09FAB that follows your long-press drag

<main class="stage">
  <section class="dg is-demo" id="dg" aria-label="A FAB that moves when you long-press and drag">
    <div class="dg__screen" id="dg-screen">
      <span class="dg__guide dg__guide--l" aria-hidden="true"></span>
      <span class="dg__guide dg__guide--r" aria-hidden="true"></span>
      <p class="dg__read" id="dg-read">Snapped to the right</p>
      <button class="dg__fab" type="button" id="dg-fab" aria-label="Move the help button">
        <span aria-hidden="true"><svg viewBox="0 0 256 256" width="1em" height="1em" fill="currentColor"><path d="M224,48V208a16,16,0,0,1-16,16H48a16,16,0,0,1-16-16V48A16,16,0,0,1,48,32H208A16,16,0,0,1,224,48Z" opacity=".2"/><path d="M72,60A12,12,0,1,1,60,48,12,12,0,0,1,72,60Zm56-12a12,12,0,1,0,12,12A12,12,0,0,0,128,48Zm68,24a12,12,0,1,0-12-12A12,12,0,0,0,196,72ZM60,116a12,12,0,1,0,12,12A12,12,0,0,0,60,116Zm68,0a12,12,0,1,0,12,12A12,12,0,0,0,128,116Zm68,0a12,12,0,1,0,12,12A12,12,0,0,0,196,116ZM60,184a12,12,0,1,0,12,12A12,12,0,0,0,60,184Zm68,0a12,12,0,1,0,12,12A12,12,0,0,0,128,184Zm68,0a12,12,0,1,0,12,12A12,12,0,0,0,196,184Z"/></svg></span>
      </button>
    </div>
    <p class="dg__hint" id="dg-hint">Hold longer than 350ms, then drag</p>
  </section>
</main>

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

// 길게 눌러 끌면 따라오는 FAB — 버튼 자체가 translate 로 움직이고 놓으면 가장자리로 스냅
$duration: $dur-base;
$easing: $ease-spring;
$color: $subject-mint;

@include stage($stage-ink);

.dg {
  display: grid;
  justify-items: center;
  gap: $sp-2;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.dg__screen {
  position: relative;
  box-sizing: border-box;
  width: min(280px, 92vw);
  height: 108px;
  border: 1px solid rgba(255, 247, 230, .22);
  border-radius: $r-card;
  background: rgba(255, 247, 230, .05);
  overflow: hidden;
}

// 스냅 가이드: 붙잡는 동안에만 살아난다
.dg__guide {
  position: absolute;
  top: $sp-2;
  bottom: $sp-2;
  width: 0;
  border-left: 2px dashed rgba(255, 247, 230, .3);
  opacity: 0;
  transition: opacity $dur-instant linear;
}
.dg__guide--l { left: $sp-2; }
.dg__guide--r { right: $sp-2; }

.dg__read {
  position: absolute;
  left: 0;
  right: 0;
  top: $sp-2;
  margin: 0;
  color: rgba(255, 247, 230, .62);
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
  text-align: center;
}

.dg__fab {
  position: absolute;
  left: $sp-2;
  bottom: $sp-2;
  display: inline-grid;
  place-items: center;
  width: 52px;
  height: 52px;
  margin: 0;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background: $color;
  color: $stage-ink;
  font-size: 26px;
  line-height: 1;
  cursor: grab;
  transform: translateX(212px);
  transition: transform $duration $easing, box-shadow $dur-instant linear;
  touch-action: none;
  user-select: none;
}
.dg__fab:focus-visible { outline: 3px solid $subject-cream; outline-offset: 3px; }

// 붙잡기 상태 — 끌기 중에는 스냅 전환을 끊어 즉시 따라오게 한다
.dg__fab.is-grab {
  cursor: grabbing;
  transition: box-shadow $dur-instant linear;
  box-shadow: 0 0 0 4px rgba(76, 212, 166, .25), $shadow-raised;
}
.dg__screen.is-holding .dg__guide { opacity: 1; }

