itach/src/utils.js

Simple Node.js module to send commands to GlobalCache iTach devices. Should handle reconnection (if connection lost), resending (on busyIR), etc.. but not abstract away the iTach API.

/**
 * Rejects a passed promise if it hasn't completed in time
 *
 * @return a promise that will be rejected when the timeout is reached otherwise the result of the passed promise
 */
const timeoutPromise = ({ promise, timeout, error }) => {
  let timer = null;

  return Promise.race([
    new Promise((resolve, reject) => {
      timer = setTimeout(reject, timeout, error);
      return timer;
    }),
    promise.then((value) => {
      clearTimeout(timer);
      return value;
    }),
  ]);
};

const createQueue = (taskFunc, concurrency = 1) => {
  const queue = [];
  let active = 0;
  let paused = false;

  const run = async function () {
    if (paused || active >= concurrency || queue.length < 1) {
      return;
    }
    active += 1;
    const queueItem = queue.shift();
    try {
      if (queueItem.timeout) {
        queueItem.resolve(
          timeoutPromise({
            promise: taskFunc(queueItem.task),
            timeout: queueItem.timeout,
            error: new Error(
              "QueueTaskTimeout: Task failed to complete before timeout was reached."
            ),
          })
        );
      } else {
        queueItem.resolve(taskFunc(queueItem.task));
      }
    } catch (error) {
      queueItem.reject(error);
    } finally {
      active -= 1;
      run();
    }
  };

  return {
    push: (task, timeout) =>
      new Promise((resolve, reject) => {
        queue.push({ task, resolve, reject, timeout });
        run();
      }),
    pause: () => {
      paused = true;
    },
    resume: () => {
      paused = false;
      run();
    },
  };
};

module.exports = { createQueue };