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/*
* Copyright (c) 2022. Deutsche Telekom AG
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* SPDX-License-Identifier: Apache-2.0
*/
import { HttpEvent, HttpHandler, HttpInterceptor, HttpRequest, HttpResponse } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Observable, of } from 'rxjs';
import { startWith, tap } from 'rxjs/operators';
import { RequestCache } from '../services/cacheservice/request-cache.service';
import { urlTileApi } from '../services/tileservice/tiles.service';
/**
* Interceptor that returns HttpResponses from cache and updates cache if outdated
* This applies to GET requests from specified urls (specified in this class)
*/
@Injectable()
// https://angular.io/guide/http#using-interceptors-for-caching
// https://github.com/angular/angular/blob/master/aio/content/examples/http/src/app/http-interceptors/caching-interceptor.ts
export class CachingInterceptor implements HttpInterceptor {
private cachedUrls: Array<string> = [
urlTileApi,
window.location.origin + '/keycloak/realms/ONAP/protocol/openid-connect/userinfo',
];
// cache is the cache service that supports get() and put()
constructor(private cache: RequestCache) {}
intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
// continue if not cacheable.
if (!this.isCacheable(request)) {
return next.handle(request);
}
const cachedResponse = this.cache.get(request);
// when a custom 'x-refresh' header is set, refresh the cash
// (see https://github.com/angular/angular/blob/master/aio/content/examples/http/src/app/package-search/package-search.service.ts)
if (request.headers.get('x-refresh')) {
const results$ = this.getUpdatedResponse(request, next, this.cache);
return cachedResponse ? results$.pipe(startWith(cachedResponse)) : results$;
}
// cache-or-fetch
return cachedResponse ? of(cachedResponse) : this.getUpdatedResponse(request, next, this.cache);
}
/**
* Checks if the request is cacheable.
* This is true if the request is a http GET and the url is defined in this method
* (-> urlTileApi)
*/
private isCacheable(req: HttpRequest<any>): boolean {
// Only GET requests are cacheable
return (
req.method === 'GET' &&
// Only the tile api is cacheable in this app
-1 < this.cachedUrls.indexOf(req.url)
);
}
/**
* Get server response observable by sending request to `next()`.
* Will add the response to the cache on the way out.
*/
private getUpdatedResponse(
req: HttpRequest<any>,
next: HttpHandler,
cache: RequestCache,
): Observable<HttpEvent<any>> {
return next.handle(req.clone()).pipe(
tap(event => {
// There may be other events besides the response.
if (event instanceof HttpResponse) {
cache.put(req, event); // Update the cache.
}
}),
);
}
}
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