06Sắp xếp lại có vạch báo vị trí thả

<main class="stage">
  <ul class="rd-list is-demo" aria-label="Danh sách ưu tiên. Trên tay cầm, dùng Alt+Lên/Xuống để sắp xếp">
    <li class="rd-item" data-i="0">
      <button class="rd-item__handle" type="button" aria-label="Sắp xếp lại, mũi tên lên/xuống">
        <svg viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M208 32v192a16 16 0 0 1-16 16H64a16 16 0 0 1-16-16V32a16 16 0 0 1 16-16h128a16 16 0 0 1 16 16" opacity=".2"/><path d="M104 60a12 12 0 1 1-12-12a12 12 0 0 1 12 12m60 12a12 12 0 1 0-12-12a12 12 0 0 0 12 12m-72 44a12 12 0 1 0 12 12a12 12 0 0 0-12-12m72 0a12 12 0 1 0 12 12a12 12 0 0 0-12-12m-72 68a12 12 0 1 0 12 12a12 12 0 0 0-12-12m72 0a12 12 0 1 0 12 12a12 12 0 0 0-12-12"/></g></svg>
      </button>
      <span>Sửa lỗi thanh toán</span>
    </li>
    <li class="rd-drop-indicator" aria-hidden="true"></li>
    <li class="rd-item rd-item--lifted" data-i="1">
      <button class="rd-item__handle" type="button" aria-label="Sắp xếp lại, mũi tên lên/xuống">
        <svg viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M208 32v192a16 16 0 0 1-16 16H64a16 16 0 0 1-16-16V32a16 16 0 0 1 16-16h128a16 16 0 0 1 16 16" opacity=".2"/><path d="M104 60a12 12 0 1 1-12-12a12 12 0 0 1 12 12m60 12a12 12 0 1 0-12-12a12 12 0 0 0 12 12m-72 44a12 12 0 1 0 12 12a12 12 0 0 0-12-12m72 0a12 12 0 1 0 12 12a12 12 0 0 0-12-12m-72 68a12 12 0 1 0 12 12a12 12 0 0 0-12-12m72 0a12 12 0 1 0 12 12a12 12 0 0 0-12-12"/></g></svg>
      </button>
      <span>QA trang đăng nhập</span>
    </li>
    <li class="rd-item" data-i="2">
      <button class="rd-item__handle" type="button" aria-label="Sắp xếp lại, mũi tên lên/xuống">
        <svg viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M208 32v192a16 16 0 0 1-16 16H64a16 16 0 0 1-16-16V32a16 16 0 0 1 16-16h128a16 16 0 0 1 16 16" opacity=".2"/><path d="M104 60a12 12 0 1 1-12-12a12 12 0 0 1 12 12m60 12a12 12 0 1 0-12-12a12 12 0 0 0 12 12m-72 44a12 12 0 1 0 12 12a12 12 0 0 0-12-12m72 0a12 12 0 1 0 12 12a12 12 0 0 0-12-12m-72 68a12 12 0 1 0 12 12a12 12 0 0 0-12-12m72 0a12 12 0 1 0 12 12a12 12 0 0 0-12-12"/></g></svg>
      </button>
      <span>Sắp xếp tài liệu triển khai</span>
    </li>
  </ul>
</main>

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

$duration: $dur-base;                                  // 들어올림·이동 시간
$easing: $ease-spring;
$color: $subject-blue;                                 // 드롭 인디케이터 색

@include stage($stage-ink);

.rd-list {
  list-style: none;
  margin: 0;
  padding: 0;
  width: min(260px, 82vw);
  display: flex;
  flex-direction: column;
}

.rd-item {
  display: flex;
  align-items: center;
  gap: $sp-2;
  padding: $sp-3 $sp-4;
  margin: $sp-1 0;
  border-radius: $r-sm;
  background: $stage-paper;
  transition: transform $duration $easing, box-shadow $duration $easing;
}
.rd-item span { font-size: 13px; color: $stage-ink; }

.rd-item.is-dragging {
  position: relative;
  z-index: 2;
  box-shadow: $shadow-raised;
  transition: none;
  cursor: grabbing;
}

.rd-item__handle {
  width: 24px;
  height: 24px;
  display: grid;
  place-items: center;
  border: 0;
  background: none;
  color: rgba(23, 20, 26, .5);
  cursor: grab;
  flex: 0 0 auto;
  touch-action: none;
}
.rd-item__handle svg { width: 14px; height: 14px; }
.rd-item__handle:focus-visible { outline: 2px solid $color; outline-offset: 2px; border-radius: $r-xs; }

.rd-drop-indicator {
  height: 0;
  margin: 0 $sp-4;
  border-radius: $r-xs;
  background: $color;
  opacity: 0;
  transition: height $duration $easing, opacity $duration $easing;
}
.rd-list.is-dragging .rd-drop-indicator { height: 8px; opacity: 1; }

