01Two-track month slide

<main class="stage">
  <div class="cal is-demo">
    <span class="cal__sr" id="cal-live" aria-live="polite">2026. 9</span>
    <div class="cal__bar">
      <button class="cal__nav" type="button" id="cal-prev" aria-label="Previous month"><svg viewBox="0 0 256 256" width="14" height="14" aria-hidden="true"><g fill="currentColor"><path d="M160 48v160l-80-80Z" opacity=".2"/><path d="M163.06 40.61a8 8 0 0 0-8.72 1.73l-80 80a8 8 0 0 0 0 11.32l80 80A8 8 0 0 0 168 208V48a8 8 0 0 0-4.94-7.39M152 188.69L91.31 128L152 67.31Z"/></g></svg></button>
      <div class="cal__titles" aria-hidden="true"><div class="cal__titlestrip" id="cal-strip"></div></div>
      <button class="cal__nav" type="button" id="cal-next" aria-label="Next month"><svg viewBox="0 0 256 256" width="14" height="14" aria-hidden="true"><g fill="currentColor"><path d="m176 128l-80 80V48Z" opacity=".2"/><path d="m181.66 122.34l-80-80A8 8 0 0 0 88 48v160a8 8 0 0 0 13.66 5.66l80-80a8 8 0 0 0 0-11.32M104 188.69V67.31L164.69 128Z"/></g></svg></button>
    </div>
    <div class="cal__dows" aria-hidden="true"><span>S</span><span>M</span><span>T</span><span>W</span><span>T</span><span>F</span><span>S</span></div>
    <div class="cal__viewport"><div class="cal__track" id="cal-track"></div></div>
  </div>
</main>

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

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

@include stage($stage-ink);

.cal {
  position: relative;
  box-sizing: border-box;
  width: min(288px, 88vw);
  color: $subject-cream;
}
.cal__sr {
  position: absolute; width: 1px; height: 1px;
  overflow: hidden; clip-path: inset(50%); white-space: nowrap;
}

// ── 상단 바: 화살표 두 개 + 미끄러지는 월 제목 트랙 ──
.cal__bar {
  display: flex; align-items: center; gap: $sp-2;
  margin: 0 0 $sp-2;
}
.cal__nav {
  flex: 0 0 auto;
  box-sizing: border-box;
  width: clamp(22px, 6.5vw, 28px); height: clamp(22px, 6.5vw, 28px);
  display: inline-flex; align-items: center; justify-content: center;
  padding: 0;
  border: 1px solid rgba(255, 255, 255, .16);
  background: rgba(255, 255, 255, .07);
  border-radius: $r-control;
  color: $subject-cream;
  cursor: pointer;
  transition: background $duration $easing, border-color $duration $easing;
}
.cal__nav:hover { background: rgba(255, 255, 255, .14); }
.cal__nav:focus-visible { outline: 2px solid $color; outline-offset: 2px; }

.cal__titles { flex: 1 1 auto; min-width: 0; overflow: hidden; }
.cal__titlestrip {
  display: flex; width: 300%;
  transform: translateX(-33.3333%);
}
.cal__t {
  flex: 0 0 33.3333%;
  text-align: center;
  font-size: clamp(12px, 3.2vw, 15px);
  line-height: 1.3;
  font-weight: 700;
  letter-spacing: .02em;
}

// ── 요일 머리 (달과 함께 미끄러지지 않는다) ──
.cal__dows {
  display: grid; grid-template-columns: repeat(7, 1fr); gap: $sp-1;
  margin: 0 0 $sp-1;
  font-size: clamp(8px, 2.2vw, 10px);
  line-height: 1.2;
  font-weight: 700;
  color: rgba(255, 255, 255, .45);
  text-align: center;
}

// ── 두 트랙: 나가는 달과 들어오는 달이 동시에 존재한다 ──
.cal__viewport { overflow: hidden; border-radius: $r-sm; }
.cal__track {
  display: flex; width: 300%;
  transform: translateX(-33.3333%);
}
.cal.is-anim .cal__track,
.cal.is-anim .cal__titlestrip { transition: transform $duration $easing; }

