@thi.ng/csp/ops.js

Primitives & operators for Communicating Sequential Processes based on async/await and async iterables

import { assert } from "@thi.ng/errors/assert";
import { Channel } from "./channel.js";
const broadcast = async (src, dest, close = true) => {
  for await (let x of src) {
    for (let chan of dest) chan.write(x);
  }
  if (close) {
    for (let chan of dest) chan.close();
  }
};
const concat = async (dest, chans, close = true) => {
  return (async () => {
    for (let c of chans) {
      await consumeWith(c, (x) => dest.write(x));
    }
    close && dest.close();
  })();
};
const consume = async (chan, res = [], num = Infinity) => {
  for (let n = 0; !chan.closed() && n < num; n++) {
    const x = await chan.read();
    if (x == void 0) break;
    res.push(x);
  }
  return res;
};
const consumeWith = async (chan, fn, num = Infinity) => {
  for (let n = 0; !chan.closed() && n < num; n++) {
    const x = await chan.read();
    if (x == void 0) break;
    fn(x, chan);
  }
};
const drain = async (chan) => await (async () => {
  const ops = [];
  for (let i = 0, n = chan.writes.length + chan.queue.length; i < n; i++) {
    ops.push(chan.read());
  }
  return Promise.all(ops);
})();
const fromAsyncIterable = (src, close = true) => pipe(src, new Channel(), close);
const merge = (src, dest, close = true) => {
  assert(src.length > 0, "no inputs given");
  dest = dest || new Channel();
  (async () => {
    while (true) {
      const [x, ch] = await select(...src);
      if (x === void 0) {
        src.splice(src.indexOf(ch), 1);
        if (!src.length) {
          close && dest.close();
          break;
        }
      } else {
        await dest.write(x);
      }
    }
  })();
  return dest;
};
const into = async (dest, src, close = false) => {
  for await (let x of src) {
    if (!dest.writable()) break;
    await dest.write(x);
  }
  close && dest.close();
};
const pipe = (src, dest, close = true) => {
  into(dest, src, close);
  return dest;
};
const select = async (input, ...rest) => {
  const inputs = [input, ...rest];
  const sel = await Promise.race(inputs.map((x) => x.race()));
  for (let chan of inputs) {
    if (chan !== sel) chan.races.shift();
  }
  if (sel.writes.readable()) {
    const [msg, write] = sel.writes.read();
    write(true);
    sel.updateQueue();
    return [msg, sel];
  }
  return [void 0, sel];
};
const timeout = (delay) => {
  const ch = new Channel();
  setTimeout(() => ch.close(), delay);
  return ch;
};
export {
  broadcast,
  concat,
  consume,
  consumeWith,
  drain,
  fromAsyncIterable,
  into,
  merge,
  pipe,
  select,
  timeout
};