arily.
      .filter(p => "extraAdServersRegexps" in p)
      // Pre-build the regular expressions.
      .map(p => {
        p.adServerAttributes = p.adServerAttributes ?? [];
        if (p.shoppingTab?.inspectRegexpInSERP) {
          p.shoppingTab.regexp = new RegExp(p.shoppingTab.regexp);
        }
        let subframes =
          p.subframes
            ?.filter(obj => obj.inspectRegexpInSERP)
            .map(obj => {
              return { ...obj, regexp: new RegExp(obj.regexp) };
            }) ?? [];
        return {
          ...p,
          searchPageRegexp: new RegExp(p.searchPageRegexp),
          extraAdServersRegexps: p.extraAdServersRegexps.map(
            r => new RegExp(r)
          ),
          subframes,
        };
      });

    return this._searchProviderInfo;
  }

  /**
   * Handles events received from sharedData notifications.
   *
   * @param {object} event The event details.
   */
  handleEvent(event) {
    switch (event.type) {
      case "change": {
        if (event.changedKeys.includes(SEARCH_TELEMETRY_SHARED.PROVIDER_INFO)) {
          // Just null out the provider information for now, we'll fetch it next
          // time we need it.
          this._searchProviderInfo = null;
        }
        break;
      }
    }
  }
}

/**
 * @typedef {object} EventListenerParam
 * @property {string} eventType
 *  The type of event the listener should listen for. If the event type is
 *  is non-standard, it should correspond to a definition in
 *  CUSTOM_EVENT_TYPE_TO_DATA that will re-map it to a standard type. TODO
 * @property {string} target
 *  The type of component that was the source of the event.
 * @property {string | null} action
 *  The action that should be reported in telemetry.
 */

/**
 * Provides a way to add listeners to elements, as well as unload them.
 */
class ListenerHelper {
  /**
   * Adds each event listener in an array of event listeners to each element
   * in an array of elements, and sets their unloading.
   *
   * @param {Array<Element>} elements
   *  DOM elements to add event listeners to.
   * @param {Array<EventListenerParam>} eventListenerParams
   *  The type of event to add the listener to.
   * @param {string} target
   */
  static addListeners(elements, eventListenerParams, target) {
    if (!elements?.length || !eventListenerParams?.length) {
      return;
    }

    let document = elements[0].ownerGlobal.document;
    let callback = documentToEventCallbackMap.get(document);
    if (!callback) {
      return;
    }

    // The map might have entries from previous callers, so we must ensure
    // we don't discard existing event listener callbacks.
    let removeListenerCallbacks = [];
    if (documentToRemoveEventListenersMap.has(document)) {
      removeListenerCallbacks = documentToRemoveEventListenersMap.get(document);
    }

    for (let params of eventListenerParams) {
      let removeListeners = ListenerHelper.addListener(
        elements,
        params,
        target,
        callback
      );
      removeListenerCallbacks = removeListenerCallbacks.concat(removeListeners);
    }

    documentToRemoveEventListenersMap.set(document, removeListenerCallbacks);
  }

  /**
   * Add an event listener to each element in an array of elements.
   *
   * @param {Array<Element>} elements
   *  DOM elements to add event listeners to.
   * @param {EventListenerParam} eventListenerParam
   * @param {string} target
   * @param {Function} callback
   * @returns {Array<Function>} Array of remove event listener functions.
   */
  static addListener(elements, eventListenerParam, target, callback) {
    let { action, eventType, target: customTarget } = eventListenerParam;

    if (customTarget) {
      target = customTarget;
    }

    if (!action) {
      action = EVENT_TYPE_TO_ACTION[eventType];
      if (!action) {
        return [];
      }
    }

    // Some events might have specific conditions we want to check before
    // registering an engagement event.
    let eventCallback;
    if (eventListenerParam.condition) {
      if (CONDITIONS[eventListenerParam.condition]) {
        let condition = CONDITIONS[eventListenerParam.condition];
        eventCallback = async event => {
          let start = ChromeUtils.now();
          if (condition(event)) {
            callback({ action, target });
          }
          ChromeUtils.addProfilerMarker(
            "SearchSERPTelemetryChild._eventCallback",
            start,
            "Call cached function before callback."
          );
        };
      } else {
        // If a component included a condition, but it wasn't found it is
        // due to the fact that it was added in a more recent Firefox version
        // than what is provided via search-telemetry-v2. Since the version of
        // Firefox the user is using doesn't include this condition,
        // we shouldn't add the event.
        return [];
      }
    } else {
      eventCallback = () => {
        callback({ action, target });
      };
    }

    let removeListenerCallbacks = [];
    for (let element of elements) {
      element.addEventListener(eventType, eventCallback);
      removeListenerCallbacks.push(() => {
        element.removeEventListener(eventType, eventCallback);
      });
    }
    return removeListenerCallbacks;
  }
}

/**
 * Scans SERPs for ad components.
 */
class SearchAdImpression {
  /**
   * A reference to ad component information that is used if an anchor
   * element could not be categorized to a specific ad component.
   *
   * @type {object}
   */
  #defaultComponent = null;

  /**
   * Maps DOM elements to AdData.
   *
   * @type {Map<Element, AdData>}
   *
   * @typedef AdData
   * @type {object}
   * @property {string} type
   *  The type of ad component.
   * @property {number} adsLoaded
   *  The number of ads counted as loaded for the component.
   * @property {boolean} countChildren
   *  Whether all the children were counted for the component.
   */
  #elementToAdDataMap = new Map();

  /**
   * An array of components to do a top-down search.
   */
  #topDownComponents = [];

  /**
   * A reference the providerInfo for this SERP.
   *
   * @type {object}
   */
  #providerInfo = null;

  set providerInfo(providerInfo) {
    if (this.#providerInfo?.telemetryId == providerInfo.telemetryId) {
      return;
    }

    this.#providerInfo = providerInfo;