.cal__month {
  flex: 0 0 33.3333%;
  display: grid; gap: $sp-1;
}
.cal__row { display: grid; grid-template-columns: repeat(7, 1fr); gap: $sp-1; }
.cal__cell {
  height: clamp(20px, 6vw, 28px);
  display: grid; place-items: center;
  background: rgba(255, 255, 255, .08);
  border-radius: $r-xs;
  font-size: clamp(9px, 2.6vw, 12px);
  line-height: 1;
  font-weight: 600;
  color: $subject-cream;
  cursor: pointer;
}
.cal__cell.is-out { background: rgba(255, 255, 255, .03); color: rgba(255, 255, 255, .72); }   // .28 은 2.51:1 이었다 — AA 4.5 (9.75:1)
.cal__cell[aria-selected="true"] { background: $color; color: $subject-cream; }
.cal__cell:focus-visible { outline: 2px solid $color; outline-offset: 1px; }

// ── 자동 루프: 가운데 → 다음 달 → 가운데 → 이전 달 → 가운데.
//    0% 와 100% 가 같은 위치라 끝 프레임이 첫 프레임으로 이어진다 (텔레포트 없음) ──
.cal.is-demo .cal__track,
.cal.is-demo .cal__titlestrip {
  animation-name: cal-slide;
  animation-duration: $dur-loop;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
@keyframes cal-slide {
  0%   { transform: translateX(-33.3333%); }   // 이번 달
  20%  { transform: translateX(-66.6667%); }   // 다음 달로
  33%  { transform: translateX(-66.6667%); }
  50%  { transform: translateX(-33.3333%); }   // 되돌아온다
  58%  { transform: translateX(-33.3333%); }
  75%  { transform: translateX(0); }           // 이전 달로
  85%  { transform: translateX(0); }
  100% { transform: translateX(-33.3333%); }   // 첫 프레임과 같은 자리 — 텔레포트 없음
}

@media (prefers-reduced-motion: reduce) {
  .cal.is-demo .cal__track,
  .cal.is-demo .cal__titlestrip { animation: none !important; }
  .cal.is-anim .cal__track,
  .cal.is-anim .cal__titlestrip,
  .cal__nav { 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);
}

.cal {
  position: relative;
  box-sizing: border-box;
  width: min(288px, 88vw);
  color: #fff7e6;
}

.cal__sr {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.cal__bar {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0 0 8px;
}

.cal__nav {
  flex: 0 0 auto;
  box-sizing: border-box;
  width: clamp(22px, 6.5vw, 28px);
  height: clamp(22px, 6.5vw, 28px);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  border: 1px solid rgba(255, 255, 255, 0.16);
  background: rgba(255, 255, 255, 0.07);
  border-radius: 12px;
  color: #fff7e6;
  cursor: pointer;
  transition: background 300ms cubic-bezier(0.2, 0.8, 0.2, 1), border-color 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.cal__nav:hover {
  background: rgba(255, 255, 255, 0.14);
}

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

.cal__titles {
  flex: 1 1 auto;
  min-width: 0;
  overflow: hidden;
}

.cal__titlestrip {
  display: flex;
  width: 300%;
  transform: translateX(-33.3333%);
}

.cal__t {
  flex: 0 0 33.3333%;
  text-align: center;
  font-size: clamp(12px, 3.2vw, 15px);
  line-height: 1.3;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.cal__dows {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 4px;
  margin: 0 0 4px;
  font-size: clamp(8px, 2.2vw, 10px);
  line-height: 1.2;
  font-weight: 700;
  color: rgba(255, 255, 255, 0.45);
  text-align: center;
}

.cal__viewport {
  overflow: hidden;
  border-radius: 8px;
}

.cal__track {
  display: flex;
  width: 300%;
  transform: translateX(-33.3333%);
}

.cal.is-anim .cal__track,
.cal.is-anim .cal__titlestrip {
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.cal__month {
  flex: 0 0 33.3333%;
  display: grid;
  gap: 4px;
}

