blob: 6fc7a17458f72afc70824b4f256ffb42c1f11693 [file] [log] [blame]
/**
* @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.
*/
export class GrAttributeHelper {
private readonly _promises = new Map<string, Promise<any>>();
// TOOD(TS): Change any to something more like HTMLElement.
constructor(public element: any) {}
_getChangedEventName(name: string): string {
return name.replace(/([a-z])([A-Z])/g, '$1-$2').toLowerCase() + '-changed';
}
/**
* Returns true if the property is defined on wrapped element.
*/
_elementHasProperty(name: string) {
return this.element[name] !== undefined;
}
_reportValue(callback: (value: any) => void, value: any) {
try {
callback(value);
} catch (e) {
console.info(e);
}
}
/**
* Binds callback to property updates.
*
* @param name Property name.
* @return Unbind function.
*/
bind(name: string, callback: (value: any) => void) {
const attributeChangedEventName = this._getChangedEventName(name);
const changedHandler = (e: CustomEvent) =>
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.
*/
get(name: string): Promise<unknown> {
if (this._elementHasProperty(name)) {
return Promise.resolve(this.element[name]);
}
if (!this._promises.has(name)) {
let resolve: (value: any) => void;
const promise = new Promise(r => (resolve = r));
const unbind = this.bind(name, value => {
resolve(value);
unbind();
});
this._promises.set(name, promise);
}
return this._promises.get(name)!;
}
/**
* Sets value and dispatches event to force notify.
*/
set(name: string, value: any) {
this.element[name] = value;
this.element.dispatchEvent(
new CustomEvent(this._getChangedEventName(name), {detail: {value}})
);
}
}