import { useState, useCallback } from 'react'
import { useQuery } from '@tanstack/react-query'
import { queryOptions } from '@tanstack/react-query'
import { api } from '@/lib/api-client'
import { usePOSStore } from '@/stores/pos.store'
import { Dialog, DialogContent, DialogHeader, DialogTitle } from '@/components/ui/dialog'
import { Input } from '@/components/ui/input'
import { Button } from '@/components/ui/button'
import { Badge } from '@/components/ui/badge'
import { Separator } from '@/components/ui/separator'
import { Search, X, History } from 'lucide-react'

interface Account {
  id: string
  name: string
  email: string | null
  phone: string | null
  accountNumber: string | null
}

interface TransactionLineItem {
  id: string
  description: string
  qty: number
  unitPrice: string
  lineTotal: string
}

interface Transaction {
  id: string
  transactionNumber: string
  total: string
  status: string
  paymentMethod: string | null
  transactionType: string
  completedAt: string | null
  createdAt: string
  lineItems?: TransactionLineItem[]
}

function accountSearchOptions(search: string) {
  return queryOptions({
    queryKey: ['pos', 'accounts', search],
    queryFn: () => api.get<{ data: Account[] }>('/v1/accounts', { q: search, limit: 10 }),
    enabled: search.length >= 2,
  })
}

function customerHistoryOptions(accountId: string | null, itemSearch?: string) {
  return queryOptions({
    queryKey: ['pos', 'customer-history', accountId, itemSearch ?? ''],
    queryFn: () => api.get<{ data: Transaction[] }>('/v1/transactions', {
      accountId,
      limit: 10,
      sort: 'created_at',
      order: 'desc',
      ...(itemSearch ? { itemSearch } : {}),
    }),
    enabled: !!accountId,
  })
}

interface POSCustomerDialogProps {
  open: boolean
  onOpenChange: (open: boolean) => void
}

export function POSCustomerDialog({ open, onOpenChange }: POSCustomerDialogProps) {
  const { accountId, accountName, setAccount, clearAccount } = usePOSStore()
  const [search, setSearch] = useState('')
  const [showHistory, setShowHistory] = useState(false)
  const [historySearch, setHistorySearch] = useState('')

  const { data: searchData, isLoading } = useQuery(accountSearchOptions(search))
  const accounts = searchData?.data ?? []

  const { data: historyData } = useQuery(customerHistoryOptions(showHistory ? accountId : null, historySearch || undefined))
  const history = historyData?.data ?? []

  function handleSelect(account: Account) {
    setAccount(account.id, account.name, account.phone, account.email)
    setSearch('')
    setShowHistory(false)
    onOpenChange(false)
  }

  function handleClear() {
    clearAccount()
    setSearch('')
    setShowHistory(false)
    onOpenChange(false)
  }

  const [expandedTxn, setExpandedTxn] = useState<string | null>(null)

  // Fetch detail for expanded transaction
  const { data: txnDetail } = useQuery({
    queryKey: ['pos', 'transaction-detail', expandedTxn],
    queryFn: () => api.get<Transaction>(`/v1/transactions/${expandedTxn}`),
    enabled: !!expandedTxn,
  })

  const toggleExpand = useCallback((id: string) => {
    setExpandedTxn((prev) => prev === id ? null : id)
  }, [])

  // History view
  if (showHistory && accountId) {
    return (
      <Dialog open={open} onOpenChange={onOpenChange}>
        <DialogContent className="max-w-md max-h-[80vh] flex flex-col">
          <DialogHeader>
            <DialogTitle className="flex items-center justify-between">
              <span>Order History — {accountName}</span>
              <Button variant="ghost" size="sm" onClick={() => { setShowHistory(false); setExpandedTxn(null) }}>Back</Button>
            </DialogTitle>
          </DialogHeader>
          {/* Search items in history */}
          <div className="relative">
            <Search className="absolute left-3 top-1/2 -translate-y-1/2 h-4 w-4 text-muted-foreground" />
            <Input
              value={historySearch}
              onChange={(e) => setHistorySearch(e.target.value)}
              placeholder="Search items (e.g. strings, bow)..."
              className="pl-10 h-10 text-sm"
            />
          </div>

