Début d'ajout pour la gestion du login

Front/skydivelogs-app/src/interceptor/caching.interceptor.ts

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+import { Injectable } from '@angular/core';
+import {
+  HttpEvent,
+  HttpRequest,
+  HttpResponse,
+  HttpInterceptor,
+  HttpHandler
+} from '@angular/common/http';
+
+import { Observable } from 'rxjs/Observable';
+import { startWith, tap } from 'rxjs/operators';
+import 'rxjs/add/observable/of';
+
+import { RequestCache } from '../services/request-cache.service';
+
+@Injectable()
+export class CachingInterceptor implements HttpInterceptor {
+  constructor(private cache: RequestCache) { }
+
+  intercept(req: HttpRequest<any>, next: HttpHandler) {
+    const cachedResponse = this.cache.get(req);
+    return cachedResponse
+      ? Observable.of(cachedResponse)
+      : this.sendRequest(req, next);
+  }
+
+  sendRequest(
+    req: HttpRequest<any>,
+    next: HttpHandler
+  ): Observable<HttpEvent<any>> {
+    return next.handle(req).pipe(
+      tap(event => {
+        if (event instanceof HttpResponse) {
+          this.cache.put(req, event);
+        }
+      })
+    );
+  }
+}