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

lib/contentFilterModule.js

Index: lib/contentFilterModule.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/contentFilterModule.js
@@ -0,0 +1,201 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-present eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+/**
+ * @fileOverview Base implementation for content filter modules.
+ */
+
+const {ElemHideExceptions} = require("./elemHideExceptions");
+
+/**
+ * Map to be used instead when a filter has a blank domains property.
+ * @type {Map.<string,boolean>}
+ * @const
+ */
+let defaultDomains = new Map([["", true]]);
+
+/**
+ * Base class for content filter modules
+ * @class
+ */
+function ContentFilterModule()
+{
+  this._filtersByDomain = new Map();
+  this._filterBySelector = new Map();
+  this._unconditionalSelectors = null;
+  this._knownFilters = new Set();
+
+  ElemHideExceptions.on("added", this._onExceptionAdded.bind(this));
+}
+
+ContentFilterModule.prototype = {
+  /**
+   * 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>>}
+   */
+  _filtersByDomain: null,
+
+  /**
+   * Lookup table, filter by selector. (Only used for selectors that are
+   * unconditionally matched for all domains.)
+   * @type {Map.<string,Filter>}
+   */
+  _filterBySelector: null,
+
+  /**
+   * 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[]}
+   */
+  _unconditionalSelectors: null,
+
+  /**
+   * Set containing known content filters
+   * @type {Set.<ContentFilter>}
+   */
+  _knownFilters: null,
+
+  /**
+   * Adds a filter to the lookup table of filters by domain.
+   * @param {Filter} filter
+   */
+  _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 = this._filtersByDomain.get(domain);
+      if (!filters)
+        this._filtersByDomain.set(domain, filters = new Map());
+      filters.set(filter, isIncluded);
+    }
+  },
+
+  /**
+   * Returns a list of selectors that apply on each website unconditionally.
+   * @returns {string[]}
+   */
+  _getUnconditionalSelectors()
+  {
+    if (!this._unconditionalSelectors)
+      this._unconditionalSelectors = [...this._filterBySelector.keys()];
+
+    return this._unconditionalSelectors;
+  },
+
+  /**
+   * Handles the event when a new element hiding exception has been added
+   * @param {ElemHideException} exception
+   */
+  _onExceptionAdded(exception)
+  {
+    let {selector} = exception;
+
+    // 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 = this._filterBySelector.get(selector);
+    if (unconditionalFilterForSelector)
+    {
+      this._addToFiltersByDomain(unconditionalFilterForSelector);
+      this._filterBySelector.delete(selector);
+      this._unconditionalSelectors = null;
+    }
+  },
+
+  /**
+   * Removes all known filters
+   */
+  clear()
+  {
+    for (let collection of [this._filtersByDomain, this._filterBySelector,
+                            this._knownFilters])

[hub, 2018/08/23 16:05:38]

I'd be for using forEach() here.

+    {
+      collection.clear();
+    }
+
+    this._unconditionalSelectors = null;
+  },
+
+  /**
+   * Add a new content filter
+   * @param {ContentFilter} filter
+   */
+  add(filter)
+  {
+    if (this._knownFilters.has(filter))
+      return;
+
+    let {selector} = filter;
+
+    if (!(filter.domains || ElemHideExceptions.hasExceptions(selector)))
+    {
+      // The new filter's selector is unconditionally applied to all domains
+      this._filterBySelector.set(selector, filter);
+      this._unconditionalSelectors = null;
+    }
+    else
+    {
+      // The new filter's selector only applies to some domains
+      this._addToFiltersByDomain(filter);
+    }
+
+    this._knownFilters.add(filter);
+  },
+
+  /**
+   * Removes a content filter
+   * @param {ContentFilter} filter
+   */
+  remove(filter)
+  {
+    if (!this._knownFilters.has(filter))
+      return;
+
+    let {selector} = filter;
+
+    // Unconditially applied content filters
+    if (this._filterBySelector.get(selector) == filter)
+    {
+      this._filterBySelector.delete(selector);
+      this._unconditionalSelectors = null;
+    }
+    // Conditionally applied content filters
+    else
+    {
+      let domains = filter.domains || defaultDomains;
+      for (let domain of domains.keys())
+      {
+        let filters = this._filtersByDomain.get(domain);
+        if (filters)
+          filters.delete(filter);
+      }
+    }
+
+    this._knownFilters.delete(filter);
+  }
+};
+
+exports.ContentFilterModule = ContentFilterModule;