src/app/store/root/effects/keep-alive.effect.ts

/********************************************************************************
 * Copyright (c) 2020 Contributors to the Eclipse Foundation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0
 *
 * SPDX-License-Identifier: EPL-2.0
 ********************************************************************************/

import {DOCUMENT} from "@angular/common";
import {Inject, Injectable} from "@angular/core";
import {Actions, createEffect, ofType} from "@ngrx/effects";
import {Observable, race, timer} from "rxjs";
import {endWith, repeat, switchMap, takeWhile} from "rxjs/operators";
import {AuthService, CoreApiService} from "../../../core";
import {fromReturningToBrowserTabEvent, ignoreError} from "../../../util";
import {keepSessionAliveAction} from "../actions";

@Injectable({providedIn: "root"})
export class KeepAliveEffect {

    public keepAliveTimeInMs = 60000;

    public keepSessionAlive$ = createEffect(() => this.actions$.pipe(
        ofType(keepSessionAliveAction),
        switchMap(() => this.keepSessionAlive())
    ), {dispatch: false});

    public constructor(
        private readonly actions$: Actions,
        private readonly authService: AuthService,
        private readonly coreApiService: CoreApiService,
        @Inject(DOCUMENT) private readonly document: Document
    ) {

    }

    public keepSessionAlive(): Observable<any> {
        const timer$ = timer(this.keepAliveTimeInMs);
        const returnToApp$ = fromReturningToBrowserTabEvent(this.document);

        // The GET is called either after a specific amount of time or when the tab is refocused:
        return race(timer$, returnToApp$).pipe(
            // The session is kept alive only if there is a token:
            switchMap(() => {
                if (this.authService.token == null) {
                    return Promise.resolve();
                }
                return this.coreApiService.keepAlive().pipe();
            }),
            // All errors are ignored here:
            ignoreError(),
            endWith(0),
            // This repeats the Observable as long as there is a token:
            repeat(),
            takeWhile(() => this.authService.token != null)
        );
    }

}