import { EventEmitter } from '../event';
import { IVisibilityStatus } from './types';
/**
 * 실행된 browser 기준으로, visibilityChange event 에 맞는 vendorPrefix 반환
 * @memberof VisibilityChangeObserver
 * @export
 * @returns {String}
 */
export declare function getVendorPrefix(): string;
/**
 * getVendorPrefix 의 값
 * @constant
 * @memberof VisibilityChangeObserver
 * @type {String}
 */
export declare const VENDOR_PREFIX: string;
/**
 * browser 상의 visibilitychange event 명
 * @constant
 * @memberof VisibilityChangeObserver
 * @type {String}
 */
export declare const VISIBILITY_EVENT_NAME: string;
/**
 * browser 상의 visibility hidden 시점의 event 명
 * @constant
 * @memberof VisibilityChangeObserver
 * @type {String}
 */
export declare const HIDDEN_METHOD_NAME: string;
/**
 * VisibilityChange Event Types
 * @event VisibilityChangeObserver#VISIBILITY_EVENTS
 * @memberof VisibilityChangeObserver
 * @property {String} CHANGE - 변경 시점
 * @property {String} GET_STATUS - 현재 상태값 체크
 */
/**
 * @export
 * @readonly
 * @enum {VISIBILITY_EVENTS}
 */
export declare enum VISIBILITY_EVENTS {
    CHANGE = "VISIBILITY_CHANGE-EVENTS-CHANGE",
    GET_STATUS = "VISIBILITY_CHANGE-EVENTS-GET_STATUS"
}
/**
 * browser 의 visibility 변화를 감지
  <iframe
    src="https://codesandbox.io/embed/nonollcode-snippet-9gko8?autoresize=1&expanddevtools=1&fontsize=14&hidenavigation=1&initialpath=%2Fobserver-VisibilityChange.html&module=%2Fobserver-VisibilityChange.html&theme=dark"
    style="width:100%; height:500px; border:1px solid black; border-radius: 4px; overflow:hidden;"
    title="@nonoll/code-snippet"
    allow="geolocation; microphone; camera; midi; vr; accelerometer; gyroscope; payment; ambient-light-sensor; encrypted-media; usb"
    sandbox="allow-modals allow-forms allow-popups allow-scripts allow-same-origin"
  ></iframe>
 * @export
 * @class VisibilityChangeObserver
 * @alias observer/VisibilityChangeObserver
 * @extends {EventEmitter}
 * @see https://developer.mozilla.org/en-US/docs/Web/API/Page_Visibility_API
 * @see https://caniuse.com/#search=visibilityState
 * @throws {Error} browser 에서 지원하지 못하는 경우 - throw new Error('VisibilityChange 지원되지 않는 브라우저입니다.');
 * @example
import { VisibilityChangeObserver, VISIBILITY_EVENTS } from '@nonoll/code-snippet/observer';

const createElement = ({ tag = 'div', id = '', style = '', value = '', text = '' }) => {
  const doc = window.document;
  const target = doc.createElement(tag);
  target.setAttribute('id', id);
  target.setAttribute('style', style);
  target.setAttribute('value', value);
  if (text) {
    target.textContent = text;
  }
  return target;
}

let observer;

const forExample = () => {
  if (observer) {
    console.log('already example');
    return;
  }

  const doc = window.document;

  observer = new VisibilityChangeObserver();

  observer.on(VISIBILITY_EVENTS.CHANGE, ({ isHidden, isShow }) => {
    console.log('change', isHidden, isShow);
  });

  observer.attach();
  observer.emit(VISIBILITY_EVENTS.GET_STATUS);

  const statusButton = createElement({ tag: 'button', text: 'status' });
  const openButton = createElement({ tag: 'button', text: 'window open' });

  doc.body.appendChild(statusButton);
  doc.body.appendChild(openButton);

  statusButton.addEventListener('click', e => {
    e.preventDefault();
    console.log('statusButton clicked');
    if (!observer) {
      return;
    }
    // observer.emit(VISIBILITY_EVENTS.GET_STATUS);
    const { isHidden, isShow } = observer.getStatus();
    console.log('getStatus', isHidden, isShow);
  });

  openButton.addEventListener('click', e => {
    e.preventDefault();
    console.log('openButton clicked');
    if (!observer) {
      return;
    }
    const browser = window.open('https://nonoll.github.io/code-snippet/');
    if (!browser) {
      console.error('팝업이 차단되어 있습니다.');
    }
  });
}

forExample();
 */
export declare class VisibilityChangeObserver extends EventEmitter {
    constructor();
    /**
     * visibilitychange event 명 반환
     * @static
     * @returns {String}
     * @memberof VisibilityChangeObserver
     */
    static visibilityEventName(): string;
    /**
     * visibility hidden event 명 반환
     * @static
     * @returns {String}
     * @memberof VisibilityChangeObserver
     */
    static hiddenMethodName(): string;
    /**
     * visibility change 지원 여부 반환
     * @static
     * @returns {boolean}
     * @memberof VisibilityChangeObserver
     */
    static isSupport(): boolean;
    /**
     * @private
     * @memberof VisibilityChangeObserver
     * @see IVisibilityStatus
     * @fires VisibilityChangeObserver#VISIBILITY_EVENTS
     */
    private onVisibilityChangeListener;
    /**
     * @private
     * @returns {Boolean}
     * @memberof VisibilityChangeObserver
     */
    private isHidden;
    /**
     * 현재 상태를 반환
     * @returns {IVisibilityStatus}
     * @memberof VisibilityChangeObserver
     */
    getStatus(): IVisibilityStatus;
    /**
     * 이벤트 감지 설정
     * @returns {VisibilityChangeObserver}
     * @memberof VisibilityChangeObserver
     */
    attach(): VisibilityChangeObserver;
    /**
     * 이벤트 감지 해제
     * @returns {VisibilityChangeObserver}
     * @memberof VisibilityChangeObserver
     */
    detach(): VisibilityChangeObserver;
    /**
     * destory
     * @returns {VisibilityChangeObserver}
     * @memberof VisibilityChangeObserver
     */
    destroy(): VisibilityChangeObserver;
}