import { useState, useEffect } from 'react'
import {
  CreditCard, Banknote, Clock, LogIn, LogOut, CheckCircle2,
  Receipt, Zap, Building2, Coffee, Car, Package, ChevronRight,
  User, AlertCircle, Printer,
} from 'lucide-react'
import { format } from 'date-fns'
import { ru } from 'date-fns/locale'
import { cn, formatCurrency } from '../lib/utils'

// ── Types ─────────────────────────────────────────────────────────────────────

interface RoomBalance {
  roomId: string
  roomNumber: string
  guestName: string
  checkIn: string
  checkOut: string
  totalAmount: number
  paidAmount: number
  nights: number
}

type PaymentMethod = 'cash' | 'terminal' | 'atol'
type ChargePurpose = 'stay' | 'breakfast' | 'transfer' | 'parking' | 'extra'

interface ReceiptRecord {
  id: string
  roomNumber: string
  guestName: string
  purposeLabel: string
  amount: number
  method: PaymentMethod
  createdAt: Date
  shiftId: string
}

// ── Mock data ──────────────────────────────────────────────────────────────────

const MOCK_BALANCES: RoomBalance[] = [
  { roomId: 'r1', roomNumber: '101', guestName: 'Дмитрий Волков',      checkIn: '2026-03-10', checkOut: '2026-03-12', totalAmount: 9000,  paidAmount: 4500,  nights: 2 },
  { roomId: 'r2', roomNumber: '201', guestName: 'Игорь Соколов',       checkIn: '2026-03-09', checkOut: '2026-03-11', totalAmount: 14000, paidAmount: 14000, nights: 2 },
  { roomId: 'r3', roomNumber: '301', guestName: 'Наталья Александрова',checkIn: '2026-03-11', checkOut: '2026-03-15', totalAmount: 48000, paidAmount: 24000, nights: 4 },
  { roomId: 'r4', roomNumber: '401', guestName: 'Михаил Орлов',        checkIn: '2026-03-10', checkOut: '2026-03-13', totalAmount: 36000, paidAmount: 0,     nights: 3 },
]

const PURPOSE_LABELS: Record<ChargePurpose, string> = {
  stay:      'Проживание',
  breakfast: 'Завтрак',
  transfer:  'Трансфер',
  parking:   'Парковка',
  extra:     'Доп. услуга',
}

const QUICK_CHARGES: { purpose: ChargePurpose; label: string; amount: number | null; Icon: any }[] = [
  { purpose: 'stay',      label: 'Проживание',  amount: null,  Icon: Building2 },
  { purpose: 'breakfast', label: 'Завтрак',     amount: 650,   Icon: Coffee },
  { purpose: 'transfer',  label: 'Трансфер',    amount: 2500,  Icon: Car },
  { purpose: 'parking',   label: 'Парковка',    amount: 500,   Icon: Package },
  { purpose: 'extra',     label: 'Доп. услуга', amount: null,  Icon: Zap },
]

const SEED_RECEIPTS: ReceiptRecord[] = [
  { id: 'rc1', roomNumber: '201', guestName: 'Игорь Соколов',         purposeLabel: 'Проживание', amount: 14000, method: 'terminal', createdAt: new Date(Date.now() - 3600000 * 3), shiftId: 'shift-today' },
  { id: 'rc2', roomNumber: '101', guestName: 'Дмитрий Волков',        purposeLabel: 'Проживание', amount: 4500,  method: 'cash',     createdAt: new Date(Date.now() - 3600000 * 2), shiftId: 'shift-today' },
  { id: 'rc3', roomNumber: '301', guestName: 'Наталья Александрова',  purposeLabel: 'Проживание', amount: 24000, method: 'terminal', createdAt: new Date(Date.now() - 3600000),     shiftId: 'shift-today' },
  { id: 'rc4', roomNumber: '101', guestName: 'Дмитрий Волков',        purposeLabel: 'Завтрак',    amount: 1300,  method: 'cash',     createdAt: new Date(Date.now() - 1800000),     shiftId: 'shift-today' },
]

// ── Component ─────────────────────────────────────────────────────────────────

export function PosPage() {
  const [shiftOpen, setShiftOpen] = useState(true)
  const [shiftStartTime] = useState<Date>(new Date(Date.now() - 3600000 * 3))
  const [shiftTimer, setShiftTimer] = useState('')
  const [receipts, setReceipts] = useState<ReceiptRecord[]>(SEED_RECEIPTS)
  const [selectedRoom, setSelectedRoom] = useState<RoomBalance | null>(MOCK_BALANCES[0])
  const [purpose, setPurpose] = useState<ChargePurpose>('stay')
  const [amount, setAmount] = useState<number>(0)
  const [method, setMethod] = useState<PaymentMethod>('terminal')
  const [notes, setNotes] = useState('')
  const [lastReceipt, setLastReceipt] = useState<ReceiptRecord | null>(null)
  const shiftId = 'shift-today'

