import type { GraphQLError } from 'graphql'
import { useMemo } from 'react'
import type { AuthenticatedItem, VisibleLists, CreateViewFieldModes } from '../../types'
import { type DocumentNode, useQuery, type QueryResult, type ServerError, type ServerParseError } from '../apollo'
import { type DeepNullable, makeDataGetter } from './dataGetter'

export type { AuthenticatedItem, VisibleLists, CreateViewFieldModes }

export function useLazyMetadata (query: DocumentNode): {
  authenticatedItem: AuthenticatedItem
  refetch: () => Promise<void>
  visibleLists: VisibleLists
  createViewFieldModes: CreateViewFieldModes
} {
  const result = useQuery(query, { errorPolicy: 'all', fetchPolicy: 'no-cache' })
  return useMemo(() => {
    const refetch = async () => {
      await result.refetch()
    }

    const dataGetter = makeDataGetter<
      DeepNullable<{
        authenticatedItem:
          | {
              __typename: string
              id: string
              [key: string]: any
            }
          | { __typename: string }
        keystone: {
          adminMeta: {
            lists: {
              key: string
              isHidden: boolean
              fields: { path: string, createView: { fieldMode: 'edit' | 'hidden' } }[]
            }[]
          }
        }
      }>
    >(result.data, result.error?.graphQLErrors)
    const authenticatedItemGetter = dataGetter.get('authenticatedItem')
    const keystoneMetaGetter = dataGetter.get('keystone')

    return {
      refetch,
      authenticatedItem: getAuthenticatedItem(
        result,
        authenticatedItemGetter.errors || (result.error?.networkError ?? undefined)
      ),
      visibleLists: getVisibleLists(
        result,
        keystoneMetaGetter.errors || (result.error?.networkError ?? undefined)
      ),
      createViewFieldModes: getCreateViewFieldModes(
        result,
        keystoneMetaGetter.errors || (result.error?.networkError ?? undefined)
      ),
    }
  }, [result])
}

function getCreateViewFieldModes (
  { data }: QueryResult,
  error?: Error | ServerParseError | ServerError | readonly [GraphQLError, ...GraphQLError[]]
): CreateViewFieldModes {
  if (error) {
    return { state: 'error', error }
  }
  if (data) {
    const lists: Record<string, Record<string, 'edit' | 'hidden'>> = {}
    data.keystone.adminMeta.lists.forEach((list: any) => {
      lists[list.key] = {}
      list.fields.forEach((field: any) => {
        lists[list.key][field.path] = field.createView.fieldMode
      })
    })
    return { state: 'loaded', lists }
  }

  return { state: 'loading' }
}

function getVisibleLists (
  { data }: QueryResult,
  error?: Error | ServerParseError | ServerError | readonly [GraphQLError, ...GraphQLError[]]
): VisibleLists {
  if (error) {
    return { state: 'error', error }
  }
  if (data) {
    const lists = new Set<string>()
    data.keystone.adminMeta.lists.forEach((list: any) => {
      if (!list.isHidden) {
        lists.add(list.key)
      }
    })
    return { state: 'loaded', lists }
  }

  return { state: 'loading' }
}

function getAuthenticatedItem (
  { data }: QueryResult,
  error?: Error | ServerParseError | ServerError | readonly [GraphQLError, ...GraphQLError[]]
): AuthenticatedItem {
  if (error) {
    return { state: 'error', error }
  }
  if (data) {
    if (
      !data.authenticatedItem ||
      // this is for the case where there is a new type
      // in the AuthenticatedItem union and the query
      // that the admin ui has doesn't get the id
      // (yes, undefined is very specific and very intentional, it should not be checking for null)
      data.authenticatedItem.id === undefined
    ) {
      return { state: 'unauthenticated' }
    }
    const labelField = Object.keys(data.authenticatedItem).filter(
      x => x !== '__typename' && x !== 'id'
    )[0]
    return {
      state: 'authenticated',
      id: data.authenticatedItem.id,
      label: data.authenticatedItem[labelField] || data.authenticatedItem.id,
      listKey: data.authenticatedItem.__typename,
    }
  }

  return { state: 'loading' }
}