import { useMemo, useState, useRef, useEffect } from 'react'
import { useTreeEditorStore } from '@/store/treeEditorStore'
import type { NodeType } from '@/types'
import { cn } from '@/lib/utils'

// Special values for creating new nodes
const CREATE_PREFIX = '__create_'
const CREATE_DECISION = `${CREATE_PREFIX}decision__`
const CREATE_ACTION = `${CREATE_PREFIX}action__`
const CREATE_SOLUTION = `${CREATE_PREFIX}solution__`

// Unicode symbols for node types (works in select options)
const NODE_TYPE_SYMBOLS: Record<NodeType, string> = {
  decision: '\u24D8',  // Information/question symbol
  action: '\u26A1',    // Lightning bolt for action
  solution: '\u2713',  // Checkmark for solution
  answer: '\u25CC'     // Dashed circle for placeholder
}

// Node type labels for UI
const NODE_TYPE_LABELS: Record<NodeType, string> = {
  decision: 'Decision',
  action: 'Action',
  solution: 'Solution',
  answer: 'Answer'
}

interface NodePickerProps {
  value: string
  onChange: (nodeId: string) => void
  /** The parent node ID - new nodes will be added as children of this node */
  parentNodeId: string
  excludeNodeId?: string
  placeholder?: string
  className?: string
  label?: string
  error?: string
  /** Callback when a new node is created (receives the new node ID) */
  onNodeCreated?: (nodeId: string) => void
  /** Whether to show the "Create New Node" options. Default: true.
   *  Set to false in inline canvas editing to prevent premature store writes. */
  allowCreate?: boolean
}

export function NodePicker({
  value,
  onChange,
  parentNodeId,
  excludeNodeId,
  placeholder = 'Select a node...',
  className,
  label,
  error,
  onNodeCreated,
  allowCreate = true
}: NodePickerProps) {
  const { getAvailableTargetNodes, addNode, updateNode } = useTreeEditorStore()
  const availableNodes = getAvailableTargetNodes(excludeNodeId)

  // State for inline node creation
  const [creatingNodeType, setCreatingNodeType] = useState<NodeType | null>(null)
  const [newNodeTitle, setNewNodeTitle] = useState('')
  const titleInputRef = useRef<HTMLInputElement>(null)

  // Focus the title input when creating a new node
  useEffect(() => {
    if (creatingNodeType && titleInputRef.current) {
      titleInputRef.current.focus()
    }
  }, [creatingNodeType])

  // Group nodes by type
  const groupedNodes = useMemo(() => {
    const decisions = availableNodes.filter(n => n.type === 'decision')
    const actions = availableNodes.filter(n => n.type === 'action')
    const solutions = availableNodes.filter(n => n.type === 'solution')
    return { decisions, actions, solutions }
  }, [availableNodes])

  const handleChange = (selectedValue: string) => {
    // Check if it's a "create new" option
    if (selectedValue.startsWith(CREATE_PREFIX)) {
      let nodeType: NodeType
      if (selectedValue === CREATE_DECISION) {
        nodeType = 'decision'
      } else if (selectedValue === CREATE_ACTION) {
        nodeType = 'action'
      } else if (selectedValue === CREATE_SOLUTION) {
        nodeType = 'solution'
      } else {
        return
      }

      // Show inline title input instead of immediately creating
      setCreatingNodeType(nodeType)
      setNewNodeTitle('')
    } else {
      // Normal selection
      onChange(selectedValue)
    }
  }

  const handleCreateNode = () => {
    if (!creatingNodeType || !newNodeTitle.trim()) return

    // Create the new node as a child of the parent
    const newNodeId = addNode(parentNodeId, creatingNodeType)

    // Set the title/question on the new node
    if (creatingNodeType === 'decision') {
      updateNode(newNodeId, { question: newNodeTitle.trim() })
    } else {
      updateNode(newNodeId, { title: newNodeTitle.trim() })
    }

    // Set this new node as the selected value
    onChange(newNodeId)

    // Notify parent if callback provided
    onNodeCreated?.(newNodeId)

    // Reset creation state
    setCreatingNodeType(null)
    setNewNodeTitle('')
  }

  const handleCancelCreate = () => {
    setCreatingNodeType(null)
    setNewNodeTitle('')
  }

