/**
 * Reservations. Filing a request only needs a session; reading the list is an
 * admin action, so `useReservations` is only ever mounted on /admin.
 *
 * Nothing here ever asks for "all the reservations": the status filter, the text
 * search and the paging are query parameters the database applies. The table
 * only grows, and an admin looking at three pending requests must not pay for
 * the archive behind them.
 */
import { computed, toValue, type MaybeRefOrGetter } from 'vue'
import { keepPreviousData, useMutation, useQuery, useQueryClient } from '@tanstack/vue-query'
import { HttpStatus } from 'http-status-ts'

import type { NewReservation, Reservation, ReservationEdit, ReservationStatus } from '@/utils/types'
import { getClient } from './client'

export const RESERVATIONS_KEY = ['reservations']
export const MY_RESERVATIONS_KEY = ['reservations', 'mine']
export const CALENDAR_KEY = ['reservations', 'calendar']

/** A window of time, as the two calendar-shaped endpoints take it */
export type Window = { from?: Date; to?: Date }

export type ReservationFilters = Window & {
  /** Empty or absent means any status */
  status?: ReservationStatus[]
  /** Free text, matched by the database across the whole reservation */
  q?: string
  limit?: number
  offset?: number
}

/** The filters in the shape the query string takes: absent means "no filter" */
function toParams(filters: ReservationFilters) {
  return {
    status: filters.status?.length ? filters.status.join(',') : undefined,
    q: filters.q?.trim() || undefined,
    from: filters.from?.toISOString(),
    to: filters.to?.toISOString(),
    limit: filters.limit,
    offset: filters.offset,
  }
}

/**
 * One page of the reservations matching `filters`, with the size of the whole
 * match so the caller can page through it.
 */
export function useReservations(
  filters: MaybeRefOrGetter<ReservationFilters> = () => ({}),
  /** Left out, the query runs; the archive dialog only wants it while open */
  options: { enabled?: MaybeRefOrGetter<boolean> } = {},
) {
  const params = computed(() => toParams(toValue(filters)))
  return useQuery({
    queryKey: computed(() => [...RESERVATIONS_KEY, 'search', params.value]),
    enabled: computed(() => toValue(options.enabled) ?? true),
    staleTime: 30 * 1000,
    // Paging or typing in the search must not blank the list under the cursor
    placeholderData: keepPreviousData,
    queryFn: async () => {
      const { data, response } = await getClient().GET('/api/reservations', {
        params: { query: params.value },
      })
      if (response.status !== HttpStatus.OK) {
        throw new Error(`Unexpected status code received: ${response.status}`)
      }
      return data ?? { items: [], total: 0 }
    },
  })
}

/**
 * The backend re-checks the state machine and answers 409 on a transition it
 * does not allow, so the buttons only have to offer the plausible ones.
 */
export function useSetReservationStatus() {
  const queryClient = useQueryClient()
  return useMutation({
    retry: 0,
    mutationFn: async ({ id, status }: { id: number; status: ReservationStatus }) => {
      await getClient().PUT('/api/reservations/{id}/status', {
        params: { path: { id } },
        body: { status },
      })
      return { id, status }
    },
    // A status change moves a reservation from one filtered list to another, so
    // every page of every list is stale — patching one of them in place would
    // leave the card in the section it just left.
    onSuccess: () => queryClient.invalidateQueries({ queryKey: RESERVATIONS_KEY }),
  })
}

/**
 * The public availability calendar: the approved and ongoing reservations over
 * the week being drawn, without any personal field. No session needed.
 */
export function useCalendarReservations(window: MaybeRefOrGetter<Window> = () => ({})) {
  const params = computed(() => {
    const { from, to } = toValue(window)
    return { from: from?.toISOString(), to: to?.toISOString() }
  })
  return useQuery({
    queryKey: computed(() => [...CALENDAR_KEY, params.value]),
    staleTime: 30 * 1000,
    placeholderData: keepPreviousData,
    queryFn: async () => {
      const { data, response } = await getClient().GET('/api/reservations/calendar', {
        params: { query: params.value },
      })
      if (response.status !== HttpStatus.OK) {
        throw new Error(`Unexpected status code received: ${response.status}`)
      }
      return data ?? []
    },
  })
}

/**
 * One page of what the session user is part of: what they filed, what they were
 * added to, and what lists their address among the Linka Go accounts — which is
 * how a reservation reaches somebody who was named before they ever logged in.
 *
 * Same filters as the admin listing; who "mine" means is the session's business,
 * not a parameter.
 */
export function useMyReservations(filters: MaybeRefOrGetter<ReservationFilters> = () => ({})) {
  const params = computed(() => toParams(toValue(filters)))
  return useQuery({
    queryKey: computed(() => [...MY_RESERVATIONS_KEY, params.value]),
    staleTime: 30 * 1000,
    placeholderData: keepPreviousData,
    queryFn: async () => {
      const { data, response } = await getClient().GET('/api/reservations/mine', {
        params: { query: params.value },
      })
      if (response.status !== HttpStatus.OK) {
        throw new Error(`Unexpected status code received: ${response.status}`)
      }
      return data ?? { items: [], total: 0 }
    },
  })
}

/**
 * Files a request. The backend fills in the requester and the `requested`
 * status, so neither is part of the body.
 */
export function useCreateReservation() {
  const queryClient = useQueryClient()
  return useMutation({
    retry: 0,
    mutationFn: async (reservation: NewReservation) => {
      const { data, response, error } = await getClient().POST('/api/reservations', {
        body: reservation,
      })
      if (response.status !== HttpStatus.CREATED) {
        // The handler answers with a plain string, which is what to show
        throw new Error(typeof error === 'string' ? error : `Unexpected status: ${response.status}`)
      }
      return data as Reservation
    },
    // Both lists are separate queries: let them refetch rather than guessing
    // where the new reservation belongs in their ordering.
    onSuccess: () => queryClient.invalidateQueries({ queryKey: RESERVATIONS_KEY }),
  })
}

/**
 * Edits the period, the bikes and the Linka Go accounts. Everything else is
 * left as stored: the backend reads it back rather than taking it from here.
 */
export function useUpdateReservation() {
  const queryClient = useQueryClient()
  return useMutation({
    retry: 0,
    mutationFn: async ({ id, ...edit }: ReservationEdit & { id: number }) => {
      const { response, error } = await getClient().PUT('/api/reservations/{id}', {
        params: { path: { id } },
        body: edit,
      })
      if (response.status !== HttpStatus.OK) {
        throw new Error(typeof error === 'string' ? error : `Unexpected status: ${response.status}`)
      }
    },
    onSuccess: () => queryClient.invalidateQueries({ queryKey: RESERVATIONS_KEY }),
  })
}