import { useEffect, useState } from 'react'

import { ActionMenu } from '#/components/action-menu'
import { ReservationDateTimeField } from '#/components/reservation-datetime-field'
import { formatDateOnly, formatDateTimeLocal } from '#/lib/datetime'
import { generateTimeOptions, getNextAvailableSlot, getOpeningRangesForWeekday } from '#/lib/opening-hours'
import {
  RESERVATION_STATUS_LABELS,
  type ReservationStatus,
  type getReservations,
  type getTables,
} from '#/lib/reservations'
import { type getReservationSettings } from '#/lib/settings'

type ReservationRow = Awaited<ReturnType<typeof getReservations>>[number]
type TableRow = Awaited<ReturnType<typeof getTables>>[number]
type SettingsRow = Awaited<ReturnType<typeof getReservationSettings>>

export type ReservationPayload = {
  tableId: number
  customerName: string
  customerEmail: string
  customerPhone: string
  message: string
  partySize: number
  reservationTime: string
}

type FormState = {
  tableId: number | string
  customerName: string
  customerEmail: string
  customerPhone: string
  message: string
  partySize: number
  reservationTime: string
}

type Props = {
  // `null` reservation with `open: true` is "create" mode.
  open: boolean
  reservation: ReservationRow | null
  tables: TableRow[]
  settings: SettingsRow
  reservations: ReservationRow[]
  onClose: () => void
  onCreate: (payload: ReservationPayload) => Promise<void>
  onUpdate: (id: number, payload: ReservationPayload) => Promise<void>
  onStatusChange: (status: ReservationStatus) => void
  isUpdatingStatus?: boolean
  onDelete: () => void
  statusError?: string | null
}

const STATUS_OPTIONS = Object.keys(RESERVATION_STATUS_LABELS) as ReservationStatus[]

const dateFormatter = new Intl.DateTimeFormat('de-DE', {
  dateStyle: 'full',
})

const timeFormatter = new Intl.DateTimeFormat('de-DE', {
  timeStyle: 'short',
})

const EMAIL_PATTERN = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
// Also used as the phone input's `pattern` attribute below, so the two stay in sync.
const PHONE_PATTERN_SOURCE = String.raw`[+]?[0-9()\-.\s]{6,30}`
const PHONE_PATTERN = new RegExp(`^${PHONE_PATTERN_SOURCE}$`)

function emptyForm(defaultTableId: number | string, settings: SettingsRow): FormState {
  const slot = getNextAvailableSlot(
    new Date(Date.now() + settings.minLeadTimeMinutes * 60_000),
    settings.reservationIntervalMinutes,
    settings.reservationDurationMinutes,
  )

  return {
    tableId: defaultTableId,
    customerName: '',
    customerEmail: '',
    customerPhone: '',
    message: '',
    partySize: 2,
    reservationTime: slot ? `${slot.date}T${slot.time}` : '',
  }
}

function formFromReservation(reservation: ReservationRow): FormState {
  return {
    tableId: reservation.tableId,
    customerName: reservation.customerName,
    customerEmail: reservation.customerEmail,
    customerPhone: reservation.customerPhone ?? '',
    message: reservation.message ?? '',
    partySize: reservation.partySize,
    reservationTime: formatDateTimeLocal(new Date(reservation.reservationTime)),
  }
}

// Rendered with a `key` (see staff.index.tsx) so a fresh instance mounts every time
// the dialog opens — that's what lets this component safely derive its initial
// state from props once, instead of syncing it via effects.
export function ReservationDialog({
  open,
  reservation,
  tables,
  settings,
  reservations,
  onClose,
  onCreate,
  onUpdate,
  onStatusChange,
  isUpdatingStatus,
  onDelete,
  statusError,
}: Props) {
  const [isEditing, setIsEditing] = useState(reservation === null)
  const [form, setForm] = useState<FormState>(() =>
    reservation ? formFromReservation(reservation) : emptyForm(tables[0]?.id ?? '', settings),
  )
  const [error, setError] = useState<string | null>(null)
  const [isSubmitting, setIsSubmitting] = useState(false)

  useEffect(() => {
    function handleKeyDown(event: KeyboardEvent) {
      if (event.key === 'Escape') onClose()
    }

    document.addEventListener('keydown', handleKeyDown)
    return () => document.removeEventListener('keydown', handleKeyDown)
  }, [onClose])

