import { useQueryClient } from '@tanstack/react-query'
import { useMemo, useState } from 'react'

import { updateOrder } from '@/api/orders'
import { Modal } from '@/components/Modal'
import '@/features/orders/OrderDetailModal.css'
import type { Order, OrderUpdate } from '@/features/orders/types'
import { formatKopecks, toKopecks } from '@/features/receipts/money'
import { RECEIPT_STATUS } from '@/features/receipts/types'

interface OrderDetailModalProps {
  order: Order
  /** Кассир/админ и по заказу ещё нет чека — карточку можно править. */
  canEdit: boolean
  onClose: () => void
}

interface GoodDraft {
  key: string
  id: string | null
  sku: string
  name: string
  price: string
  quantity: string
  discount: string
}

interface Draft {
  recipient_name: string
  recipient_phone: string
  recipient_email: string
  waybill_number: string
  notes: string
  total: string
  goods: GoodDraft[]
}

type TextField = Exclude<keyof Draft, 'goods' | 'total'>

/** Количество в тысячных (конвенция Checkbox: 1 шт = 1000). */
function toThousandths(value: string): number | null {
  const normalized = value.trim().replace(',', '.')
  if (!/^\d+(\.\d{1,3})?$/.test(normalized)) return null
  return Math.round(Number(normalized) * 1000)
}

/** Сумма строки после скидки в копейках; null — в строке некорректные числа. */
function lineAmount(good: GoodDraft): number | null {
  const price = toKopecks(good.price)
  const quantity = toThousandths(good.quantity)
  const discount = toKopecks(good.discount)
  if (price === null || quantity === null || discount === null) return null
  return Math.round((price * quantity) / 1000) - discount
}

function goodsSum(goods: GoodDraft[]): number | null {
  let sum = 0
  for (const good of goods) {
    const amount = lineAmount(good)
    if (amount === null) return null
    sum += amount
  }
  return sum
}

let newGoodSeq = 0

function toDraft(order: Order): Draft {
  return {
    recipient_name: order.recipient_name ?? '',
    recipient_phone: order.recipient_phone ?? '',
    recipient_email: order.recipient_email ?? '',
    waybill_number: order.waybill_number ?? '',
    notes: order.notes ?? '',
    total: order.total_amount,
    goods: order.goods.map((good) => {
      // Скидку строки выводим из amount, как бэкенд при сборке чека, — не из discount_amount/percent.
      const gross = Math.round(((toKopecks(good.price) ?? 0) * (toThousandths(good.quantity) ?? 0)) / 1000)
      const discount = Math.max(gross - (toKopecks(good.amount) ?? gross), 0)
      return {
        key: good.id,
        id: good.id,
        sku: good.sku,
        name: good.name,
        price: good.price,
        quantity: good.quantity,
        discount: formatKopecks(discount),
      }
    }),
  }
}

function orderDiscountOf(draft: Draft): number {
  return (goodsSum(draft.goods) ?? 0) - (toKopecks(draft.total) ?? 0)
}

/** Проверяет черновик и собирает тело PATCH; строка — текст ошибки для кассира. */
function toPayload(draft: Draft): OrderUpdate | string {
  if (draft.goods.length === 0) return 'Добавьте хотя бы один товар'
  const goods = []
  for (const good of draft.goods) {
    const label = good.name.trim() || 'без названия'
    if (!good.name.trim()) return 'У товара не указано наименование'
    const price = toKopecks(good.price)
    const quantity = toThousandths(good.quantity)
    const discount = toKopecks(good.discount)
    if (price === null) return `Товар «${label}»: некорректная цена`
    if (quantity === null || quantity <= 0) return `Товар «${label}»: некорректное количество`
    if (discount === null) return `Товар «${label}»: некорректная скидка`
    if ((lineAmount(good) ?? 0) < 0) return `Товар «${label}»: скидка больше суммы строки`
    goods.push({
      id: good.id,
      sku: good.sku.trim(),
      name: good.name.trim(),
      price: formatKopecks(price),
      quantity: (quantity / 1000).toFixed(3),
      discount_amount: formatKopecks(discount),
    })
  }
  const total = toKopecks(draft.total)
  if (total === null) return 'Некорректная сумма заказа'
  const sum = goodsSum(draft.goods) ?? 0
  if (total > sum) return `Сумма заказа больше суммы товаров (${formatKopecks(sum)} ₴)`

  return {
    recipient_name: draft.recipient_name,
    recipient_phone: draft.recipient_phone,
    recipient_email: draft.recipient_email,
    waybill_number: draft.waybill_number,
    notes: draft.notes,
    total_amount: formatKopecks(total),
    goods,
  }
}

