import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpResponse, HttpClient } from '@angular/common/http';
import { Observable, of, throwError, timer } from 'rxjs';
import { mergeMap } from 'rxjs/operators';

const interceptedUrls = [
    {regex: /\/loans$/, method: 'GET', filename: 'summary.json', returnStatusCode: 200},
    {regex: /\/loans\/\d+$/, method: 'GET', filename: 'detail.json', returnStatusCode: 200}
]

const jsonResponsesBasePath: string = 'assets/fake-backend-responses/'

@Injectable()
export class FakeBackendInterceptor implements HttpInterceptor {

    constructor(private http: HttpClient) {}


    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

        for (const element of interceptedUrls) {
            if(request.url.match(element.regex) && request.method === element.method) {
                return this.http.get<any>(  jsonResponsesBasePath + element.filename).pipe(
                    mergeMap((data) => {
                        return buildHttpResponse(data, element.returnStatusCode);
                    })
                );
            }
        }

        return next.handle(request);

        function buildHttpResponse(body?, status=200, delay=500): Observable<HttpResponse<any>> {
            if (status >= 200 && status < 300) {
                return timer(delay).pipe(
                    mergeMap(() => of(new HttpResponse({ status, body })))
                );

            } else {
                timer(delay).pipe(
                    mergeMap(() => throwError(new HttpResponse({ status, body })))
                );
            }
        }
    }
}