  if (!open) return null

  // Other reservations already sitting on the currently selected table + date, so the
  // time picker can block them instead of letting staff pick a slot the server will
  // just reject as double-booked. A reservation occupies its whole configured
  // duration, not just its exact start time, so every interval-grid slot that falls
  // inside that window counts as taken too. `minLeadTimeMinutes` is reused here as a
  // table turnover buffer, extending the taken window on both sides so back-to-back
  // bookings on the same table always leave that much of a gap.
  const [selectedDate] = form.reservationTime.split('T')
  const otherReservationsOnSelection = reservations.filter(
    (r) =>
      r.id !== reservation?.id &&
      String(r.tableId) === String(form.tableId) &&
      formatDateOnly(new Date(r.reservationTime)) === selectedDate,
  )
  const turnoverBufferMs = settings.minLeadTimeMinutes * 60_000
  const bookedTimesForForm = selectedDate
    ? generateTimeOptions(
        getOpeningRangesForWeekday(new Date(`${selectedDate}T00:00`).getDay()),
        settings.reservationIntervalMinutes,
        settings.reservationDurationMinutes,
      ).filter((option) => {
        const slotStart = new Date(`${selectedDate}T${option}`).getTime()
        return otherReservationsOnSelection.some((r) => {
          const otherStart = new Date(r.reservationTime).getTime() - turnoverBufferMs
          const otherEnd = otherStart + r.durationMinutes * 60_000 + 2 * turnoverBufferMs
          return slotStart >= otherStart && slotStart < otherEnd
        })
      })
    : []

  // Mirrors the form fields' own `required`/`type`/`pattern`/`min`/`max` constraints,
  // so the submit button is disabled until they'd all actually pass — instead of only
  // catching an invalid table/time on submit and leaving everything else to the
  // browser's native validation popup.
  const isFormValid =
    Boolean(form.tableId) &&
    form.customerName.trim().length > 0 &&
    EMAIL_PATTERN.test(form.customerEmail) &&
    PHONE_PATTERN.test(form.customerPhone) &&
    form.partySize >= 1 &&
    form.partySize <= 20 &&
    Boolean(form.reservationTime.split('T')[1])

  function startEditing() {
    if (reservation) setForm(formFromReservation(reservation))
    setError(null)
    setIsEditing(true)
  }

  function cancelEditing() {
    if (!reservation) {
      onClose()
      return
    }
    setForm(formFromReservation(reservation))
    setError(null)
    setIsEditing(false)
  }

  async function handleSubmit(event: React.FormEvent) {
    event.preventDefault()
    setError(null)

    if (!form.tableId) {
      setError('Bitte wählen Sie einen Tisch aus')
      return
    }

    if (!form.reservationTime.split('T')[1]) {
      setError('Bitte wählen Sie eine gültige Uhrzeit aus')
      return
    }

    setIsSubmitting(true)
    try {
      const payload: ReservationPayload = {
        tableId: Number(form.tableId),
        customerName: form.customerName,
        customerEmail: form.customerEmail,
        customerPhone: form.customerPhone,
        message: form.message,
        partySize: Number(form.partySize),
        reservationTime: new Date(form.reservationTime).toISOString(),
      }

      if (reservation) {
        await onUpdate(reservation.id, payload)
      } else {
        await onCreate(payload)
      }
      onClose()
    } catch (err) {
      setError(err instanceof Error ? err.message : 'Etwas ist schiefgelaufen')
    } finally {
      setIsSubmitting(false)
    }
  }

  const title = reservation
    ? isEditing
      ? `Reservierung von ${reservation.customerName} bearbeiten`
      : `Reservierung von ${reservation.customerName}`
    : 'Neue Reservierung'

  return (
    <div className="confirm-dialog-backdrop" onClick={onClose}>
      <div
        className={`confirm-dialog reservation-detail-dialog${isEditing ? ' reservation-dialog-editing' : ''}`}
        role="dialog"
        aria-modal="true"
        aria-labelledby="reservation-dialog-title"
        onClick={(event) => event.stopPropagation()}
      >
        <div className="confirm-dialog-header">
          <h2 id="reservation-dialog-title" className="confirm-dialog-title">
            {title}
          </h2>
          {reservation && !isEditing && (
            <div className="confirm-dialog-header-actions">
              <ActionMenu label={`Weitere Aktionen für Reservierung von ${reservation.customerName}`}>
                <button type="button" className="btn btn-danger" onClick={onDelete}>
                  Löschen
                </button>
              </ActionMenu>
            </div>
          )}
        </div>

        {isEditing ? (
          <form className="reservation-form reservation-form-dialog" onSubmit={handleSubmit}>
            <label>
              Tisch
              <select
                value={form.tableId}
                onChange={(e) => setForm((f) => ({ ...f, tableId: e.target.value }))}
                required
              >
                <option value="" disabled>
                  Tisch auswählen
                </option>
                {tables.map((table) => (
                  <option key={table.id} value={table.id}>
                    {table.name} ({table.seats} Plätze)
                  </option>
                ))}
              </select>
            </label>

            <div className="form-row">
              <label>
                Name
                <input
                  type="text"
                  value={form.customerName}
                  onChange={(e) => setForm((f) => ({ ...f, customerName: e.target.value }))}
                  required
                />
              </label>