.dg__hint {
  margin: 0;
  color: rgba(255, 247, 230, .62);
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
  text-align: center;
}

// ── 격자 미리보기 전용 2초 루프: 오른쪽 → 붙잡음 → 왼쪽 → 놓음 → 오른쪽 ──
@keyframes dg-loop-move {
  0%, 8% { transform: translateX(212px); }
  12% { transform: translateX(212px) scale(1.12); }
  42% { transform: translateX(0px) scale(1.12); }
  46%, 52% { transform: translateX(0px) scale(1); }
  58% { transform: translateX(0px) scale(1.12); }
  86% { transform: translateX(212px) scale(1.12); }
  90%, 100% { transform: translateX(212px) scale(1); }
}
@keyframes dg-loop-guide-l {
  0%, 11% { opacity: 0; }
  12%, 44% { opacity: 1; }
  46%, 100% { opacity: 0; }
}
@keyframes dg-loop-guide-r {
  0%, 11% { opacity: 0; }
  12%, 88% { opacity: 1; }
  90%, 100% { opacity: 0; }
}
@keyframes dg-loop-read {
  0%, 11% { opacity: 1; }
  12%, 43% { opacity: .3; }
  44%, 57% { opacity: 1; }
  58%, 87% { opacity: .3; }
  88%, 100% { opacity: 1; }
}
.dg.is-demo {
  .dg__fab {
    animation-name: dg-loop-move;
    animation-duration: $dur-loop;
    animation-timing-function: $easing;
    animation-iteration-count: infinite;
  }
  .dg__guide--l {
    animation-name: dg-loop-guide-l;
    animation-duration: $dur-loop;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
  .dg__guide--r {
    animation-name: dg-loop-guide-r;
    animation-duration: $dur-loop;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
  .dg__read {
    animation-name: dg-loop-read;
    animation-duration: $dur-loop;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
}

@media (max-width: 340px) {
  .dg__screen { height: 96px; }
  .dg__fab { width: 44px; height: 44px; font-size: 22px; }
  .dg__read { font-size: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  .dg.is-demo .dg__fab,
  .dg.is-demo .dg__guide--l,
  .dg.is-demo .dg__guide--r,
  .dg.is-demo .dg__read { animation: none !important; transform: none !important; }
  // 붙잡힌 순간의 결과만 남긴다 — 큰 상태로 왼쪽에 멈춘다
  .dg.is-demo .dg__fab { transform: translateX(0px) scale(1.12) !important; }
  .dg.is-demo .dg__guide--l { opacity: 1 !important; }
  .dg.is-demo .dg__guide--r { opacity: 0 !important; }
  .dg.is-demo .dg__read { opacity: 1 !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);
}

.dg {
  display: grid;
  justify-items: center;
  gap: 8px;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.dg__screen {
  position: relative;
  box-sizing: border-box;
  width: min(280px, 92vw);
  height: 108px;
  border: 1px solid rgba(255, 247, 230, 0.22);
  border-radius: 16px;
  background: rgba(255, 247, 230, 0.05);
  overflow: hidden;
}

.dg__guide {
  position: absolute;
  top: 8px;
  bottom: 8px;
  width: 0;
  border-left: 2px dashed rgba(255, 247, 230, 0.3);
  opacity: 0;
  transition: opacity 140ms linear;
}

.dg__guide--l {
  left: 8px;
}

.dg__guide--r {
  right: 8px;
}

.dg__read {
  position: absolute;
  left: 0;
  right: 0;
  top: 8px;
  margin: 0;
  color: rgba(255, 247, 230, 0.62);
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
  text-align: center;
}

.dg__fab {
  position: absolute;
  left: 8px;
  bottom: 8px;
  display: inline-grid;
  place-items: center;
  width: 52px;
  height: 52px;
  margin: 0;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background: #4cd4a6;
  color: #17141a;
  font-size: 26px;
  line-height: 1;
  cursor: grab;
  transform: translateX(212px);
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1), box-shadow 140ms linear;
  touch-action: none;
  user-select: none;
}

