/* * Copyright (C) 2020-2021 Yomichan Authors * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program 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 this program. If not, see <https://www.gnu.org/licenses/>. */ /** * Class which is used to observe elements matching a selector in specific element. */ class SelectorObserver { /** * Creates a new instance. * @param selector A string CSS selector used to find elements. * @param ignoreSelector A string CSS selector used to filter elements, or null for no filtering. * @param onAdded A function which is invoked for each element that is added that matches the selector. * The signature is (element) => data. * @param onRemoved A function which is invoked for each element that is removed, or null. * The signature is (element, data) => void. * @param onChildrenUpdated A function which is invoked for each element which has its children updated, or null. * The signature is (element, data) => void. * @param isStale A function which checks if the data is stale for a given element, or null. * If the element is stale, it will be removed and potentially re-added. * The signature is (element, data) => bool. */ constructor({selector, ignoreSelector=null, onAdded=null, onRemoved=null, onChildrenUpdated=null, isStale=null}) { this._selector = selector; this._ignoreSelector = ignoreSelector; this._onAdded = onAdded; this._onRemoved = onRemoved; this._onChildrenUpdated = onChildrenUpdated; this._isStale = isStale; this._observingElement = null; this._mutationObserver = new MutationObserver(this._onMutation.bind(this)); this._elementMap = new Map(); // Map([element => observer]...) this._elementAncestorMap = new Map(); // Map([element => Set([observer]...)]...) this._isObserving = false; } /** * Returns whether or not an element is currently being observed. * @returns True if an element is being observed, false otherwise. */ get isObserving() { return this._observingElement !== null; } /** * Starts DOM mutation observing the target element. * @param element The element to observe changes in. * @param attributes A boolean for whether or not attribute changes should be observed. * @throws An error if element is null. * @throws An error if an element is already being observed. */ observe(element, attributes=false) { if (element === null) { throw new Error('Invalid element'); } if (this.isObserving) { throw new Error('Instance is already observing an element'); } this._observingElement = element; this._mutationObserver.observe(element, { attributes: !!attributes, childList: true, subtree: true }); this._onMutation([{ type: 'childList', target: element.parentNode, addedNodes: [element], removedNodes: [] }]); } /** * Stops observing the target element. */ disconnect() { if (!this.isObserving) { return; } this._mutationObserver.disconnect(); this._observingElement = null; for (const observer of this._elementMap.values()) { this._removeObserver(observer); } } /** * Returns an iterable list of [element, data] pairs. * @yields A sequence of [element, data] pairs. */ *entries() { for (const [element, {data}] of this._elementMap) { yield [element, data]; } } /** * Returns an iterable list of data for every element. * @yields A sequence of data values. */ *datas() { for (const {data} of this._elementMap.values()) { yield data; } } // Private _onMutation(mutationList) { for (const mutation of mutationList) { switch (mutation.type) { case 'childList': this._onChildListMutation(mutation); break; case 'attributes': this._onAttributeMutation(mutation); break; } } } _onChildListMutation({addedNodes, removedNodes, target}) { const selector = this._selector; const ELEMENT_NODE = Node.ELEMENT_NODE; for (const node of removedNodes) { const observers = this._elementAncestorMap.get(node); if (typeof observers === 'undefined') { continue; } for (const observer of observers) { this._removeObserver(observer); } } for (const node of addedNodes) { if (node.nodeType !== ELEMENT_NODE) { continue; } if (node.matches(selector)) { this._createObserver(node); } for (const childNode of node.querySelectorAll(selector)) { this._createObserver(childNode); } } if ( this._onChildrenUpdated !== null && (addedNodes.length !== 0 || addedNodes.length !== 0) ) { for (let node = target; node !== null; node = node.parentNode) { const observer = this._elementMap.get(node); if (typeof observer !== 'undefined') { this._onObserverChildrenUpdated(observer); } } } } _onAttributeMutation({target}) { const selector = this._selector; const observers = this._elementAncestorMap.get(target); if (typeof observers !== 'undefined') { for (const observer of observers) { const element = observer.element; if ( !element.matches(selector) || this._shouldIgnoreElement(element) || this._isObserverStale(observer) ) { this._removeObserver(observer); } } } if (target.matches(selector)) { this._createObserver(target); } } _createObserver(element) { if (this._elementMap.has(element) || this._shouldIgnoreElement(element) || this._onAdded === null) { return; } const data = this._onAdded(element); const ancestors = this._getAncestors(element); const observer = {element, ancestors, data}; this._elementMap.set(element, observer); for (const ancestor of ancestors) { let observers = this._elementAncestorMap.get(ancestor); if (typeof observers === 'undefined') { observers = new Set(); this._elementAncestorMap.set(ancestor, observers); } observers.add(observer); } } _removeObserver(observer) { const {element, ancestors, data} = observer; this._elementMap.delete(element); for (const ancestor of ancestors) { const observers = this._elementAncestorMap.get(ancestor); if (typeof observers === 'undefined') { continue; } observers.delete(observer); if (observers.size === 0) { this._elementAncestorMap.delete(ancestor); } } if (this._onRemoved !== null) { this._onRemoved(element, data); } } _onObserverChildrenUpdated(observer) { this._onChildrenUpdated(observer.element, observer.data); } _isObserverStale(observer) { return (this._isStale !== null && this._isStale(observer.element, observer.data)); } _shouldIgnoreElement(element) { return (this._ignoreSelector !== null && element.matches(this._ignoreSelector)); } _getAncestors(node) { const root = this._observingElement; const results = []; while (true) { results.push(node); if (node === root) { break; } node = node.parentNode; if (node === null) { break; } } return results; } }