refactor: use cross tab timeout

Signed-off-by: Camila Belo <camilaibs@gmail.com>

plugins/techdocs/src/client.ts

@@ -31,6 +31,8 @@ import {
 } from '@backstage/plugin-techdocs-react';
 import { EventSourcePolyfill } from 'event-source-polyfill';
 
+const EXPIRES_AT_STORAGE_KEY = 'backstage-techdocs-cookie-expires-at';
+
 /**
  * API to talk to `techdocs-backend`.
  *
@@ -40,7 +42,10 @@ export class TechDocsClient implements TechDocsApi {
   public configApi: Config;
   public discoveryApi: DiscoveryApi;
   private fetchApi: FetchApi;
-  private cookieRefreshTimeoutId: NodeJS.Timeout | undefined;
+  private locked = false;
+  private readonly channel = new BroadcastChannel(
+    'backstage-techdocs-cookie-refresh',
+  );
 
   constructor(options: {
     configApi: Config;
@@ -50,6 +55,20 @@ export class TechDocsClient implements TechDocsApi {
     this.configApi = options.configApi;
     this.discoveryApi = options.discoveryApi;
     this.fetchApi = options.fetchApi;
+    this.channel.onmessage = event => {
+      const { action, payload } = event.data;
+      if (action === 'REFRESH_COOKIE') {
+        this.locked = payload.locked;
+      }
+    };
+  }
+
+  set expiresAt(value: string) {
+    localStorage.setItem(EXPIRES_AT_STORAGE_KEY, value);
+  }
+
+  get expiresAt(): string | null {
+    return localStorage.getItem(EXPIRES_AT_STORAGE_KEY);
   }
 
   private async getCookie(): Promise<{ expiresAt: string }> {
@@ -64,42 +83,46 @@ export class TechDocsClient implements TechDocsApi {
     return await response.json();
   }
 
-  public async issueUserCookie(): Promise<{ expiresAt: string }> {
-    const expiresAtStorageKey = 'backstage-auth-cookie-last-refresh-expires-at';
-    const formatedExpiresAt = localStorage.getItem(expiresAtStorageKey);
-    const expiresAt = formatedExpiresAt ? new Date(formatedExpiresAt) : null;
+  private refreshUserCookie(options: { expiresAt: string }) {
+    const { expiresAt } = options;
+    const tenMinutesInMilliseconds = 10 * 60000;
+    const intervalId = setInterval(() => {
+      if (this.locked) return;
+      if (Date.parse(expiresAt) - Date.now() - tenMinutesInMilliseconds > 0)
+        return;
 
-    // get a new cookie if it doesn't exist or has expired
-    if (
-      // first time issuing a cookie or user deleted the stored expiration date
-      !expiresAt ||
-      // the application was reloaded and the cookie was not refreshed
-      expiresAt.getTime() < Date.now()
-    ) {
-      return this.getCookie().then(response => {
-        const newExpiresAt = new Date(response.expiresAt);
-        // refresh the cookie 5 minutes before it expires
-        newExpiresAt.setMinutes(newExpiresAt.getMinutes() - 5);
-        // store the expiration date to keep it even if the application is reloaded
-        localStorage.setItem(expiresAtStorageKey, newExpiresAt.toISOString());
-        // maintain the timeout id per tab instance so we know that there is a timeout running
-        this.cookieRefreshTimeoutId = setTimeout(
-          this.issueUserCookie,
-          newExpiresAt.getTime(),
-        );
-        return { expiresAt: newExpiresAt.toISOString() };
+      this.channel.postMessage({
+        action: 'REFRESH_COOKIE',
+        payload: { locked: true },
+      });
+
+      this.issueUserCookie({ force: true })
+        .then(() => clearInterval(intervalId))
+        .finally(() => {
+          this.locked = false;
+          this.channel.postMessage({
+            action: 'REFRESH_COOKIE',
+            payload: { locked: false },
+          });
+        });
+    }, tenMinutesInMilliseconds);
+
+    return { expiresAt };
+  }
+
+  public async issueUserCookie(
+    options: {
+      force?: boolean;
+    } = {},
+  ): Promise<{ expiresAt: string }> {
+    const { force } = options;
+    if (force || !this.expiresAt || Date.parse(this.expiresAt) < Date.now()) {
+      return this.getCookie().then(({ expiresAt }) => {
+        this.expiresAt = expiresAt;
+        return this.refreshUserCookie({ expiresAt });
       });
     }
-
-    // restart timeout when the cookie is still valid but the application was reloaded
-    if (!this.cookieRefreshTimeoutId) {
-      this.cookieRefreshTimeoutId = setTimeout(
-        this.issueUserCookie,
-        expiresAt.getTime(),
-      );
-    }
-
-    return { expiresAt: expiresAt.toISOString() };
+    return this.refreshUserCookie({ expiresAt: this.expiresAt });
   }
 
   async getApiOrigin(): Promise<string> {