helix-front/client/app/core/helix.service.ts

import { throwError as observableThrowError, Observable } from 'rxjs';

import { catchError } from 'rxjs/operators';
import { Injectable } from '@angular/core';
import { HttpHeaders, HttpClient, HttpResponse } from '@angular/common/http';
import { Router } from '@angular/router';

import { Settings } from './settings';

@Injectable()
export class HelixService {
  constructor(protected router: Router, private http: HttpClient) {}

  public can(): Observable<any> {
    return this.http
      .get(`${Settings.userAPI}/can`, { headers: this.getHeaders() })
      .pipe(catchError(this.errorHandler));
  }

  protected request(path: string, helix?: string): Observable<any> {
    if (helix == null) {
      helix = this.getHelixKey();
    }

    return this.http
      .get(`${Settings.helixAPI}${helix}${path}`, {
        headers: this.getHeaders(),
      })
      .pipe(catchError(this.errorHandler));
  }

  protected post(path: string, data: string): Observable<any> {
    return this.http
      .post(`${Settings.helixAPI}${this.getHelixKey()}${path}`, data, {
        headers: this.getHeaders(),
      })
      .pipe(catchError(this.errorHandler));
  }

  protected put(path: string, data: string): Observable<any> {
    return this.http
      .put(`${Settings.helixAPI}${this.getHelixKey()}${path}`, data, {
        headers: this.getHeaders(),
      })
      .pipe(catchError(this.errorHandler));
  }

  protected delete(path: string): Observable<any> {
    return this.http
      .delete(`${Settings.helixAPI}${this.getHelixKey()}${path}`, {
        headers: this.getHeaders(),
      })
      .pipe(catchError(this.errorHandler));
  }

  protected getHelixKey(): string {
    // fetch helix key from url
    return `/${this.router.url.split('/')[1]}`;
  }

  protected getHeaders() {
    const headers = new HttpHeaders();
    headers.append('Accept', 'application/json');
    headers.append('Content-Type', 'application/json');
    return headers;
  }

  protected errorHandler(error: any) {
    console.error(error);

    let message = error.message || 'Cannot reach Helix restful service.';

    if (error instanceof HttpResponse) {
      if (error.status == 404) {
        // rest api throws 404 directly to app without any wrapper
        message = 'Not Found';
      } else {
        message = error;
        try {
          message = JSON.parse(message).error;
        } catch (e) {}
      }
    }

    return observableThrowError(message);
  }
}