    // Reset values.
    this.#topDownComponents = [];

    for (let component of this.#providerInfo.components) {
      if (component.default) {
        this.#defaultComponent = component;
        continue;
      }
      if (component.topDown) {
        this.#topDownComponents.push(component);
      }
    }
  }

  /**
   * Check if the page has a shopping tab.
   *
   * @param {Document} document
   * @return {boolean}
   *   Whether the page has a shopping tab. Defaults to false.
   */
  hasShoppingTab(document) {
    if (!this.#providerInfo?.shoppingTab) {
      return false;
    }

    // If a provider has the inspectRegexpInSERP, we assume there must be an
    // associated regexp that must be used on any hrefs matched by the elements
    // found using the selector. If inspectRegexpInSERP is false, then check if
    // the number of items found using the selector matches exactly one element
    // to ensure we've used a fine-grained search.
    let elements = document.querySelectorAll(
      this.#providerInfo.shoppingTab.selector
    );
    if (this.#providerInfo.shoppingTab.inspectRegexpInSERP) {
      let regexp = this.#providerInfo.shoppingTab.regexp;
      for (let element of elements) {
        let href = element.getAttribute("href");
        if (href && regexp.test(href)) {
          this.#recordElementData(element, {
            type: "shopping_tab",
            count: 1,
          });
          return true;
        }
      }
    } else if (elements.length == 1) {
      this.#recordElementData(elements[0], {
        type: "shopping_tab",
        count: 1,
      });
      return true;
    }
    return false;
  }

  /**
   * Examine the list of anchors and the document object and find components
   * on the page.
   *
   * With the list of anchors, go through each and find the component it
   * belongs to and save it in elementToAdDataMap.
   *
   * Then, with the document object find components and save the results to
   * elementToAdDataMap.
   *
   * Lastly, combine the results together in a new Map that contains the number
   * of loaded, visible, and blocked results for the component.
   *
   * @param {HTMLCollectionOf<HTMLAnchorElement>} anchors
   * @param {Document} document
   *
   * @returns {Map<string, object>}
   *  A map where the key is a string containing the type of ad component
   *  and the value is an object containing the number of adsLoaded,
   *  adsVisible, and adsHidden within the component.
   */
  categorize(anchors, document) {
    // Used for various functions to make relative URLs absolute.
    let origin = new URL(document.documentURI).origin;

    // Bottom up approach.
    this.#categorizeAnchors(anchors, origin);

    // Top down approach.
    this.#categorizeDocument(document);

    let componentToVisibilityMap = new Map();
    let hrefToComponentMap = new Map();

    let innerWindowHeight = document.ownerGlobal.innerHeight;
    let scrollY = document.ownerGlobal.scrollY;

    // Iterate over the results:
    // - If it's searchbox add event listeners.
    // - If it is a non_ads_link, map its href to component type.
    // - For others, map its component type and check visibility.
    for (let [element, data] of this.#elementToAdDataMap.entries()) {
      if (data.type == "incontent_searchbox") {
        // Bug 1880413: Deprecate hard coding the incontent search box.
        // If searchbox has child elements, observe those, otherwise
        // fallback to its parent element.
        let searchElements = data.childElements.length
          ? data.childElements
          : [element];
        ListenerHelper.addListeners(
          searchElements,
          [
            { eventType: "click", target: data.type },
            {
              eventType: "keydown",
              target: data.type,
              action: "submitted",
              condition: "keydownEnter",
            },
          ],
          data.type
        );
        continue;
      }
      if (data.childElements.length) {
        for (let child of data.childElements) {
          let href = this.#extractHref(child, origin);
          if (href) {
            hrefToComponentMap.set(href, data.type);
          }
        }
      } else {
        let href = this.#extractHref(element, origin);
        if (href) {
          hrefToComponentMap.set(href, data.type);
        }
      }

      // If the component is a non_ads_link, skip visibility checks.
      if (data.type == "non_ads_link") {
        continue;
      }

      // If proxy children were found, check the visibility of all of them
      // otherwise just check the visiblity of the first child.
      let childElements;
      if (data.proxyChildElements.length) {
        childElements = data.proxyChildElements;
      } else if (data.childElements.length) {
        childElements = [data.childElements[0]];
      }

      let count = this.#countVisibleAndHiddenAds(
        element,
        data.adsLoaded,
        childElements,
        innerWindowHeight,
        scrollY
      );
      if (componentToVisibilityMap.has(data.type)) {
        let componentInfo = componentToVisibilityMap.get(data.type);
        componentInfo.adsLoaded += data.adsLoaded;
        componentInfo.adsVisible += count.adsVisible;
        componentInfo.adsHidden += count.adsHidden;
      } else {
        componentToVisibilityMap.set(data.type, {
          adsLoaded: data.adsLoaded,
          adsVisible: count.adsVisible,
          adsHidden: count.adsHidden,
        });
      }
    }

    // Release the DOM elements from the Map.
    this.#elementToAdDataMap.clear();

    return { componentToVisibilityMap, hrefToComponentMap };
  }

  /**
   * Given an element, find the href that is most likely to make the request if
   * the element is clicked. If the element contains a specific data attribute
   * known to contain the url used to make the initial request, use it,
   * otherwise use its href. Specific character conversions are done to mimic
   * conversions likely to take place when urls are observed in network
   * activity.
   *
   * @param {Element} element
   *  The element to inspect.
   * @param {string} origin
   *  The origin for relative urls.
   * @returns {string}
   *   The href of the element.
   */
  #extractHref(element, origin) {
    let href;
    // Prioritize the href from a known data attribute value instead of
    // its href property, as the former is the initial url the page will
    // navigate to before being re-directed to the href.
    for (let name of this.#providerInfo.adServerAttributes) {
      if (
        element.dataset[name] &&
        this.#providerInfo.extraAdServersRegexps.some(regexp =>
          regexp.test(element.dataset[name])
        )
      ) {
        href = element.dataset[name];
        break;
      }
    }
    // If a data attribute value was not found, fallback to the href.
    href = href ?? element.getAttribute("href");
    if (!href) {
      return "";
    }

