Fix issue with using expired token for camera image view.

src/cached-value-controller.ts

@@ -0,0 +1,73 @@
+import { ReactiveController, ReactiveControllerHost } from 'lit';
+
+export class CachedValueController<T> implements ReactiveController {
+  public value?: T;
+
+  protected _host: ReactiveControllerHost;
+  protected _timerSeconds: number;
+  protected _callback: () => T;
+  protected _timerID?: number;
+
+  constructor(host: ReactiveControllerHost, timerSeconds: number, callback: () => T) {
+    this._timerSeconds = timerSeconds;
+    this._callback = callback;
+    (this._host = host).addController(this);
+  }
+
+  /**
+   * Remove the controller for the host.
+   */
+  public removeController(): void {
+    this._host.removeController(this);
+  }
+
+  /**
+   * Update the cached value (and reset the timer).
+   */
+  public updateValue(): void {
+    this.value = this._callback();
+    this._setTimer();
+  }
+
+  /**
+   * Update the value and render it.
+   */
+  protected _updateValueAndRender(): void {
+    this.updateValue();
+    this._host.requestUpdate();
+  }
+
+  /**
+   * Remove the timer.
+   */
+  protected _removeTimer(): void {
+    clearInterval(this._timerID);
+    this._timerID = undefined;
+  }
+
+  /**
+   * Set the timer.
+   */
+   protected _setTimer(): void {
+    clearInterval(this._timerID);
+    if (this._timerSeconds > 0) {
+      this._timerID = window.setInterval(() => {
+          this._updateValueAndRender();
+      }, this._timerSeconds * 1000);
+    }
+  }
+
+  /**
+   * Host has connected to the cache.
+   */
+  hostConnected(): void {
+    this._updateValueAndRender();
+  }
+
+  /**
+   * Host has disconnected from the cache.
+   */
+  hostDisconnected(): void {
+    this._removeTimer();
+  }
+}