base.service.ts

import { HttpClient, HttpParams, HttpHeaders } from '@angular/common/http';
import { Observable } from 'rxjs';

type ValidHeaders = HttpHeaders | { [header: string]: string | string[] };

export abstract class BaseService {
  protected url: string;

  /**
   * Use the base service class to create your services.
   * @param http Angular HTTP service.
   * @param apiUrl Base URL of the API without the trailing slash. For example: http://example.com
   * @param resource Prefix to use with the service. For example: 'auth';
   */
  constructor(private readonly http: HttpClient, apiUrl: string, resource: string = null) {
    // Use this property to populate your API base URL
    this.url = resource ? `${apiUrl}/${resource}` : `${apiUrl}`;
  }

  /**
   * Triggers a HTTP GET to the server with the specified endpoint and query parameters.
   * @param [endpoint=''] The endpoint to GET from. Defaults to empty string.
   * @param [params] Any data to be sent to the server. Keys must match query parameter name.
   * @param [headers=null] Additional headers to pass to the request.
   * @returns An observable in the format of ApiResponse<T>.
   */
  protected get<T>(
    endpoint: string = '',
    params?: HttpParams,
    headers: ValidHeaders = null
  ): Observable<T> {
    const requestUrl = `${this.url}/${endpoint}`;

    return this.http.get<T>(requestUrl, { params, headers });
  }

  /**
   * Triggers a HTTP GET to the specified URL and query parameters.
   * @param url URL of the service to call.
   * @param [params] Any data to be sent to the server. Keys must match query parameter name.
   * @param [headers=null] Additional headers to pass to the request.
   * @returns An observable in the format of ApiResponse<T>.
   */
  protected getExternal<T>(
    url: string,
    params?: HttpParams,
    headers: ValidHeaders = null
  ): Observable<T> {
    return this.http.get<T>(url, { params, headers });
  }

  /**
   * Triggers a HTTP POST to the server with the specified endpoint and data.
   * @param [endpoint=''] The endpoint to POST to. Defaults to empty string.
   * @param [data=null] Any data to be sent to the server.
   * @returns An observable in the format of ApiResponse<T>.
   */
  protected post<T>(
    endpoint: string = '',
    data: any = null,
    headers: ValidHeaders = null
  ): Observable<T> {
    return this.http.post<T>(`${this.url}/${endpoint}`, data, { headers });
  }

  /**
   * Triggers a HTTP PUT to the server with the specified endpoint and query parameters.
   * @param [endpoint=''] The endpoint to PUT at. Defaults to empty string.
   * @param [data=null] Any data to be sent to the server.
   * @returns An observable in the format of ApiResponse<T>.
   */
  protected put<T>(
    endpoint: string = '',
    data: any = null,
    headers: ValidHeaders = null
  ): Observable<T> {
    return this.http.put<T>(`${this.url}/${endpoint}`, data, { headers });
  }

  /**
   * Triggers a HTTP PATCH to the server with the specified endpoint and query parameters.
   * @param [endpoint=''] The endpoint to PATCH at. Defaults to empty string.
   * @param [data=null] Any data to be sent to the server.
   * @returns An observable in the format of ApiResponse<T>.
   */
  protected patch<T>(
    endpoint: string = '',
    data: any = null,
    headers: ValidHeaders = null
  ): Observable<T> {
    return this.http.patch<T>(`${this.url}/${endpoint}`, data, { headers });
  }

  /**
   * Triggers a HTTP DELETE to the server with the specified endpoint and query parameters.
   * @param [endpoint=''] The endpoint to DELETE from. Defaults to empty string.
   * @param [params] Any data to be sent to the server. Keys must match query parameter name.
   * @param [headers=null] Additional headers to pass to the request.
   * @returns An observable in the format of ApiResponse<T>.
   */
  protected delete<T>(
    endpoint: string = '',
    params?: HttpParams,
    headers: ValidHeaders = null
  ): Observable<T> {
    return this.http.delete<T>(`${this.url}/${endpoint}`, {
      params,
      headers,
    });
  }
}