.dg__fab:focus-visible {
  outline: 3px solid #fff7e6;
  outline-offset: 3px;
}

.dg__fab.is-grab {
  cursor: grabbing;
  transition: box-shadow 140ms linear;
  box-shadow: 0 0 0 4px rgba(76, 212, 166, 0.25), 0 14px 24px rgba(23, 20, 26, 0.32);
}

.dg__screen.is-holding .dg__guide {
  opacity: 1;
}

.dg__hint {
  margin: 0;
  color: rgba(255, 247, 230, 0.62);
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
  text-align: center;
}

@keyframes dg-loop-move {
  0%, 8% {
    transform: translateX(212px);
  }
  12% {
    transform: translateX(212px) scale(1.12);
  }
  42% {
    transform: translateX(0px) scale(1.12);
  }
  46%, 52% {
    transform: translateX(0px) scale(1);
  }
  58% {
    transform: translateX(0px) scale(1.12);
  }
  86% {
    transform: translateX(212px) scale(1.12);
  }
  90%, 100% {
    transform: translateX(212px) scale(1);
  }
}
@keyframes dg-loop-guide-l {
  0%, 11% {
    opacity: 0;
  }
  12%, 44% {
    opacity: 1;
  }
  46%, 100% {
    opacity: 0;
  }
}
@keyframes dg-loop-guide-r {
  0%, 11% {
    opacity: 0;
  }
  12%, 88% {
    opacity: 1;
  }
  90%, 100% {
    opacity: 0;
  }
}
@keyframes dg-loop-read {
  0%, 11% {
    opacity: 1;
  }
  12%, 43% {
    opacity: 0.3;
  }
  44%, 57% {
    opacity: 1;
  }
  58%, 87% {
    opacity: 0.3;
  }
  88%, 100% {
    opacity: 1;
  }
}
.dg.is-demo .dg__fab {
  animation-name: dg-loop-move;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}
.dg.is-demo .dg__guide--l {
  animation-name: dg-loop-guide-l;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.dg.is-demo .dg__guide--r {
  animation-name: dg-loop-guide-r;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.dg.is-demo .dg__read {
  animation-name: dg-loop-read;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

@media (max-width: 340px) {
  .dg__screen {
    height: 96px;
  }
  .dg__fab {
    width: 44px;
    height: 44px;
    font-size: 22px;
  }
  .dg__read {
    font-size: 10px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .dg.is-demo .dg__fab,
  .dg.is-demo .dg__guide--l,
  .dg.is-demo .dg__guide--r,
  .dg.is-demo .dg__read {
    animation: none !important;
    transform: none !important;
  }
  .dg.is-demo .dg__fab {
    transform: translateX(0px) scale(1.12) !important;
  }
  .dg.is-demo .dg__guide--l {
    opacity: 1 !important;
  }
  .dg.is-demo .dg__guide--r {
    opacity: 0 !important;
  }
  .dg.is-demo .dg__read {
    opacity: 1 !important;
  }
}

