react-query/packages/svelte-query/src/createBaseQuery.ts

import { derived, get, readable } from 'svelte/store'
import { noop, notifyManager } from '@tanstack/query-core'
import { useIsRestoring } from './useIsRestoring.js'
import { useQueryClient } from './useQueryClient.js'
import { isSvelteStore } from './utils.js'
import type {
  QueryClient,
  QueryKey,
  QueryObserver,
  QueryObserverResult,
} from '@tanstack/query-core'
import type {
  CreateBaseQueryOptions,
  CreateBaseQueryResult,
  StoreOrVal,
} from './types.js'

export function createBaseQuery<
  TQueryFnData,
  TError,
  TData,
  TQueryData,
  TQueryKey extends QueryKey,
>(
  options: StoreOrVal<
    CreateBaseQueryOptions<TQueryFnData, TError, TData, TQueryData, TQueryKey>
  >,
  Observer: typeof QueryObserver,
  queryClient?: QueryClient,
): CreateBaseQueryResult<TData, TError> {
  /** Load query client */
  const client = useQueryClient(queryClient)
  const isRestoring = useIsRestoring()
  /** Converts options to a svelte store if not already a store object */
  const optionsStore = isSvelteStore(options) ? options : readable(options)

  /** Creates a store that has the default options applied */
  const defaultedOptionsStore = derived(
    [optionsStore, isRestoring],
    ([$optionsStore, $isRestoring]) => {
      const defaultedOptions = client.defaultQueryOptions($optionsStore)
      defaultedOptions._optimisticResults = $isRestoring
        ? 'isRestoring'
        : 'optimistic'
      return defaultedOptions
    },
  )

  /** Creates the observer */
  const observer = new Observer<
    TQueryFnData,
    TError,
    TData,
    TQueryData,
    TQueryKey
  >(client, get(defaultedOptionsStore))

  defaultedOptionsStore.subscribe(($defaultedOptions) => {
    observer.setOptions($defaultedOptions)
  })

  const result = derived<
    typeof isRestoring,
    QueryObserverResult<TData, TError>
  >(isRestoring, ($isRestoring, set) => {
    const unsubscribe = $isRestoring
      ? noop
      : observer.subscribe(notifyManager.batchCalls(set))
    observer.updateResult()
    return unsubscribe
  })

  /** Subscribe to changes in result and defaultedOptionsStore */
  const { subscribe } = derived(
    [result, defaultedOptionsStore],
    ([$result, $defaultedOptionsStore]) => {
      $result = observer.getOptimisticResult($defaultedOptionsStore)
      return !$defaultedOptionsStore.notifyOnChangeProps
        ? observer.trackResult($result)
        : $result
    },
  )

  return { subscribe }
}