feat: cache the endpoint url for the mock-provider in session storage (…

…#1979)

* feat: set the endpoint URL for mock-provide in session storage

* refactor: test to check the storage exists, rename to SessionCache

* refactor: use better access modifiers for properties and methods

packages/mgt-element/src/mock/MockGraph.ts

@@ -15,6 +15,7 @@ import {
   RetryHandlerOptions,
   TelemetryHandler
 } from '@microsoft/microsoft-graph-client';
+import { SessionCache, storageAvailable } from '../utils/SessionCache';
 import { MgtBaseComponent } from '../components/baseComponent';
 import { Graph } from '../Graph';
 import { chainMiddleware } from '../utils/GraphHelpers';
@@ -74,13 +75,21 @@ class MockMiddleware implements Middleware {
    */
   private _nextMiddleware: Middleware;
 
-  private static _baseUrl;
+  private _baseUrl: string;
+
+  private _session: SessionCache;
+
+  constructor() {
+    if (storageAvailable('sessionStorage')) {
+      this._session = new SessionCache();
+    }
+  }
 
   // tslint:disable-next-line: completed-docs
   public async execute(context: Context): Promise<void> {
     try {
-      const baseUrl = await MockMiddleware.getBaseUrl();
-      context.request = baseUrl + escape(context.request as string);
+      const baseUrl = await this.getBaseUrl();
+      context.request = baseUrl + encodeURIComponent(context.request as string);
     } catch (error) {
       // ignore error
     }
@@ -96,15 +105,21 @@ class MockMiddleware implements Middleware {
     this._nextMiddleware = next;
   }
 
-  private static async getBaseUrl() {
+  private async getBaseUrl() {
     if (!this._baseUrl) {
-      try {
-        // get the url we should be using from the endpoint service
-        let response = await fetch('https://cdn.graph.office.net/en-us/graph/api/proxy/endpoint');
-        this._baseUrl = (await response.json()) + '?url=';
-      } catch {
-        // fallback to hardcoded value
-        this._baseUrl = 'https://proxy.apisandbox.msdn.microsoft.com/svc?url=';
+      const sessionEndpoint = this._session?.getItem('endpointURL');
+      if (sessionEndpoint) {
+        this._baseUrl = sessionEndpoint;
+      } else {
+        try {
+          // get the url we should be using from the endpoint service
+          let response = await fetch('https://cdn.graph.office.net/en-us/graph/api/proxy/endpoint');
+          this._baseUrl = (await response.json()) + '?url=';
+        } catch {
+          // fallback to hardcoded value
+          this._baseUrl = 'https://proxy.apisandbox.msdn.microsoft.com/svc?url=';
+        }
+        this._session?.setItem('endpointURL', this._baseUrl);
       }
     }
 

packages/mgt-element/src/utils/SessionCache.ts

@@ -0,0 +1,63 @@
+/**
+ * -------------------------------------------------------------------------------------------
+ * Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.
+ * See License in the project root for license information.
+ * -------------------------------------------------------------------------------------------
+ */
+
+/**
+ * Wrapper around the window.sessionStorage API. Use
+ * this to set, get and clear session items.
+ */
+export class SessionCache {
+  private session: Storage;
+
+  constructor() {
+    this.session = window.sessionStorage;
+  }
+
+  setItem(key: string, value: string) {
+    this.session.setItem(key, value);
+  }
+
+  getItem(key: string): string {
+    return this.session.getItem(key);
+  }
+
+  clear() {
+    this.session.clear();
+  }
+}
+
+/**
+ * Checks if a sessionStorage or a localStorage is available
+ * for use in a browser.
+ * @param storageType can be 'sessionStorage' or 'localStorage'.
+ * @returns true if the storage is available for use.
+ */
+export function storageAvailable(storageType: string): boolean {
+  let storage: Storage;
+  try {
+    storage = window[storageType];
+    const x = '__storage_test__';
+    storage.setItem(x, x);
+    storage.removeItem(x);
+    return true;
+  } catch (e) {
+    return (
+      e instanceof DOMException &&
+      // everything except Firefox
+      (e.code === 22 ||
+        // Firefox
+        e.code === 1014 ||
+        // test name field too, because code might not be present
+        // everything except Firefox
+        e.name === 'QuotaExceededError' ||
+        // Firefox
+        e.name === 'NS_ERROR_DOM_QUOTA_REACHED') &&
+      // acknowledge QuotaExceededError only if there's something already stored
+      storage &&
+      storage.length !== 0
+    );
+  }
+}