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/**
* @license
* Copyright (C) 2017 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(window) {
'use strict';
/** @constructor */
function GrAttributeHelper(element) {
this.element = element;
this._promises = {};
}
GrAttributeHelper.prototype._getChangedEventName = function(name) {
return name.replace(/([a-z])([A-Z])/g, '$1-$2').toLowerCase() + '-changed';
};
/**
* Returns true if the property is defined on wrapped element.
*
* @param {string} name
* @return {boolean}
*/
GrAttributeHelper.prototype._elementHasProperty = function(name) {
return this.element[name] !== undefined;
};
GrAttributeHelper.prototype._reportValue = function(callback, value) {
try {
callback(value);
} catch (e) {
console.info(e);
}
};
/**
* Binds callback to property updates.
*
* @param {string} name Property name.
* @param {function(?)} callback
* @return {function()} Unbind function.
*/
GrAttributeHelper.prototype.bind = function(name, callback) {
const attributeChangedEventName = this._getChangedEventName(name);
const changedHandler = e => this._reportValue(callback, e.detail.value);
const unbind = () => this.element.removeEventListener(
attributeChangedEventName, changedHandler);
this.element.addEventListener(
attributeChangedEventName, changedHandler);
if (this._elementHasProperty(name)) {
this._reportValue(callback, this.element[name]);
}
return unbind;
};
/**
* Get value of the property from wrapped object. Waits for the property
* to be initialized if it isn't defined.
*
* @param {string} name Property name.
* @return {!Promise<?>}
*/
GrAttributeHelper.prototype.get = function(name) {
if (this._elementHasProperty(name)) {
return Promise.resolve(this.element[name]);
}
if (!this._promises[name]) {
let resolve;
const promise = new Promise(r => resolve = r);
const unbind = this.bind(name, value => {
resolve(value);
unbind();
});
this._promises[name] = promise;
}
return this._promises[name];
};
/**
* Sets value and dispatches event to force notify.
*
* @param {string} name Property name.
* @param {?} value
*/
GrAttributeHelper.prototype.set = function(name, value) {
this.element[name] = value;
this.element.dispatchEvent(
new CustomEvent(this._getChangedEventName(name), {detail: {value}}));
};
window.GrAttributeHelper = GrAttributeHelper;
})(window);