              <label>
                E-Mail
                <input
                  type="email"
                  value={form.customerEmail}
                  onChange={(e) => setForm((f) => ({ ...f, customerEmail: e.target.value }))}
                  required
                />
              </label>
            </div>

            <div className="form-row">
              <label>
                Telefon
                <input
                  type="tel"
                  inputMode="tel"
                  pattern={PHONE_PATTERN_SOURCE}
                  title="Nur Ziffern, Leerzeichen und + ( ) - ."
                  value={form.customerPhone}
                  onChange={(e) => setForm((f) => ({ ...f, customerPhone: e.target.value }))}
                  required
                />
              </label>

              <label>
                Anzahl Personen
                <input
                  type="number"
                  inputMode="numeric"
                  min={1}
                  max={20}
                  value={form.partySize}
                  onChange={(e) => setForm((f) => ({ ...f, partySize: Number(e.target.value) }))}
                  required
                />
              </label>
            </div>

            <label>
              Datum &amp; Uhrzeit
              <ReservationDateTimeField
                value={form.reservationTime}
                onChange={(reservationTime) => setForm((f) => ({ ...f, reservationTime }))}
                bookedTimes={bookedTimesForForm}
                intervalMinutes={settings.reservationIntervalMinutes}
                minLeadTimeMinutes={settings.minLeadTimeMinutes}
                durationMinutes={settings.reservationDurationMinutes}
                maxLeadTimeDays={settings.maxLeadTimeDays}
              />
            </label>

            <label>
              Nachricht (optional)
              <textarea
                rows={2}
                maxLength={500}
                value={form.message}
                onChange={(e) => setForm((f) => ({ ...f, message: e.target.value }))}
              />
            </label>

            {error && <p className="message message-error">{error}</p>}

            <div className="confirm-dialog-actions">
              <button type="button" className="btn btn-secondary" onClick={cancelEditing}>
                Abbrechen
              </button>
              <button type="submit" className="btn btn-primary" disabled={isSubmitting || !isFormValid}>
                {isSubmitting ? 'Wird gespeichert …' : reservation ? 'Speichern' : 'Anlegen'}
              </button>
            </div>
          </form>
        ) : (
          reservation && (
            <>
              <div className="status-options">
                {STATUS_OPTIONS.map((status) => (
                  <button
                    key={status}
                    type="button"
                    className={`status-badge status-option status-${status}${
                      reservation.status === status ? ' is-active' : ''
                    }`}
                    disabled={isUpdatingStatus}
                    onClick={() => onStatusChange(status)}
                  >
                    {RESERVATION_STATUS_LABELS[status]}
                  </button>
                ))}
              </div>

              <dl className="detail-list">
                {reservation.tableNumber !== null && (
                  <div>
                    <dt>Tischnummer</dt>
                    <dd>{reservation.tableNumber}</dd>
                  </div>
                )}
                <div>
                  <dt>Tisch</dt>
                  <dd>{reservation.tableName}</dd>
                </div>
                <div>
                  <dt>Datum</dt>
                  <dd>{dateFormatter.format(new Date(reservation.reservationTime))}</dd>
                </div>
                <div>
                  <dt>Start</dt>
                  <dd>{timeFormatter.format(new Date(reservation.reservationTime))}</dd>
                </div>
                <div>
                  <dt>Ende</dt>
                  <dd>
                    {timeFormatter.format(
                      new Date(new Date(reservation.reservationTime).getTime() + reservation.durationMinutes * 60_000),
                    )}
                  </dd>
                </div>
                <div>
                  <dt>Personen</dt>
                  <dd>{reservation.partySize}</dd>
                </div>
                <div>
                  <dt>E-Mail</dt>
                  <dd>
                    <a href={`mailto:${reservation.customerEmail}`}>{reservation.customerEmail}</a>
                  </dd>
                </div>
                {reservation.customerPhone && (
                  <div>
                    <dt>Telefon</dt>
                    <dd>
                      <a href={`tel:${reservation.customerPhone}`}>{reservation.customerPhone}</a>
                    </dd>
                  </div>
                )}
              </dl>

              {reservation.message && (
                <div className="detail-message">
                  <span className="detail-message-label">Nachricht</span>
                  <p>{reservation.message}</p>
                </div>
              )}

              {statusError && <p className="message message-error">{statusError}</p>}

              <div className="confirm-dialog-actions confirm-dialog-actions-split">
                <button type="button" className="btn btn-ghost" onClick={startEditing}>
                  Bearbeiten
                </button>
                <button type="button" className="btn btn-secondary" onClick={onClose}>
                  Schließen
                </button>
              </div>
            </>
          )
        )}
      </div>
    </div>
  )
}