    let url = URL.parse(href, origin);
    if (!url || (url.protocol !== "https:" && url.protocol !== "http:")) {
      return "";
    }

    return url.href;
  }

  /**
   * Given a list of anchor elements, group them into ad components.
   *
   * The first step in the process is to check if the anchor should be
   * inspected. This is based on whether it contains an href or a
   * data-attribute values that matches an ad link, or if it contains a
   * pattern caught by a components included regular expression.
   *
   * Determine which component it belongs to and the number of matches for
   * the component. The heuristic is described in findDataForAnchor.
   * If there was a result and we haven't seen it before, save it in
   * elementToAdDataMap.
   *
   * @param {HTMLCollectionOf<HTMLAnchorElement>} anchors
   *  The list of anchors to inspect.
   * @param {string} origin
   *  The origin of the document the anchors belong to.
   */
  #categorizeAnchors(anchors, origin) {
    for (let anchor of anchors) {
      if (this.#shouldInspectAnchor(anchor, origin)) {
        let result;
        try {
          // We use a schema to ensure the values for each search provider
          // aligns to what is expected, but tests don't enforce the schema
          // and thus, can technically input faulty values.
          result = this.#findDataForAnchor(anchor);
        } catch (ex) {
          lazy.logConsole.error("Could not find data for anchor:", ex);
          continue;
        }
        if (result) {
          this.#recordElementData(result.element, {
            type: result.type,
            count: result.count,
            proxyChildElements: result.proxyChildElements,
            childElements: result.childElements,
          });
        }
        if (result?.relatedElements?.length) {
          // Bug 1880413: Deprecate related elements.
          // Bottom-up approach with related elements are only used for
          // non-link elements related to ads, like carousel arrows.
          ListenerHelper.addListeners(
            result.relatedElements,
            [
              {
                action: "expanded",
                eventType: "click",
              },
            ],
            result.type
          );
        }
      }
    }
  }

  /**
   * Find components from the document object. This is mostly relevant for
   * components that are non-ads and don't have an obvious regular expression
   * that could match the pattern of the href.
   *
   * @param {Document} document
   */
  #categorizeDocument(document) {
    // using the subset of components that are top down,
    // go through each one.
    for (let component of this.#topDownComponents) {
      // Top-down searches must have the topDown attribute.
      if (!component.topDown) {
        continue;
      }
      // Top down searches must include a parent.
      if (!component.included?.parent) {
        continue;
      }
      let parents = document.querySelectorAll(
        component.included.parent.selector
      );
      if (parents.length) {
        let eventListeners = component.included.parent.eventListeners;
        if (eventListeners?.length) {
          ListenerHelper.addListeners(parents, eventListeners, component.type);
        }
        for (let parent of parents) {
          // Bug 1880413: Deprecate related elements.
          // Top-down related elements are either used for auto-suggested
          // elements of a searchbox, or elements on a page which we can't
          // find through a bottom up approach but we want an add a listener,
          // like carousels with arrows.
          if (component.included.related?.selector) {
            let relatedElements = parent.querySelectorAll(
              component.included.related.selector
            );
            if (relatedElements.length) {
              // For the search box, related elements with event listeners are
              // auto-suggested terms. For everything else (e.g. carousels)
              // they are expanded.
              ListenerHelper.addListeners(
                relatedElements,
                [
                  {
                    action:
                      component.type == "incontent_searchbox"
                        ? "submitted"
                        : "expanded",
                    eventType: "click",
                  },
                ],
                component.type
              );
            }
          }
          if (component.included.children) {
            for (let child of component.included.children) {
              let childElements = parent.querySelectorAll(child.selector);
              if (childElements.length) {
                if (child.eventListeners) {
                  childElements = Array.from(childElements);
                  ListenerHelper.addListeners(
                    childElements,
                    child.eventListeners,
                    child.type ?? component.type
                  );
                }
                if (!child.skipCount) {
                  this.#recordElementData(parent, {
                    type: component.type,
                    childElements: Array.from(childElements),
                  });
                }
              }
            }
          } else if (!component.included.parent.skipCount) {
            this.#recordElementData(parent, {
              type: component.type,
            });
          }
        }
      }
    }
  }

  /**
   * Evaluates whether an anchor should be inspected based on matching
   * regular expressions on either its href or specified data-attribute values.
   *
   * @param {HTMLAnchorElement} anchor
   * @param {string} origin
   * @returns {boolean}
   */
  #shouldInspectAnchor(anchor, origin) {
    let href = anchor.getAttribute("href");
    if (!href) {
      return false;
    }

    // Some hrefs might be relative.
    if (!href.startsWith("https://") && !href.startsWith("http://")) {
      href = origin + href;
    }

    let regexps = this.#providerInfo.extraAdServersRegexps;
    // Anchors can contain ad links in a data-attribute.
    for (let name of this.#providerInfo.adServerAttributes) {
      let attributeValue = anchor.dataset[name];
      if (
        attributeValue &&
        regexps.some(regexp => regexp.test(attributeValue))
      ) {
        return true;
      }
    }
    // Anchors can contain ad links in a specific href.
    if (regexps.some(regexp => regexp.test(href))) {
      return true;
    }
    return false;
  }