  // Update amount when room or purpose changes
  useEffect(() => {
    if (!selectedRoom) { setAmount(0); return }
    if (purpose === 'stay') {
      setAmount(Math.max(0, selectedRoom.totalAmount - selectedRoom.paidAmount))
    } else {
      const qc = QUICK_CHARGES.find(q => q.purpose === purpose)
      setAmount(qc?.amount ?? 0)
    }
  }, [selectedRoom, purpose])

  // Shift timer
  useEffect(() => {
    if (!shiftOpen) return
    const tick = () => {
      const diff = Math.floor((Date.now() - shiftStartTime.getTime()) / 1000)
      const h = Math.floor(diff / 3600)
      const m = Math.floor((diff % 3600) / 60)
      const s = diff % 60
      setShiftTimer(`${String(h).padStart(2, '0')}:${String(m).padStart(2, '0')}:${String(s).padStart(2, '0')}`)
    }
    tick()
    const id = setInterval(tick, 1000)
    return () => clearInterval(id)
  }, [shiftOpen, shiftStartTime])

  const shiftReceipts = receipts.filter(r => r.shiftId === shiftId)
  const shiftRevenue  = shiftReceipts.reduce((s, r) => s + r.amount, 0)
  const cashRevenue   = shiftReceipts.filter(r => r.method === 'cash').reduce((s, r) => s + r.amount, 0)
  const termRevenue   = shiftReceipts.filter(r => r.method === 'terminal').reduce((s, r) => s + r.amount, 0)

  const handlePay = () => {
    if (!selectedRoom || amount <= 0 || !shiftOpen) return
    const rec: ReceiptRecord = {
      id: `rc-${Date.now()}`,
      roomNumber:   selectedRoom.roomNumber,
      guestName:    selectedRoom.guestName,
      purposeLabel: PURPOSE_LABELS[purpose],
      amount,
      method,
      createdAt: new Date(),
      shiftId,
    }
    setReceipts(prev => [rec, ...prev])
    setLastReceipt(rec)
    setNotes('')
  }

  const balance = selectedRoom ? Math.max(0, selectedRoom.totalAmount - selectedRoom.paidAmount) : 0
  const isPaid  = selectedRoom ? selectedRoom.paidAmount >= selectedRoom.totalAmount : false

  return (
    <div className="flex h-full flex-col">
      {/* ── Top bar ── */}
      <div className="shrink-0 px-4 py-3 border-b border-slate-200 dark:border-slate-700 bg-white dark:bg-slate-800">
        <div className="flex items-center justify-between flex-wrap gap-2">
          <div>
            <h1 className="text-lg font-bold text-slate-900 dark:text-slate-100">Касса</h1>
            <p className="text-xs text-slate-500 dark:text-slate-400">
              {format(new Date(), 'd MMMM yyyy', { locale: ru })} · Елена Смирнова
            </p>
          </div>
          <div className="flex items-center gap-3">
            {shiftOpen && (
              <div className="flex items-center gap-2 px-3 py-1.5 rounded-xl bg-emerald-50 dark:bg-emerald-900/20 border border-emerald-200 dark:border-emerald-700">
                <Clock size={13} className="text-emerald-600" />
                <span className="text-xs font-mono font-semibold text-emerald-700 dark:text-emerald-300">{shiftTimer}</span>
              </div>
            )}
            <button
              onClick={() => setShiftOpen(v => !v)}
              className={cn(
                'flex items-center gap-1.5 px-3 py-1.5 rounded-xl text-sm font-medium border-2 transition-colors',
                shiftOpen
                  ? 'bg-red-50 border-red-300 text-red-700 dark:bg-red-900/20 dark:border-red-700 dark:text-red-300'
                  : 'bg-emerald-50 border-emerald-300 text-emerald-700 dark:bg-emerald-900/20 dark:border-emerald-700 dark:text-emerald-300',
              )}
            >
              {shiftOpen ? <><LogOut size={14} />Закрыть смену</> : <><LogIn size={14} />Открыть смену</>}
            </button>
          </div>
        </div>

