1 files changed, 79 insertions, 0 deletions
diff --git a/browser/components/newtab/lib/AWScreenUtils.jsm b/browser/components/newtab/lib/AWScreenUtils.jsm
new file mode 100644
index 0000000000..93da92f630
--- /dev/null
+++ b/browser/components/newtab/lib/AWScreenUtils.jsm
@@ -0,0 +1,79 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+
+const lazy = {};
+
+XPCOMUtils.defineLazyModuleGetters(lazy, {
+  ASRouter: "resource://activity-stream/lib/ASRouter.jsm",
+  ASRouterTargeting: "resource://activity-stream/lib/ASRouterTargeting.jsm",
+});
+
+const AWScreenUtils = {
+  /**
+   * Filter the given screens in place with a predicate.
+   *
+   * @param {object[]} screens - The screens to filter.
+   * @param {Function} callback - The predicate for filtering the screens.
+   */
+  async removeScreens(screens, callback) {
+    for (let i = 0; i < screens?.length; i++) {
+      if (await callback(screens[i], i)) {
+        screens.splice(i--, 1);
+      }
+    }
+  },
+  /**
+   * Given a JEXL expression, returns the evaluation of the expression or returns
+   * true if the expression did not evaluate successfully
+   * @param {string} targeting - The JEXL expression that will be evaluated
+   * @returns {boolean}
+   */
+  async evaluateScreenTargeting(targeting) {
+    const result = await lazy.ASRouter.evaluateExpression({
+      expression: targeting,
+      context: lazy.ASRouterTargeting.Environment,
+    });
+    if (result?.evaluationStatus?.success) {
+      return result.evaluationStatus.result;
+    }
+
+    return true;
+  },
+  /**
+   * Filter out screens whose targeting do not match.
+   *
+   * Given an array of screens, each screen will have it's `targeting` property
+   * evaluated, and removed if it's targeting evaluates to false
+   *
+   * @param {object[]} screens - An array of screens that will be looped
+   * through to be evaluated for removal
+   * @returns {object[]} - A new array containing the screens that were not removed
+   */
+  async evaluateTargetingAndRemoveScreens(screens) {
+    const filteredScreens = [...screens];
+    await this.removeScreens(filteredScreens, async screen => {
+      if (screen.targeting === undefined) {
+        // Don't remove the screen if we don't have a targeting property
+        return false;
+      }
+
+      const result = await this.evaluateScreenTargeting(screen.targeting);
+      // Flipping the value because a true evaluation means we
+      // don't want to remove the screen, while false means we do
+      return !result;
+    });
+
+    return filteredScreens;
+  },
+
+  async addScreenImpression(screen) {
+    await lazy.ASRouter.addScreenImpression(screen);
+  },
+};
+
+const EXPORTED_SYMBOLS = ["AWScreenUtils"];