cygnal/src/sw.js

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JavaScript
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import localforage from 'localforage';
import {
TILE_SERVERS,
VERSION as CACHE_NAME,
} from '@/constants';
import { loadDataFromStorage } from '@/storage';
const DEBUG = (process.env.NODE_ENV !== 'production');
// Define the assets to cache
const { assets } = global.serviceWorkerOption;
let assetsToCache = [...assets, './'];
assetsToCache = assetsToCache.map(
path => new URL(path, global.location).toString(),
);
assetsToCache = assetsToCache.filter(
// Remove some assets from cache, such as Webpack hot-reload stuff
url => !url.endsWith('hot-update.json'),
);
// Define the locations from which we allow caching
const ALLOW_CACHING_FROM = [
global.location.origin,
];
const TILE_SERVERS_ORIGINS = [];
// Allow alterations of tile servers requests
Object.keys(TILE_SERVERS).forEach((tileServer) => {
const tileServerURL = TILE_SERVERS[tileServer].url;
if (tileServerURL.indexOf('{a-c}') !== -1) {
TILE_SERVERS_ORIGINS.push(
(new URL(tileServerURL.replace('{a-c}', 'a'))).origin,
);
TILE_SERVERS_ORIGINS.push(
(new URL(tileServerURL.replace('{a-c}', 'b'))).origin,
);
TILE_SERVERS_ORIGINS.push(
(new URL(tileServerURL.replace('{a-c}', 'c'))).origin,
);
} else {
TILE_SERVERS_ORIGINS.push((new URL(tileServerURL)).origin);
}
});
// Get duration (in s) before (cache) expiration from headers of a fetch
// request.
function _getExpiresFromHeaders(headers) {
// Try to use the Cache-Control header (and max-age)
if (headers.get('cache-control')) {
const maxAge = headers.get('cache-control').match(/max-age=(\d+)/);
return parseInt(maxAge ? maxAge[1] : 0, 10);
}
// Otherwise try to get expiration duration from the Expires header
if (headers.get('expires')) {
return (
parseInt(
(new Date(headers.get('expires'))).getTime() / 1000,
10,
)
- (new Date()).getTime()
);
}
return null;
}
// Get tile caching duration from config
function _getTileCachingDurationPromise() {
// Get tile caching duration from settings
let tileCachingDurationPromise = (
Promise.resolve(0) // no caching by default
);
if (
localforage.driver() === localforage.INDEXEDDB
) {
tileCachingDurationPromise = loadDataFromStorage(
'settings', 'tileCachingDuration',
);
}
return tileCachingDurationPromise;
}
// Check expiration of an item in cache
// Return the response is not expired. Deletes it from cache and returns null
// otherwise.
function _checkExpiration(cache, request, response) {
return _getTileCachingDurationPromise().then((cachingDurationFromConfig) => {
const cachedDate = Date.parse(response.headers.get('sw-cached-date'));
const now = new Date();
// Check wether it is expired according to config
if (cachingDurationFromConfig > 0) {
const expirationDateFromConfig = new Date(cachedDate.valueOf());
expirationDateFromConfig.setSeconds(
expirationDateFromConfig.getSeconds() + cachingDurationFromConfig,
);
if (expirationDateFromConfig > now) {
DEBUG && console.log(`SW: Found ${request.url} in cache.`);
return response;
}
DEBUG && console.log(`SW: Deleting expired ${request.url} from cache.`);
cache.delete(request);
}
// If no special caching from config or not expired from config, check
// whether it is expired from HTTP headers.
const cachingDurationFromHeaders = response.headers.get('sw-http-cache-duration');
const expirationDateFromHeaders = new Date(cachedDate.valueOf());
expirationDateFromHeaders.setSeconds(
expirationDateFromHeaders.getSeconds() + cachingDurationFromHeaders,
);
if (expirationDateFromHeaders > now) {
return response;
}
DEBUG && console.log(`SW: Deleting expired ${request.url} from cache.`);
cache.delete(request);
return null;
});
}
global.self.addEventListener('install', (event) => {
DEBUG && console.log('SW: installing…');
event.waitUntil(
global.caches.open(CACHE_NAME) // Don't cache during dev
.then((cache) => {
DEBUG && console.log('SW: cache opened.');
cache.addAll(assetsToCache).then(
() => {
if (DEBUG) {
console.log(`SW: cached assets ${assetsToCache}.`);
console.log('SW: successfully installed!');
}
return global.self.skipWaiting(); // Immediately update the SW
},
);
}),
);
});
global.self.addEventListener('activate', (event) => {
DEBUG && console.log('SW: activating…');
event.waitUntil(
// Delete all caches but the current one
global.caches.keys().then(
cacheNames => Promise.all(
cacheNames.map((cacheName) => {
if (cacheName.indexOf(CACHE_NAME) !== 0) {
DEBUG && console.log(`SW: Deleting unused cache ${cacheName}.`);
return global.caches.delete(cacheName);
}
return null;
}),
).then(() => DEBUG && console.log('SW: activated!')),
),
);
});
global.self.addEventListener('fetch', (event) => {
const { request } = event;
// Do not touch requests which are not GET
if (request.method !== 'GET') {
DEBUG && console.log(`SW: ignore non-GET request: ${request.method}.`);
return;
}
// Only touch requests which we can cache or from tiles servers.
