Issue 6665 - Split out element hiding exceptions into their own module

lib/elemHideExceptions.js

Index: lib/elemHideExceptions.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/elemHideExceptions.js
@@ -0,0 +1,130 @@
+/*
+ * 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 Element hiding exceptions implementation.

[Manish Jethani, 2018/05/17 05:42:48]

The relevant parts from lib/elemHide.js have been copied into this file with no
further modifications, plus this module also emits "added" and "removed" events
(as well as "elemhideupdate") when a filter is added or removed respectively.

+ */
+
+const {EventEmitter} = require("./events");
+const {FilterNotifier} = require("./filterNotifier");
+
+/**
+ * Lookup table, lists of element hiding exceptions by selector
+ * @type {Map.<string,ElemHideException[]>}
+ */
+let exceptions = new Map();
+
+/**
+ * Set containing known element exceptions
+ * @type {Set.<ElemHideException>}
+ */
+let knownExceptions = new Set();
+
+/**
+ * Container for element hiding exceptions
+ * @class
+ */
+exports.ElemHideExceptions = Object.assign(Object.create(new EventEmitter()), {
+  /**
+   * Removes all known exceptions
+   */
+  clear()
+  {
+    exceptions.clear();
+    knownExceptions.clear();
+
+    FilterNotifier.emit("elemhideupdate");
+  },
+
+  /**
+   * Add a new element hiding exception
+   * @param {ElemHideException} exception
+   */
+  add(exception)
+  {
+    if (knownExceptions.has(exception))
+      return;
+
+    let {selector} = exception;
+    let list = exceptions.get(selector);
+    if (list)
+      list.push(exception);
+    else
+      exceptions.set(selector, [exception]);
+
+    knownExceptions.add(exception);
+
+    this.emit("added", exception);
+
+    FilterNotifier.emit("elemhideupdate");
+  },
+
+  /**
+   * Removes an element hiding exception
+   * @param {ElemHideException} exception
+   */
+  remove(exception)
+  {
+    if (!knownExceptions.has(exception))
+      return;
+
+    let list = exceptions.get(exception.selector);
+    let index = list.indexOf(exception);
+    if (index >= 0)
+      list.splice(index, 1);
+
+    knownExceptions.delete(exception);
+
+    this.emit("removed", exception);
+
+    FilterNotifier.emit("elemhideupdate");
+  },
+
+  /**
+   * Checks whether any exception rules are registered for a selector
+   * @param {string} selector
+   * @returns {boolean}
+   */
+  hasExceptions(selector)
+  {
+    return exceptions.has(selector);
+  },
+
+  /**
+   * Checks whether an exception rule is registered for a filter on a particular
+   * domain.
+   * @param {ElemHideFilter|ElemHideEmulationFilter} filter
+   * @param {?string} docDomain
+   * @return {?ElemHideException}
+   */
+  getException(filter, docDomain)
+  {
+    let list = exceptions.get(filter.selector);
+    if (!list)
+      return null;
+
+    for (let i = list.length - 1; i >= 0; i--)
+    {
+      if (list[i].isActiveOnDomain(docDomain))
+        return list[i];
+    }
+
+    return null;
+  }
+});