06Drag-to-reorder photo grid

<main class="stage">
  <ul class="rg-list is-demo" aria-label="Drag or use arrow keys to reorder photos">
    <li class="rg-tile" tabindex="0"><span class="rg-tile__img rg-tile__img--a"></span><span class="rg-tile__handle" aria-hidden="true">⠿</span></li>
    <li class="rg-tile" tabindex="0"><span class="rg-tile__img rg-tile__img--b"></span><span class="rg-tile__handle" aria-hidden="true">⠿</span></li>
    <li class="rg-tile" tabindex="0"><span class="rg-tile__img rg-tile__img--c"></span><span class="rg-tile__handle" aria-hidden="true">⠿</span></li>
  </ul>
</main>

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

$duration: $dur-quick;                                    // 스왑 스냅 시간
$easing: $ease-out;
$color: $subject-blue;                                    // 핸들·포커스 색

@include stage($stage-paper);

.rg-list {
  position: relative;
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: $sp-2;
}
.rg-tile {
  position: relative;
  width: 64px;
  height: 64px;
  border-radius: $r-sm;
  outline: none;
  cursor: grab;
  touch-action: none;
  box-shadow: $shadow-press;
  transition: transform $duration $easing;
  &.is-dragging { transition: none; z-index: 2; box-shadow: $shadow-raised; cursor: grabbing; }
}
.rg-tile:focus-visible { outline: 2px solid $color; outline-offset: 2px; }
.rg-tile__img { position: absolute; inset: 0; border-radius: inherit; }
.rg-tile__img--a { background: linear-gradient(155deg, $color 0%, $stage-ink 100%); }
.rg-tile__img--b { background: linear-gradient(205deg, $subject-cream 0%, $color 100%); }
.rg-tile__img--c { background: linear-gradient(115deg, $color 0%, $subject-cream 60%); }
.rg-tile__handle {
  position: absolute;
  right: 2px; bottom: 2px;
  width: 16px; height: 16px;
  display: grid;
  place-items: center;
  background: rgba(255, 255, 255, .88);
  border-radius: $r-xs;
  font-size: 9px;
  line-height: 1;
  color: $stage-ink;
}

.rg-list.is-demo .rg-tile:nth-child(1) { animation: swap-a $dur-loop $easing infinite; }
.rg-list.is-demo .rg-tile:nth-child(2) { animation: swap-b $dur-loop $easing infinite; }

@keyframes swap-a {
  0%, 10%   { transform: translateX(0); }
  45%, 65%  { transform: translateX(72px); }
  95%, 100% { transform: translateX(0); }
}
@keyframes swap-b {
  0%, 10%   { transform: translateX(0); }
  45%, 65%  { transform: translateX(-72px); }
  95%, 100% { transform: translateX(0); }
}

@media (prefers-reduced-motion: reduce) {
  .rg-tile { transition: none; }
  .rg-list.is-demo .rg-tile:nth-child(1),
  .rg-list.is-demo .rg-tile:nth-child(2) { animation: none; }
}

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);
}

.rg-list {
  position: relative;
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: 8px;
}

.rg-tile {
  position: relative;
  width: 64px;
  height: 64px;
  border-radius: 8px;
  outline: none;
  cursor: grab;
  touch-action: none;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  transition: transform 220ms ease-out;
}
.rg-tile.is-dragging {
  transition: none;
  z-index: 2;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  cursor: grabbing;
}

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

.rg-tile__img {
  position: absolute;
  inset: 0;
  border-radius: inherit;
}

.rg-tile__img--a {
  background: linear-gradient(155deg, #2f6df6 0%, #17141a 100%);
}

.rg-tile__img--b {
  background: linear-gradient(205deg, #fff7e6 0%, #2f6df6 100%);
}

.rg-tile__img--c {
  background: linear-gradient(115deg, #2f6df6 0%, #fff7e6 60%);
}

.rg-tile__handle {
  position: absolute;
  right: 2px;
  bottom: 2px;
  width: 16px;
  height: 16px;
  display: grid;
  place-items: center;
  background: rgba(255, 255, 255, 0.88);
  border-radius: 4px;
  font-size: 9px;
  line-height: 1;
  color: #17141a;
}

.rg-list.is-demo .rg-tile:nth-child(1) {
  animation: swap-a 2s ease-out infinite;
}

.rg-list.is-demo .rg-tile:nth-child(2) {
  animation: swap-b 2s ease-out infinite;
}

@keyframes swap-a {
  0%, 10% {
    transform: translateX(0);
  }
  45%, 65% {
    transform: translateX(72px);
  }
  95%, 100% {
    transform: translateX(0);
  }
}
@keyframes swap-b {
  0%, 10% {
    transform: translateX(0);
  }
  45%, 65% {
    transform: translateX(-72px);
  }
  95%, 100% {
    transform: translateX(0);
  }
}
@media (prefers-reduced-motion: reduce) {
  .rg-tile {
    transition: none;
  }
  .rg-list.is-demo .rg-tile:nth-child(1),
  .rg-list.is-demo .rg-tile:nth-child(2) {
    animation: none;
  }
}