  /**
   * Find the component data for an anchor.
   *
   * To categorize the anchor, we iterate over the list of possible components
   * the anchor could be categorized. If the component is default, we skip
   * checking because the fallback option for all anchor links is the default.
   *
   * First, get the "parent" of the anchor which best represents the DOM element
   * that contains the anchor links for the component and no other component.
   * This parent will be cached so that other anchors that share the same
   * parent can be counted together.
   *
   * The check for a parent is a loop because we can define more than one best
   * parent since on certain SERPs, it's possible for a "better" DOM element
   * parent to appear occassionally.
   *
   * If no parent is found, skip this component.
   *
   * If a parent was found, check for specific child elements.
   *
   * Finding child DOM elements of a parent is optional. One reason to do so is
   * to use child elements instead of anchor links to count the number of ads for
   * a component via the `countChildren` property. This is provided because some ads
   * (i.e. carousels) have multiple ad links in a single child element that go to the
   * same location. In this scenario, all instances of the child are recorded as ads.
   * Subsequent anchor elements that map to the same parent are ignored.
   *
   * Whether or not a child was found, return the information that was found,
   * including whether or not all child elements were counted instead of anchors.
   *
   * If another anchor belonging to a parent that was previously recorded is the input
   * for this function, we either increment the ad count by 1 or don't increment the ad
   * count because the parent used `countChildren` completed the calculation in a
   * previous step.
   *
   * @param {HTMLAnchorElement} anchor
   *  The anchor to be inspected.
   * @returns {object | null}
   *  An object containing the element representing the root DOM element for
   *  the component, the type of component, how many ads were counted,
   *  and whether or not the count was of all the children.
   * @throws {Error}
   *  Will throw an error if certain properties of a component are missing.
   *  Required properties are listed in search-telemetry-v2-schema.json.
   */
  #findDataForAnchor(anchor) {
    for (let component of this.#providerInfo.components) {
      // First, check various conditions for skipping a component.

      // A component should always have at least one included statement.
      if (!component.included) {
        continue;
      }

      // Top down searches are done after the bottom up search.
      if (component.topDown) {
        continue;
      }

      // The default component doesn't need to be checked,
      // as it will be the fallback option.
      if (component.default) {
        continue;
      }

      // The anchor shouldn't belong to an excluded parent component if one
      // is provided.
      if (
        component.excluded?.parent?.selector &&
        anchor.closest(component.excluded.parent.selector)
      ) {
        continue;
      }

      // All components with included should have a parent entry.
      if (!component.included.parent) {
        continue;
      }

      // Find the parent of the anchor.
      let parent = anchor.closest(component.included.parent.selector);

      if (!parent) {
        continue;
      }

      // If a parent was found, we may want to ignore reporting the element
      // to telemetry.
      if (component.included.parent.skipCount) {
        return null;
      }

      // If we've already inspected the parent, add the child element to the
      // list of anchors. Don't increment the ads loaded count, as we only care
      // about grouping the anchor with the correct parent.
      if (this.#elementToAdDataMap.has(parent)) {
        return {
          element: parent,
          childElements: [anchor],
        };
      }

      let relatedElements = [];
      if (component.included.related?.selector) {
        relatedElements = parent.querySelectorAll(
          component.included.related.selector
        );
      }

      // If the component has no defined children, return the parent element.
      if (component.included.children) {
        // Look for the first instance of a matching child selector.
        for (let child of component.included.children) {
          // If counting by child, get all of them at once.
          if (child.countChildren) {
            let proxyChildElements = parent.querySelectorAll(child.selector);
            if (child.skipCount) {
              return null;
            }
            if (proxyChildElements.length) {
              return {
                element: parent,
                type: child.type ?? component.type,
                proxyChildElements: Array.from(proxyChildElements),
                count: proxyChildElements.length,
                childElements: [anchor],
                relatedElements,
              };
            }
          } else if (parent.querySelector(child.selector)) {
            if (child.skipCount) {
              return null;
            }
            return {
              element: parent,
              type: child.type ?? component.type,
              childElements: [anchor],
              relatedElements,
            };
          }
        }
      }
      // If no children were defined for this component, or none were found
      // in the DOM, use the default definition.
      return {
        element: parent,
        type: component.type,
        childElements: [anchor],
        relatedElements,
      };
    }
    // If no component was found, use default values.
    return {
      element: anchor,
      type: this.#defaultComponent.type,
    };
  }

  /**
   * Determines whether or not an ad was visible or hidden.
   *
   * An ad is considered visible if the parent element containing the
   * component has non-zero dimensions, and all child element in the
   * component have non-zero dimensions and mostly (50% height) fits within
   * the window at the time when the impression was taken. If the element is to
   * the left of the visible area, we also consider it viewed as it's possible
   * the user interacted with a carousel which typically scrolls new content
   * leftward.
   *
   * For some components, like text ads, we don't send every child
   * element for visibility, just the first text ad. For other components
   * like carousels, we send all child elements because we do care about
   * counting how many elements of the carousel were visible.
   *
   * @param {Element} element
   *  Element to be inspected
   * @param {number} adsLoaded
   *  Number of ads initially determined to be loaded for this element.
   * @param {Array<Element>} childElements
   *  List of children belonging to element.
   * @param {number} innerWindowHeight
   *  Current height of the window containing the elements.
   * @param {number} scrollY
   *  Current distance the window has been scrolled.
   * @returns {object}
   *  Contains adsVisible which is the number of ads shown for the element
   *  and adsHidden, the number of ads not visible to the user.
   */
  #countVisibleAndHiddenAds(
    element,
    adsLoaded,
    childElements,
    innerWindowHeight,
    scrollY
  ) {
    let elementRect =
      element.ownerGlobal.windowUtils.getBoundsWithoutFlushing(element);

    // If the parent element is not visible, assume all ads within are
    // also not visible.
    if (
      !element.checkVisibility({
        visibilityProperty: true,
        opacityProperty: true,
      })
    ) {
      Glean.serp.adsBlockedCount.hidden_parent.add();
      return {
        adsVisible: 0,
        adsHidden: adsLoaded,
      };
    }

    // If an ad is far above the possible visible area of a window, an
    // adblocker might be doing it as a workaround for blocking the ad.
    if (
      elementRect.bottom < 0 &&
      innerWindowHeight + scrollY + elementRect.bottom < 0
    ) {
      Glean.serp.adsBlockedCount.beyond_viewport.add();
      return {
        adsVisible: 0,
        adsHidden: adsLoaded,
      };
    }

