147 lines
4.1 KiB
JavaScript
147 lines
4.1 KiB
JavaScript
/**
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* @license
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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(function() {
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'use strict';
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const HLJS_PATH = 'bower_components/highlightjs/highlight.min.js';
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const DARK_THEME_PATH = 'styles/themes/dark-theme.html';
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Polymer({
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is: 'gr-lib-loader',
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properties: {
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_hljsState: {
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type: Object,
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// NOTE: intended singleton.
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value: {
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configured: false,
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loading: false,
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callbacks: [],
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},
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},
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},
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/**
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* Get the HLJS library. Returns a promise that resolves with a reference to
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* the library after it's been loaded. The promise resolves immediately if
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* it's already been loaded.
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* @return {!Promise<Object>}
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*/
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getHLJS() {
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return new Promise((resolve, reject) => {
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// If the lib is totally loaded, resolve immediately.
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if (this._getHighlightLib()) {
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resolve(this._getHighlightLib());
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return;
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}
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// If the library is not currently being loaded, then start loading it.
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if (!this._hljsState.loading) {
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this._hljsState.loading = true;
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this._loadScript(this._getHLJSUrl())
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.then(this._onHLJSLibLoaded.bind(this)).catch(reject);
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}
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this._hljsState.callbacks.push(resolve);
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});
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},
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/**
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* Loads the dark theme document. Returns a promise that resolves with a
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* custom-style DOM element.
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* @return {!Promise<Element>}
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*/
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getDarkTheme() {
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return new Promise((resolve, reject) => {
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this.importHref(this._getLibRoot() + DARK_THEME_PATH, () => {
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const module = document.createElement('style', 'custom-style');
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module.setAttribute('include', 'dark-theme');
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resolve(module);
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});
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});
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},
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/**
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* Execute callbacks awaiting the HLJS lib load.
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*/
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_onHLJSLibLoaded() {
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const lib = this._getHighlightLib();
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this._hljsState.loading = false;
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for (const cb of this._hljsState.callbacks) {
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cb(lib);
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}
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this._hljsState.callbacks = [];
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},
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/**
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* Get the HLJS library, assuming it has been loaded. Configure the library
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* if it hasn't already been configured.
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* @return {!Object}
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*/
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_getHighlightLib() {
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const lib = window.hljs;
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if (lib && !this._hljsState.configured) {
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this._hljsState.configured = true;
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lib.configure({classPrefix: 'gr-diff gr-syntax gr-syntax-'});
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}
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return lib;
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},
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/**
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* Get the resource path used to load the application. If the application
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* was loaded through a CDN, then this will be the path to CDN resources.
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* @return {string}
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*/
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_getLibRoot() {
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if (window.STATIC_RESOURCE_PATH) {
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return window.STATIC_RESOURCE_PATH + '/';
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}
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return '/';
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},
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/**
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* Load and execute a JS file from the lib root.
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* @param {string} src The path to the JS file without the lib root.
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* @return {Promise} a promise that resolves when the script's onload
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* executes.
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*/
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_loadScript(src) {
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return new Promise((resolve, reject) => {
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const script = document.createElement('script');
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if (!src) {
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reject(new Error('Unable to load blank script url.'));
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return;
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}
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script.src = src;
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script.onload = resolve;
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script.onerror = reject;
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Polymer.dom(document.head).appendChild(script);
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});
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},
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_getHLJSUrl() {
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const root = this._getLibRoot();
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if (!root) { return null; }
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return root + HLJS_PATH;
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},
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});
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})();
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