import {Injectable} from '@angular/core';
import {Http} from "@angular/http";
import {Observable} from "rxjs/Observable";
import {Location} from "@angular/common";


@Injectable()
export class SelfUpdaterService {

    private appRevision: number = 0;
    private initFailed: boolean = false;

    constructor(
        private httpService: Http,
        private locationService: Location,
    ) {
        this.getDeployedRevision().subscribe(
            result => this.appRevision = result,
            () => {
                console.log(
                    "%c Couldn't load initial revision data from server. Self update disabled.",
                    "background: #222; color: #bada55;"
                );
                this.initFailed = true;
            }
        );
    }

    private getDeployedRevision(): Observable<number> {
        return this.httpService.get(this.locationService.prepareExternalUrl("/revision.json")).map(result => result.json());
    }

    public checkAndReloadIfNecessary() {
        if (!this.initFailed) {
            this.getDeployedRevision().subscribe(
                result => {
                    if (result > this.appRevision) {
                        document.location.reload(true);
                    }
                },
                () => {}
            );
        }
    }
}