    // If the element has no child elements, check if the element
    // was ever viewed by the user at this moment.
    if (!childElements?.length) {
      // Most ads don't require horizontal scrolling to view it. Thus, we only
      // check if it could've appeared with some vertical scrolling.
      let visible = VisibilityHelper.elementWasVisibleVertically(
        elementRect,
        innerWindowHeight,
        VISIBILITY_THRESHOLD
      );
      return {
        adsVisible: visible ? 1 : 0,
        adsHidden: 0,
      };
    }

    let adsVisible = 0;
    let adsHidden = 0;
    for (let child of childElements) {
      if (
        !child.checkVisibility({
          visibilityProperty: true,
          opacityProperty: true,
        })
      ) {
        adsHidden += 1;
        Glean.serp.adsBlockedCount.hidden_child.add();
        continue;
      }

      let itemRect =
        child.ownerGlobal.windowUtils.getBoundsWithoutFlushing(child);
      // If the child element is to the right of the containing element and
      // can't be viewed, skip it. We do this check because some elements like
      // carousels can hide additional content horizontally. We don't apply the
      // same logic if the element is to the left because we assume carousels
      // scroll elements to the left when the user wants to see more contents.
      // Thus, the elements to the left must've been visible.
      if (
        !VisibilityHelper.childElementWasVisibleHorizontally(
          elementRect,
          itemRect,
          VISIBILITY_THRESHOLD
        )
      ) {
        continue;
      }

      // If the height of child element is not visible, skip it.
      if (
        !VisibilityHelper.elementWasVisibleVertically(
          itemRect,
          innerWindowHeight,
          VISIBILITY_THRESHOLD
        )
      ) {
        continue;
      }
      ++adsVisible;
    }

    return {
      adsVisible,
      adsHidden,
    };
  }

  /**
   * Caches ad data for a DOM element. The key of the map is by Element rather
   * than Component for fast lookup on whether an Element has been already been
   * categorized as a component. Subsequent calls to this passing the same
   * element will update the list of child elements.
   *
   * @param {Element} element
   *  The element considered to be the root for the component.
   * @param {object} params
   *  Various parameters that can be recorded. Whether the input values exist
   *  or not depends on which component was found, which heuristic should be used
   *  to determine whether an ad was visible, and whether we've already seen this
   *  element.
   * @param {string | null} params.type
   *  The type of component.
   * @param {number} params.count
   *  The number of ads found for a component. The number represents either
   *  the number of elements that match an ad expression or the number of DOM
   *  elements containing an ad link.
   * @param {Array<Element>} params.proxyChildElements
   *  An array of DOM elements that should be inspected for visibility instead
   *  of the actual child elements, possibly because they are grouped.
   * @param {Array<Element>} params.childElements
   *  An array of DOM elements to inspect.
   */
  #recordElementData(
    element,
    { type, count = 1, proxyChildElements = [], childElements = [] } = {}
  ) {
    if (this.#elementToAdDataMap.has(element)) {
      let recordedValues = this.#elementToAdDataMap.get(element);
      if (childElements.length) {
        recordedValues.childElements =
          recordedValues.childElements.concat(childElements);
      }
    } else {
      this.#elementToAdDataMap.set(element, {
        type,
        adsLoaded: count,
        proxyChildElements,
        childElements,
      });
    }
  }
}

export class VisibilityHelper {
  /**
   * Whether the element was vertically visible. It assumes elements above the
   * viewable area were visible at some point in time.
   *
   * @param {DOMRect} rect
   *   The bounds of the element.
   * @param {number} innerWindowHeight
   *   The height of the window.
   * @param {number} threshold
   *   What percentage of the element should vertically be visible.
   * @returns {boolean}
   *   Whether the element was visible.
   */
  static elementWasVisibleVertically(rect, innerWindowHeight, threshold) {
    return rect.top + rect.height * threshold <= innerWindowHeight;
  }

  /**
   * Whether the child element was horizontally visible. It assumes elements to
   * the left were visible at some point in time.
   *
   * @param {DOMRect} parentRect
   *   The bounds of the element that contains the child.
   * @param {DOMRect} childRect
   *   The bounds of the child element.
   * @param {number} threshold
   *   What percentage of the child element should horizontally be visible.
   * @returns {boolean}
   *   Whether the child element was visible.
   */
  static childElementWasVisibleHorizontally(parentRect, childRect, threshold) {
    return (
      childRect.left + childRect.width * threshold <=
      parentRect.left + parentRect.width
    );
  }
}

/**
 * An object indicating which elements to examine for domains to extract and
 * which heuristic technique to use to extract that element's domain.
 *
 * @typedef {object} ExtractorInfo
 * @property {string} selectors
 *  A string representing the CSS selector that targets the elements on the
 *  page that contain domains we want to extract.
 * @property {string} method
 *  A string representing which domain extraction heuristic to use.
 *  One of: "href", "dataAttribute" or "textContent".
 * @property {object | null} options
 *  Options related to the domain extraction heuristic used.
 * @property {string | null} options.dataAttributeKey
 *  The key name of the data attribute to lookup.
 * @property {string | null} options.queryParamKey
 *  The key name of the query param value to lookup.
 * @property {boolean | null} options.queryParamValueIsHref
 *  Whether the query param value is expected to contain an href.
 */

