTw {
  animation-name: lts-panel-tw;
}

@keyframes lts-indicator {
  0% {
    transform: translateX(0) scaleX(1);
  }
  30% {
    transform: translateX(43.2px) scaleX(1.14);
  }
  60% {
    transform: translateX(92.58px) scaleX(1.55);
  }
  88% {
    transform: translateX(0) scaleX(1);
  }
  100% {
    transform: translateX(0) scaleX(1);
  }
}
@keyframes lts-tab-css {
  0% {
    color: #fff7e6;
  }
  30% {
    color: rgba(255, 247, 230, 0.72);
  }
  88% {
    color: #fff7e6;
  }
  100% {
    color: #fff7e6;
  }
}
@keyframes lts-tab-scss {
  0% {
    color: rgba(255, 247, 230, 0.72);
  }
  30% {
    color: #fff7e6;
  }
  60% {
    color: rgba(255, 247, 230, 0.72);
  }
  100% {
    color: rgba(255, 247, 230, 0.72);
  }
}
@keyframes lts-tab-tw {
  0% {
    color: rgba(255, 247, 230, 0.72);
  }
  60% {
    color: #fff7e6;
  }
  88% {
    color: rgba(255, 247, 230, 0.72);
  }
  100% {
    color: rgba(255, 247, 230, 0.72);
  }
}
@keyframes lts-panel-css {
  0% {
    opacity: 1;
  }
  30% {
    opacity: 0;
  }
  88% {
    opacity: 1;
  }
  100% {
    opacity: 1;
  }
}
@keyframes lts-panel-scss {
  0% {
    opacity: 0;
  }
  30% {
    opacity: 1;
  }
  60% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes lts-panel-tw {
  0% {
    opacity: 0;
  }
  60% {
    opacity: 1;
  }
  88% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@media (max-width: 340px) {
  .pane {
    width: 100%;
  }
  .pane__body {
    font-size: 10px;
    line-height: 16px;
    padding: 8px;
    height: 118px;
  }
  .panel {
    inset: 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .lts.is-demo .tabs__indicator,
  .lts.is-demo #tabCss,
  .lts.is-demo #tabScss,
  .lts.is-demo #tabTw,
  .lts.is-demo #panelCss,
  .lts.is-demo #panelScss,
  .lts.is-demo #panelTw {
    animation: none !important;
  }
  .lts.is-demo #panelScss,
  .lts.is-demo #panelTw {
    opacity: 0;
  }
}

var root = document.getElementById('root');
var tablist = document.getElementById('tablist');
var indicator = document.getElementById('indicator');
var tabs = [document.getElementById('tabCss'), document.getElementById('tabScss'), document.getElementById('tabTw')];
var panels = [document.getElementById('panelCss'), document.getElementById('panelScss'), document.getElementById('panelTw')];

function moveIndicator(tab) {
  var tabsRect = tablist.getBoundingClientRect();
  var r = tab.getBoundingClientRect();
  var base = tabs[0].getBoundingClientRect().width;
  var left = r.left - tabsRect.left;
  var scale = r.width / base;
  indicator.style.transform = 'translateX(' + left + 'px) scaleX(' + scale + ')';
}

function select(i) {
  tabs.forEach(function (t, idx) {
    var on = idx === i;
    t.setAttribute('aria-selected', on ? 'true' : 'false');
    t.tabIndex = on ? 0 : -1;
    panels[idx].hidden = !on;
  });
  moveIndicator(tabs[i]);
}

tabs.forEach(function (t, i) {
  t.addEventListener('click', function () {
    root.classList.remove('is-demo');
    select(i);
  });
});

tablist.addEventListener('keydown', function (e) {
  var i = tabs.findIndex(function (t) { return t.getAttribute('aria-selected') === 'true'; });
  if (e.key === 'ArrowRight' || e.key === 'ArrowLeft') {
    root.classList.remove('is-demo');
    var next = e.key === 'ArrowRight' ? (i + 1) % tabs.length : (i - 1 + tabs.length) % tabs.length;
    select(next);
    tabs[next].focus({ preventScroll: true });
    e.preventDefault();
  }
});

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

export type LanguageTabSwitchProps = {
  tablistLabel?: string;
  /** 자동 재생 루프 (갤러리용). 사람이 누르면 꺼진다 */
  demo?: boolean;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T | null };
type KeyEvt = { key: string; preventDefault(): void };

const LANGS = ["css", "scss", "tailwind"] as const;
type Lang = (typeof LANGS)[number];
const LABELS: Record<Lang, string> = { css: "CSS", scss: "SCSS", tailwind: "Tailwind" };
const TAB_CLASS_KEY: Record<Lang, "tabCss" | "tabScss" | "tabTw"> = { css: "tabCss", scss: "tabScss", tailwind: "tabTw" };

