import { QueriesObserver, noop, notifyManager } from '@tanstack/query-core'
import { derived, get, readable } from 'svelte/store'
import { useIsRestoring } from './useIsRestoring.js'
import { useQueryClient } from './useQueryClient.js'
import { isSvelteStore } from './utils.js'
import type { Readable } from 'svelte/store'
import type { StoreOrVal } from './types.js'
import type {
  DefaultError,
  DefinedQueryObserverResult,
  OmitKeyof,
  QueriesObserverOptions,
  QueriesPlaceholderDataFunction,
  QueryClient,
  QueryFunction,
  QueryKey,
  QueryObserverOptions,
  QueryObserverResult,
  ThrowOnError,
} from '@tanstack/query-core'

// This defines the `CreateQueryOptions` that are accepted in `QueriesOptions` & `GetOptions`.
// `placeholderData` function always gets undefined passed
type QueryObserverOptionsForCreateQueries<
  TQueryFnData = unknown,
  TError = DefaultError,
  TData = TQueryFnData,
  TQueryKey extends QueryKey = QueryKey,
> = OmitKeyof<
  QueryObserverOptions<TQueryFnData, TError, TData, TQueryFnData, TQueryKey>,
  'placeholderData'
> & {
  placeholderData?: TQueryFnData | QueriesPlaceholderDataFunction<TQueryFnData>
}

// Avoid TS depth-limit error in case of large array literal
type MAXIMUM_DEPTH = 20

// Widen the type of the symbol to enable type inference even if skipToken is not immutable.
type SkipTokenForUseQueries = symbol

type GetQueryObserverOptionsForCreateQueries<T> =
  // Part 1: responsible for applying explicit type parameter to function arguments, if object { queryFnData: TQueryFnData, error: TError, data: TData }
  T extends {
    queryFnData: infer TQueryFnData
    error?: infer TError
    data: infer TData
  }
    ? QueryObserverOptionsForCreateQueries<TQueryFnData, TError, TData>
    : T extends { queryFnData: infer TQueryFnData; error?: infer TError }
      ? QueryObserverOptionsForCreateQueries<TQueryFnData, TError>
      : T extends { data: infer TData; error?: infer TError }
        ? QueryObserverOptionsForCreateQueries<unknown, TError, TData>
        : // Part 2: responsible for applying explicit type parameter to function arguments, if tuple [TQueryFnData, TError, TData]
          T extends [infer TQueryFnData, infer TError, infer TData]
          ? QueryObserverOptionsForCreateQueries<TQueryFnData, TError, TData>
          : T extends [infer TQueryFnData, infer TError]
            ? QueryObserverOptionsForCreateQueries<TQueryFnData, TError>
            : T extends [infer TQueryFnData]
              ? QueryObserverOptionsForCreateQueries<TQueryFnData>
              : // Part 3: responsible for inferring and enforcing type if no explicit parameter was provided
                T extends {
                    queryFn?:
                      | QueryFunction<infer TQueryFnData, infer TQueryKey>
                      | SkipTokenForUseQueries
                    select?: (data: any) => infer TData
                    throwOnError?: ThrowOnError<any, infer TError, any, any>
                  }
                ? QueryObserverOptionsForCreateQueries<
                    TQueryFnData,
                    unknown extends TError ? DefaultError : TError,
                    unknown extends TData ? TQueryFnData : TData,
                    TQueryKey
                  >
                : // Fallback
                  QueryObserverOptionsForCreateQueries

// A defined initialData setting should return a DefinedQueryObserverResult rather than CreateQueryResult
type GetDefinedOrUndefinedQueryResult<T, TData, TError = unknown> = T extends {
  initialData?: infer TInitialData
}
  ? unknown extends TInitialData
    ? QueryObserverResult<TData, TError>
    : TInitialData extends TData
      ? DefinedQueryObserverResult<TData, TError>
      : TInitialData extends () => infer TInitialDataResult
        ? unknown extends TInitialDataResult
          ? QueryObserverResult<TData, TError>
          : TInitialDataResult extends TData
            ? DefinedQueryObserverResult<TData, TError>
            : QueryObserverResult<TData, TError>
        : QueryObserverResult<TData, TError>
  : QueryObserverResult<TData, TError>

type GetCreateQueryResult<T> =
  // Part 1: responsible for mapping explicit type parameter to function result, if object
  T extends { queryFnData: any; error?: infer TError; data: infer TData }
    ? GetDefinedOrUndefinedQueryResult<T, TData, TError>
    : T extends { queryFnData: infer TQueryFnData; error?: infer TError }
      ? GetDefinedOrUndefinedQueryResult<T, TQueryFnData, TError>
      : T extends { data: infer TData; error?: infer TError }
        ? GetDefinedOrUndefinedQueryResult<T, TData, TError>
        : // Part 2: responsible for mapping explicit type parameter to function result, if tuple
          T extends [any, infer TError, infer TData]
          ? GetDefinedOrUndefinedQueryResult<T, TData, TError>
          : T extends [infer TQueryFnData, infer TError]
            ? GetDefinedOrUndefinedQueryResult<T, TQueryFnData, TError>
            : T extends [infer TQueryFnData]
              ? GetDefinedOrUndefinedQueryResult<T, TQueryFnData>
              : // Part 3: responsible for mapping inferred type to results, if no explicit parameter was provided
                T extends {
                    queryFn?:
                      | QueryFunction<infer TQueryFnData, any>
                      | SkipTokenForUseQueries
                    select?: (data: any) => infer TData
                    throwOnError?: ThrowOnError<any, infer TError, any, any>
                  }
                ? GetDefinedOrUndefinedQueryResult<
                    T,
                    unknown extends TData ? TQueryFnData : TData,
                    unknown extends TError ? DefaultError : TError
                  >
                : // Fallback
                  QueryObserverResult

