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export type Factory<T> = (  emit: (t: T) => unknown,  done: () => unknown,) => unknown;
function makeDeferral<T = void>() {  let resolve: (t: T) => unknown;  const promise = new Promise<T>((_res) => {    resolve = _res;  });
  // @ts-ignore: resolve is not used before it is defined since the code above runs synchronously  return [resolve, promise] as const;}
async function defer() {  const [resolve, promise] = makeDeferral();  resolve();
  return promise;}
/** * Given a factory function, creates an asynchronous iterator which emits items passed to its * callback. */export default async function* listenator<T>(factory: Factory<T>) {  // Set up iterator state  const queue: Array<T> = [];  let done = false;  let [resolve, prom] = makeDeferral();
  // Call the factory function with state modifying functions  factory(    // emit    (t: T) => {      if (done) {        return;      }      queue.push(t);      resolve();    },    // done    () => {      done = true;      resolve();    },  );
  // Asynchronous iterator loop  while (true) {    await prom;    // Flush all queued values    while (queue.length > 0) {      yield queue.shift();      await defer();    }    // At this point the queue is empty, should we complete the iterator?    if (done) {      break;    }    // If we aren't done yet, set up `resolve` and `prom` for the next value    [resolve, prom] = makeDeferral();  }}