function CssCode() {
  return (
    <code>
      <span className={styles.k}>.btn</span> {"{"}
      {"\n  "}
      <span className={styles.k}>display</span>: <span className={styles.s}>flex</span>;
      {"\n  "}
      <span className={styles.k}>align-items</span>: <span className={styles.s}>center</span>;
      {"\n  "}
      <span className={styles.k}>gap</span>: <span className={styles.n}>8px</span>;
      {"\n  "}
      <span className={styles.k}>padding</span>: <span className={styles.n}>8px</span> <span className={styles.n}>16px</span>;
      {"\n}"}
    </code>
  );
}
function ScssCode() {
  return (
    <code>
      <span className={styles.k}>.btn</span> {"{"}
      {"\n  "}
      <span className={styles.k}>display</span>: <span className={styles.s}>flex</span>;
      {"\n  "}
      <span className={styles.k}>gap</span>: <span className={styles.n}>8px</span>;
      {"\n  "}
      <span className={styles.k}>&amp;:hover</span> {"{ "}
      <span className={styles.k}>opacity</span>: <span className={styles.n}>.8</span>; {"}"}
      {"\n}"}
    </code>
  );
}
function TailwindCode() {
  return (
    <code>
      <span className={styles.c}>{'<button class="'}</span>
      {"\n  "}
      <span className={styles.s}>flex items-center gap-2</span>
      {"\n  "}
      <span className={styles.s}>px-4 py-2 rounded-xl</span>
      {"\n"}
      <span className={styles.c}>{'">'}</span>
      {"\n  Copy\n"}
      <span className={styles.c}>{"</button>"}</span>
    </code>
  );
}
const CODES: Record<Lang, () => ReactNode> = { css: CssCode, scss: ScssCode, tailwind: TailwindCode };

export default function LanguageTabSwitch({
  tablistLabel = "Select language",
  demo = true,
  duration = 220,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
}: LanguageTabSwitchProps) {
  const [live, setLive] = useState(demo);
  const [active, setActive] = useState<Lang>("css");
  const [ind, setInd] = useState<{ left: number; scale: number }>({ left: 0, scale: 1 });
  const tablistRef = useRef<HTMLDivElement>(null) as Box<HTMLDivElement>;
  const tabRefs = useRef<Record<Lang, HTMLButtonElement | null>>({ css: null, scss: null, tailwind: null }) as Box<
    Record<Lang, HTMLButtonElement | null>
  >;

  function measure(lang: Lang) {
    const list = tablistRef.current;
    const map = tabRefs.current;
    if (!list || !map) return;
    const base = map.css;
    const tab = map[lang];
    if (!base || !tab) return;
    const listRect = list.getBoundingClientRect();
    const baseRect = base.getBoundingClientRect();
    const tabRect = tab.getBoundingClientRect();
    setInd({ left: tabRect.left - listRect.left, scale: tabRect.width / baseRect.width });
  }

  function select(lang: Lang) {
    setLive(false);
    setActive(lang);
    measure(lang);
  }

  function onKeyDown(e: KeyEvt) {
    if (e.key !== "ArrowRight" && e.key !== "ArrowLeft") return;
    e.preventDefault();
    const i = LANGS.indexOf(active);
    const next = e.key === "ArrowRight" ? (i + 1) % LANGS.length : (i - 1 + LANGS.length) % LANGS.length;
    select(LANGS[next]);
    const btn = tabRefs.current ? tabRefs.current[LANGS[next]] : null;
    if (btn) btn.focus({ preventScroll: true });
  }

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const ActiveCode = CODES[active];

  function setTabRef(lang: Lang, el: HTMLButtonElement | null) {
    const map = tabRefs.current;
    if (map) map[lang] = el;
  }

  return (
    <div className={[styles.lts, live ? styles.isDemo : ""].join(" ")} style={vars}>
      <div className={styles.pane}>
        <div className={styles.paneHead}>
          <div
            className={styles.tabs}
            role="tablist"
            aria-label={tablistLabel}
            ref={tablistRef}
            onKeyDown={onKeyDown}
          >
            {LANGS.map((lang) => (
              <button
                key={lang}
                className={[styles.tab, styles[TAB_CLASS_KEY[lang]]].join(" ")}
                role="tab"
                type="button"
                aria-selected={live ? undefined : active === lang}
                tabIndex={live ? -1 : active === lang ? 0 : -1}
                ref={(el: HTMLButtonElement | null) => setTabRef(lang, el)}
                onClick={() => select(lang)}
              >
                {LABELS[lang]}
              </button>
            ))}
            <span
              className={styles.tabsIndicator}
              aria-hidden="true"
              style={live ? undefined : { transform: `translateX(${ind.left}px) scaleX(${ind.scale})` }}
            />
          </div>
        </div>
        <div className={styles.paneBody}>
          {live ? (
            <>
              <pre className={[styles.panel, styles.panelCss].join(" ")}>
                <CssCode />
              </pre>
              <pre className={[styles.panel, styles.panelScss].join(" ")}>
                <ScssCode />
              </pre>
              <pre className={[styles.panel, styles.panelTw].join(" ")}>
                <TailwindCode />
              </pre>
            </>
          ) : (
            <pre className={styles.panel}>
              <ActiveCode />
            </pre>
          )}
        </div>
      </div>
    </div>
  );
}