import { Observable } from 'rxjs';
import { filter, find, flatMap, map, take, tap } from 'rxjs/operators';
import { hasValue, hasValueOperator, isNotEmpty } from '../../shared/empty.util';
import { DSOSuccessResponse, RestResponse } from '../cache/response.models';
import { RemoteData } from '../data/remote-data';
import { RestRequest } from '../data/request.models';
import { RequestEntry } from '../data/request.reducer';
import { RequestService } from '../data/request.service';
import { BrowseDefinition } from './browse-definition.model';
import { DSpaceObject } from './dspace-object.model';
import { PaginatedList } from '../data/paginated-list';
import { SearchResult } from '../../+search-page/search-result.model';
import { Item } from './item.model';
import { Router } from '@angular/router';

/**
 * This file contains custom RxJS operators that can be used in multiple places
 */

export const getRequestFromRequestHref = (requestService: RequestService) =>
  (source: Observable<string>): Observable<RequestEntry> =>
    source.pipe(
      flatMap((href: string) => requestService.getByHref(href)),
      hasValueOperator()
    );

export const getRequestFromRequestUUID = (requestService: RequestService) =>
  (source: Observable<string>): Observable<RequestEntry> =>
    source.pipe(
      flatMap((uuid: string) => requestService.getByUUID(uuid)),
      hasValueOperator()
    );

export const filterSuccessfulResponses = () =>
  (source: Observable<RequestEntry>): Observable<RestResponse> =>
    source.pipe(
      getResponseFromEntry(),
      filter((response: RestResponse) => response.isSuccessful === true),
    );

export const getResponseFromEntry = () =>
  (source: Observable<RequestEntry>): Observable<RestResponse> =>
    source.pipe(
      filter((entry: RequestEntry) => hasValue(entry) && hasValue(entry.response)),
      map((entry: RequestEntry) => entry.response)
    );

export const getResourceLinksFromResponse = () =>
  (source: Observable<RequestEntry>): Observable<string[]> =>
    source.pipe(
      filterSuccessfulResponses(),
      map((response: DSOSuccessResponse) => response.resourceSelfLinks),
    );

export const configureRequest = (requestService: RequestService, forceBypassCache?: boolean) =>
  (source: Observable<RestRequest>): Observable<RestRequest> =>
    source.pipe(tap((request: RestRequest) => requestService.configure(request, forceBypassCache)));

export const getRemoteDataPayload = () =>
  <T>(source: Observable<RemoteData<T>>): Observable<T> =>
    source.pipe(map((remoteData: RemoteData<T>) => remoteData.payload));

export const getSucceededRemoteData = () =>
  <T>(source: Observable<RemoteData<T>>): Observable<RemoteData<T>> =>
    source.pipe(find((rd: RemoteData<T>) => rd.hasSucceeded));

/**
 * Operator that checks if a remote data object contains a page not found error
 * When it does contain such an error, it will redirect the user to a page not found, without altering the current URL
 * @param router The router used to navigate to a new page
 */
export const redirectToPageNotFoundOn404 = (router: Router) =>
  <T>(source: Observable<RemoteData<T>>): Observable<RemoteData<T>> =>
    source.pipe(
      tap((rd: RemoteData<T>) => {
        if (rd.hasFailed && rd.error.statusCode === 404) {
          router.navigateByUrl('/404', { skipLocationChange: true });
        }
      }));

export const getFinishedRemoteData = () =>
  <T>(source: Observable<RemoteData<T>>): Observable<RemoteData<T>> =>
    source.pipe(find((rd: RemoteData<T>) => !rd.isLoading));

export const getAllSucceededRemoteData = () =>
  <T>(source: Observable<RemoteData<T>>): Observable<RemoteData<T>> =>
    source.pipe(filter((rd: RemoteData<T>) => rd.hasSucceeded));

export const toDSpaceObjectListRD = () =>
  <T extends DSpaceObject>(source: Observable<RemoteData<PaginatedList<SearchResult<T>>>>): Observable<RemoteData<PaginatedList<T>>> =>
    source.pipe(
      filter((rd: RemoteData<PaginatedList<SearchResult<T>>>) => rd.hasSucceeded),
      map((rd: RemoteData<PaginatedList<SearchResult<T>>>) => {
        const dsoPage: T[] = rd.payload.page.filter((result) => hasValue(result)).map((searchResult: SearchResult<T>) => searchResult.indexableObject);
        const payload = Object.assign(rd.payload, { page: dsoPage }) as PaginatedList<T>;
        return Object.assign(rd, { payload: payload });
      })
    );

/**
 * Get the browse links from a definition by ID given an array of all definitions
 * @param {string} definitionID
 * @returns {(source: Observable<RemoteData<BrowseDefinition[]>>) => Observable<any>}
 */
export const getBrowseDefinitionLinks = (definitionID: string) =>
  (source: Observable<RemoteData<BrowseDefinition[]>>): Observable<any> =>
    source.pipe(
      getRemoteDataPayload(),
      map((browseDefinitions: BrowseDefinition[]) => browseDefinitions
        .find((def: BrowseDefinition) => def.id === definitionID)
      ),
      map((def: BrowseDefinition) => {
        if (isNotEmpty(def)) {
          return def._links;
        } else {
          throw new Error(`No metadata browse definition could be found for id '${definitionID}'`);
        }
      })
    );

/**
 * Get the first occurrence of an object within a paginated list
 */
export const getFirstOccurrence = () =>
  <T extends DSpaceObject>(source: Observable<RemoteData<PaginatedList<T>>>): Observable<RemoteData<T>> =>
    source.pipe(
      map((rd) => Object.assign(rd, { payload: rd.payload.page.length > 0 ? rd.payload.page[0] : undefined }))
    );