import { useEffect, useState } from 'react'
import { useNavigate, Link } from 'react-router-dom'
import { useAuthStore } from '@/store/auth'
import { useCartStore } from '@/store/cart'
import { api } from '@/lib/api'
import { Button } from '@/components/ui/button'
import { Card, CardContent } from '@/components/ui/card'
import { Input } from '@/components/ui/input'
import { Label } from '@/components/ui/label'

function formatPrice(price: number): string {
  return new Intl.NumberFormat('ja-JP', { style: 'currency', currency: 'JPY' }).format(price)
}

interface ShippingAddress {
  postal_code: string
  prefecture: string
  city: string
  address_line1: string
  address_line2: string
  recipient_name: string
  phone: string
}

const EMPTY_ADDRESS: ShippingAddress = {
  postal_code: '',
  prefecture: '',
  city: '',
  address_line1: '',
  address_line2: '',
  recipient_name: '',
  phone: '',
}

export function CheckoutPage() {
  const { user } = useAuthStore()
  const { items, total, clearCart } = useCartStore()
  const navigate = useNavigate()
  const [address, setAddress] = useState<ShippingAddress>(EMPTY_ADDRESS)
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState<string | null>(null)

  useEffect(() => {
    if (!user) {
      navigate('/login')
    }
  }, [user, navigate])

  if (!user) return null

  if (items.length === 0) {
    return (
      <div className="container mx-auto px-4 py-24 text-center">
        <h1 className="text-2xl font-bold mb-4">カートが空です</h1>
        <Link to="/products">
          <Button>商品一覧を見る</Button>
        </Link>
      </div>
    )
  }

  function handleChange(field: keyof ShippingAddress, value: string) {
    setAddress(prev => ({ ...prev, [field]: value }))
  }

  async function handlePlaceOrder() {
    setError(null)
    const required: (keyof ShippingAddress)[] = ['postal_code', 'prefecture', 'city', 'address_line1', 'recipient_name', 'phone']
    for (const field of required) {
      if (!address[field].trim()) {
        setError('必須項目を入力してください。 (Please fill in all required fields.)')
        return
      }
    }

    setLoading(true)
    try {
      const order = await api.post<{ id: string }>('/orders', {
        items: items.map(i => ({ product_id: i.product_id, quantity: i.quantity })),
        shipping_address: address,
      })
      clearCart()
      navigate(`/account/orders/${order.id}`)
    } catch (err: unknown) {
      const message = err instanceof Error ? err.message : '注文に失敗しました。'
      setError(message)
    } finally {
      setLoading(false)
    }
  }

  return (
    <div className="container mx-auto px-4 py-10 max-w-4xl">
      <h1 className="text-2xl font-bold mb-8">チェックアウト (Checkout)</h1>

      <div className="grid grid-cols-1 md:grid-cols-2 gap-8">
        {/* Shipping Address Form */}
        <div>
          <h2 className="text-lg font-semibold mb-4">配送先情報</h2>
          <div className="space-y-4">
            <div>
              <Label htmlFor="recipient_name">お名前 *</Label>
              <Input
                id="recipient_name"
                value={address.recipient_name}
                onChange={e => handleChange('recipient_name', e.target.value)}
                placeholder="山田 太郎"
                className="mt-1"
              />
            </div>

            <div>
              <Label htmlFor="postal_code">郵便番号 *</Label>
              <Input
                id="postal_code"
                value={address.postal_code}
                onChange={e => handleChange('postal_code', e.target.value)}
                placeholder="123-4567"
                className="mt-1"
              />
            </div>

            <div>
              <Label htmlFor="prefecture">都道府県 *</Label>
              <Input
                id="prefecture"
                value={address.prefecture}
                onChange={e => handleChange('prefecture', e.target.value)}
                placeholder="東京都"
                className="mt-1"
              />
            </div>

            <div>
              <Label htmlFor="city">市区町村 *</Label>
              <Input
                id="city"
                value={address.city}
                onChange={e => handleChange('city', e.target.value)}
                placeholder="渋谷区"
                className="mt-1"
              />
            </div>

            <div>
              <Label htmlFor="address_line1">番地 *</Label>
              <Input
                id="address_line1"
                value={address.address_line1}
                onChange={e => handleChange('address_line1', e.target.value)}
                placeholder="1-2-3"
                className="mt-1"
              />
            </div>

            <div>
              <Label htmlFor="address_line2">建物名・部屋番号 (任意)</Label>
              <Input
                id="address_line2"
                value={address.address_line2}
                onChange={e => handleChange('address_line2', e.target.value)}
                placeholder="マンション101号室"
                className="mt-1"
              />
            </div>

            <div>
              <Label htmlFor="phone">電話番号 *</Label>
              <Input
                id="phone"
                value={address.phone}
                onChange={e => handleChange('phone', e.target.value)}
                placeholder="090-1234-5678"
                className="mt-1"
              />
            </div>
          </div>
        </div>

        {/* Order Summary */}
        <div>
          <h2 className="text-lg font-semibold mb-4">注文内容確認</h2>
          <Card>
            <CardContent className="p-4 space-y-3">
              {items.map(item => (
                <div key={item.product_id} className="flex justify-between items-start gap-2">
                  <div className="flex-1 min-w-0">
                    <p className="text-sm font-medium truncate">{item.name}</p>
                    <p className="text-xs text-muted-foreground">
                      {formatPrice(item.price)} x {item.quantity}
                    </p>
                  </div>
                  <p className="text-sm font-semibold flex-shrink-0">
                    {formatPrice(item.price * item.quantity)}
                  </p>
                </div>
              ))}
              <div className="border-t pt-3 flex justify-between font-bold text-lg">
                <span>合計</span>
                <span className="text-primary">{formatPrice(total)}</span>
              </div>
            </CardContent>
          </Card>

          {error && (
            <div className="mt-4 p-3 bg-red-50 border border-red-200 rounded-md text-sm text-red-700">
              {error}
            </div>
          )}

          <Button
            size="lg"
            className="w-full mt-4"
            onClick={handlePlaceOrder}
            disabled={loading}
          >
            {loading ? '注文処理中...' : '注文を確定する'}
          </Button>
          <p className="text-xs text-center text-muted-foreground mt-2">
            注文確定後のキャンセルは注文詳細ページから可能です。
          </p>
        </div>
      </div>
    </div>
  )
}