02Horizontal splitter

<main class="stage">
  <div class="hs is-demo" id="hs-root">
    <div class="hs__box" id="hs-box">
      <section class="hs__pane hs__pane--code" aria-label="Editor area">
        <span class="hs__tok hs__tok--a"></span>
        <span class="hs__tok hs__tok--b"></span>
        <span class="hs__tok hs__tok--c"></span>
        <span class="hs__tok hs__tok--b"></span>
      </section>
      <div class="hs__bar" id="hs-bar" role="separator" tabindex="0"
           aria-orientation="horizontal" aria-label="Editor area height" aria-valuemin="20" aria-valuemax="80" aria-valuenow="50">
        <i class="hs__grip" aria-hidden="true"></i>
      </div>
      <section class="hs__pane hs__pane--out" aria-label="Result area">
        <span class="hs__chip">Result</span>
        <span class="hs__bars"><i></i><i></i><i></i><i></i><i></i></span>
      </section>
    </div>
    <p class="hs__cap">Drag up and down, or use the arrow keys</p>
  </div>
</main>

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

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

@include stage($stage-paper);

@property --splitY {
  syntax: "<percentage>";
  inherits: true;
  initial-value: 50%;
}

.hs {
  --splitY: 50%;
  width: min(288px, 86vw);
  display: flex;
  flex-direction: column;
  gap: $sp-2;
}
.hs__box {
  display: grid;
  grid-template-rows: var(--splitY) 10px 1fr;
  height: clamp(112px, 40vh, 132px);
  border-radius: $r-card;
  overflow: hidden;
  border: 1px solid rgba(23, 20, 26, .12);
  background: #fbf9f5;
}
.hs__pane {
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: $sp-2;
  padding: $sp-2 $sp-3;
  overflow: hidden;
}
.hs__pane--code { background: rgba(47, 109, 246, .08); }
.hs__pane--out {
  align-items: flex-start;
  justify-content: center;
  background: rgba(23, 20, 26, .05);
}

.hs__tok {
  flex: 0 0 auto;
  height: 7px;
  border-radius: $r-xs;
  background: rgba(23, 20, 26, .2);
}
.hs__tok--a { width: 72%; background: $color; }
.hs__tok--b { width: 52%; }
.hs__tok--c { width: 84%; }

.hs__chip {
  flex: 0 0 auto;
  padding: 0 $sp-2;
  border-radius: $r-pill;
  background: $subject-ink;
  color: $subject-cream;
  font-size: 10px;
  line-height: 14px;
  font-weight: 700;
}
.hs__bars {
  display: flex;
  align-items: flex-end;
  gap: $sp-1;
  height: 24px;
}
.hs__bars i {
  display: block;
  width: 12px;
  border-radius: $r-xs $r-xs 0 0;
  background: $color;
}
.hs__bars i:nth-child(1) { height: 40%; }
.hs__bars i:nth-child(2) { height: 76%; }
.hs__bars i:nth-child(3) { height: 56%; }
.hs__bars i:nth-child(4) { height: 96%; background: $subject-ink; }
.hs__bars i:nth-child(5) { height: 64%; }

.hs__bar {
  display: grid;
  place-items: center;
  background: rgba(23, 20, 26, .1);
  cursor: row-resize;
  touch-action: none;
  transition: background $duration $easing;
}
.hs__grip {
  display: block;
  width: 32px;
  height: 2px;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .45);
  transition: transform $duration $easing;
}
.hs__bar:hover,
.hs.is-drag .hs__bar { background: $color; }
.hs__bar:hover .hs__grip,
.hs.is-drag .hs__grip { transform: scaleX(1.4); background: #ffffff; }
.hs__bar:focus-visible { outline: 2px solid $subject-ink; outline-offset: -2px; }

.hs__cap {
  margin: 0;
  font-size: 11px;
  line-height: 14px;
  font-weight: 600;
  color: rgba(23, 20, 26, .72);   // AA 4.5 (blog-design)
  text-align: center;
}

// ── 자동 루프: 위 칸이 커졌다 작아졌다. 86% 에 제자리 ──
.hs.is-demo { animation: hs-split $dur-loop $easing infinite; }
@keyframes hs-split {
  0%, 8% { --splitY: 50%; }
  34% { --splitY: 76%; }
  62% { --splitY: 24%; }
  86%, 100% { --splitY: 50%; }
}
.hs.is-demo .hs__bar { animation: hs-hot $dur-loop $easing infinite; }
@keyframes hs-hot {
  0%, 8% { background: rgba(23, 20, 26, .1); }
  20%, 74% { background: $subject-blue; }
  86%, 100% { background: rgba(23, 20, 26, .1); }
}