(function () {
  var list = document.querySelector('.rg-list');
  Array.prototype.forEach.call(list.children, function (tile) {
    var startX = 0, dx = 0, dragging = false;
    tile.addEventListener('pointerdown', function (e) {
      list.classList.remove('is-demo');
      dragging = true; startX = e.clientX; tile.classList.add('is-dragging');
      tile.setPointerCapture(e.pointerId);
    });
    tile.addEventListener('pointermove', function (e) {
      if (!dragging) return;
      dx = e.clientX - startX;
      tile.style.transform = 'translateX(' + dx + 'px)';
    });
    function end() {
      if (!dragging) return;
      dragging = false; tile.classList.remove('is-dragging');
      var target = dx > 30 ? tile.nextElementSibling : dx < -30 ? tile.previousElementSibling : null;
      tile.style.transform = '';
      if (target) list.insertBefore(dx > 0 ? target : tile, dx > 0 ? tile : target);
      dx = 0;
    }
    tile.addEventListener('pointerup', end);
    tile.addEventListener('pointercancel', end);
    tile.addEventListener('keydown', function (e) {
      list.classList.remove('is-demo');
      var sib = e.key === 'ArrowRight' ? tile.nextElementSibling : e.key === 'ArrowLeft' ? tile.previousElementSibling : null;
      if (!sib) return;
      e.preventDefault();
      if (e.key === 'ArrowRight') list.insertBefore(sib, tile); else list.insertBefore(tile, sib);
      tile.focus({ preventScroll: true });
    });
  });
})();

import { useRef, useState } from "react";
import type { CSSProperties, PointerEvent as ReactPointerEvent } from "react";
import styles from "./DragReorderPhotoGrid.module.scss";

type ReactKeyboardEvent<T> = { key: string; preventDefault: () => void; currentTarget: T };

export type DragReorderPhotoGridProps = {
  /** 스왑 스냅 시간 (기본 220ms) */
  duration?: number;
  easing?: string;
  /** 핸들 색 */
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

const TONES = ["a", "b", "c"] as const;

/** 사진 칸을 밀어 옆 칸과 자리를 바꾼다 — 손가락·마우스 드래그, 좌우 화살표 키 둘 다 된다 */
export default function DragReorderPhotoGrid({
  duration = 220,
  easing = "ease-out",
  color = "#2f6df6",
}: DragReorderPhotoGridProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const [order, setOrder] = useState<number[]>([0, 1, 2]);
  const dragState = useRef<{ pos: number; startX: number; dx: number } | null>(null);
  const [dragging, setDragging] = useState<number | null>(null);
  const [offset, setOffset] = useState(0);

  function swap(pos: number, dir: 1 | -1) {
    setOrder((prev) => {
      const next = [...prev];
      const target = pos + dir;
      if (target < 0 || target >= next.length) return prev;
      [next[pos], next[target]] = [next[target], next[pos]];
      return next;
    });
  }

  function onPointerDown(e: ReactPointerEvent<HTMLLIElement>, pos: number) {
    (e.target as Element).setPointerCapture(e.pointerId);
    dragState.current = { pos, startX: e.clientX, dx: 0 };
    setDragging(pos);
  }
  function onPointerMove(e: ReactPointerEvent<HTMLLIElement>) {
    if (!dragState.current) return;
    dragState.current.dx = e.clientX - dragState.current.startX;
    setOffset(dragState.current.dx);
  }
  function onPointerUp() {
    if (!dragState.current) return;
    const { pos, dx } = dragState.current;
    if (dx > 30) swap(pos, 1);
    else if (dx < -30) swap(pos, -1);
    dragState.current = null;
    setDragging(null);
    setOffset(0);
  }
  function onKeyDown(e: ReactKeyboardEvent<HTMLLIElement>, pos: number) {
    if (e.key === "ArrowRight") { e.preventDefault(); swap(pos, 1); }
    else if (e.key === "ArrowLeft") { e.preventDefault(); swap(pos, -1); }
  }

  return (
    <ul className={styles.list} style={vars} aria-label="Drag or use arrow keys to reorder photos">
      {order.map((tileId, pos) => (
        <li
          key={tileId}
          tabIndex={0}
          className={`${styles.tile} ${dragging === pos ? styles.isDragging : ""}`}
          style={dragging === pos ? { transform: `translateX(${offset}px)` } : undefined}
          onPointerDown={(e: ReactPointerEvent<HTMLLIElement>) => onPointerDown(e, pos)}
          onPointerMove={onPointerMove}
          onPointerUp={onPointerUp}
          onPointerCancel={onPointerUp}
          onKeyDown={(e: ReactKeyboardEvent<HTMLLIElement>) => onKeyDown(e, pos)}
        >
          <span className={`${styles.img} ${styles["img-" + TONES[tileId]]}`} />
          <span className={styles.handle} aria-hidden="true">⠿</span>
        </li>
      ))}
    </ul>
  );
}