// 제스처 FAB: 길게 누르면 붙잡고, 끌면 버튼 자체가 움직이며, 놓으면 가까운 가장자리로 스냅된다
var dg = document.getElementById('dg');
var dgFab = document.getElementById('dg-fab');
var dgScreen = document.getElementById('dg-screen');
var dgRead = document.getElementById('dg-read');
var dgHold = null;   // 길게 누름 타이머
var dgGrab = false;  // 붙잡기 상태
function dgSide(x) {
  var box = dgScreen.getBoundingClientRect();
  return x < box.left + box.width / 2 ? 'left' : 'right';
}
function dgSnap(x) {
  var side = dgSide(x);
  var box = dgScreen.getBoundingClientRect();
  var maxX = box.width - dgFab.offsetWidth - 8;
  dgFab.style.transform = 'translateX(' + (side === 'left' ? 0 : maxX) + 'px)';
  dgRead.textContent = side === 'left' ? 'Snapped to the left' : 'Snapped to the right';
}
function dgClearHold() {
  window.clearTimeout(dgHold);
  dgHold = null;
}
dgFab.addEventListener('pointerdown', function (e) {
  dg.classList.remove('is-demo');
  dgHold = window.setTimeout(function () {
    dgGrab = true;
    dgFab.classList.add('is-grab');
    dgScreen.classList.add('is-holding');
    try { dgFab.setPointerCapture(e.pointerId); } catch (err) { }
    dgRead.textContent = 'Held · release to snap';
  }, 350);
});
dgFab.addEventListener('pointermove', function (e) {
  if (!dgGrab) return;
  var box = dgScreen.getBoundingClientRect();
  var maxX = box.width - dgFab.offsetWidth - 8;
  var x = Math.min(Math.max(e.clientX - box.left - dgFab.offsetWidth / 2, 0), maxX);
  dgFab.style.transform = 'translateX(' + x + 'px)';
});
dgFab.addEventListener('pointerup', function (e) {
  dgClearHold();
  dgScreen.classList.remove('is-holding');
  if (!dgGrab) return;
  dgGrab = false;
  dgFab.classList.remove('is-grab');
  dgSnap(e.clientX);
});
dgFab.addEventListener('keydown', function (e) {
  dg.classList.remove('is-demo');
  var box = dgScreen.getBoundingClientRect();
  var maxX = box.width - dgFab.offsetWidth - 8;
  if (e.key === 'ArrowLeft') dgFab.style.transform = 'translateX(0px)';
  if (e.key === 'ArrowRight') dgFab.style.transform = 'translateX(' + maxX + 'px)';
});

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

export type DragMoveFabProps = {
  fabLabel?: string;
  leftRead?: string;
  rightRead?: string;
  grabbedRead?: string;
  hint?: string;
  groupLabel?: string;
  /** 붙잡기로 넘어가는 길게 누름 시간(ms) */
  holdMs?: number;
  /** 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 에 KeyboardEvent 가 없다 — 쓰는 필드만 로컬로 선언한다
type KeyEvt = { key: string; currentTarget: HTMLButtonElement };

type Box = { left: number; width: number; maxX: number };

/** 화면 안쪽 여백 — 스냅 자리는 양 끝에서 이만큼 떨어진다 */
const EDGE = 8;

function Dots() {
  return (
    <svg viewBox="0 0 256 256" width="1em" height="1em" fill="currentColor">
      <path d="M224,48V208a16,16,0,0,1-16,16H48a16,16,0,0,1-16-16V48A16,16,0,0,1,48,32H208A16,16,0,0,1,224,48Z" opacity=".2" />
      <path d="M72,60A12,12,0,1,1,60,48,12,12,0,0,1,72,60Zm56-12a12,12,0,1,0,12,12A12,12,0,0,0,128,48Zm68,24a12,12,0,1,0-12-12A12,12,0,0,0,196,72ZM60,116a12,12,0,1,0,12,12A12,12,0,0,0,60,116Zm68,0a12,12,0,1,0,12,12A12,12,0,0,0,128,116Zm68,0a12,12,0,1,0,12,12A12,12,0,0,0,196,116ZM60,184a12,12,0,1,0,12,12A12,12,0,0,0,60,184Zm68,0a12,12,0,1,0,12,12A12,12,0,0,0,128,184Zm68,0a12,12,0,1,0,12,12A12,12,0,0,0,196,184Z" />
    </svg>
  );
}