/**
 * QueriesOptions reducer recursively unwraps function arguments to infer/enforce type param
 */
export type QueriesOptions<
  T extends Array<any>,
  TResults extends Array<any> = [],
  TDepth extends ReadonlyArray<number> = [],
> = TDepth['length'] extends MAXIMUM_DEPTH
  ? Array<QueryObserverOptionsForCreateQueries>
  : T extends []
    ? []
    : T extends [infer Head]
      ? [...TResults, GetQueryObserverOptionsForCreateQueries<Head>]
      : T extends [infer Head, ...infer Tails]
        ? QueriesOptions<
            [...Tails],
            [...TResults, GetQueryObserverOptionsForCreateQueries<Head>],
            [...TDepth, 1]
          >
        : ReadonlyArray<unknown> extends T
          ? T
          : // If T is *some* array but we couldn't assign unknown[] to it, then it must hold some known/homogenous type!
            // use this to infer the param types in the case of Array.map() argument
            T extends Array<
                QueryObserverOptionsForCreateQueries<
                  infer TQueryFnData,
                  infer TError,
                  infer TData,
                  infer TQueryKey
                >
              >
            ? Array<
                QueryObserverOptionsForCreateQueries<
                  TQueryFnData,
                  TError,
                  TData,
                  TQueryKey
                >
              >
            : // Fallback
              Array<QueryObserverOptionsForCreateQueries>

/**
 * QueriesResults reducer recursively maps type param to results
 */
export type QueriesResults<
  T extends Array<any>,
  TResults extends Array<any> = [],
  TDepth extends ReadonlyArray<number> = [],
> = TDepth['length'] extends MAXIMUM_DEPTH
  ? Array<QueryObserverResult>
  : T extends []
    ? []
    : T extends [infer Head]
      ? [...TResults, GetCreateQueryResult<Head>]
      : T extends [infer Head, ...infer Tails]
        ? QueriesResults<
            [...Tails],
            [...TResults, GetCreateQueryResult<Head>],
            [...TDepth, 1]
          >
        : { [K in keyof T]: GetCreateQueryResult<T[K]> }

export function createQueries<
  T extends Array<any>,
  TCombinedResult = QueriesResults<T>,
>(
  {
    queries,
    ...options
  }: {
    queries:
      | StoreOrVal<[...QueriesOptions<T>]>
      | StoreOrVal<
          [...{ [K in keyof T]: GetQueryObserverOptionsForCreateQueries<T[K]> }]
        >
    combine?: (result: QueriesResults<T>) => TCombinedResult
  },
  queryClient?: QueryClient,
): Readable<TCombinedResult> {
  const client = useQueryClient(queryClient)
  const isRestoring = useIsRestoring()

  const queriesStore = isSvelteStore(queries) ? queries : readable(queries)

  const defaultedQueriesStore = derived(
    [queriesStore, isRestoring],
    ([$queries, $isRestoring]) => {
      return $queries.map((opts) => {
        const defaultedOptions = client.defaultQueryOptions(
          opts as QueryObserverOptions,
        )
        // Make sure the results are already in fetching state before subscribing or updating options
        defaultedOptions._optimisticResults = $isRestoring
          ? 'isRestoring'
          : 'optimistic'
        return defaultedOptions
      })
    },
  )
  const observer = new QueriesObserver<TCombinedResult>(
    client,
    get(defaultedQueriesStore),
    options as QueriesObserverOptions<TCombinedResult>,
  )

  defaultedQueriesStore.subscribe(($defaultedQueries) => {
    // Do not notify on updates because of changes in the options because
    // these changes should already be reflected in the optimistic result.
    observer.setQueries(
      $defaultedQueries,
      options as QueriesObserverOptions<TCombinedResult>,
    )
  })

  const result = derived([isRestoring], ([$isRestoring], set) => {
    const unsubscribe = $isRestoring
      ? noop
      : observer.subscribe(notifyManager.batchCalls(set))

    return () => unsubscribe()
  })

  const { subscribe } = derived(
    [result, defaultedQueriesStore],
    // @ts-expect-error svelte-check thinks this is unused
    ([$result, $defaultedQueriesStore]) => {
      const [rawResult, combineResult, trackResult] =
        observer.getOptimisticResult(
          $defaultedQueriesStore,
          (options as QueriesObserverOptions<TCombinedResult>).combine,
        )
      $result = rawResult
      return combineResult(trackResult())
    },
  )

  return { subscribe }
}