/**
 * DomainExtractor examines elements on a page to retrieve the domains.
 */
class DomainExtractor {
  /**
   * Extract domains from the page using an array of information pertaining to
   * the SERP.
   *
   * @param {Document} document
   *  The document for the SERP we are extracting domains from.
   * @param {Array<ExtractorInfo>} extractorInfos
   *  Information used to target the domains we need to extract.
   * @param {string} providerName
   *  Name of the search provider.
   * @return {Set<string>}
   *  A set of the domains extracted from the page.
   */
  extractDomainsFromDocument(document, extractorInfos, providerName) {
    let extractedDomains = new Set();
    if (!extractorInfos?.length) {
      return extractedDomains;
    }

    for (let extractorInfo of extractorInfos) {
      if (!extractorInfo.selectors) {
        continue;
      }

      let elements = document.querySelectorAll(extractorInfo.selectors);
      if (!elements.length) {
        continue;
      }

      switch (extractorInfo.method) {
        case "href": {
          // Origin is used in case a URL needs to be made absolute.
          let origin = new URL(document.documentURI).origin;
          this.#fromElementsConvertHrefsIntoDomains(
            elements,
            origin,
            providerName,
            extractedDomains,
            extractorInfo.options?.queryParamKey,
            extractorInfo.options?.queryParamValueIsHref
          );
          break;
        }
        case "dataAttribute": {
          this.#fromElementsRetrieveDataAttributeValues(
            elements,
            providerName,
            extractorInfo.options?.dataAttributeKey,
            extractedDomains
          );
          break;
        }
        case "textContent": {
          this.#fromElementsRetrieveTextContent(
            elements,
            extractedDomains,
            providerName
          );
          break;
        }
      }
    }

    return extractedDomains;
  }

  /**
   * Given a list of elements, extract domains using href attributes. If the
   * URL in the href includes the specified query param, the domain will be
   * that query param's value. Otherwise it will be the hostname of the href
   * attribute's URL.
   *
   * @param {NodeList<Element>} elements
   *  A list of elements from the page whose href attributes we want to
   *  inspect.
   * @param {string} origin
   *  Origin of the current page.
   * @param {string} providerName
   *  The name of the search provider.
   * @param {Set<string>} extractedDomains
   *  The result set of domains extracted from the page.
   * @param {string | null} queryParam
   *  An optional query param to search for in an element's href attribute.
   * @param {boolean | null} queryParamValueIsHref
   *  Whether the query param value is expected to contain an href.
   */
  #fromElementsConvertHrefsIntoDomains(
    elements,
    origin,
    providerName,
    extractedDomains,
    queryParam,
    queryParamValueIsHref
  ) {
    for (let element of elements) {
      if (this.#exceedsThreshold(extractedDomains.size)) {
        return;
      }

      let href = element.getAttribute("href");

      let url = URL.parse(href, origin);
      if (!url) {
        continue;
      }

      // Ignore non-standard protocols.
      if (url.protocol != "https:" && url.protocol != "http:") {
        continue;
      }

      if (queryParam) {
        let paramValue = url.searchParams.get(queryParam);
        if (queryParamValueIsHref) {
          paramValue = URL.parse(paramValue)?.hostname;
          if (!paramValue) {
            continue;
          }
          paramValue = this.#processDomain(paramValue, providerName);
        }
        if (paramValue && !extractedDomains.has(paramValue)) {
          extractedDomains.add(paramValue);
        }
      } else if (url.hostname) {
        let processedHostname = this.#processDomain(url.hostname, providerName);
        if (processedHostname && !extractedDomains.has(processedHostname)) {
          extractedDomains.add(processedHostname);
        }
      }
    }
  }

  /**
   * Given a list of elements, examine each for the specified data attribute.
   * If found, add that data attribute's value to the result set of extracted
   * domains as is.
   *
   * @param {NodeList<Element>} elements
   *  A list of elements from the page whose data attributes we want to
   *  inspect.
   * @param {string} providerName
   *  The name of the search provider.
   * @param {string} attribute
   *  The name of a data attribute to search for within an element.
   * @param {Set<string>} extractedDomains
   *  The result set of domains extracted from the page.
   */
  #fromElementsRetrieveDataAttributeValues(
    elements,
    providerName,
    attribute,
    extractedDomains
  ) {
    for (let element of elements) {
      if (this.#exceedsThreshold(extractedDomains.size)) {
        return;
      }
      let value = element.dataset[attribute];
      value = this.#processDomain(value, providerName);
      if (value && !extractedDomains.has(value)) {
        extractedDomains.add(value);
      }
    }
  }

  /**
   * Given a list of elements, examine the text content for each element, which
   * may be 1) a URL from which we can extract a domain or 2) text we can fix
   * up to create a best guess as to a URL. If either condition is met, we add
   * the domain to the result set.
   *
   * @param {NodeList<Element>} elements
   *  A list of elements from the page whose text content we want to inspect.
   * @param {Set<string>} extractedDomains
   *  The result set of domains extracted from the page.
   * @param {string} providerName
   *  The name of the search provider.
   */
  #fromElementsRetrieveTextContent(elements, extractedDomains, providerName) {
    // Not an exhaustive regex, but it fits our purpose for this method.
    const LOOSE_URL_REGEX =
      /^(?:https?:\/\/)?(?:www\.)?(?:[\w\-]+\.)+(?:[\w\-]{2,})/i;

    // Known but acceptable limitations to this function, where the return
    // value won't be correctly fixed up:
    //   1) A url is embedded within other text. Ex: "xkcd.com is cool."
    //   2) The url contains legal but unusual characters. Ex: $ ! * '
    function fixup(textContent) {
      return textContent
        .toLowerCase()
        .replaceAll(" ", "")
        .replace(/\.$/, "")
        .concat(".com");
    }

    for (let element of elements) {
      if (this.#exceedsThreshold(extractedDomains.size)) {
        return;
      }
      let textContent = element.textContent;
      if (!textContent) {
        continue;
      }

      let domain;
      if (LOOSE_URL_REGEX.test(textContent)) {
        // Creating a new URL object will throw if the protocol is missing.
        if (!/^https?:\/\//.test(textContent)) {
          textContent = "https://" + textContent;
        }

        domain = URL.parse(textContent)?.hostname;
        if (!domain) {
          domain = fixup(textContent);
        }
      } else {
        domain = fixup(textContent);
      }

      let processedDomain = this.#processDomain(domain, providerName);
      if (processedDomain && !extractedDomains.has(processedDomain)) {
        extractedDomains.add(processedDomain);
      }
    }
  }