        {/* Shift stats */}
        {shiftOpen && (
          <div className="grid grid-cols-4 gap-2 mt-3">
            {[
              { label: 'Выручка за смену',   value: formatCurrency(shiftRevenue), color: 'text-slate-900 dark:text-slate-100' },
              { label: 'Наличные',            value: formatCurrency(cashRevenue),  color: 'text-emerald-600 dark:text-emerald-400' },
              { label: 'Терминал / АТОЛ',     value: formatCurrency(termRevenue),  color: 'text-blue-600 dark:text-blue-400' },
              { label: 'Чеков',               value: shiftReceipts.length,         color: 'text-slate-900 dark:text-slate-100' },
            ].map(s => (
              <div key={s.label} className="rounded-xl bg-slate-50 dark:bg-slate-700/50 px-3 py-2">
                <p className={cn('text-base font-bold', s.color)}>{s.value}</p>
                <p className="text-[10px] text-slate-500 dark:text-slate-400">{s.label}</p>
              </div>
            ))}
          </div>
        )}
      </div>

      {/* ── Shift closed ── */}
      {!shiftOpen ? (
        <div className="flex-1 flex items-center justify-center flex-col gap-4 text-slate-400">
          <Receipt size={56} className="opacity-20" />
          <div className="text-center">
            <p className="text-lg font-semibold text-slate-600 dark:text-slate-300">Смена закрыта</p>
            <p className="text-sm">Откройте смену для начала работы</p>
          </div>
          <button onClick={() => setShiftOpen(true)} className="btn-primary">
            <LogIn size={15} />Открыть смену
          </button>
        </div>
      ) : (
        <div className="flex flex-1 overflow-hidden">

          {/* ── Left: active bookings ── */}
          <div className="w-64 flex flex-col border-r border-slate-200 dark:border-slate-700 bg-slate-50 dark:bg-slate-800/50 shrink-0 overflow-y-auto">
            <div className="px-3 py-2.5 border-b border-slate-200 dark:border-slate-700">
              <p className="text-xs font-semibold text-slate-500 dark:text-slate-400 uppercase tracking-wide">
                Активные заезды
              </p>
            </div>
            <div className="flex-1 p-2 space-y-1.5">
              {MOCK_BALANCES.map(rb => {
                const debt = Math.max(0, rb.totalAmount - rb.paidAmount)
                const paid = debt === 0
                const sel  = selectedRoom?.roomId === rb.roomId
                return (
                  <button
                    key={rb.roomId}
                    onClick={() => setSelectedRoom(rb)}
                    className={cn(
                      'w-full text-left rounded-xl p-3 border transition-all',
                      sel
                        ? 'border-brand-400 bg-brand-50 dark:bg-brand-900/20 dark:border-brand-600'
                        : 'border-slate-200 dark:border-slate-600 bg-white dark:bg-slate-800 hover:border-brand-300',
                    )}
                  >
                    <div className="flex items-center justify-between mb-1">
                      <span className="text-sm font-bold text-slate-900 dark:text-slate-100">№{rb.roomNumber}</span>
                      {paid
                        ? <span className="text-[10px] bg-emerald-100 text-emerald-700 dark:bg-emerald-900/30 dark:text-emerald-300 px-1.5 py-0.5 rounded-full font-medium">Оплачен</span>
                        : <span className="text-[10px] bg-red-100 text-red-700 dark:bg-red-900/30 dark:text-red-300 px-1.5 py-0.5 rounded-full font-medium">Долг</span>
                      }
                    </div>
                    <p className="text-xs text-slate-600 dark:text-slate-400 truncate">{rb.guestName}</p>
                    <p className="text-xs text-slate-400 mt-0.5">
                      {rb.checkIn} → {rb.checkOut}
                    </p>
                    {!paid && (
                      <p className="text-xs font-semibold text-red-600 dark:text-red-400 mt-1.5">
                        Остаток: {formatCurrency(debt)}
                      </p>
                    )}
                  </button>
                )
              })}
            </div>
          </div>