const requestURL = new URL(request.url);
if (
ALLOW_CACHING_FROM.indexOf(requestURL.origin) === -1
&& TILE_SERVERS_ORIGINS.indexOf(requestURL.origin) === -1
) {
DEBUG && console.log(`SW: ignore different origin ${requestURL.origin}.`);
return;
}
// Never touch requests going from / to the API
if (requestURL.pathname.startsWith('/api')) {
// Note that if API is on a different location, it will be ignored by
// the previous rule.
DEBUG && console.log(`SW: ignore API call ${requestURL.pathname}.`);
return;
}
// Serve tiles from cache or download and cache them
if (TILE_SERVERS_ORIGINS.indexOf(requestURL.origin) !== -1) {
event.respondWith(global.caches.open(`${CACHE_NAME}-tiles`).then(
cache => cache.match(request).then(
(response) => {
// Helper function to fetch data from the network
const _fetchFromNetwork = (
// Note: We HAVE to use fetch(request.url) here to ensure we
// have a CORS-compliant request. Otherwise, we could get back
// an opaque response which we cannot inspect
// (https://developer.mozilla.org/en-US/docs/Web/API/Response/type).
() => fetch(request.url).then(
liveResponse => _getTileCachingDurationPromise().then(
(cachingDurationFromConfig) => {
// This is caching duration specified in HTTP headers
const cachingDurationFromHeaders = _getExpiresFromHeaders(
liveResponse.headers,
) || 0;
// If any form of caching is possible, do it
if (
cachingDurationFromConfig > 0
|| cachingDurationFromHeaders > 0
) {
// Recreate a Response object from scratch to put
// it in the cache, with the extra header for
// managing cache expiration.
const cachedResponseFields = {
status: liveResponse.status,
statusText: liveResponse.statusText,
headers: {
'SW-Cached-Date': (new Date()).toUTCString(),
'SW-HTTP-Cache-Duration': cachingDurationFromHeaders,
},
};
liveResponse.headers.forEach((v, k) => {
cachedResponseFields.headers[k] = v;
});
// We will consume body of the live response, so
// clone it before to be able to return it
// afterwards.
const returnedResponse = liveResponse.clone();
return liveResponse.blob().then((body) => {
DEBUG && console.log(
`SW: caching tiles ${request.url}.`,
);
// Put the duplicated Response in the cache
cache.put(
request, new Response(body, cachedResponseFields),
);
// Return the live response from the network
return returnedResponse;
});
}
// Otherwise, just return the live result from the network
return liveResponse;
},
),
)
);
// If there is a match from the cache
if (response) {
DEBUG && console.log(`SW: Found ${request.url} in cache.`);
return _checkExpiration(cache, request, response).then(
(notExpiredResponse) => {
if (notExpiredResponse) {
DEBUG && console.log(`SW: Serving ${request.url} from cache.`);
return notExpiredResponse;
}
DEBUG && console.log(`SW: Serving ${request.url} from network, expired in cache.`);
return _fetchFromNetwork();
},
);
}
// Otherwise, let's fetch it from the network
DEBUG && console.log(`SW: no match in cache for ${request.url}, using network.`);
return _fetchFromNetwork();
},
),
));
return;
}
// For the other requests, try to match it in the cache, otherwise do a
// network call
if (DEBUG) {
// Never match from cache in development
return;
}
const resource = global.caches.open(CACHE_NAME).then(
cache => cache.match(request).then(
(response) => {
if (response) {
DEBUG && console.log(`SW: serving ${request.url} from cache.`);
return response;
}
DEBUG && console.log(`SW: no match in cache for ${request.url}, using network.`);
return fetch(request);
},
),
);
event.respondWith(resource);
});
global.self.addEventListener('message', (event) => {
console.log(`SW: received message ${event.data}.`);
const eventData = JSON.parse(event.data);
// Clean tiles cache
if (eventData.action === 'PURGE_EXPIRED_TILES') {
DEBUG && console.log('SW: purging expired tiles from cache.');
global.caches.open(`${CACHE_NAME}-tiles`).then(
cache => cache.keys().then(
keys => keys.forEach(
key => cache.match(key).then((cachedResponse) => {
_checkExpiration(cache, key, cachedResponse);
}),
),
),
);
}
});