.cal__row {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 4px;
}

.cal__cell {
  height: clamp(20px, 6vw, 28px);
  display: grid;
  place-items: center;
  background: rgba(255, 255, 255, 0.08);
  border-radius: 4px;
  font-size: clamp(9px, 2.6vw, 12px);
  line-height: 1;
  font-weight: 600;
  color: #fff7e6;
  cursor: pointer;
}

.cal__cell.is-out {
  background: rgba(255, 255, 255, 0.03);
  color: rgba(255, 255, 255, 0.72);
}

.cal__cell[aria-selected=true] {
  background: #2f6df6;
  color: #fff7e6;
}

.cal__cell:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 1px;
}

.cal.is-demo .cal__track,
.cal.is-demo .cal__titlestrip {
  animation-name: cal-slide;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@keyframes cal-slide {
  0% {
    transform: translateX(-33.3333%);
  }
  20% {
    transform: translateX(-66.6667%);
  }
  33% {
    transform: translateX(-66.6667%);
  }
  50% {
    transform: translateX(-33.3333%);
  }
  58% {
    transform: translateX(-33.3333%);
  }
  75% {
    transform: translateX(0);
  }
  85% {
    transform: translateX(0);
  }
  100% {
    transform: translateX(-33.3333%);
  }
}
@media (prefers-reduced-motion: reduce) {
  .cal.is-demo .cal__track,
  .cal.is-demo .cal__titlestrip {
    animation: none !important;
  }
  .cal.is-anim .cal__track,
  .cal.is-anim .cal__titlestrip,
  .cal__nav {
    transition: none;
  }
}

(function () {
  var cal = document.querySelector('.cal');
  var track = document.getElementById('cal-track');
  var strip = document.getElementById('cal-strip');
  var live = document.getElementById('cal-live');
  var BASE = -100 / 3, busy = false, idx = 16;
  var cur = new Date(2026, 8, 1);

  function pad(n) { return (n < 10 ? '0' : '') + n; }
  function label(d) { return d.getFullYear() + '. ' + (d.getMonth() + 1); }
  function cells() {
    return [].slice.call(track.children[1].children).reduce(function (a, r) { return a.concat([].slice.call(r.children)); }, []);
  }
  function build(d) {
    var y = d.getFullYear(), m = d.getMonth(), off = 1 - new Date(y, m, 1).getDay();
    var g = document.createElement('div');
    g.className = 'cal__month'; g.setAttribute('role', 'grid'); g.setAttribute('aria-label', label(d));
    for (var w = 0; w < 5; w++) {
      var r = document.createElement('div');
      r.className = 'cal__row'; r.setAttribute('role', 'row');
      for (var i = 0; i < 7; i++) {
        var t = new Date(y, m, off + w * 7 + i), c = document.createElement('div');
        c.className = 'cal__cell' + (t.getMonth() === m ? '' : ' is-out');
        c.setAttribute('role', 'gridcell');
        c.setAttribute('aria-selected', 'false');
        c.setAttribute('aria-label', t.getFullYear() + '-' + pad(t.getMonth() + 1) + '-' + pad(t.getDate()));
        c.tabIndex = -1; c.textContent = t.getDate();
        r.appendChild(c);
      }
      g.appendChild(r);
    }
    return g;
  }
  function render() {
    track.textContent = ''; strip.textContent = '';
    [-1, 0, 1].forEach(function (k) {
      var d = new Date(cur.getFullYear(), cur.getMonth() + k, 1);
      track.appendChild(build(d));
      var s = document.createElement('span');
      s.className = 'cal__t'; s.textContent = label(d);
      strip.appendChild(s);
    });
    cells()[idx].tabIndex = 0;
  }
  function move(n) {
    var cs = cells(); n = Math.max(0, Math.min(cs.length - 1, n));
    cs.forEach(function (c, k) { c.tabIndex = k === n ? 0 : -1; c.setAttribute('aria-selected', String(k === n)); });
    cs[n].focus({ preventScroll: true }); idx = n;
  }
  function finish(dir) {
    if (!busy) return;
    busy = false; cal.classList.remove('is-anim');
    cur = new Date(cur.getFullYear(), cur.getMonth() + dir, 1);
    render();                                   // 리셋은 transition 이 꺼진 순간에 — 눈에 보이지 않는다
    track.style.transform = ''; strip.style.transform = '';
    live.textContent = label(cur);
  }
  function go(dir) {
    if (busy) return;
    busy = true; cal.classList.remove('is-demo'); cal.classList.add('is-anim');
    var to = BASE - dir * (100 / 3);
    track.style.transform = strip.style.transform = 'translateX(' + to + '%)';
    var done = function () { track.removeEventListener('transitionend', done); finish(dir); };
    track.addEventListener('transitionend', done);
    window.setTimeout(done, 700);
  }
  document.getElementById('cal-prev').addEventListener('click', function () { go(-1); });
  document.getElementById('cal-next').addEventListener('click', function () { go(1); });
  track.addEventListener('click', function (e) {
    var c = e.target.closest ? e.target.closest('.cal__cell') : null;
    var n = c ? cells().indexOf(c) : -1;
    if (n < 0) return;
    cal.classList.remove('is-demo'); move(n);
  });
  track.addEventListener('keydown', function (e) {
    var n = cells().indexOf(document.activeElement);
    if (n < 0) return;
    var to = null;
    if (e.key === 'ArrowRight') to = n + 1;
    else if (e.key === 'ArrowLeft') to = n - 1;
    else if (e.key === 'ArrowDown') to = n + 7;
    else if (e.key === 'ArrowUp') to = n - 7;
    else if (e.key === 'Home') to = n - (n % 7);
    else if (e.key === 'End') to = n - (n % 7) + 6;
    else return;
    e.preventDefault(); cal.classList.remove('is-demo'); move(to);
  });
  render();
})();