          {/* ── Center: payment form ── */}
          <div className="flex-1 flex flex-col overflow-y-auto p-5 gap-5">
            {selectedRoom ? (
              <>
                {/* Guest info */}
                <div className="card p-4">
                  <div className="flex items-center gap-3">
                    <div className="w-10 h-10 rounded-full bg-brand-100 dark:bg-brand-900/30 flex items-center justify-center shrink-0">
                      <User size={18} className="text-brand-600 dark:text-brand-400" />
                    </div>
                    <div className="flex-1">
                      <p className="font-semibold text-slate-900 dark:text-slate-100">{selectedRoom.guestName}</p>
                      <p className="text-xs text-slate-500 dark:text-slate-400">
                        Номер {selectedRoom.roomNumber} · {selectedRoom.nights} {selectedRoom.nights === 1 ? 'ночь' : selectedRoom.nights < 5 ? 'ночи' : 'ночей'}
                      </p>
                    </div>
                    <div className="text-right">
                      <p className="text-xs text-slate-500 dark:text-slate-400">К оплате</p>
                      <p className={cn(
                        'text-lg font-bold',
                        isPaid ? 'text-emerald-600 dark:text-emerald-400' : 'text-red-600 dark:text-red-400',
                      )}>
                        {formatCurrency(balance)}
                      </p>
                    </div>
                  </div>
                  {/* Balance bar */}
                  <div className="mt-3">
                    <div className="flex items-center justify-between text-xs text-slate-500 mb-1">
                      <span>Оплачено {formatCurrency(selectedRoom.paidAmount)}</span>
                      <span>Всего {formatCurrency(selectedRoom.totalAmount)}</span>
                    </div>
                    <div className="h-2 rounded-full bg-slate-200 dark:bg-slate-600 overflow-hidden">
                      <div
                        className="h-full rounded-full bg-emerald-500 transition-all"
                        style={{ width: `${Math.min(100, (selectedRoom.paidAmount / selectedRoom.totalAmount) * 100)}%` }}
                      />
                    </div>
                  </div>
                </div>

                {/* Quick charge buttons */}
                <div>
                  <p className="text-xs font-semibold text-slate-500 dark:text-slate-400 uppercase tracking-wide mb-2">Назначение платежа</p>
                  <div className="grid grid-cols-5 gap-2">
                    {QUICK_CHARGES.map(qc => (
                      <button
                        key={qc.purpose}
                        onClick={() => setPurpose(qc.purpose)}
                        className={cn(
                          'flex flex-col items-center gap-1.5 p-3 rounded-xl border-2 text-xs font-medium transition-all',
                          purpose === qc.purpose
                            ? 'border-brand-500 bg-brand-50 dark:bg-brand-900/20 text-brand-700 dark:text-brand-300'
                            : 'border-slate-200 dark:border-slate-600 bg-white dark:bg-slate-800 text-slate-600 dark:text-slate-400 hover:border-brand-300',
                        )}
                      >
                        <qc.Icon size={18} />
                        {qc.label}
                      </button>
                    ))}
                  </div>
                </div>

                {/* Amount */}
                <div>
                  <label className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1.5">Сумма (₽)</label>
                  <input
                    type="number"
                    min={0}
                    className="input text-2xl font-bold h-14 w-full"
                    value={amount || ''}
                    onChange={e => setAmount(Math.max(0, parseInt(e.target.value) || 0))}
                    placeholder="0"
                  />
                </div>

                {/* Payment method */}
                <div>
                  <p className="text-sm font-medium text-slate-700 dark:text-slate-300 mb-2">Способ оплаты</p>
                  <div className="grid grid-cols-3 gap-2">
                    {([
                      { key: 'cash',     label: 'Наличные',     Icon: Banknote,    cls: 'emerald' },
                      { key: 'terminal', label: 'Терминал',     Icon: CreditCard,  cls: 'blue' },
                      { key: 'atol',     label: 'АТОЛ',         Icon: Printer,     cls: 'violet' },
                    ] as const).map(m => (
                      <button
                        key={m.key}
                        onClick={() => setMethod(m.key)}
                        className={cn(
                          'flex flex-col items-center gap-2 py-3 rounded-xl border-2 text-sm font-medium transition-colors',
                          method === m.key
                            ? m.cls === 'emerald' ? 'bg-emerald-600 border-emerald-600 text-white'
                            : m.cls === 'blue'    ? 'bg-blue-600 border-blue-600 text-white'
                            :                       'bg-violet-600 border-violet-600 text-white'
                            : 'border-slate-200 dark:border-slate-600 bg-white dark:bg-slate-800 text-slate-700 dark:text-slate-300 hover:border-slate-300',
                        )}
                      >
                        <m.Icon size={18} />
                        {m.label}
                        {m.key === 'atol' && <span className="text-[10px] opacity-70">интеграция</span>}
                      </button>
                    ))}
                  </div>
                  {method === 'atol' && (
                    <div className="mt-2 flex items-center gap-2 p-2.5 rounded-lg bg-violet-50 dark:bg-violet-900/20 border border-violet-200 dark:border-violet-700">
                      <AlertCircle size={13} className="text-violet-600 shrink-0" />
                      <p className="text-xs text-violet-700 dark:text-violet-300">АТОЛ: интеграция будет настроена в разделе Настройки → Оборудование</p>
                    </div>
                  )}
                </div>