  /**
   * Processes a raw domain extracted from the SERP into its final form before
   * categorization.
   *
   * @param {string} domain
   *   The domain extracted from the page.
   * @param {string} providerName
   *   The provider associated with the page.
   * @returns {string}
   *   The domain without any subdomains.
   */
  #processDomain(domain, providerName) {
    if (
      domain.startsWith(`${providerName}.`) ||
      domain.includes(`.${providerName}.`)
    ) {
      return "";
    }
    return this.#stripDomainOfSubdomains(domain);
  }

  /**
   * Helper to strip domains of any subdomains.
   *
   * @param {string} domain
   *   The domain to strip of any subdomains.
   * @returns {object} browser
   *   The given domain with any subdomains removed.
   */
  #stripDomainOfSubdomains(domain) {
    let tld;
    // Can throw an exception if the input has too few domain levels.
    try {
      tld = Services.eTLD.getKnownPublicSuffixFromHost(domain);
    } catch (ex) {
      return "";
    }

    let domainWithoutTLD = domain.substring(0, domain.length - tld.length);
    let secondLevelDomain = domainWithoutTLD.split(".").at(-2);

    return secondLevelDomain ? `${secondLevelDomain}.${tld}` : "";
  }

  /**
   * Per a request from Data Science, we need to limit the number of domains
   * categorized to 10 non-ad domains and 10 ad domains.
   *
   * @param {number} nDomains The number of domains processed.
   * @returns {boolean} Whether or not the threshold was exceeded.
   */
  #exceedsThreshold(nDomains) {
    return nDomains >= CATEGORIZATION_SETTINGS.MAX_DOMAINS_TO_CATEGORIZE;
  }
}

export const domainExtractor = new DomainExtractor();
const searchProviders = new SearchProviders();
const searchAdImpression = new SearchAdImpression();

const documentToEventCallbackMap = new WeakMap();
const documentToRemoveEventListenersMap = new WeakMap();
const documentToSubmitMap = new WeakMap();

/**
 * SearchTelemetryChild monitors for pages that are partner searches, and
 * looks through them to find links which looks like adverts and sends back
 * a notification to SearchTelemetry for possible telemetry reporting.
 *
 * Only the partner details and the fact that at least one ad was found on the
 * page are returned to SearchTelemetry. If no ads are found, no notification is
 * given.
 */
export class SearchSERPTelemetryChild extends JSWindowActorChild {
  /**
   * Amount of time to wait after a page event before examining the page
   * for ads.
   *
   * @type {number | null}
   */
  #adTimeout;

  /**
   * Determines if there is a provider that matches the supplied URL and returns
   * the information associated with that provider.
   *
   * @param {string} url The url to check
   * @returns {Array | null} Returns null if there's no match, otherwise an array
   *   of provider name and the provider information.
   */
  _getProviderInfoForUrl(url) {
    return searchProviders.info?.find(info => info.searchPageRegexp.test(url));
  }

  /**
   * Checks to see if the page is a partner and has an ad link within it. If so,
   * it will notify SearchTelemetry.
   */
  _checkForAdLink(eventType) {
    try {
      if (!this.contentWindow) {
        return;
      }
    } catch (ex) {
      // unload occurred before the timer expired
      return;
    }

    let doc = this.document;
    let url = doc.documentURI;
    let providerInfo = this._getProviderInfoForUrl(url);
    if (!providerInfo) {
      return;
    }

    let regexps = providerInfo.extraAdServersRegexps;
    let anchors = doc.getElementsByTagName("a");
    let hasAds = false;
    for (let anchor of anchors) {
      if (!anchor.href) {
        continue;
      }
      for (let name of providerInfo.adServerAttributes) {
        hasAds = regexps.some(regexp => regexp.test(anchor.dataset[name]));
        if (hasAds) {
          break;
        }
      }
      if (!hasAds) {
        hasAds = regexps.some(regexp => regexp.test(anchor.href));
      }
      if (hasAds) {
        break;
      }
    }

    // If there are no ads in hrefs, they could be present in a subframe.
    if (!hasAds) {
      hasAds = this.#checkForSponsoredSubframes(this.document, providerInfo);
    }

    if (hasAds) {
      this.sendAsyncMessage("SearchTelemetry:PageInfo", {
        hasAds,
        url,
      });
    }

    if (
      providerInfo.components?.length &&
      (eventType == "load" || eventType == "pageshow")
    ) {
      // Start performance measurements.
      let start = ChromeUtils.now();
      let timerId = Glean.serp.categorizationDuration.start();

      let pageActionCallback = info => {
        if (info.action == "submitted") {
          documentToSubmitMap.set(doc, true);
        }
        this.sendAsyncMessage("SearchTelemetry:Action", {
          target: info.target,
          action: info.action,
        });
      };
      documentToEventCallbackMap.set(this.document, pageActionCallback);

      let componentToVisibilityMap, hrefToComponentMap;
      try {
        let result = searchAdImpression.categorize(anchors, doc);
        componentToVisibilityMap = result.componentToVisibilityMap;
        hrefToComponentMap = result.hrefToComponentMap;
      } catch (e) {
        // Cancel the timer if an error encountered.
        Glean.serp.categorizationDuration.cancel(timerId);
      }

      if (componentToVisibilityMap && hrefToComponentMap) {
        // End measurements.
        ChromeUtils.addProfilerMarker(
          "SearchSERPTelemetryChild._checkForAdLink",
          start,
          "Checked anchors for visibility"
        );
        Glean.serp.categorizationDuration.stopAndAccumulate(timerId);
        this.sendAsyncMessage("SearchTelemetry:AdImpressions", {
          adImpressions: componentToVisibilityMap,
          hrefToComponentMap,
          url,
        });
      }
    }

    if (
      lazy.serpEventTelemetryCategorization &&
      lazy.serpEventTelemetryCategorizationRegionEnabled &&
      providerInfo.domainExtraction &&
      (eventType == "load" || eventType == "pageshow")
    ) {
      let start = ChromeUtils.now();
      let nonAdDomains = domainExtractor.extractDomainsFromDocument(
        doc,
        providerInfo.domainExtraction.nonAds,
        providerInfo.telemetryId
      );

      let adDomains = domainExtractor.extractDomainsFromDocument(
        doc,
        providerInfo.domainExtraction.ads,
        providerInfo.telemetryId
      );

      this.sendAsyncMessage("SearchTelemetry:Domains", {
        url,
        nonAdDomains,
        adDomains,
      });

