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