chrome/browser/resources/welcome/landing_view_proxy.js

// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

const NUX_LANDING_PAGE_INTERACTION_METRIC_NAME =
    'FirstRun.NewUserExperience.LandingPageInteraction';

/**
 * NuxLandingPageInteractions enum.
 * These values are persisted to logs and should not be renumbered or re-used.
 * See tools/metrics/histograms/enums.xml.
 * @enum {number}
 */
const NuxLandingPageInteractions = {
  PageShown: 0,
  NavigatedAway: 1,
  NewUser: 2,
  ExistingUser: 3,
};

const NUX_LANDING_PAGE_INTERACTIONS_COUNT =
    Object.keys(NuxLandingPageInteractions).length;

/** @interface */
export class LandingViewProxy {
  recordPageShown() {}

  recordNavigatedAway() {}

  recordNewUser() {}

  recordExistingUser() {}
}

/** @implements {LandingViewProxy} */
export class LandingViewProxyImpl {
  /** @override */
  recordPageShown() {
    this.recordInteraction_(NuxLandingPageInteractions.PageShown);
  }

  /** @override */
  recordNavigatedAway() {
    this.recordInteraction_(NuxLandingPageInteractions.NavigatedAway);
  }

  /** @override */
  recordNewUser() {
    this.recordInteraction_(NuxLandingPageInteractions.NewUser);
  }

  /** @override */
  recordExistingUser() {
    this.recordInteraction_(NuxLandingPageInteractions.ExistingUser);
  }

  /**
   * @param {number} interaction
   * @private
   */
  recordInteraction_(interaction) {
    chrome.metricsPrivate.recordEnumerationValue(
        NUX_LANDING_PAGE_INTERACTION_METRIC_NAME, interaction,
        NUX_LANDING_PAGE_INTERACTIONS_COUNT);
  }

  /** @return {!LandingViewProxy} */
  static getInstance() {
    return instance || (instance = new LandingViewProxyImpl());
  }

  /** @param {!LandingViewProxy} obj */
  static setInstance(obj) {
    instance = obj;
  }
}

/** @type {?LandingViewProxy} */
let instance = null;