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/* global clients, MessageChannel, ReadableStream, Response */
/* eslint-env serviceworker */
const portTimeoutDuration = 5000
let cancellable = false
const listener = event => {
const { url } = event.request
if (!url.includes(self.registration.scope + 'webtorrent/')) return null
if (url.includes(self.registration.scope + 'webtorrent/keepalive/')) return new Response()
if (url.includes(self.registration.scope + 'webtorrent/cancel/')) {
return new Response(new ReadableStream({
cancel () {
cancellable = true
}
}))
}
return serve(event)
}
export default listener
async function serve ({ request }) {
const { url, method, headers, destination } = request
const clientlist = await clients.matchAll({ type: 'window', includeUncontrolled: true })
const [data, port] = await new Promise(resolve => {
// Use race condition for whoever controls the response stream
for (const client of clientlist) {
const messageChannel = new MessageChannel()
const { port1, port2 } = messageChannel
port1.onmessage = ({ data }) => {
resolve([data, port1])
}
client.postMessage({
url,
method,
headers: Object.fromEntries(headers.entries()),
scope: self.registration.scope,
destination,
type: 'webtorrent'
}, [port2])
}
})
let timeOut = null
const cleanup = () => {
port.postMessage(false) // send a cancel request
clearTimeout(timeOut)
port.onmessage = null
}
if (data.body !== 'STREAM') {
cleanup()
return new Response(data.body, data)
}
return new Response(new ReadableStream({
pull (controller) {
return new Promise(resolve => {
port.onmessage = ({ data }) => {
if (data) {
controller.enqueue(data) // data is Uint8Array
} else {
cleanup()
controller.close() // data is null, means the stream ended
}
resolve()
}
if (!cancellable) {
// firefox doesn't support cancelling of Readable Streams in service workers,
// so we just empty it after 5s of inactivity, the browser will request another port anyways
clearTimeout(timeOut)
if (destination !== 'document') {
timeOut = setTimeout(() => {
cleanup()
resolve()
}, portTimeoutDuration)
}
}
port.postMessage(true) // send a pull request
})
},
cancel () {
cleanup()
}
}), data)
}
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