export default function DragMoveFab({
  fabLabel = "Move the help button",
  leftRead = "Docked on the left",
  rightRead = "Docked on the right",
  grabbedRead = "Grabbed · release to snap",
  hint = "Press for longer than 350ms, then drag",
  groupLabel = "FAB you press and hold to drag around",
  holdMs = 350,
  demo = true,
  duration = 300,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#4cd4a6",
}: DragMoveFabProps) {
  const [tx, setTx] = useState<number | null>(null);   // null 이면 CSS 기본 자리(오른쪽)
  const [grab, setGrab] = useState(false);
  const [holding, setHolding] = useState(false);
  const [live, setLive] = useState(demo);
  const [read, setRead] = useState(rightRead);
  const screenRef = useRef<HTMLDivElement>(null);
  const holdT = useRef<number>(null);

  useEffect(() => () => {
    if (holdT.current !== null) window.clearTimeout(holdT.current);
  }, []);

  function clearHold() {
    if (holdT.current !== null) {
      window.clearTimeout(holdT.current);
      holdT.current = null;
    }
  }

  function bounds(fab: HTMLButtonElement): Box | null {
    const screen = screenRef.current;
    if (!screen) return null;
    const box = screen.getBoundingClientRect();
    return { left: box.left, width: box.width, maxX: box.width - fab.offsetWidth - EDGE };
  }

  // 길게 누름이 채워져야 붙잡기로 넘어간다 — 짧은 누름은 그냥 클릭이다
  function down(e: PointerEvent<HTMLButtonElement>) {
    setLive(false);
    const fab = e.currentTarget;
    const pid: number = e.pointerId;
    clearHold();
    holdT.current = window.setTimeout(() => {
      setGrab(true);
      setHolding(true);
      try { fab.setPointerCapture(pid); } catch { /* 캡처를 못 해도 끌기는 된다 */ }
      setRead(grabbedRead);
    }, holdMs);
  }

  function move(e: PointerEvent<HTMLButtonElement>) {
    if (!grab) return;
    const fab = e.currentTarget;
    const b = bounds(fab);
    if (!b) return;
    setTx(Math.min(Math.max(e.clientX - b.left - fab.offsetWidth / 2, 0), b.maxX));
  }

  // 놓으면 가까운 가장자리로 스냅된다
  function up(e: PointerEvent<HTMLButtonElement>) {
    clearHold();
    setHolding(false);
    if (!grab) return;
    setGrab(false);
    const b = bounds(e.currentTarget);
    if (!b) return;
    const left = e.clientX < b.left + b.width / 2;
    setTx(left ? 0 : b.maxX);
    setRead(left ? leftRead : rightRead);
  }

  // 키보드 경로 — vanilla 판은 transform 만 바꾸지만 읽어주는 문구도 같이 맞춘다
  function key(e: KeyEvt) {
    setLive(false);
    const b = bounds(e.currentTarget);
    if (!b) return;
    if (e.key === "ArrowLeft") { setTx(0); setRead(leftRead); }
    if (e.key === "ArrowRight") { setTx(b.maxX); setRead(rightRead); }
  }

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const fabStyle: CSSProperties = tx === null ? {} : { transform: `translateX(${tx}px)` };
  const cls = [styles.dg, live ? styles.isDemo : ""].filter(Boolean).join(" ");
  const screenCls = [styles.screen, holding ? styles.isHolding : ""].filter(Boolean).join(" ");
  const fabCls = [styles.fab, grab ? styles.isGrab : ""].filter(Boolean).join(" ");

  return (
    <section className={cls} style={vars} aria-label={groupLabel}>
      <div className={screenCls} ref={screenRef}>
        <span className={[styles.guide, styles.guideL].join(" ")} aria-hidden="true" />
        <span className={[styles.guide, styles.guideR].join(" ")} aria-hidden="true" />
        <p className={styles.read} aria-live="polite">{read}</p>
        <button
          className={fabCls}
          style={fabStyle}
          type="button"
          aria-label={fabLabel}
          onPointerDown={down}
          onPointerMove={move}
          onPointerUp={up}
          onKeyDown={key}
        >
          <span aria-hidden="true"><Dots /></span>
        </button>
      </div>
      <p className={styles.hint}>{hint}</p>
    </section>
  );
}