@media (prefers-reduced-motion: reduce) {
  .hs.is-demo,
  .hs.is-demo .hs__bar { animation: none !important; }
  .hs__bar, .hs__grip { transition: none; }
}

@media (max-width: 340px) {
  .hs__box { height: 108px; }
  .hs__pane { padding: $sp-1 $sp-2; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

@property --splitY {
  syntax: "<percentage>";
  inherits: true;
  initial-value: 50%;
}
.hs {
  --splitY: 50%;
  width: min(288px, 86vw);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.hs__box {
  display: grid;
  grid-template-rows: var(--splitY) 10px 1fr;
  height: clamp(112px, 40vh, 132px);
  border-radius: 16px;
  overflow: hidden;
  border: 1px solid rgba(23, 20, 26, 0.12);
  background: #fbf9f5;
}

.hs__pane {
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 8px;
  padding: 8px 12px;
  overflow: hidden;
}

.hs__pane--code {
  background: rgba(47, 109, 246, 0.08);
}

.hs__pane--out {
  align-items: flex-start;
  justify-content: center;
  background: rgba(23, 20, 26, 0.05);
}

.hs__tok {
  flex: 0 0 auto;
  height: 7px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.2);
}

.hs__tok--a {
  width: 72%;
  background: #2f6df6;
}

.hs__tok--b {
  width: 52%;
}

.hs__tok--c {
  width: 84%;
}

.hs__chip {
  flex: 0 0 auto;
  padding: 0 8px;
  border-radius: 999px;
  background: #17141a;
  color: #fff7e6;
  font-size: 10px;
  line-height: 14px;
  font-weight: 700;
}

.hs__bars {
  display: flex;
  align-items: flex-end;
  gap: 4px;
  height: 24px;
}

.hs__bars i {
  display: block;
  width: 12px;
  border-radius: 4px 4px 0 0;
  background: #2f6df6;
}

.hs__bars i:nth-child(1) {
  height: 40%;
}

.hs__bars i:nth-child(2) {
  height: 76%;
}

.hs__bars i:nth-child(3) {
  height: 56%;
}

.hs__bars i:nth-child(4) {
  height: 96%;
  background: #17141a;
}

.hs__bars i:nth-child(5) {
  height: 64%;
}

.hs__bar {
  display: grid;
  place-items: center;
  background: rgba(23, 20, 26, 0.1);
  cursor: row-resize;
  touch-action: none;
  transition: background 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.hs__grip {
  display: block;
  width: 32px;
  height: 2px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.45);
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.hs__bar:hover,
.hs.is-drag .hs__bar {
  background: #2f6df6;
}

.hs__bar:hover .hs__grip,
.hs.is-drag .hs__grip {
  transform: scaleX(1.4);
  background: #ffffff;
}

.hs__bar:focus-visible {
  outline: 2px solid #17141a;
  outline-offset: -2px;
}

.hs__cap {
  margin: 0;
  font-size: 11px;
  line-height: 14px;
  font-weight: 600;
  color: rgba(23, 20, 26, 0.72);
  text-align: center;
}

.hs.is-demo {
  animation: hs-split 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes hs-split {
  0%, 8% {
    --splitY: 50%;
  }
  34% {
    --splitY: 76%;
  }
  62% {
    --splitY: 24%;
  }
  86%, 100% {
    --splitY: 50%;
  }
}
.hs.is-demo .hs__bar {
  animation: hs-hot 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes hs-hot {
  0%, 8% {
    background: rgba(23, 20, 26, 0.1);
  }
  20%, 74% {
    background: #2f6df6;
  }
  86%, 100% {
    background: rgba(23, 20, 26, 0.1);
  }
}
@media (prefers-reduced-motion: reduce) {
  .hs.is-demo,
  .hs.is-demo .hs__bar {
    animation: none !important;
  }
  .hs__bar, .hs__grip {
    transition: none;
  }
}
@media (max-width: 340px) {
  .hs__box {
    height: 108px;
  }
  .hs__pane {
    padding: 4px 8px;
  }
}

