// https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream#convert_async_iterator_to_stream
function iteratorToStream(iterator: any) {
  return new ReadableStream({
    async pull(controller) {
      const { value, done } = await iterator.next()

      if (done) {
        controller.close()
      } else {
        controller.enqueue(value)
      }
    },
  })
}

function sleep(time) {
  return new Promise((resolve) => {
    setTimeout(resolve, time)
  }) 
}

const encoder = new TextEncoder()

async function* makeIterator() {
  yield encoder.encode('<p>one</p>')
  await sleep(200)
  yield encoder.encode('<p>two</p>')
  await sleep(200)
  yield encoder.encode('<p>three</p>')
}

export async function GET() {
  const iterator = makeIterator()
  const stream = iteratorToStream(iterator)

  return new Response(stream)
}