      ChromeUtils.addProfilerMarker(
        "SearchSERPTelemetryChild._checkForAdLink",
        start,
        "Extract domains from elements"
      );
    }
  }

  /**
   * Checks for the presence of certain components on the page that are
   * required for recording the page impression.
   */
  #checkForPageImpressionComponents() {
    let url = this.document.documentURI;
    let providerInfo = this._getProviderInfoForUrl(url);
    if (providerInfo.components?.length) {
      searchAdImpression.providerInfo = providerInfo;
      let start = ChromeUtils.now();
      let shoppingTabDisplayed = searchAdImpression.hasShoppingTab(
        this.document
      );
      ChromeUtils.addProfilerMarker(
        "SearchSERPTelemetryChild.#recordImpression",
        start,
        "Checked for shopping tab"
      );
      this.sendAsyncMessage("SearchTelemetry:PageImpression", {
        url,
        shoppingTabDisplayed,
      });
    }
  }

  #checkForSponsoredSubframes(document, providerInfo) {
    if (!providerInfo.subframes?.length) {
      return false;
    }

    let subframes = document.querySelectorAll("iframe");
    for (let subframe of subframes) {
      let foundMatch = providerInfo.subframes.some(obj =>
        obj.regexp?.test(subframe.src)
      );
      if (
        foundMatch &&
        subframe.checkVisibility({
          visibilityProperty: true,
          contentVisibilityAuto: true,
        })
      ) {
        return true;
      }
    }

    return false;
  }

  #removeEventListeners() {
    let callbacks = documentToRemoveEventListenersMap.get(this.document);
    if (callbacks) {
      for (let callback of callbacks) {
        callback();
      }
      documentToRemoveEventListenersMap.delete(this.document);
    }
  }

  /**
   * Handles events received from the actor child notifications.
   *
   * @param {object} event The event details.
   */
  handleEvent(event) {
    if (!this.#urlIsSERP()) {
      return;
    }
    switch (event.type) {
      case "pageshow": {
        // If a page is loaded from the bfcache, we won't get a "DOMContentLoaded"
        // event, so we need to rely on "pageshow" in this case. Note: we do this
        // so that we remain consistent with the *.in-content:sap* count for the
        // SEARCH_COUNTS histogram.
        if (event.persisted) {
          this.#checkForPageImpressionComponents();
          this.#check(event.type);
        }
        break;
      }
      case "DOMContentLoaded": {
        this.#check(event.type);
        break;
      }
      case "load": {
        this.#checkForPageImpressionComponents();
        // We check both DOMContentLoaded and load in case the page has
        // taken a long time to load and the ad is only detected on load.
        // We still check at DOMContentLoaded because if the page hasn't
        // finished loading and the user navigates away, we still want to know
        // if there were ads on the page or not at that time.
        this.#check(event.type);
        break;
      }
      case "pagehide": {
        let callbacks = documentToRemoveEventListenersMap.get(this.document);
        if (callbacks) {
          for (let removeEventListenerCallback of callbacks) {
            removeEventListenerCallback();
          }
          documentToRemoveEventListenersMap.delete(this.document);
        }
        this.#cancelCheck();
        break;
      }
    }
  }

  async receiveMessage(message) {
    switch (message.name) {
      case "SearchSERPTelemetry:WaitForSPAPageLoad":
        lazy.setTimeout(() => {
          this.#checkForPageImpressionComponents();
          this._checkForAdLink("load");
        }, Services.cpmm.sharedData.get(SEARCH_TELEMETRY_SHARED.SPA_LOAD_TIMEOUT));
        break;
      case "SearchSERPTelemetry:StopTrackingDocument":
        this.#removeDocumentFromSubmitMap();
        this.#removeEventListeners();
        break;
      case "SearchSERPTelemetry:DidSubmit":
        return this.#didSubmit();
    }
    return null;
  }

  #didSubmit() {
    return documentToSubmitMap.get(this.document);
  }

  #removeDocumentFromSubmitMap() {
    documentToSubmitMap.delete(this.document);
  }

  #urlIsSERP() {
    let provider = this._getProviderInfoForUrl(this.document.documentURI);
    if (provider) {
      // Some URLs can match provider info but also be the provider's homepage
      // instead of a SERP.
      // e.g. https://example.com/ vs. https://example.com/?foo=bar
      // To check this, we look for the presence of the query parameter
      // that contains a search term.
      let queries = URL.fromURI(this.document.documentURIObject).searchParams;
      for (let queryParamName of provider.queryParamNames) {
        if (queries.get(queryParamName)) {
          return true;
        }
      }
    }
    return false;
  }

  #cancelCheck() {
    if (this._waitForContentTimeout) {
      lazy.clearTimeout(this._waitForContentTimeout);
    }
  }

  #check(eventType) {
    if (!this.#adTimeout) {
      this.#adTimeout = Services.cpmm.sharedData.get(
        SEARCH_TELEMETRY_SHARED.LOAD_TIMEOUT
      );
    }
    this.#cancelCheck();
    this._waitForContentTimeout = lazy.setTimeout(() => {
      this._checkForAdLink(eventType);
    }, this.#adTimeout);
  }
}
PK