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sw.js
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sw.js
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/* global clients */
const MEDIA_FILE_NAME = 'MEDIA_FILE';
/**
* Call skipWaiting and claim to take control immediately.
*/
self.addEventListener('install', () => {
self.skipWaiting();
});
self.addEventListener('activate', () => {
clients.claim();
});
/**
* @function
* @param {Client} client
* @param {*} msg
*/
const getData = (() => {
const promises = {};
let n = 0;
self.addEventListener('message', event => {
const { id, msg } = event.data;
promises[id](msg);
});
return (client, msg) => {
return new Promise(res => {
promises[n] = res;
client.postMessage({ id: n, msg });
n += 1;
});
};
})();
self.addEventListener('fetch', event => {
const url = new URL(event.request.url);
if (!url.pathname.endsWith(`/${MEDIA_FILE_NAME}`)) return;
event.respondWith((async () => {
const client = await clients.get(event.clientId);
// Size of the file is set as a query parameter
const size = parseInt(new URLSearchParams(url.search).get('size'));
const startByte = parseInt(
event.request.headers.get('Range').match(/bytes=([0-9]*)-/)[1]
);
const buffer = await getData(client, startByte);
const blob = new Blob([buffer], { type: 'octet/stream' });
return new Response(blob, {
status: 206,
headers: new Headers({
'Content-Range': `bytes ${startByte}-${size - 1}/${size}`,
'Content-Length': size - startByte
})
});
})());
});