feat: add FlowCanvas main React Flow component with zoom/pan/minimap

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/tree-editor/FlowCanvas.tsx

@@ -0,0 +1,176 @@
+import { useCallback, useMemo, useState, useEffect } from 'react'
+import {
+  ReactFlow,
+  Background,
+  Controls,
+  MiniMap,
+  BackgroundVariant,
+  useReactFlow,
+  useNodesState,
+  useEdgesState,
+  ReactFlowProvider,
+  PanOnScrollMode,
+  type NodeMouseHandler,
+} from '@xyflow/react'
+import '@xyflow/react/dist/style.css'
+
+import { FlowCanvasNode, NODE_TYPE_CONFIG } from './FlowCanvasNode'
+import { FlowCanvasAnswerNode } from './FlowCanvasAnswerNode'
+import { useTreeLayout } from './useTreeLayout'
+import { cn } from '@/lib/utils'
+import { Map as MapIcon, MapPinOff } from 'lucide-react'
+import type { FlowCanvasNodeData } from './FlowCanvasNode'
+import type { FlowCanvasAnswerNodeData } from './FlowCanvasAnswerNode'
+
+const nodeTypes = {
+  flowNode: FlowCanvasNode,
+  answerStub: FlowCanvasAnswerNode,
+}
+
+interface FlowCanvasProps {
+  selectedNodeId: string | null
+  onNodeSelect: (nodeId: string | null) => void
+  onSelectAnswerType: (nodeId: string, type: 'decision' | 'action' | 'solution') => void
+}
+
+function FlowCanvasInner({ selectedNodeId, onNodeSelect, onSelectAnswerType }: FlowCanvasProps) {
+  const { fitView, setCenter } = useReactFlow()
+  const { nodes: layoutNodes, edges: layoutEdges, collapsedNodeIds, toggleCollapse, onNodesMeasured } = useTreeLayout()
+  const [minimapVisible, setMinimapVisible] = useState(true)
+
+  // Inject callbacks into node data (because useTreeLayout creates placeholder functions)
+  const nodesWithCallbacks = useMemo(() => {
+    return layoutNodes.map(n => {
+      if (n.type === 'flowNode') {
+        const data = n.data as unknown as FlowCanvasNodeData
+        return {
+          ...n,
+          selected: n.id === selectedNodeId,
+          data: { ...data, onToggleCollapse: toggleCollapse },
+        }
+      }
+      if (n.type === 'answerStub') {
+        const data = n.data as unknown as FlowCanvasAnswerNodeData
+        return {
+          ...n,
+          selected: n.id === selectedNodeId,
+          data: { ...data, onSelectType: onSelectAnswerType },
+        }
+      }
+      return n
+    })
+  }, [layoutNodes, selectedNodeId, toggleCollapse, onSelectAnswerType])
+
+  const [nodes, setNodes, onNodesChange] = useNodesState(nodesWithCallbacks)
+  const [edges, setEdges, onEdgesChange] = useEdgesState(layoutEdges)
+
+  // Sync layout changes into React Flow state
+  useEffect(() => {
+    setNodes(nodesWithCallbacks)
+    setEdges(layoutEdges)
+  }, [nodesWithCallbacks, layoutEdges, setNodes, setEdges])
+
+  // Fit view after layout changes
+  useEffect(() => {
+    // Small delay to let React Flow process the node updates
+    const timer = setTimeout(() => {
+      fitView({ padding: 0.1, duration: 200 })
+    }, 50)
+    return () => clearTimeout(timer)
+  }, [layoutNodes.length, collapsedNodeIds.size]) // eslint-disable-line react-hooks/exhaustive-deps
+
+  // Auto-center on selected node when panel opens
+  useEffect(() => {
+    if (!selectedNodeId) return
+    const node = nodes.find(n => n.id === selectedNodeId)
+    if (node) {
+      const x = node.position.x + 140 // center of 280px node
+      const y = node.position.y + 50
+      setCenter(x, y, { duration: 300, zoom: 1 })
+    }
+  }, [selectedNodeId]) // eslint-disable-line react-hooks/exhaustive-deps
+
+  // Height measurement correction
+  useEffect(() => {
+    if (nodes.length > 0 && nodes.some(n => n.measured?.height)) {
+      onNodesMeasured(nodes)
+    }
+  }, [nodes]) // eslint-disable-line react-hooks/exhaustive-deps
+
+  const handleNodeClick: NodeMouseHandler = useCallback((_event, node) => {
+    onNodeSelect(node.id)
+  }, [onNodeSelect])
+
+  const handlePaneClick = useCallback(() => {
+    onNodeSelect(null)
+  }, [onNodeSelect])
+
+  // Custom minimap node color based on actual tree node type
+  const minimapNodeColor = useCallback((rfNode: { data?: unknown }) => {
+    const data = rfNode.data as (FlowCanvasNodeData & FlowCanvasAnswerNodeData) | undefined
+    if (!data || !('node' in data)) return '#6b7280'
+    const treeNode = data.node
+    if (treeNode.type === 'answer') return '#6b7280'
+    const config = NODE_TYPE_CONFIG[treeNode.type as keyof typeof NODE_TYPE_CONFIG]
+    return config?.minimapColor ?? '#6b7280'
+  }, [])
+
+  return (
+    <div className="relative h-full w-full">
+      <ReactFlow
+        nodes={nodes}
+        edges={edges}
+        onNodesChange={onNodesChange}
+        onEdgesChange={onEdgesChange}
+        nodeTypes={nodeTypes}
+        onNodeClick={handleNodeClick}
+        onPaneClick={handlePaneClick}
+        fitView
+        minZoom={0.25}
+        maxZoom={2}
+        zoomOnScroll={false}
+        zoomOnPinch={true}
+        panOnScroll={true}
+        panOnScrollMode={PanOnScrollMode.Vertical}
+        selectionOnDrag={false}
+        nodesDraggable={false}
+        nodesConnectable={false}
+        proOptions={{ hideAttribution: true }}
+        className="bg-background"
+      >
+        <Background variant={BackgroundVariant.Dots} gap={24} size={1} color="hsl(var(--border))" />
+        <Controls showInteractive={false} className="!bg-card !border-border !shadow-lg" />
+        {minimapVisible && (
+          <MiniMap
+            pannable
+            zoomable
+            nodeColor={minimapNodeColor}
+            className="!bg-card !border-border"
+            nodeStrokeWidth={2}
+          />
+        )}
+      </ReactFlow>
+
+      {/* Minimap toggle button */}
+      <button
+        onClick={() => setMinimapVisible(v => !v)}
+        className={cn(
+          'absolute bottom-2 right-2 z-10 rounded-lg border border-border bg-card p-2 text-muted-foreground shadow-lg hover:bg-accent hover:text-foreground transition-colors',
+          minimapVisible && 'bottom-[170px]'
+        )}
+        title={minimapVisible ? 'Hide minimap' : 'Show minimap'}
+      >
+        {minimapVisible ? <MapPinOff className="h-4 w-4" /> : <MapIcon className="h-4 w-4" />}
+      </button>
+    </div>
+  )
+}
+
+// Wrap in ReactFlowProvider (required by useReactFlow hook)
+export function FlowCanvas(props: FlowCanvasProps) {
+  return (
+    <ReactFlowProvider>
+      <FlowCanvasInner {...props} />
+    </ReactFlowProvider>
+  )
+}