09Size segment picker

<main class="stage">
  <div class="sg is-demo">
    <span class="sg__label" id="sg-label">Size</span>
    <div class="sg__track" id="sg-track" role="listbox" aria-labelledby="sg-label" tabindex="0" aria-activedescendant="sg-o1">
      <span class="sg__pill" aria-hidden="true"></span>
      <span class="sg__cell" id="sg-o1" role="option" aria-selected="true">S</span>
      <span class="sg__cell" id="sg-o2" role="option" aria-selected="false">M</span>
      <span class="sg__cell" id="sg-o3" role="option" aria-selected="false">L</span>
      <span class="sg__cell sg__cell--out" id="sg-o4" role="option" aria-selected="false" aria-disabled="true">XL</span>
    </div>
    <p class="sg__note">XL sold out</p>
  </div>
</main>

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

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

@include stage($stage-ink);

.sg {
  box-sizing: border-box;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}
.sg__label {
  display: block;
  font-size: 10px; line-height: 12px; font-weight: 800;
  letter-spacing: .04em;
  color: rgba(255, 255, 255, .6);
  margin: 0 0 $sp-2;
}
.sg__track {
  position: relative;
  box-sizing: border-box;
  width: 232px;
  display: flex;
  padding: $sp-1;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .1);
}
.sg__track:focus-visible { outline: 2px solid $color; outline-offset: 4px; }
.sg__pill {
  position: absolute;
  top: $sp-1; left: $sp-1;
  width: 56px; height: 34px;
  border-radius: $r-pill;
  background: $color;
  box-shadow: $shadow-press;
  transform: translateX(0);
  transition: transform $duration $easing;
}
.sg__cell {
  position: relative;
  z-index: 1;
  flex: 0 0 56px;
  height: 34px;
  display: flex; align-items: center; justify-content: center;
  font-size: 13px; font-weight: 800;
  color: rgba(255, 255, 255, .72);
  cursor: pointer;
  transition: color $duration $easing;
}
.sg__cell[aria-selected="true"] { color: #fff; }
.sg__cell--out {
  color: rgba(255, 255, 255, .72);
  cursor: not-allowed;
}
.sg__cell--out::after {
  content: "";
  position: absolute;
  left: 14px; right: 14px; top: 50%;
  height: 1px;
  background: rgba(255, 255, 255, .32);
  transform: rotate(-14deg);
}
.sg__note {
  margin: $sp-2 0 0;
  font-size: 10px; font-weight: 700;
  color: rgba(255, 255, 255, .72);
}

// ── 자동 루프: 알약이 S→M→L 로 갔다가 같은 길로 되돌아온다 (품절 XL 은 건너뛴다) ──
.sg.is-demo .sg__pill { animation: sg-slide $dur-loop $easing infinite; }
@keyframes sg-slide {
  0%   { transform: translateX(0); }
  25%  { transform: translateX(56px); }
  50%  { transform: translateX(112px); }
  75%  { transform: translateX(56px); }
  100% { transform: translateX(0); }
}

@media (prefers-reduced-motion: reduce) {
  .sg.is-demo .sg__pill { animation: none !important; }
  .sg__pill, .sg__cell { 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);
}

.sg {
  box-sizing: border-box;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.sg__label {
  display: block;
  font-size: 10px;
  line-height: 12px;
  font-weight: 800;
  letter-spacing: 0.04em;
  color: rgba(255, 255, 255, 0.6);
  margin: 0 0 8px;
}

.sg__track {
  position: relative;
  box-sizing: border-box;
  width: 232px;
  display: flex;
  padding: 4px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.1);
}

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

.sg__pill {
  position: absolute;
  top: 4px;
  left: 4px;
  width: 56px;
  height: 34px;
  border-radius: 999px;
  background: #2f6df6;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  transform: translateX(0);
  transition: transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.sg__cell {
  position: relative;
  z-index: 1;
  flex: 0 0 56px;
  height: 34px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
  font-weight: 800;
  color: rgba(255, 255, 255, 0.72);
  cursor: pointer;
  transition: color 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.sg__cell[aria-selected=true] {
  color: #fff;
}

.sg__cell--out {
  color: rgba(255, 255, 255, 0.72);
  cursor: not-allowed;
}

.sg__cell--out::after {
  content: "";
  position: absolute;
  left: 14px;
  right: 14px;
  top: 50%;
  height: 1px;
  background: rgba(255, 255, 255, 0.32);
  transform: rotate(-14deg);
}

