# PWA初始

    //cachestorage名称，可以加上版本号予以区分
    const OFFLINE_CACHE_PREFIX = 'sxf_offline_page_';
    const CACHE_VERSION = 'v1.0';
    const OFFLINE_CACHE_NAME = OFFLINE_CACHE_PREFIX + CACHE_VERSION;

    //Service Worker安装事件，其中可以预缓存资源
    this.addEventListener('install', function(event) {
        console.log('install');
        //需要缓存的页面资源这里缓存了三个资源。在安装过程中最好不要缓存太多，可能导致安装失败
        var urlsToPrefetch = [
            'index.html',
            'main.css',
            'icon.png'
        ];

        event.waitUntil(
            caches.open(OFFLINE_CACHE_NAME).then(function(cache) {
                return cache.addAll(urlsToPrefetch);
            })
        );
    });

    //Service Worker激活事件
    this.addEventListener('activate', function(event) {
        //在激活事件中清除非当前版本的缓存避免用户存储空间急剧膨胀
        event.waitUntil(caches.keys().then(function(cacheNames) {
            return Promise.all(cacheNames.map(function(cacheName) {
                if (cacheName !== OFFLINE_CACHE_NAME) {
                    if(cacheName.indexOf(OFFLINE_CACHE_PREFIX) != -1) {
                        return caches.delete(cacheName);
                    }
                }
            }));
        }));
    });


    //Service Worker 请求拦截事件
    this.addEventListener('fetch', function(event)  {
        event.respondWith(
            caches.open(OFFLINE_CACHE_NAME).then(function(cache) {
                return cache.match(event.request.url);
            }).then(function(response){
                //response为空表明未匹配成功，交由fetch方法去网络拉取
                if(response) {
                    return response;
                }
                return fetch(event.request);
            })
        );
    });

	// 检测浏览器是否支持SW
        /**
         * base64的相关操作，具体可以参考
         * https://github.com/web-push-libs/web-push#using-vapid-key-for-applicationserverkey
         */
        window.urlBase64ToUint8Array = function (base64String) {
            const padding = '='.repeat((4 - base64String.length % 4) % 4);
            const base64 = (base64String + padding)
                .replace(/\-/g, '+')
                .replace(/_/g, '/');

            const rawData = window.atob(base64);
            const outputArray = new Uint8Array(rawData.length);

            for (let i = 0; i < rawData.length; ++i) {
                outputArray[i] = rawData.charCodeAt(i);
            }
            return outputArray;
        }

		// if(navigator.serviceWorker != null){
		// 	navigator.serviceWorker.register('sxf_sw.js').then(function (registortion) {
		// 		console.log('支持sw', registortion.scope);
		// 	}).catch(function (whut) {
		// 		console.log('service worker has registered failure!');
		// 	})
		// }

        function registerServiceWorker(file) {
            return navigator.serviceWorker.register(file);
        }

        function subscribeUserToPush(registration, publicKey) {
            var subscribeOptions = {
                userVisibleOnly: true,
                applicationServerKey: window.urlBase64ToUint8Array(publicKey)
            };
            return registration.pushManager.subscribe(subscribeOptions).then(function (pushSubscription) {
                console.log('Received PushSubscription: ', JSON.stringify(pushSubscription));
                return pushSubscription;
            });
        }

        if ('serviceWorker' in navigator && 'PushManager' in window) {
            var publicKey = 'BOEQSjdhorIf8M0XFNlwohK3sTzO9iJwvbYU-fuXRF0tvRpPPMGO6d_gJC_pUQwBT7wD8rKutpNTFHOHN3VqJ0A';
            // 注册service worker
            registerServiceWorker('sxf_sw.js').then(function (registration) {
                console.log('Service Worker 注册成功');
                // 开启该客户端的消息推送订阅功能
                return subscribeUserToPush(registration, publicKey);
            }).then(function (subscription) {
                var body = {subscription: subscription};
                // 为了方便之后的推送，为每个客户端简单生成一个标识
                body.uniqueid = new Date().getTime();
                console.log('uniqueid', body.uniqueid);
                // 将生成的客户端订阅信息存储在自己的服务器上
                return sendSubscriptionToServer(JSON.stringify(body));
            }).then(function (res) {
                console.log(res);
            }).catch(function (err) {
                console.log(err);
            });
        }


        function sendSubscriptionToServer (endpointobj) {
            console.log("存储成功"+endpointobj.toString())
        }

// 监听推送的消息
self.addEventListener('push', function (e) {
    var data = e.data;
    if (e.data) {
        data = data.json();
        console.log('push的数据为：', data);
        self.registration.showNotification(data.text);
    }
    else {
        console.log('push没有任何数据');
    }
});