优化

web/src/hooks/useDragReorder.ts

@@ -0,0 +1,86 @@
+import { useCallback, useState, type DragEvent } from 'react'
+
+/** 一组可直接展开到可拖拽元素上的事件处理器。 */
+export type DragReorderHandlers = {
+  draggable: boolean
+  onDragStart: (event: DragEvent) => void
+  onDragOver: (event: DragEvent) => void
+  onDragLeave: (event: DragEvent) => void
+  onDrop: (event: DragEvent) => void
+  onDragEnd: () => void
+}
+
+/**
+ * 把 `fromId` 移动到 `toId` 当前所在的位置，返回新数组；不改动入参。
+ * 任一 id 不存在，或两者相同时返回 null，表示无需重排。
+ */
+export function moveIdToPosition(ids: string[], fromId: string, toId: string): string[] | null {
+  const fromIndex = ids.indexOf(fromId)
+  const toIndex = ids.indexOf(toId)
+  if (fromIndex < 0 || toIndex < 0 || fromIndex === toIndex) return null
+  const next = [...ids]
+  const [moved] = next.splice(fromIndex, 1)
+  next.splice(toIndex, 0, moved)
+  return next
+}
+
+/**
+ * 列表拖拽排序的通用状态机：只负责「一串稳定 id」的拖拽与重排计算，
+ * 不关心渲染。调用方把 `dragProps(id)` 展开到拖拽柄上，并用返回的
+ * `draggingId` / `dragOverId` 决定高亮样式。
+ *
+ * 落点语义：把被拖项插入到目标项所在的位置。未传 `onReorder` 时整体禁用。
+ */
+export function useDragReorder(
+  ids: string[],
+  onReorder?: (orderedIds: string[]) => void | Promise<void>,
+): {
+  draggingId: string | null
+  dragOverId: string | null
+  dragProps: (id: string) => DragReorderHandlers
+} {
+  const [draggingId, setDraggingId] = useState<string | null>(null)
+  const [dragOverId, setDragOverId] = useState<string | null>(null)
+
+  const enabled = Boolean(onReorder)
+
+  const dragProps = useCallback(
+    (id: string): DragReorderHandlers => ({
+      draggable: enabled,
+      onDragStart: (event) => {
+        if (!enabled) return
+        event.dataTransfer.effectAllowed = 'move'
+        event.dataTransfer.setData('text/plain', id)
+        setDraggingId(id)
+        setDragOverId(null)
+      },
+      onDragOver: (event) => {
+        if (!enabled || draggingId === id) return
+        event.preventDefault()
+        event.dataTransfer.dropEffect = 'move'
+        setDragOverId((prev) => (prev === id ? prev : id))
+      },
+      onDragLeave: () => {
+        setDragOverId((prev) => (prev === id ? null : prev))
+      },
+      onDrop: (event) => {
+        if (!enabled) return
+        event.preventDefault()
+        // 拖拽期间 state 可能尚未提交，优先信任 dataTransfer 里的来源 id。
+        const fromId = draggingId ?? event.dataTransfer.getData('text/plain')
+        setDraggingId(null)
+        setDragOverId(null)
+        if (!fromId || fromId === id) return
+        const next = moveIdToPosition(ids, fromId, id)
+        if (next) void onReorder?.(next)
+      },
+      onDragEnd: () => {
+        setDraggingId(null)
+        setDragOverId(null)
+      },
+    }),
+    [enabled, draggingId, ids, onReorder],
+  )
+
+  return { draggingId, dragOverId, dragProps }
+}