mitm.html

<!--
	mitm.html is the lite "man in the middle"

	This is only meant to signal the opener's messageChannel to
	the service worker - when that is done this mitm can be closed

	The service worker is capable of intercepting all request and fork their
	own "fake" response - wish we are going to craft
	when the worker then receives a stream then the worker will tell the opener
	to open up a link that will start the download
-->
<script>
let host = "jimmywarting.github.io"

// Service worker only works on https, 127.0.0.1 and localhost
// So we just redirect asap
if (window.location.host == host && window.location.protocol != "https:")
    window.location.protocol = "https:"

// message event is the first thing we need to setup a listner for
// don't want the opener to do a random timeout - instead they can listen for
// the ready event
window.onmessage = event => {
	let {data, ports} = event

	// It's important to have a messageChannel, don't want to interfere
	// with other simultaneous downloads
    if(!ports || !ports.length)
        throw new TypeError("Mehhh! You didn't send a messageChannel")

    // Register the worker, then forward the dataChannel to the worker
    // So they can talk directly, so we don't have to be "the middle man" any
    // longer
    navigator.serviceWorker.getRegistration('./').then(swReg => {
		return swReg || navigator.serviceWorker.register('sw.js', {scope: './'})
    }).then(swReg => {
		// This sends the message data as well as transferring
		// messageChannel.port2 to the service worker. The service worker can
		// then use the transferred port to reply via postMessage(), which
		// will in turn trigger the onmessage handler on messageChannel.port1.
		let swRegTmp = swReg.installing || swReg.waiting

		if (swReg.active)
			return swReg.active.postMessage(data, [ports[0]])

		swRegTmp.onstatechange = () => {
			if (swRegTmp.state === 'activated')
				swReg.active.postMessage(data, [ports[0]])
		}
    })
}

// The opener can't listen to onload event, so we need to help em out!
// (telling them that we are ready to accept postMessage's)
opener && opener.postMessage('StreamSaver::loadedPopup', '*')
</script>