.sg__note {
  margin: 8px 0 0;
  font-size: 10px;
  font-weight: 700;
  color: rgba(255, 255, 255, 0.72);
}

.sg.is-demo .sg__pill {
  animation: sg-slide 2s cubic-bezier(0.2, 1.4, 0.4, 1) infinite;
}

@keyframes sg-slide {
  0% {
    transform: translateX(0);
  }
  25% {
    transform: translateX(56px);
  }
  50% {
    transform: translateX(112px);
  }
  75% {
    transform: translateX(56px);
  }
  100% {
    transform: translateX(0);
  }
}
@media (prefers-reduced-motion: reduce) {
  .sg.is-demo .sg__pill {
    animation: none !important;
  }
  .sg__pill, .sg__cell {
    transition: none;
  }
}

// 실제 동작: 알약이 칸 폭(56px)만큼 옮겨 간다. 품절 칸은 aria-disabled 라 옮겨가지 않는다.
var root = document.querySelector('.sg');
var track = document.getElementById('sg-track');
var pill = root.querySelector('.sg__pill');
var cells = [].slice.call(track.querySelectorAll('.sg__cell'));
var W = 56;
var at = 0;
function pick(i) {
  if (i < 0 || i >= cells.length) return;
  if (cells[i].getAttribute('aria-disabled') === 'true') return;
  root.classList.remove('is-demo');
  at = i;
  pill.style.transform = 'translateX(' + (i * W) + 'px)';
  cells.forEach(function (c, k) { c.setAttribute('aria-selected', String(k === i)); });
  track.setAttribute('aria-activedescendant', cells[i].id);
}
cells.forEach(function (c, i) { c.addEventListener('click', function () { pick(i); }); });
track.addEventListener('keydown', function (e) {
  if (e.key === 'ArrowRight') { pick(at + 1); e.preventDefault(); }
  else if (e.key === 'ArrowLeft') { pick(at - 1); e.preventDefault(); }
  else if (e.key === 'Home') { pick(0); e.preventDefault(); }
  else if (e.key === 'End') { pick(cells.length - 1); e.preventDefault(); }
});

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

export type SizeOption = { label: string; soldOut?: boolean };

export type SizeSegmentProps = {
  label?: string;
  note?: string;
  sizes?: SizeOption[];
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type KeyEvt = { key: string; preventDefault: () => void };
type ChangeEvt = { target: { value: string } };
type ClickEvt = { stopPropagation: () => void };

const CELL = 56;

const DEFAULT_SIZES: SizeOption[] = [
  { label: "S" },
  { label: "M" },
  { label: "L" },
  { label: "XL", soldOut: true },
];

export default function SizeSegment({
  label = "Size",
  note = "XL sold out",
  sizes = DEFAULT_SIZES,
  duration = 180,
  easing = "cubic-bezier(.34,1.56,.64,1)",
  color = "#2f6df6",
}: SizeSegmentProps) {
  const [picked, setPicked] = useState(0);
  const trackRef = useRef<HTMLDivElement>(null);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  function pick(i: number) {
    if (i < 0 || i >= sizes.length) return;
    if (sizes[i].soldOut) return;
    setPicked(i);
  }

  return (
    <div className={styles.sg} style={vars}>
      <span className={styles.label} id="sg-label">{label}</span>
      <div
        ref={trackRef}
        id="sg-track"
        className={styles.track}
        role="listbox"
        aria-labelledby="sg-label"
        tabIndex={0}
        aria-activedescendant={`sg-o${picked}`}
        onKeyDown={(e: KeyEvt) => {
          if (e.key === "ArrowRight") { pick(picked + 1); e.preventDefault(); }
          else if (e.key === "ArrowLeft") { pick(picked - 1); e.preventDefault(); }
          else if (e.key === "Home") { pick(0); e.preventDefault(); }
          else if (e.key === "End") { pick(sizes.length - 1); e.preventDefault(); }
        }}
      >
        <span
          className={styles.pill}
          aria-hidden="true"
          style={{ transform: `translateX(${picked * CELL}px)` }}
        />
        {sizes.map((s, i) => (
          <span
            key={s.label}
            id={`sg-o${i}`}
            className={`${styles.cell} ${s.soldOut ? styles.isOut : ""}`}
            role="option"
            aria-selected={i === picked}
            aria-disabled={s.soldOut ? true : undefined}
            onClick={() => pick(i)}
          >
            {s.label}
          </span>
        ))}
      </div>
      <p className={styles.note}>{note}</p>
    </div>
  );
}