// 데모 강제 루프 — 가운데 항목이 들리고, 그 아래 자리에 드롭 인디케이터가 나타났다 정리되는 흐름
.rd-list.is-demo .rd-item--lifted {
  animation: rd-lift-loop $dur-loop $easing infinite;
}
.rd-list.is-demo .rd-drop-indicator {
  animation: rd-gap-loop $dur-loop $easing infinite;
}

@keyframes rd-lift-loop {
  0%, 10%   { transform: translateY(0) scale(1); box-shadow: none; }
  40%, 65%  { transform: translateY(52px) scale(1.03); box-shadow: $shadow-raised; }
  95%, 100% { transform: translateY(0) scale(1); box-shadow: none; }
}
@keyframes rd-gap-loop {
  0%, 10%   { height: 0; opacity: 0; }
  40%, 65%  { height: 8px; opacity: 1; }
  95%, 100% { height: 0; opacity: 0; }
}

@media (prefers-reduced-motion: reduce) {
  .rd-item, .rd-drop-indicator { 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);
}

.rd-list {
  list-style: none;
  margin: 0;
  padding: 0;
  width: min(260px, 82vw);
  display: flex;
  flex-direction: column;
}

.rd-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 16px;
  margin: 4px 0;
  border-radius: 8px;
  background: #ffffff;
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1), box-shadow 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.rd-item span {
  font-size: 13px;
  color: #17141a;
}

.rd-item.is-dragging {
  position: relative;
  z-index: 2;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  transition: none;
  cursor: grabbing;
}

.rd-item__handle {
  width: 24px;
  height: 24px;
  display: grid;
  place-items: center;
  border: 0;
  background: none;
  color: rgba(23, 20, 26, 0.5);
  cursor: grab;
  flex: 0 0 auto;
  touch-action: none;
}

.rd-item__handle svg {
  width: 14px;
  height: 14px;
}

.rd-item__handle:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 2px;
  border-radius: 4px;
}

.rd-drop-indicator {
  height: 0;
  margin: 0 16px;
  border-radius: 4px;
  background: #2f6df6;
  opacity: 0;
  transition: height 300ms cubic-bezier(0.2, 0.8, 0.2, 1), opacity 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.rd-list.is-dragging .rd-drop-indicator {
  height: 8px;
  opacity: 1;
}

.rd-list.is-demo .rd-item--lifted {
  animation: rd-lift-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

.rd-list.is-demo .rd-drop-indicator {
  animation: rd-gap-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes rd-lift-loop {
  0%, 10% {
    transform: translateY(0) scale(1);
    box-shadow: none;
  }
  40%, 65% {
    transform: translateY(52px) scale(1.03);
    box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  }
  95%, 100% {
    transform: translateY(0) scale(1);
    box-shadow: none;
  }
}
@keyframes rd-gap-loop {
  0%, 10% {
    height: 0;
    opacity: 0;
  }
  40%, 65% {
    height: 8px;
    opacity: 1;
  }
  95%, 100% {
    height: 0;
    opacity: 0;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rd-item, .rd-drop-indicator {
    transition: none;
  }
}

(function () {
  var list = document.querySelector('.rd-list');
  var indicator = list.querySelector('.rd-drop-indicator');
  function order() { return Array.prototype.slice.call(list.querySelectorAll('.rd-item')); }

  order().forEach(function (item) {
    var handle = item.querySelector('.rd-item__handle');
    var dragging = false, startY = 0;

    handle.addEventListener('pointerdown', function (e) {
      list.classList.remove('is-demo');
      dragging = true;
      startY = e.clientY;
      item.classList.add('is-dragging');
      list.classList.add('is-dragging');
      handle.setPointerCapture(e.pointerId);
    });
    handle.addEventListener('pointermove', function (e) {
      if (!dragging) return;
      item.style.transform = 'translateY(' + (e.clientY - startY) + 'px)';
      var rest = order().filter(function (r) { return r !== item; });
      var target = rest.filter(function (r) {
        var rect = r.getBoundingClientRect();
        return e.clientY < rect.top + rect.height / 2;
      })[0];
      if (target) list.insertBefore(indicator, target);
      else list.insertBefore(indicator, null);
    });
    function drop() {
      if (!dragging) return;
      dragging = false;
      item.style.transform = '';
      item.classList.remove('is-dragging');
      list.classList.remove('is-dragging');
      list.insertBefore(item, indicator);
    }
    handle.addEventListener('pointerup', drop);
    handle.addEventListener('pointercancel', drop);

    handle.addEventListener('keydown', function (e) {
      if ((e.key !== 'ArrowUp' && e.key !== 'ArrowDown') || !e.altKey) return;
      e.preventDefault();
      list.classList.remove('is-demo');
      var o = order();
      var idx = o.indexOf(item);
      var targetIdx = e.key === 'ArrowUp' ? idx - 1 : idx + 1;
      if (targetIdx < 0 || targetIdx >= o.length) return;
      if (e.key === 'ArrowUp') list.insertBefore(item, o[targetIdx]);
      else list.insertBefore(item, o[targetIdx].nextSibling);
      handle.focus({ preventScroll: true });
    });
  });
})();