          <div className="flex-1 overflow-y-auto">
            {history.length === 0 ? (
              <p className="text-sm text-muted-foreground text-center py-8">
                {historySearch ? `No orders with "${historySearch}"` : 'No transactions found'}
              </p>
            ) : (
              <div className="divide-y divide-border">
                {history.map((txn) => (
                  <div key={txn.id}>
                    <button
                      onClick={() => toggleExpand(txn.id)}
                      className="w-full text-left py-2.5 px-1 hover:bg-accent/50 rounded transition-colors"
                    >
                      <div className="flex items-center justify-between">
                        <span className="text-sm font-mono">{txn.transactionNumber}</span>
                        <span className="text-sm font-semibold">${parseFloat(txn.total).toFixed(2)}</span>
                      </div>
                      <div className="flex items-center gap-2 mt-0.5">
                        <Badge variant={txn.status === 'completed' ? 'default' : 'outline'} className="text-[10px]">
                          {txn.status}
                        </Badge>
                        {txn.paymentMethod && (
                          <span className="text-xs text-muted-foreground">{txn.paymentMethod.replace('_', ' ')}</span>
                        )}
                        <span className="text-xs text-muted-foreground ml-auto">
                          {new Date(txn.completedAt ?? txn.createdAt).toLocaleDateString()}
                        </span>
                      </div>
                    </button>
                    {expandedTxn === txn.id && txnDetail?.lineItems && (
                      <div className="px-3 pb-2 space-y-1">
                        {txnDetail.lineItems.map((item) => (
                          <div key={item.id} className="flex justify-between text-xs text-muted-foreground">
                            <span>{item.qty} x {item.description}</span>
                            <span>${parseFloat(item.lineTotal).toFixed(2)}</span>
                          </div>
                        ))}
                      </div>
                    )}
                  </div>
                ))}
              </div>
            )}
          </div>
        </DialogContent>
      </Dialog>
    )
  }

  return (
    <Dialog open={open} onOpenChange={onOpenChange}>
      <DialogContent className="max-w-md max-h-[80vh] flex flex-col">
        <DialogHeader>
          <DialogTitle>Customer</DialogTitle>
        </DialogHeader>

        {/* Current selection */}
        {accountId && (
          <>
            <div className="flex items-center justify-between p-3 rounded-md border bg-muted/30">
              <div>
                <p className="font-medium text-sm">{accountName}</p>
                <p className="text-xs text-muted-foreground">Selected customer</p>
              </div>
              <div className="flex gap-1">
                <Button variant="ghost" size="sm" onClick={() => setShowHistory(true)}>
                  <History className="h-4 w-4 mr-1" />
                  History
                </Button>
                <Button variant="ghost" size="icon" className="h-8 w-8" onClick={handleClear}>
                  <X className="h-4 w-4 text-destructive" />
                </Button>
              </div>
            </div>
            <Separator />
          </>
        )}

        {/* Search */}
        <div className="relative">
          <Search className="absolute left-3 top-1/2 -translate-y-1/2 h-4 w-4 text-muted-foreground" />
          <Input
            value={search}
            onChange={(e) => setSearch(e.target.value)}
            placeholder="Search by name, phone, email, account #..."
            className="pl-10 h-11"
            autoFocus
          />
        </div>

        {/* Results */}
        <div className="flex-1 overflow-y-auto">
          {isLoading ? (
            <p className="text-sm text-muted-foreground text-center py-4">Searching...</p>
          ) : search.length >= 2 && accounts.length === 0 ? (
            <p className="text-sm text-muted-foreground text-center py-4">No customers found</p>
          ) : (
            <div className="divide-y divide-border">
              {accounts.map((account) => (
                <button
                  key={account.id}
                  onClick={() => handleSelect(account)}
                  className="w-full text-left px-2 py-3 hover:bg-accent rounded-md transition-colors"
                >
                  <p className="font-medium text-sm">{account.name}</p>
                  <div className="flex gap-3 text-xs text-muted-foreground mt-0.5">
                    {account.phone && <span>{account.phone}</span>}
                    {account.email && <span>{account.email}</span>}
                    {account.accountNumber && <span>#{account.accountNumber}</span>}
                  </div>
                </button>
              ))}
            </div>
          )}
        </div>

        {/* Walk-in button */}
        {accountId && (
          <Button variant="outline" className="w-full h-11" onClick={handleClear}>
            Clear Customer (Walk-in)
          </Button>
        )}
      </DialogContent>
    </Dialog>
  )
}