const TEXT_FIELDS: { field: TextField; label: string; type?: string }[] = [
  { field: 'recipient_name', label: 'Клиент' },
  { field: 'recipient_phone', label: 'Телефон', type: 'tel' },
  { field: 'recipient_email', label: 'Email', type: 'email' },
  { field: 'waybill_number', label: 'Номер ТТН' },
]

export function OrderDetailModal({ order, canEdit, onClose }: OrderDetailModalProps) {
  const queryClient = useQueryClient()
  const [draft, setDraft] = useState<Draft>(() => toDraft(order))
  const [saved, setSaved] = useState<Draft>(draft)
  // Скидка на весь заказ (итог товаров − сумма заказа): держим её при правке товаров.
  const [orderDiscount, setOrderDiscount] = useState(() => orderDiscountOf(draft))
  const [saving, setSaving] = useState(false)
  const [message, setMessage] = useState<{ tone: 'ok' | 'error'; text: string } | null>(null)

  const dirty = useMemo(() => JSON.stringify(draft) !== JSON.stringify(saved), [draft, saved])
  const editable = canEdit && !order.has_receipt

  function requestClose() {
    if (dirty && !window.confirm('Есть несохранённые изменения. Закрыть без сохранения?')) return
    onClose()
  }

  function setField(field: TextField, value: string) {
    setDraft((prev) => ({ ...prev, [field]: value }))
    setMessage(null)
  }

  /** Меняет товары и пересчитывает итог с сохранением скидки на заказ. */
  function setGoods(update: (goods: GoodDraft[]) => GoodDraft[]) {
    const goods = update(draft.goods)
    const sum = goodsSum(goods)
    setDraft({ ...draft, goods, total: sum === null ? draft.total : formatKopecks(Math.max(sum - orderDiscount, 0)) })
    setMessage(null)
  }

  function setTotal(value: string) {
    setDraft({ ...draft, total: value })
    const sum = goodsSum(draft.goods)
    const total = toKopecks(value)
    if (sum !== null && total !== null) setOrderDiscount(sum - total)
    setMessage(null)
  }

  function setGood(key: string, field: keyof GoodDraft, value: string) {
    setGoods((goods) => goods.map((good) => (good.key === key ? { ...good, [field]: value } : good)))
  }

  function addGood() {
    newGoodSeq += 1
    setGoods((goods) => [
      ...goods,
      { key: `new-${newGoodSeq}`, id: null, sku: '', name: '', price: '0.00', quantity: '1', discount: '0.00' },
    ])
  }

  async function handleSave() {
    const payload = toPayload(draft)
    if (typeof payload === 'string') {
      setMessage({ tone: 'error', text: payload })
      return
    }
    setSaving(true)
    try {
      const updated = await updateOrder(order.id, payload)
      const next = toDraft(updated)
      setDraft(next)
      setSaved(next)
      setOrderDiscount(orderDiscountOf(next))
      setMessage({ tone: 'ok', text: 'Изменения сохранены' })
      await queryClient.invalidateQueries({ queryKey: ['orders'] })
    } catch (err) {
      setMessage({ tone: 'error', text: err instanceof Error ? err.message : 'Не удалось сохранить заказ' })
    } finally {
      setSaving(false)
    }
  }

  return (
    <Modal onClose={requestClose} wide={editable}>
      <div className="order-modal">
        <div className="order-modal-header">
          <h3>
            Заказ {order.id}
            {order.edited && <span className="order-modal-edited">изменён вручную</span>}
          </h3>
          <button type="button" className="order-modal-close" onClick={requestClose} aria-label="Закрыть">
            ×
          </button>
        </div>

        <div className="order-modal-meta">
          <div>
            <span className="order-modal-label">Дата</span>
            <span>{order.create_date_time}</span>
          </div>
          <div>
            <span className="order-modal-label">Статус ТТН</span>
            <span>{order.np_status || 'Нет данных'}</span>
          </div>
          <div>
            <span className="order-modal-label">Наложенный платёж</span>
            <span>{order.np_cod_amount ? `${order.np_cod_amount} ₴` : '—'}</span>
          </div>
          <div>
            <span className="order-modal-label">Оплачено</span>
            <span>
              {order.np_payment_status === 'Payed'
                ? 'Да'
                : order.np_payment_status === 'NeedPayment'
                  ? 'Нет'
                  : '—'}
            </span>
          </div>
          {TEXT_FIELDS.map(({ field, label, type }) =>
            editable ? (
              <label key={field}>
                <span className="order-modal-label">{label}</span>
                <input
                  type={type ?? 'text'}
                  className="order-modal-input"
                  value={draft[field]}
                  onChange={(e) => setField(field, e.target.value)}
                />
              </label>
            ) : (
              (field !== 'recipient_email' || draft[field]) && (
                <div key={field}>
                  <span className="order-modal-label">{label}</span>
                  <span>{draft[field] || '—'}</span>
                </div>
              )
            ),
          )}
        </div>

