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/** Monitor when the consumer finishes reading the response body.
that's as close as we can get to `res.on('close')` using web APIs.
*/
export function trackBodyConsumed(
body: string | ReadableStream,
onEnd: () => void
): BodyInit {
if (typeof body === 'string') {
const generator = async function* generate() {
const encoder = new TextEncoder()
yield encoder.encode(body)
onEnd()
}
// @ts-expect-error BodyInit typings doesn't seem to include AsyncIterables even though it's supported in practice
return generator()
} else {
return trackStreamConsumed(body, onEnd)
}
}
export function trackStreamConsumed<TChunk>(
stream: ReadableStream<TChunk>,
onEnd: () => void
): ReadableStream<TChunk> {
// NOTE: This function must handle `stream` being aborted or cancelled,
// so it can't just be this:
//
// return stream.pipeThrough(new TransformStream({ flush() { onEnd() } }))
//
// because that doesn't handle cancellations.
// (and cancellation handling via `Transformer.cancel` is only available in node >20)
const dest = new TransformStream()
const runOnEnd = () => onEnd()
stream.pipeTo(dest.writable).then(runOnEnd, runOnEnd)
return dest.readable
}
export class CloseController {
private target = new EventTarget()
listeners = 0
isClosed = false
onClose(callback: () => void) {
if (this.isClosed) {
throw new Error('Cannot subscribe to a closed CloseController')
}
this.target.addEventListener('close', callback)
this.listeners++
}
dispatchClose() {
if (this.isClosed) {
throw new Error('Cannot close a CloseController multiple times')
}
if (this.listeners > 0) {
this.target.dispatchEvent(new Event('close'))
}
this.isClosed = true
}
}
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