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

export type MonthSlideCalendarProps = {
  /** 시작 달 (기본: 오늘) */
  initialMonth?: Date;
  /** 슬라이드 시간(ms) */
  duration?: number;
  easing?: string;
  color?: string;
  dayNames?: string[];
  prevLabel?: string;
  nextLabel?: string;
};

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

const BASE = -100 / 3;

function pad(n: number) {
  return (n < 10 ? "0" : "") + n;
}
function label(d: Date) {
  return d.getFullYear() + ". " + (d.getMonth() + 1);
}
/** 한 달을 5주 × 7일 = 35칸으로. 6행은 좁은 폭에서 넘친다 */
function monthCells(d: Date) {
  const y = d.getFullYear();
  const m = d.getMonth();
  const off = 1 - new Date(y, m, 1).getDay();
  const out: { date: Date; outside: boolean }[] = [];
  for (let i = 0; i < 35; i++) {
    const t = new Date(y, m, off + i);
    out.push({ date: t, outside: t.getMonth() !== m });
  }
  return out;
}

export default function MonthSlideCalendar({
  initialMonth,
  duration = 300,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
  dayNames = ["S", "M", "T", "W", "T", "F", "S"],
  prevLabel = "Previous month",
  nextLabel = "Next month",
}: MonthSlideCalendarProps) {
  const first = initialMonth ?? new Date();
  const [cur, setCur] = useState(new Date(first.getFullYear(), first.getMonth(), 1));
  const [shift, setShift] = useState(0); // -1 · 0 · +1 트랙 오프셋
  const [animating, setAnimating] = useState(false);
  const [focused, setFocused] = useState(16);
  const busy = useRef(false);
  const cellRefs = useRef<(HTMLDivElement | null)[]>([]);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  const months = [-1, 0, 1].map((k) => new Date(cur.getFullYear(), cur.getMonth() + k, 1));

  function go(dir: number) {
    if (busy.current) return;
    busy.current = true;
    setAnimating(true);
    setShift(dir);
    window.setTimeout(() => {
      // 전환이 끝나면 들어온 달이 유일한 트랙이 된다. 리셋은 transition 이 꺼진 프레임에
      setAnimating(false);
      setShift(0);
      setCur((c) => new Date(c.getFullYear(), c.getMonth() + dir, 1));
      busy.current = false;
    }, duration);
  }

  function setCell(n: number) {
    return (el: HTMLDivElement | null) => {
      const a = cellRefs.current;
      if (a) a[n] = el;
    };
  }

