src/app/store/geo/effects/open-gis/open-gis.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 {HttpClient} from "@angular/common/http";
import {Inject, Injectable} from "@angular/core";
import {Actions, createEffect, ofType} from "@ngrx/effects";
import {Action} from "@ngrx/store";
import {Observable, of} from "rxjs";
import {ignoreElements, switchMap} from "rxjs/operators";
import {APP_CONFIGURATION, GeoApiService, IAPIGeographicPositions, IAppConfiguration, WINDOW} from "../../../../core";
import {ILeafletBounds} from "../../../../features/map";
import {catchErrorTo, ignoreError} from "../../../../util/rxjs";
import {EErrorCode, setErrorAction} from "../../../root";
import {openGisAction} from "../../actions";

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

    public open$ = createEffect(() => this.actions.pipe(
        ofType(openGisAction),
        switchMap((action) => this.openGis(action.bounds, action.user))
    ));

    /**
     * URL Template to connect with GIS.
     */
    public gisUrlTemplate = this.configuration.gis.urlTemplate;

    /**
     * Expected projection format for the given Leaflet coordinates.
     */
    public projectionFrom = this.configuration.gis.projectionFrom;

    /**
     * Expected projection required for the GIS.
     */
    public projectionTo = this.configuration.gis.projectionTo;

    /**
     * Search parameter keys which are transformed in the GIS URL template.
     */
    public coordinateKeys: Array<keyof ILeafletBounds> = ["center", "northEast", "northWest", "southEast", "southWest"];

    public constructor(
        public actions: Actions,
        public geoApiService: GeoApiService,
        public http: HttpClient,
        @Inject(WINDOW) public window: Window,
        @Inject(APP_CONFIGURATION) public configuration: IAppConfiguration
    ) {

    }

    public openGis(bounds: ILeafletBounds, user: string): Observable<Action> {
        return of(bounds).pipe(
            switchMap(() => this.transform(this.extractGeographicPositionFromBounds(bounds))),
            switchMap((geographicPositions) => {
                const gisUrl = this.generateUrl(geographicPositions, user);
                return this.http.get(gisUrl, {responseType: "text"}).pipe(ignoreError());
            }),
            ignoreElements(),
            catchErrorTo(setErrorAction({error: EErrorCode.UNEXPECTED}))
        );
    }

    /**
     * Extract all required geographic positions from the given Leaflet bounds.
     */
    public extractGeographicPositionFromBounds(bounds: ILeafletBounds): IAPIGeographicPositions {
        const geographicPositions: IAPIGeographicPositions = {};
        this.coordinateKeys.forEach((key) => {
            const value = bounds[key];
            if (typeof value !== "object") {
                return;
            }
            const tokens = [`{${key}X}`, `{${key}Y}`];
            if (tokens.some((token) => this.gisUrlTemplate.indexOf(token) > -1)) {
                geographicPositions[key] = {
                    x: value.lng,
                    y: value.lat
                };
            }
        });
        return geographicPositions;
    }

    /**
     * Transforms a set of geographic positions via an API back end call.
     */
    public transform(geographicPositions: IAPIGeographicPositions): Observable<IAPIGeographicPositions> {
        return Object.keys(geographicPositions).length > 0 ?
            this.geoApiService.transform(geographicPositions, this.projectionFrom, this.projectionTo) :
            of(geographicPositions);
    }

    /**
     * Generate the URL to the GIS with a set of given geographic positions.
     */
    public generateUrl(geographicPositions: IAPIGeographicPositions, user: string) {
        let result = this.gisUrlTemplate;
        Object.entries(geographicPositions).forEach(([key, value]) => {
            result = result.replace(new RegExp(`{${key}X}`, "g"), "" + value.x);
            result = result.replace(new RegExp(`{${key}Y}`, "g"), "" + value.y);
        });
        result = result.replace(new RegExp(`{user}`, "g"), user);
        return result;
    }

}