// 실제 동작: 포인터 Y 델타 → 위 트랙 높이(--splitY). 최소 40px 을 clamp 로 지킨다.
var root = document.getElementById('hs-root');
var box = document.getElementById('hs-box');
var bar = document.getElementById('hs-bar');
var MIN = 40, BAR = 10, dragging = false;

function clamp(v, lo, hi) { return Math.max(lo, Math.min(v, hi)); }
function set(pct) {
  var h = box.clientHeight;
  var v = clamp(pct, MIN / h * 100, (h - MIN - BAR) / h * 100);
  root.style.setProperty('--splitY', v.toFixed(1) + '%');
  bar.setAttribute('aria-valuenow', String(Math.round(v)));
}
function stop() { root.classList.remove('is-demo'); }

bar.addEventListener('pointerdown', function (e) {
  stop();
  dragging = true;
  bar.setPointerCapture(e.pointerId);
  root.classList.add('is-drag');
  e.preventDefault();
});
bar.addEventListener('pointermove', function (e) {
  if (!dragging) return;
  set((e.clientY - box.getBoundingClientRect().top) / box.clientHeight * 100);
});
function drop() { dragging = false; root.classList.remove('is-drag'); }
bar.addEventListener('pointerup', drop);
bar.addEventListener('pointercancel', drop);
bar.addEventListener('keydown', function (e) {
  var d = e.key === 'ArrowUp' ? -5 : e.key === 'ArrowDown' ? 5 : 0;
  if (!d) return;
  stop();
  set(Number(bar.getAttribute('aria-valuenow')) + d);
  bar.focus({ preventScroll: true });
  e.preventDefault();
});

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

export type HorizontalSplitterProps = {
  start?: number;
  minHeight?: number;
  duration?: number;
  easing?: string;
  color?: string;
};

type PEvt = { clientY: number; pointerId: number; preventDefault(): void; currentTarget: { setPointerCapture(id: number): void } };
type KeyEvt = { key: string; preventDefault(): void };
type Vars = CSSProperties & { "--splitY"?: string; "--duration"?: string; "--easing"?: string; "--color"?: string };

const BAR = 10;
function clamp(v: number, lo: number, hi: number): number { return Math.max(lo, Math.min(v, hi)); }

export default function HorizontalSplitter({
  start = 50,
  minHeight = 40,
  duration = 220,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
}: HorizontalSplitterProps) {
  const [split, setSplit] = useState(start);
  const [drag, setDrag] = useState(false);
  const boxRef = useRef<HTMLDivElement>(null);

  function set(pct: number): void {
    const box = boxRef.current;
    if (!box) return;
    const h = box.clientHeight;
    setSplit(clamp(pct, (minHeight / h) * 100, ((h - minHeight - BAR) / h) * 100));
  }
  function onDown(e: PEvt): void {
    setDrag(true);
    e.currentTarget.setPointerCapture(e.pointerId);
    e.preventDefault();
  }
  function onMove(e: PEvt): void {
    const box = boxRef.current;
    if (!drag || !box) return;
    set(((e.clientY - box.getBoundingClientRect().top) / box.clientHeight) * 100);
  }
  function onUp(): void { setDrag(false); }
  function onKey(e: KeyEvt): void {
    const d = e.key === "ArrowUp" ? -5 : e.key === "ArrowDown" ? 5 : 0;
    if (!d) return;
    set(split + d);
    e.preventDefault();
  }

  const vars: Vars = {
    "--splitY": `${split.toFixed(1)}%`,
    "--duration": `${duration}ms`,
    "--easing": easing,
    "--color": color,
  };

  return (
    <div className={drag ? `${styles.hs} ${styles.isDrag}` : styles.hs} style={vars}>
      <div className={styles.box} ref={boxRef}>
        <section className={`${styles.pane} ${styles.paneCode}`} aria-label="Editor area">
          <span className={`${styles.tok} ${styles.tokA}`} />
          <span className={`${styles.tok} ${styles.tokB}`} />
          <span className={`${styles.tok} ${styles.tokC}`} />
          <span className={`${styles.tok} ${styles.tokB}`} />
        </section>
        <div
          className={styles.bar}
          role="separator"
          tabIndex={0}
          aria-orientation="horizontal"
          aria-label="Editor area height"
          aria-valuemin={20}
          aria-valuemax={80}
          aria-valuenow={Math.round(split)}
          onPointerDown={onDown}
          onPointerMove={onMove}
          onPointerUp={onUp}
          onPointerCancel={onUp}
          onKeyDown={onKey}
        >
          <i className={styles.grip} aria-hidden="true" />
        </div>
        <section className={`${styles.pane} ${styles.paneOut}`} aria-label="Result area">
          <span className={styles.chip}>Result</span>
          <span className={styles.bars}>
            <i /><i /><i /><i /><i />
          </span>
        </section>
      </div>
      <p className={styles.cap}>Drag up and down, or use the arrow keys</p>
    </div>
  );
}