@thi.ng/rstream/async.js

Reactive streams & subscription primitives for constructing dataflow graphs / pipelines

import { SEMAPHORE } from "@thi.ng/api/api";
import { State } from "./api.js";
import { stream } from "./stream.js";
const fromAsync = (src, opts) => stream(($stream) => {
  let active = true;
  (async () => {
    try {
      for await (let x of src) {
        if (!active) return;
        $stream.next(x);
      }
      $stream.done();
    } catch (e) {
      $stream.error(e);
    }
  })();
  return () => active = false;
}, opts);
async function* asAsync(src) {
  let resolve;
  let initial;
  const $newInitial = () => {
    return initial = new Promise(($resolve) => {
      resolve = $resolve;
    });
  };
  const promises = [$newInitial()];
  src.subscribe({
    next(x) {
      if (initial) {
        resolve(x);
        initial = void 0;
      } else promises.push(Promise.resolve(x));
    },
    done() {
      if (initial) {
        resolve(SEMAPHORE);
        initial = void 0;
      } else promises.push(Promise.resolve(SEMAPHORE));
    }
  });
  while (promises.length && src.getState() < State.ERROR) {
    const res = await promises.shift();
    if (res === SEMAPHORE) break;
    if (!promises.length) promises[0] = $newInitial();
    yield res;
  }
}
export {
  asAsync,
  fromAsync
};