  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === 'Enter' && newNodeTitle.trim()) {
      e.preventDefault()
      handleCreateNode()
    } else if (e.key === 'Escape') {
      e.preventDefault()
      handleCancelCreate()
    }
  }

  // Find the label for the currently selected node
  const selectedNode = availableNodes.find(n => n.id === value)

  return (
    <div className={className}>
      {label && (
        <label className="mb-1 block text-sm font-medium text-foreground">
          {label}
        </label>
      )}

      {/* Inline node creation UI */}
      {creatingNodeType ? (
        <div className="space-y-2">
          <div className="flex items-center gap-2 rounded-md border border-border bg-accent/50 p-2">
            <span className="text-xs font-medium text-foreground">
              New {NODE_TYPE_LABELS[creatingNodeType]}:
            </span>
            <input
              ref={titleInputRef}
              type="text"
              value={newNodeTitle}
              onChange={(e) => setNewNodeTitle(e.target.value)}
              onKeyDown={handleKeyDown}
              placeholder={creatingNodeType === 'decision' ? 'Enter question...' : 'Enter title...'}
              className={cn(
                'flex-1 rounded-md border border-border px-2 py-1 text-sm',
                'bg-card text-foreground placeholder:text-muted-foreground',
                'focus:border-primary focus:outline-none focus:ring-1 focus:ring-primary/20'
              )}
            />
          </div>
          <div className="flex gap-2">
            <button
              type="button"
              onClick={handleCancelCreate}
              className="flex-1 rounded-md border border-border px-3 py-1.5 text-xs font-medium text-muted-foreground hover:bg-accent hover:text-foreground"
            >
              Cancel
            </button>
            <button
              type="button"
              onClick={handleCreateNode}
              disabled={!newNodeTitle.trim()}
              className={cn(
                'flex-1 rounded-md px-3 py-1.5 text-xs font-medium',
                'bg-gradient-brand text-white shadow-lg shadow-primary/20 hover:opacity-90',
                'disabled:opacity-50 disabled:cursor-not-allowed'
              )}
            >
              Create
            </button>
          </div>
        </div>
      ) : (
        <>
          <select
            value={value || ''}
            onChange={(e) => handleChange(e.target.value)}
            className={cn(
              'block w-full rounded-md border px-3 py-2 text-sm',
              'bg-card text-foreground',
              'focus:border-primary focus:outline-none focus:ring-1 focus:ring-primary/20',
              error ? 'border-red-400' : 'border-border'
            )}
          >
            <option value="">{placeholder}</option>

            {/* Create new options — hidden when allowCreate=false (e.g. canvas inline editing) */}
            {allowCreate && (
              <optgroup label="Create New Node">
                <option value={CREATE_DECISION}>+ New Decision (question)</option>
                <option value={CREATE_ACTION}>+ New Action (task)</option>
                <option value={CREATE_SOLUTION}>+ New Solution (endpoint)</option>
              </optgroup>
            )}

            {/* Existing nodes grouped by type */}
            {groupedNodes.decisions.length > 0 && (
              <optgroup label="── Decisions ──">
                {groupedNodes.decisions.map((node) => (
                  <option key={node.id} value={node.id}>
                    {NODE_TYPE_SYMBOLS.decision} {node.label}
                  </option>
                ))}
              </optgroup>
            )}

            {groupedNodes.actions.length > 0 && (
              <optgroup label="── Actions ──">
                {groupedNodes.actions.map((node) => (
                  <option key={node.id} value={node.id}>
                    {NODE_TYPE_SYMBOLS.action} {node.label}
                  </option>
                ))}
              </optgroup>
            )}

            {groupedNodes.solutions.length > 0 && (
              <optgroup label="── Solutions ──">
                {groupedNodes.solutions.map((node) => (
                  <option key={node.id} value={node.id}>
                    {NODE_TYPE_SYMBOLS.solution} {node.label}
                  </option>
                ))}
              </optgroup>
            )}
          </select>

          {/* Show what's selected */}
          {value && selectedNode && (
            <p className="mt-1 text-xs text-muted-foreground">
              → {selectedNode.label}
            </p>
          )}
        </>
      )}

      {error && <p className="mt-1 text-xs text-red-400">{error}</p>}
    </div>
  )
}

export default NodePicker