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

export type ReorderIndicatorDropGapProps = {
  items: string[];
  /** 들어올림·이동 시간 (기본 300ms) */
  duration?: number;
  easing?: string;
  /** 드롭 인디케이터 색 */
  color?: string;
};

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

/**
 * 손잡이를 드래그하면 항목이 통째로 밀리는 대신 놓일 자리에 빈 줄 인디케이터가 먼저 나타난다.
 * 마우스를 못 쓰는 사람은 손잡이 포커스 후 Alt+화살표로 같은 순서 변경을 할 수 있다.
 */
export default function ReorderIndicatorDropGap({
  items,
  duration = 300,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
}: ReorderIndicatorDropGapProps) {
  const [order, setOrder] = useState(items);
  const [dragIdx, setDragIdx] = useState<number | null>(null);
  const [dragY, setDragY] = useState(0);
  const [dropIdx, setDropIdx] = useState<number | null>(null);
  const rowRefs = useRef<Array<HTMLLIElement | null>>([]);
  const startY = useRef(0);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  const move = (i: number, dir: -1 | 1) => {
    const j = i + dir;
    if (j < 0 || j >= order.length) return;
    const next = order.slice();
    [next[i], next[j]] = [next[j], next[i]];
    setOrder(next);
  };

  const down = (i: number, e: any) => {
    setDragIdx(i);
    setDropIdx(i);
    startY.current = e.clientY;
    e.currentTarget.setPointerCapture(e.pointerId);
  };
  const dragMove = (e: any) => {
    if (dragIdx === null) return;
    setDragY(e.clientY - (startY.current ?? e.clientY));
    let target = order.length;
    const refs = rowRefs.current ?? [];
    for (let k = 0; k < order.length; k++) {
      const el = refs[k];
      if (!el || k === dragIdx) continue;
      const rect = el.getBoundingClientRect();
      if (e.clientY < rect.top + rect.height / 2) { target = k; break; }
    }
    setDropIdx(target);
  };
  const drop = () => {
    if (dragIdx === null || dropIdx === null) { setDragIdx(null); return; }
    const next = order.slice();
    const [moved] = next.splice(dragIdx, 1);
    next.splice(dropIdx > dragIdx ? dropIdx - 1 : dropIdx, 0, moved);
    setOrder(next);
    setDragIdx(null); setDropIdx(null); setDragY(0);
  };

  const rows = order.flatMap((label, i) => {
    const nodes = [];
    if (dropIdx === i && dragIdx !== null) {
      nodes.push(<li key={`gap-${label}`} className={styles.indicator} aria-hidden="true" />);
    }
    nodes.push(
      <li
        key={label}
        ref={(el: HTMLLIElement | null) => { if (rowRefs.current) rowRefs.current[i] = el; }}
        className={`${styles.item} ${dragIdx === i ? styles.dragging : ""}`}
        style={dragIdx === i ? { transform: `translateY(${dragY}px)` } : undefined}
      >
        <button
          className={styles.handle}
          type="button"
          aria-label="순서 변경, 위/아래 화살표"
          onPointerDown={(e: any) => down(i, e)}
          onPointerMove={dragMove}
          onPointerUp={drop}
          onPointerCancel={drop}
          onKeyDown={(e: any) => {
            if ((e.key === "ArrowUp" || e.key === "ArrowDown") && e.altKey) {
              e.preventDefault();
              move(i, e.key === "ArrowUp" ? -1 : 1);
            }
          }}
        >
          <svg viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><path d="M208 32v192a16 16 0 0 1-16 16H64a16 16 0 0 1-16-16V32a16 16 0 0 1 16-16h128a16 16 0 0 1 16 16" opacity=".2" /><path d="M104 60a12 12 0 1 1-12-12a12 12 0 0 1 12 12m60 12a12 12 0 1 0-12-12a12 12 0 0 0 12 12m-72 44a12 12 0 1 0 12 12a12 12 0 0 0-12-12m72 0a12 12 0 1 0 12 12a12 12 0 0 0-12-12m-72 68a12 12 0 1 0 12 12a12 12 0 0 0-12-12m72 0a12 12 0 1 0 12 12a12 12 0 0 0-12-12" /></g></svg>
        </button>
        <span>{label}</span>
      </li>
    );
    return nodes;
  });

  return (
    <ul className={styles.list} style={vars} aria-label="우선순위 목록. 손잡이에서 화살표 키(Alt+위/아래)로 순서 변경">
      {rows}
      {dropIdx === order.length && dragIdx !== null && <li className={styles.indicator} aria-hidden="true" />}
    </ul>
  );
}