sw.js

'use strict';const OFFLINE_DATA_FILE="offline.json";const CACHE_NAME_PREFIX="c3offline";const BROADCASTCHANNEL_NAME="offline";const CONSOLE_PREFIX="[SW] ";const LAZYLOAD_KEYNAME="";const broadcastChannel=typeof BroadcastChannel==="undefined"?null:new BroadcastChannel(BROADCASTCHANNEL_NAME);
class PromiseThrottle{constructor(maxParallel){this._maxParallel=maxParallel;this._queue=[];this._activeCount=0}Add(func){return new Promise((resolve,reject)=>{this._queue.push({func,resolve,reject});this._MaybeStartNext()})}async _MaybeStartNext(){if(!this._queue.length||this._activeCount>=this._maxParallel)return;this._activeCount++;const job=this._queue.shift();try{const result=await job.func();job.resolve(result)}catch(err){job.reject(err)}this._activeCount--;this._MaybeStartNext()}}
const networkThrottle=new PromiseThrottle(20);function PostBroadcastMessage(o){if(!broadcastChannel)return;setTimeout(()=>broadcastChannel.postMessage(o),3E3)}function Broadcast(type){PostBroadcastMessage({"type":type})}function BroadcastDownloadingUpdate(version){PostBroadcastMessage({"type":"downloading-update","version":version})}function BroadcastUpdateReady(version){PostBroadcastMessage({"type":"update-ready","version":version})}
function IsUrlInLazyLoadList(url,lazyLoadList){if(!lazyLoadList)return false;try{for(const lazyLoadRegex of lazyLoadList)if((new RegExp(lazyLoadRegex)).test(url))return true}catch(err){console.error(CONSOLE_PREFIX+"Error matching in lazy-load list: ",err)}return false}function WriteLazyLoadListToStorage(lazyLoadList){if(typeof localforage==="undefined")return Promise.resolve();else return localforage.setItem(LAZYLOAD_KEYNAME,lazyLoadList)}
function ReadLazyLoadListFromStorage(){if(typeof localforage==="undefined")return Promise.resolve([]);else return localforage.getItem(LAZYLOAD_KEYNAME)}function GetCacheBaseName(){return CACHE_NAME_PREFIX+"-"+self.registration.scope}function GetCacheVersionName(version){return GetCacheBaseName()+"-v"+version}async function GetAvailableCacheNames(){const cacheNames=await caches.keys();const cacheBaseName=GetCacheBaseName();return cacheNames.filter(n=>n.startsWith(cacheBaseName))}
async function IsUpdatePending(){const availableCacheNames=await GetAvailableCacheNames();return availableCacheNames.length>=2}async function GetMainPageUrl(){const allClients=await clients.matchAll({includeUncontrolled:true,type:"window"});for(const c of allClients){let url=c.url;if(url.startsWith(self.registration.scope))url=url.substring(self.registration.scope.length);if(url&&url!=="/"){if(url.startsWith("?"))url="/"+url;return url}}return""}
function fetchWithBypass(request,bypassCache){if(typeof request==="string")request=new Request(request);if(bypassCache)return fetch(request.url,{headers:request.headers,mode:request.mode,credentials:request.credentials,redirect:request.redirect,cache:"no-store"});else return fetch(request)}
async function CreateCacheFromFileList(cacheName,fileList,bypassCache){const responses=await Promise.all(fileList.map(url=>networkThrottle.Add(()=>fetchWithBypass(url,bypassCache))));let allOk=true;for(const response of responses)if(!response.ok){allOk=false;console.error(CONSOLE_PREFIX+"Error fetching '"+response.url+"' ("+response.status+" "+response.statusText+")")}if(!allOk)throw new Error("not all resources were fetched successfully");const cache=await caches.open(cacheName);try{return await Promise.all(responses.map((response,
i)=>cache.put(fileList[i],response)))}catch(err){console.error(CONSOLE_PREFIX+"Error writing cache entries: ",err);caches.delete(cacheName);throw err;}}
async function UpdateCheck(isFirst){try{const response=await fetchWithBypass(OFFLINE_DATA_FILE,true);if(!response.ok)throw new Error(OFFLINE_DATA_FILE+" responded with "+response.status+" "+response.statusText);const data=await response.json();const version=data.version;const fileList=data.fileList;const lazyLoadList=data.lazyLoad;const currentCacheName=GetCacheVersionName(version);const cacheExists=await caches.has(currentCacheName);if(cacheExists){const isUpdatePending=await IsUpdatePending();if(isUpdatePending){console.log(CONSOLE_PREFIX+
"Update pending");Broadcast("update-pending")}else{console.log(CONSOLE_PREFIX+"Up to date");Broadcast("up-to-date")}return}const mainPageUrl=await GetMainPageUrl();fileList.unshift("./");if(mainPageUrl&&fileList.indexOf(mainPageUrl)===-1)fileList.unshift(mainPageUrl);console.log(CONSOLE_PREFIX+"Caching "+fileList.length+" files for offline use");if(isFirst)Broadcast("downloading");else BroadcastDownloadingUpdate(version);if(lazyLoadList)await WriteLazyLoadListToStorage(lazyLoadList);await CreateCacheFromFileList(currentCacheName,
fileList,!isFirst);const isUpdatePending=await IsUpdatePending();if(isUpdatePending){console.log(CONSOLE_PREFIX+"All resources saved, update ready");BroadcastUpdateReady(version)}else{console.log(CONSOLE_PREFIX+"All resources saved, offline support ready");Broadcast("offline-ready")}}catch(err){console.warn(CONSOLE_PREFIX+"Update check failed: ",err)}}self.addEventListener("install",event=>{event.waitUntil(UpdateCheck(true).catch(()=>null))});
async function GetCacheNameToUse(availableCacheNames,doUpdateCheck){if(availableCacheNames.length===1||!doUpdateCheck)return availableCacheNames[0];const allClients=await clients.matchAll();if(allClients.length>1)return availableCacheNames[0];const latestCacheName=availableCacheNames[availableCacheNames.length-1];console.log(CONSOLE_PREFIX+"Updating to new version");await Promise.all(availableCacheNames.slice(0,-1).map(c=>caches.delete(c)));return latestCacheName}
async function HandleFetch(event,doUpdateCheck){const availableCacheNames=await GetAvailableCacheNames();if(!availableCacheNames.length)return fetch(event.request);const useCacheName=await GetCacheNameToUse(availableCacheNames,doUpdateCheck);const cache=await caches.open(useCacheName);const cachedResponse=await cache.match(event.request);if(cachedResponse)return cachedResponse;const result=await Promise.all([fetch(event.request),ReadLazyLoadListFromStorage()]);const fetchResponse=result[0];const lazyLoadList=
result[1];if(IsUrlInLazyLoadList(event.request.url,lazyLoadList))try{await cache.put(event.request,fetchResponse.clone())}catch(err){console.warn(CONSOLE_PREFIX+"Error caching '"+event.request.url+"': ",err)}return fetchResponse}
self.addEventListener("fetch",event=>{if((new URL(event.request.url)).origin!==location.origin)return;const doUpdateCheck=event.request.mode==="navigate";const responsePromise=HandleFetch(event,doUpdateCheck);if(doUpdateCheck)event.waitUntil(responsePromise.then(()=>UpdateCheck(false)));event.respondWith(responsePromise)});