        {editable ? (
          <label className="order-modal-notes">
            <span className="order-modal-label">Заметки</span>
            <textarea
              className="order-modal-input"
              rows={2}
              value={draft.notes}
              onChange={(e) => setField('notes', e.target.value)}
            />
          </label>
        ) : (
          draft.notes && (
            <div className="order-modal-notes">
              <span className="order-modal-label">Заметки</span>
              <p>{draft.notes}</p>
            </div>
          )
        )}

        <table className="order-modal-goods">
          <thead>
            <tr>
              <th>Наименование</th>
              <th>SKU</th>
              <th>Цена</th>
              <th>Кол-во</th>
              <th>Скидка</th>
              <th>Сумма</th>
              {editable && <th aria-label="Удалить" />}
            </tr>
          </thead>
          <tbody>
            {draft.goods.map((good) => {
              const amount = lineAmount(good)
              return (
                <tr key={good.key}>
                  {editable ? (
                    <>
                      <td>
                        <input
                          className="order-modal-input"
                          value={good.name}
                          onChange={(e) => setGood(good.key, 'name', e.target.value)}
                        />
                      </td>
                      <td>
                        <input
                          className="order-modal-input order-modal-input--sku"
                          value={good.sku}
                          onChange={(e) => setGood(good.key, 'sku', e.target.value)}
                        />
                      </td>
                      {(['price', 'quantity', 'discount'] as const).map((field) => (
                        <td key={field}>
                          <input
                            className="order-modal-input order-modal-input--num"
                            inputMode="decimal"
                            value={good[field]}
                            onChange={(e) => setGood(good.key, field, e.target.value)}
                          />
                        </td>
                      ))}
                    </>
                  ) : (
                    <>
                      <td>{good.name}</td>
                      <td>{good.sku}</td>
                      <td>{good.price}</td>
                      <td>{good.quantity}</td>
                      <td>{good.discount !== '0.00' ? good.discount : '—'}</td>
                    </>
                  )}
                  <td className={amount === null || amount < 0 ? 'order-modal-invalid' : undefined}>
                    {amount === null ? '—' : formatKopecks(amount)}
                  </td>
                  {editable && (
                    <td>
                      <button
                        type="button"
                        className="order-modal-remove"
                        aria-label={`Удалить товар ${good.name}`}
                        onClick={() => setGoods((goods) => goods.filter((g) => g.key !== good.key))}
                      >
                        ×
                      </button>
                    </td>
                  )}
                </tr>
              )
            })}
            {draft.goods.length === 0 && (
              <tr>
                <td colSpan={editable ? 7 : 6} className="order-modal-goods-empty">
                  Товары не указаны
                </td>
              </tr>
            )}
          </tbody>
        </table>

        {editable && (
          <button type="button" className="order-modal-add" onClick={addGood}>
            + Добавить товар
          </button>
        )}

        <div className="order-modal-total">
          <span>Итого</span>
          {editable ? (
            <span>
              <input
                className="order-modal-input order-modal-input--num"
                inputMode="decimal"
                value={draft.total}
                title="Сумма заказа после всех скидок"
                onChange={(e) => setTotal(e.target.value)}
              />{' '}
              ₴
            </span>
          ) : (
            <span>{order.total_amount} ₴</span>
          )}
        </div>

        {order.receipt_status && (
          <div className="order-modal-meta">
            <div>
              <span className="order-modal-label">ЕТТН-чек Checkbox</span>
              <span className={`orders-status orders-status--${RECEIPT_STATUS[order.receipt_status].tone}`}>
                {RECEIPT_STATUS[order.receipt_status].label}
              </span>
            </div>
            <div>
              <span className="order-modal-label">Предоплата в чеке</span>
              <span>{order.receipt_prepayment ? `${order.receipt_prepayment} ₴` : '—'}</span>
            </div>
            {order.receipt_error && (
              <div>
                <span className="order-modal-label">Ошибка</span>
                <span>{order.receipt_error}</span>
              </div>
            )}
          </div>
        )}

        {message && <div className={`order-modal-message order-modal-message--${message.tone}`}>{message.text}</div>}

        <div className="order-modal-actions">
          {editable && (
            <button
              type="button"
              className="order-modal-save-btn"
              disabled={!dirty || saving}
              onClick={() => void handleSave()}
            >
              {saving ? 'Сохранение…' : 'Сохранить'}
            </button>
          )}
          <button type="button" className="order-modal-close-btn" onClick={requestClose}>
            Закрыть
          </button>
        </div>
      </div>
    </Modal>
  )
}