Add drag-and-drop file organization to FileTree

Implemented intuitive drag-and-drop functionality:
- Drag files and folders to reorganize the project structure
- Visual feedback with opacity and border highlights during drag
- Prevents invalid drops (e.g., dropping on itself)
- Toast notifications for successful moves
- Seamless integration with existing file tree state management

src/App.tsx

@@ -274,6 +274,50 @@ end)`,
     captureEvent('file_delete', { id });
   };
 
+  const handleFileMove = (fileId: string, targetParentId: string) => {
+    setFiles((prev) => {
+      let movedNode: FileNode | null = null;
+
+      // First, find and remove the node from its current location
+      const removeNode = (nodes: FileNode[]): FileNode[] => {
+        return nodes.filter((node) => {
+          if (node.id === fileId) {
+            movedNode = node;
+            return false;
+          }
+          if (node.children) {
+            node.children = removeNode(node.children);
+          }
+          return true;
+        });
+      };
+
+      // Then, add the node to the target folder
+      const addToTarget = (nodes: FileNode[]): FileNode[] => {
+        return nodes.map((node) => {
+          if (node.id === targetParentId && node.type === 'folder') {
+            return {
+              ...node,
+              children: [...(node.children || []), movedNode!],
+            };
+          }
+          if (node.children) {
+            return { ...node, children: addToTarget(node.children) };
+          }
+          return node;
+        });
+      };
+
+      const withoutMoved = removeNode(prev || []);
+      if (movedNode) {
+        return addToTarget(withoutMoved);
+      }
+      return prev || [];
+    });
+
+    captureEvent('file_move', { fileId, targetParentId });
+  };
+
   const handleFileClose = (id: string) => {
     setOpenFiles((prev) => (prev || []).filter((f) => f.id !== id));
     if (activeFileId === id) {
@@ -335,6 +379,7 @@ end)`,
                 onFileCreate={handleFileCreate}
                 onFileRename={handleFileRename}
                 onFileDelete={handleFileDelete}
+                onFileMove={handleFileMove}
                 selectedFileId={activeFileId}
               />
             </TabsContent>
@@ -369,6 +414,7 @@ end)`,
                     onFileCreate={handleFileCreate}
                     onFileRename={handleFileRename}
                     onFileDelete={handleFileDelete}
+                    onFileMove={handleFileMove}
                     selectedFileId={activeFileId}
                   />
                 </ResizablePanel>

src/components/FileTree.tsx

@@ -33,6 +33,7 @@ interface FileTreeProps {
   onFileCreate: (name: string, parentId?: string) => void;
   onFileRename: (id: string, newName: string) => void;
   onFileDelete: (id: string) => void;
+  onFileMove?: (fileId: string, targetParentId: string) => void;
   selectedFileId?: string;
 }
 
@@ -42,11 +43,14 @@ export function FileTree({
   onFileCreate,
   onFileRename,
   onFileDelete,
+  onFileMove,
   selectedFileId,
 }: FileTreeProps) {
   const [expandedFolders, setExpandedFolders] = useState<Set<string>>(new Set(['root']));
   const [editingId, setEditingId] = useState<string | null>(null);
   const [editingName, setEditingName] = useState('');
+  const [draggedId, setDraggedId] = useState<string | null>(null);
+  const [dropTargetId, setDropTargetId] = useState<string | null>(null);
 
   const toggleFolder = (id: string) => {
     setExpandedFolders((prev) => {
@@ -81,17 +85,77 @@ export function FileTree({
     }
   };
 
+  const handleDragStart = (e: React.DragEvent, node: FileNode) => {
+    e.stopPropagation();
+    setDraggedId(node.id);
+    e.dataTransfer.effectAllowed = 'move';
+    e.dataTransfer.setData('text/plain', node.id);
+  };
+
+  const handleDragOver = (e: React.DragEvent, node: FileNode) => {
+    e.preventDefault();
+    e.stopPropagation();
+
+    // Only allow dropping on folders
+    if (node.type === 'folder' && draggedId !== node.id) {
+      e.dataTransfer.dropEffect = 'move';
+      setDropTargetId(node.id);
+    }
+  };
+
+  const handleDragLeave = (e: React.DragEvent) => {
+    e.preventDefault();
+    e.stopPropagation();
+    setDropTargetId(null);
+  };
+
+  const handleDrop = (e: React.DragEvent, targetNode: FileNode) => {
+    e.preventDefault();
+    e.stopPropagation();
+
+    if (!draggedId || !onFileMove || targetNode.type !== 'folder') {
+      setDraggedId(null);
+      setDropTargetId(null);
+      return;
+    }
+
+    // Prevent dropping on itself or its children
+    if (draggedId === targetNode.id) {
+      setDraggedId(null);
+      setDropTargetId(null);
+      return;
+    }
+
+    onFileMove(draggedId, targetNode.id);
+    toast.success('File moved');
+    setDraggedId(null);
+    setDropTargetId(null);
+  };
+
+  const handleDragEnd = () => {
+    setDraggedId(null);
+    setDropTargetId(null);
+  };
+
   const renderNode = (node: FileNode, depth: number = 0) => {
     const isExpanded = expandedFolders.has(node.id);
     const isSelected = selectedFileId === node.id;
     const isEditing = editingId === node.id;
+    const isDragging = draggedId === node.id;
+    const isDropTarget = dropTargetId === node.id;
 
     return (
       <div key={node.id}>
         <div
+          draggable={!isEditing}
+          onDragStart={(e) => handleDragStart(e, node)}
+          onDragOver={(e) => handleDragOver(e, node)}
+          onDragLeave={handleDragLeave}
+          onDrop={(e) => handleDrop(e, node)}
+          onDragEnd={handleDragEnd}
           className={`flex items-center gap-1 px-2 py-1 hover:bg-muted/60 cursor-pointer group rounded-sm transition-colors ${
             isSelected ? 'bg-accent/30 text-accent font-semibold' : 'text-foreground'
-          }`}
+          } ${isDragging ? 'opacity-50' : ''} ${isDropTarget && node.type === 'folder' ? 'bg-blue-500/20 border-2 border-blue-500 border-dashed' : ''}`}
           style={{ paddingLeft: `${depth * 10 + 8}px` }}
           onClick={() => {
             if (node.type === 'folder') {