DND Patterns Skill

# DND Patterns Skill

## Purpose
Drag and drop implementation using DND Kit for reordering tune versions.

## Basic Setup
```javascript
import { DndContext, closestCenter } from '@dnd-kit/core';
import { SortableContext, verticalListSortingStrategy, useSortable } from '@dnd-kit/sortable';
import { CSS } from '@dnd-kit/utilities';

function SortableItem({ id, children }) {
  const { attributes, listeners, setNodeRef, transform, transition } = useSortable({ id });

  const style = {
    transform: CSS.Transform.toString(transform),
    transition
  };

  return (
    <div ref={setNodeRef} style={style} {...attributes} {...listeners}>
      {children}
    </div>
  );
}

function SortableList({ items, onReorder }) {
  const handleDragEnd = (event) => {
    const { active, over } = event;
    if (active.id !== over.id) {
      const oldIndex = items.findIndex(i => i.id === active.id);
      const newIndex = items.findIndex(i => i.id === over.id);
      onReorder(oldIndex, newIndex);
    }
  };

  return (
    <DndContext collisionDetection={closestCenter} onDragEnd={handleDragEnd}>
      <SortableContext items={items} strategy={verticalListSortingStrategy}>
        {items.map(item => (
          <SortableItem key={item.id} id={item.id}>
            {item.content}
          </SortableItem>
        ))}
      </SortableContext>
    </DndContext>
  );
}
```

## Best Practices
✅ Use unique IDs for items
✅ Provide visual feedback during drag
✅ Persist reordering to database
❌ Don't forget collision detection
❌ Don't mutate state directly