                {/* Notes */}
                <div>
                  <label className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1.5">Примечание</label>
                  <input
                    type="text"
                    className="input"
                    placeholder="Необязательно"
                    value={notes}
                    onChange={e => setNotes(e.target.value)}
                  />
                </div>

                {/* Pay button */}
                <button
                  onClick={handlePay}
                  disabled={amount <= 0}
                  className="btn-primary w-full justify-center py-4 text-base disabled:opacity-40 disabled:cursor-not-allowed"
                >
                  <ChevronRight size={18} />
                  Провести оплату {amount > 0 ? formatCurrency(amount) : ''}
                </button>
              </>
            ) : (
              <div className="flex-1 flex items-center justify-center text-slate-400">
                <p className="text-sm">Выберите гостя из списка слева</p>
              </div>
            )}
          </div>

          {/* ── Right: receipts ── */}
          <div className="w-72 flex flex-col border-l border-slate-200 dark:border-slate-700 bg-white dark:bg-slate-800 shrink-0 overflow-hidden">
            <div className="px-4 py-2.5 border-b border-slate-200 dark:border-slate-700 flex items-center gap-2">
              <Receipt size={14} className="text-slate-400" />
              <p className="text-xs font-semibold text-slate-500 dark:text-slate-400 uppercase tracking-wide">Чеки за смену</p>
              <span className="ml-auto text-xs bg-slate-100 dark:bg-slate-700 text-slate-600 dark:text-slate-400 px-2 py-0.5 rounded-full">
                {shiftReceipts.length}
              </span>
            </div>
            <div className="flex-1 overflow-y-auto p-2 space-y-1.5">
              {shiftReceipts.map(r => (
                <div key={r.id} className="rounded-xl border border-slate-100 dark:border-slate-700 bg-slate-50 dark:bg-slate-700/50 p-3">
                  <div className="flex items-center justify-between mb-1">
                    <span className="text-xs font-semibold text-slate-700 dark:text-slate-300">№{r.roomNumber}</span>
                    <div className="flex items-center gap-1">
                      {r.method === 'cash'
                        ? <Banknote size={11} className="text-emerald-600" />
                        : r.method === 'terminal'
                        ? <CreditCard size={11} className="text-blue-600" />
                        : <Printer size={11} className="text-violet-600" />
                      }
                      <span className="text-[10px] text-slate-400">{format(r.createdAt, 'HH:mm')}</span>
                    </div>
                  </div>
                  <p className="text-xs text-slate-500 dark:text-slate-400 truncate mb-1">{r.guestName}</p>
                  <div className="flex items-center justify-between">
                    <span className="text-[10px] text-slate-400">{r.purposeLabel}</span>
                    <span className="text-sm font-bold text-slate-900 dark:text-slate-100">{formatCurrency(r.amount)}</span>
                  </div>
                </div>
              ))}
            </div>
          </div>
        </div>
      )}

      {/* ── Receipt success overlay ── */}
      {lastReceipt && (
        <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/50">
          <div className="bg-white dark:bg-slate-800 rounded-2xl shadow-2xl p-8 w-80 text-center space-y-4">
            <CheckCircle2 size={56} className="text-emerald-500 mx-auto" />
            <div>
              <p className="text-xl font-bold text-slate-900 dark:text-slate-100">Оплата принята</p>
              <p className="text-3xl font-bold text-emerald-600 mt-1">{formatCurrency(lastReceipt.amount)}</p>
              <p className="text-sm text-slate-500 mt-1">
                {lastReceipt.method === 'cash' ? 'Наличными' : lastReceipt.method === 'terminal' ? 'Терминал' : 'АТОЛ'} · {format(lastReceipt.createdAt, 'HH:mm')}
              </p>
            </div>
            <div className="text-left bg-slate-50 dark:bg-slate-700/50 rounded-xl p-3 space-y-1">
              <div className="flex justify-between text-sm">
                <span className="text-slate-500">Гость</span>
                <span className="font-medium text-slate-800 dark:text-slate-200">{lastReceipt.guestName}</span>
              </div>
              <div className="flex justify-between text-sm">
                <span className="text-slate-500">Номер</span>
                <span className="font-medium text-slate-800 dark:text-slate-200">№{lastReceipt.roomNumber}</span>
              </div>
              <div className="flex justify-between text-sm">
                <span className="text-slate-500">Назначение</span>
                <span className="font-medium text-slate-800 dark:text-slate-200">{lastReceipt.purposeLabel}</span>
              </div>
            </div>
            <button onClick={() => setLastReceipt(null)} className="btn-primary w-full justify-center">
              Готово
            </button>
          </div>
        </div>
      )}
    </div>
  )
}