import { useState, useRef, useEffect } from 'react'

export default function NodeEditor({ nodes, setNodes, connections, setConnections, selectedNode, setSelectedNode }) {
  const canvasRef = useRef(null)
  const [isConnecting, setIsConnecting] = useState(false)
  const [connectionStart, setConnectionStart] = useState(null)
  const [draggedNode, setDraggedNode] = useState(null)
  const [mousePos, setMousePos] = useState({ x: 0, y: 0 })

  useEffect(() => {
    const handleDragOver = (e) => {
      e.preventDefault()
      setMousePos({ x: e.clientX, y: e.clientY })
    }

    const handleDrop = (e) => {
      e.preventDefault()
      const nodeType = e.dataTransfer.getData('node-type')
      if (nodeType && canvasRef.current) {
        const rect = canvasRef.current.getBoundingClientRect()
        const newNode = {
          id: `node-${Date.now()}`,
          type: nodeType,
          x: e.clientX - rect.left - 75,
          y: e.clientY - rect.top - 30,
          properties: {
            name: nodeType,
            units: 128,
            activation: 'relu'
          }
        }
        setNodes(prev => [...prev, newNode])
      }
    }

    const canvas = canvasRef.current
    if (canvas) {
      canvas.addEventListener('dragover', handleDragOver)
      canvas.addEventListener('drop', handleDrop)
    }

    return () => {
      if (canvas) {
        canvas.removeEventListener('dragover', handleDragOver)
        canvas.removeEventListener('drop', handleDrop)
      }
    }
  }, [setNodes])

  const handleNodeMouseDown = (e, nodeId) => {
    if (e.target.dataset.handle === 'output') {
      setIsConnecting(true)
      setConnectionStart(nodeId)
    } else {
      setDraggedNode(nodeId)
      setSelectedNode(nodeId)
    }
  }

  const handleNodeMouseUp = (e, nodeId) => {
    if (isConnecting && connectionStart && connectionStart !== nodeId) {
      const newConnection = {
        id: `conn-${Date.now()}`,
        from: connectionStart,
        to: nodeId
      }
      setConnections(prev => [...prev, newConnection])
    }
    setIsConnecting(false)
    setConnectionStart(null)
  }

  const handleMouseMove = (e) => {
    if (draggedNode && canvasRef.current) {
      const rect = canvasRef.current.getBoundingClientRect()
      setNodes(prev => prev.map(node => 
        node.id === draggedNode 
          ? { ...node, x: e.clientX - rect.left - 75, y: e.clientY - rect.top - 30 }
          : node
      ))
    }
    setMousePos({ x: e.clientX, y: e.clientY })
  }

  const handleMouseUp = () => {
    setDraggedNode(null)
    setIsConnecting(false)
    setConnectionStart(null)
  }

  return (
    <div 
      ref={canvasRef}
      className="flex-1 bg-gray-100 relative overflow-hidden"
      data-tutorial-target="canvas"
      onMouseMove={handleMouseMove}
      onMouseUp={handleMouseUp}
      onMouseLeave={handleMouseUp}
    >
      {/* Grid Background */}
      <div className="absolute inset-0 opacity-10">
        <div className="h-full w-full" style={{
          backgroundImage: 'linear-gradient(#000 1px, transparent 1px), linear-gradient(90deg, #000 1px, transparent 1px)',
          backgroundSize: '20px 20px'
        }} />
      </div>

      {/* Connections */}
      <svg className="absolute inset-0 pointer-events-none" style={{ width: '100%', height: '100%' }}>
        {connections.map(conn => {
          const fromNode = nodes.find(n => n.id === conn.from)
          const toNode = nodes.find(n => n.id === conn.to)
          if (!fromNode || !toNode) return null
          
          return (
            <g key={conn.id}>
              <line
                x1={fromNode.x + 150}
                y1={fromNode.y + 30}
                x2={toNode.x}
                y2={toNode.y + 30}
                stroke="#3b82f6"
                strokeWidth="2"
                markerEnd="url(#arrowhead)"
              />
            </g>
          )
        })}
        {isConnecting && connectionStart && (() => {
          const fromNode = nodes.find(n => n.id === connectionStart)
          if (!fromNode) return null
          return (
            <line
              x1={fromNode.x + 150}
              y1={fromNode.y + 30}
              x2={mousePos.x - canvasRef.current?.getBoundingClientRect().left}
              y2={mousePos.y - canvasRef.current?.getBoundingClientRect().top}
              stroke="#3b82f6"
              strokeWidth="2"
              strokeDasharray="5,5"
            />
          )
        })()}
        <defs>
          <marker id="arrowhead" markerWidth="10" markerHeight="7" refX="9" refY="3.5" orient="auto">
            <polygon points="0 0, 10 3.5, 0 7" fill="#3b82f6" />
          </marker>
        </defs>
      </svg>

      {/* Nodes */}
      {nodes.map(node => (
        <div
          key={node.id}
          className={`absolute bg-white rounded-lg shadow-lg border-2 cursor-move select-none ${
            selectedNode === node.id ? 'border-primary-500' : 'border-gray-300'
          }`}
          style={{ left: node.x, top: node.y, width: '150px' }}
          onMouseDown={(e) => handleNodeMouseDown(e, node.id)}
          onMouseUp={(e) => handleNodeMouseUp(e, node.id)}
        >
          <div className="px-3 py-2 bg-gray-50 border-b border-gray-200 rounded-t-lg">
            <h3 className="text-sm font-semibold text-gray-900">{node.properties.name}</h3>
          </div>
          <div className="p-3">
            <div className="text-xs text-gray-600 mb-2">{node.type}</div>
            <div className="text-xs text-gray-500">Units: {node.properties.units}</div>
          </div>
          <div className="absolute left-0 top-1/2 -translate-y-1/2 -translate-x-2">
            <div
              data-handle="input"
              className="w-4 h-4 bg-gray-400 rounded-full cursor-crosshair hover:bg-primary-500"
            />
          </div>
          <div className="absolute right-0 top-1/2 -translate-y-1/2 translate-x-2">
            <div
              data-handle="output"
              className="w-4 h-4 bg-gray-400 rounded-full cursor-crosshair hover:bg-primary-500"
            />
          </div>
        </div>
      ))}

      {/* Empty State */}
      {nodes.length === 0 && (
        <div className="absolute top-1/2 left-1/2 transform -translate-x-1/2 -translate-y-1/2 text-center">
          <div className="w-24 h-24 bg-gray-200 rounded-full flex items-center justify-center mx-auto mb-4">
            <Layers className="w-12 h-12 text-gray-400" />
          </div>
          <h3 className="text-xl font-semibold text-gray-700 mb-2">Start Building Your Architecture</h3>
          <p className="text-gray-500 mb-6">Drag layers from the toolbar onto the canvas</p>
          <button
            onClick={() => window.dispatchEvent(new CustomEvent('start-tutorial'))}
            className="px-6 py-2 bg-primary-600 text-white rounded-lg hover:bg-primary-700 transition-colors"
          >
            Start Tutorial
          </button>
        </div>
      )}
    </div>
  )
}