Issue 6665 - Abstract element hiding container logic into its own module

lib/elemHide.js

Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -16,174 +16,50 @@
  */
 
 "use strict";
 
 /**
  * @fileOverview Element hiding implementation.
  */
 
+const {ContentFilterModule} = require("./contentFilterModule");
 const {ElemHideExceptions} = require("./elemHideExceptions");
 const {FilterNotifier} = require("./filterNotifier");
 
 /**
- * Lookup table, active flag, by filter by domain.
- * (Only contains filters that aren't unconditionally matched for all domains.)
- * @type {Map.<string,Map.<Filter,boolean>>}
- */
-let filtersByDomain = new Map();
-
-/**
- * Lookup table, filter by selector. (Only used for selectors that are
- * unconditionally matched for all domains.)
- * @type {Map.<string,Filter>}
- */
-let filterBySelector = new Map();
-
-/**
- * This array caches the keys of filterBySelector table (selectors
- * which unconditionally apply on all domains). It will be null if the
- * cache needs to be rebuilt.
- * @type {?string[]}
- */
-let unconditionalSelectors = null;
-
-/**
- * Map to be used instead when a filter has a blank domains property.
- * @type {Map.<string,boolean>}
- * @const
- */
-let defaultDomains = new Map([["", true]]);
-
-/**
- * Set containing known element hiding filters
- * @type {Set.<ElemHideFilter>}
- */
-let knownFilters = new Set();
-
-/**
- * Adds a filter to the lookup table of filters by domain.
- * @param {Filter} filter
- */
-function addToFiltersByDomain(filter)
-{
-  let domains = filter.domains || defaultDomains;
-  for (let [domain, isIncluded] of domains)
-  {
-    // There's no need to note that a filter is generically disabled.
-    if (!isIncluded && domain == "")
-      continue;
-
-    let filters = filtersByDomain.get(domain);
-    if (!filters)
-      filtersByDomain.set(domain, filters = new Map());
-    filters.set(filter, isIncluded);
-  }
-}
-
-/**
- * Returns a list of selectors that apply on each website unconditionally.
- * @returns {string[]}
- */
-function getUnconditionalSelectors()
-{
-  if (!unconditionalSelectors)
-    unconditionalSelectors = [...filterBySelector.keys()];
-
-  return unconditionalSelectors;
-}
-
-ElemHideExceptions.on("added", ({selector}) =>
-{
-  // If this is the first exception for a previously unconditionally applied
-  // element hiding selector we need to take care to update the lookups.
-  let unconditionalFilterForSelector = filterBySelector.get(selector);
-  if (unconditionalFilterForSelector)
-  {
-    addToFiltersByDomain(unconditionalFilterForSelector);
-    filterBySelector.delete(selector);
-    unconditionalSelectors = null;
-  }
-});
-
-/**
  * Container for element hiding filters
  * @class
  */
-exports.ElemHide = {
-  /**
-   * Removes all known filters
-   */
+exports.ElemHide = Object.assign(new ContentFilterModule(), {
   clear()
   {
-    for (let collection of [filtersByDomain, filterBySelector, knownFilters])
-      collection.clear();
+    ContentFilterModule.prototype.clear.call(this);
 
-    unconditionalSelectors = null;
     FilterNotifier.emit("elemhideupdate");
   },
 
-  /**
-   * Add a new element hiding filter
-   * @param {ElemHideFilter} filter
-   */
   add(filter)
   {
-    if (knownFilters.has(filter))
-      return;
-
-    let {selector} = filter;
+    let {size} = this._knownFilters;
 
-    if (!(filter.domains || ElemHideExceptions.hasExceptions(selector)))
-    {
-      // The new filter's selector is unconditionally applied to all domains
-      filterBySelector.set(selector, filter);
-      unconditionalSelectors = null;
-    }
-    else
-    {
-      // The new filter's selector only applies to some domains
-      addToFiltersByDomain(filter);
-    }
+    ContentFilterModule.prototype.add.call(this, filter);
 
-    knownFilters.add(filter);
-    FilterNotifier.emit("elemhideupdate");
+    if (size != this._knownFilters.size)
+      FilterNotifier.emit("elemhideupdate");
   },
 
-  /**
-   * Removes an element hiding filter
-   * @param {ElemHideFilter} filter
-   */
   remove(filter)
   {
-    if (!knownFilters.has(filter))
-      return;
-
-    let {selector} = filter;
+    let {size} = this._knownFilters;
 
-    // Unconditially applied element hiding filters
-    if (filterBySelector.get(selector) == filter)
-    {
-      filterBySelector.delete(selector);
-      unconditionalSelectors = null;
-    }
-    // Conditionally applied element hiding filters
-    else
-    {
-      let domains = filter.domains || defaultDomains;
-      for (let domain of domains.keys())
-      {
-        let filters = filtersByDomain.get(domain);
-        if (filters)
-          filters.delete(filter);
-      }
-    }
+    ContentFilterModule.prototype.remove.call(this, filter);
 
-    knownFilters.delete(filter);
-    FilterNotifier.emit("elemhideupdate");
+    if (size != this._knownFilters.size)
+      FilterNotifier.emit("elemhideupdate");
   },
 
   /**
    * Determines from the current filter list which selectors should be applied
    * on a particular host name.
    * @param {string} domain
    * @param {boolean} [specificOnly] true if generic filters should not apply.
    * @returns {string[]} List of selectors.
@@ -197,17 +73,17 @@
 
     // This code is a performance hot-spot, which is why we've made certain
     // micro-optimisations. Please be careful before making changes.
     while (true)
     {
       if (specificOnly && currentDomain == "")
         break;
 
-      let filters = filtersByDomain.get(currentDomain);
+      let filters = this._filtersByDomain.get(currentDomain);
       if (filters)
       {
         for (let [filter, isIncluded] of filters)
         {
           if (!isIncluded)
           {
             excluded.add(filter);
           }
@@ -226,13 +102,13 @@
       if (currentDomain == "")
         break;
 
       let nextDot = currentDomain.indexOf(".");
       currentDomain = nextDot == -1 ? "" : currentDomain.substr(nextDot + 1);
     }
 
     if (!specificOnly)
-      selectors = getUnconditionalSelectors().concat(selectors);
+      selectors = this._getUnconditionalSelectors().concat(selectors);
 
     return selectors;
   }
-};
+});