base.service

import { Injectable } from "@angular/core";
import { HttpClient, HttpRequest, HttpEventType, HttpErrorResponse } from '@angular/common/http';
import { HttpUtilsService } from '../metronic/core/_base/crud';
import { FilterGroups } from '../models/filters';
import { Observable, throwError } from 'rxjs';
import { Paginate } from '../models/paginate.model';
import { map } from 'rxjs/internal/operators/map';
import { catchError } from 'rxjs/operators';

@Injectable()
export class BaseService<TModel> {
    constructor(protected http: HttpClient,
        protected httpUtils: HttpUtilsService) { }

    protected request<T = any>(req: HttpRequest<T>) {
        switch (req.method.toLowerCase()) {
            case 'PUT':
            case 'POST':
                req.headers.append('Content-Type','application/json')
                break;

            default:
                break;
        }
        return this.http.request<T>(req).pipe(
            map(event => {
                switch (event.type) {
                    case HttpEventType.Response:
                        return event.body as T;
                    default:
                        return event;
                }
            }),
            catchError(this.handleError)
        )
        //.toPromise()
        ;
    }

    private handleError(error: HttpErrorResponse) {
        if (error.error instanceof ErrorEvent) {
            // A client-side or network error occurred. Handle it accordingly.
            console.error('An error occurred:', error.error.message);
        } else {
            // The backend returned an unsuccessful response code.
            // The response body may contain clues as to what went wrong,
            console.error(
                `Backend returned code ${error.status}, ` +
                `body was: ${error.error}`);
        }
        // return an observable with a user-facing error message
        return throwError(
            'Something bad happened; please try again later.');
    };

    protected getByFilterHandler(url: string, filters: FilterGroups<TModel>, page: number, limit: number): Observable<Paginate<TModel>> {

        if (page && page > 0) {
            page = page - 1;
        }

        let _params = 'page=' + page.toString();
        _params += '&resultsPerPage=' + limit.toString();

        return this.http.post<Paginate<TModel>>(url, { method: 'POST', body: filters, search: _params });
    }
}