src/app/services/base-http.service.ts

/**
******************************************************************************
* Copyright © 2017-2018 PTA GmbH.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* 
*     http://www.eclipse.org/legal/epl-v10.html
* 
******************************************************************************
*/
import { Injectable } from '@angular/core';
import { Http, Response, Headers } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/map';
import 'rxjs/add/observable/throw';
import { UUID } from 'angular2-uuid';
import { Globals } from '../common/globals';
import { SessionContext } from '../common/session-context';
import { MessageService } from './message.service';
import { BannerMessage } from '../common/banner-message';
import { ErrorType } from '../common/enums';

@Injectable()
export class BaseHttpService {

    constructor(protected messageService: MessageService) {
    }

    protected getBaseUrl(): string {
        return Globals.BASE_URL;
    }

    protected createCommonHeaders(headers: Headers, sessionContext: SessionContext) {
        headers.append('Accept', 'application/json');
        headers.append('content-Type', 'application/json');
        headers.append('Access-Control-Allow-Origin', '*');
        headers.set('Authorization', 'Bearer ' + sessionContext.getAccessToken());
        headers.append('unique-TAN', UUID.UUID());
        if (sessionContext.getCurrSessionId() !== null) {
            headers.append(Globals.SESSION_TOKEN_TAG, sessionContext.getCurrSessionId());
        }
    }

    protected extractData(res: Response, _sessContext: SessionContext) {
        // let the interested 'people' know about our result
        _sessContext.centralHttpResultCode$.emit( res.status );
    
        if (res.status !== 302 && (res.status < 200 || res.status >= 300) ) {
            throw new Error('Bad response status: ' + res.status);
        }
    
        const data = res.json();
        return data || {};
    }

    protected extractSessionId(headers: Headers, sessionContext: SessionContext) {
        if (headers != null) {
            if (headers.has(Globals.SESSION_TOKEN_TAG)) {
                sessionContext.setCurrSessionId(headers.get(Globals.SESSION_TOKEN_TAG));
            }
        }
    }

    protected handleErrorPromise(error: any) {
        // In a real world app, we might use a remote logging infrastructure
        let errMsg: string;
        let body = null;

        if (error instanceof Response) {
            body = error.json() || '';            
            const err = body.error || JSON.stringify(body);
            errMsg = `${error.status} - ${error.statusText || ''} ${err}`;
        } else {
            errMsg = error.message ? error.message : error.toString();
        }

        if (body !== null && body.errorCode === 401 && this.messageService) {
            const bannerMessage = new BannerMessage();
            bannerMessage.errorType = ErrorType.authentication;
            this.messageService.errorOccured$.emit(bannerMessage);
        }

        console.error(errMsg);
        return Observable.throw(errMsg);
    }

}