  function move(n: number) {
    const to = Math.max(0, Math.min(34, n));
    setFocused(to);
    cellRefs.current?.[to]?.focus({ preventScroll: true });
  }

  function onKeyDown(e: KeyEvt, n: number) {
    let to: number | null = null;
    if (e.key === "ArrowRight") to = n + 1;
    else if (e.key === "ArrowLeft") to = n - 1;
    else if (e.key === "ArrowDown") to = n + 7;
    else if (e.key === "ArrowUp") to = n - 7;
    else if (e.key === "Home") to = n - (n % 7);
    else if (e.key === "End") to = n - (n % 7) + 6;
    if (to === null) return;
    e.preventDefault();
    move(to);
  }

  const offset = `translateX(${BASE - shift * (100 / 3)}%)`;
  const trackStyle: CSSProperties = { transform: offset };

  return (
    <div className={styles.cal} style={vars}>
      <span className={styles.sr} aria-live="polite">{label(cur)}</span>
      <div className={styles.bar}>
        <button type="button" className={styles.nav} aria-label={prevLabel} onClick={() => go(-1)}>
          <svg viewBox="0 0 256 256" width="14" height="14" aria-hidden="true">
            <g fill="currentColor">
              <path d="M160 48v160l-80-80Z" opacity=".2" />
              <path d="M163.06 40.61a8 8 0 0 0-8.72 1.73l-80 80a8 8 0 0 0 0 11.32l80 80A8 8 0 0 0 168 208V48a8 8 0 0 0-4.94-7.39M152 188.69L91.31 128L152 67.31Z" />
            </g>
          </svg>
        </button>
        <div className={styles.titles} aria-hidden="true">
          <div className={`${styles.titlestrip} ${animating ? styles.isAnim : ""}`} style={trackStyle}>
            {months.map((m) => (
              <span key={m.getTime()} className={styles.t}>{label(m)}</span>
            ))}
          </div>
        </div>
        <button type="button" className={styles.nav} aria-label={nextLabel} onClick={() => go(1)}>
          <svg viewBox="0 0 256 256" width="14" height="14" aria-hidden="true">
            <g fill="currentColor">
              <path d="m176 128l-80 80V48Z" opacity=".2" />
              <path d="m181.66 122.34l-80-80A8 8 0 0 0 88 48v160a8 8 0 0 0 13.66 5.66l80-80a8 8 0 0 0 0-11.32M104 188.69V67.31L164.69 128Z" />
            </g>
          </svg>
        </button>
      </div>
      <div className={styles.dows} aria-hidden="true">
        {dayNames.map((d, i) => <span key={`${d}-${i}`}>{d}</span>)}
      </div>
      <div className={styles.viewport}>
        <div className={`${styles.track} ${animating ? styles.isAnim : ""}`} style={trackStyle}>
          {months.map((m, mi) => (
            <div key={m.getTime()} className={styles.month} role="grid" aria-label={label(m)}>
              {[0, 1, 2, 3, 4].map((w) => (
                <div key={w} className={styles.row} role="row">
                  {monthCells(m).slice(w * 7, w * 7 + 7).map((c, i) => {
                    const n = w * 7 + i;
                    const live = mi === 1; // 가운데(현재) 달만 키보드 대상
                    return (
                      <div
                        key={c.date.getTime()}
                        ref={live ? setCell(n) : undefined}
                        className={`${styles.cell} ${c.outside ? styles.isOut : ""}`}
                        role="gridcell"
                        aria-selected={live && n === focused}
                        aria-label={`${c.date.getFullYear()}-${pad(c.date.getMonth() + 1)}-${pad(c.date.getDate())}`}
                        tabIndex={live && n === focused ? 0 : -1}
                        onClick={() => { if (live) move(n); }}
                        onKeyDown={(e: KeyEvt) => { if (live) onKeyDown(e, n); }}
                      >
                        {c.date.getDate()}
                      </div>
                    );
                  })}
                </div>
              ))}
            </div>
          ))}
        </div>
      </div>
    </div>
  );
}