cql-worker/src/cql-worker-thread.js

A library for executing Clinical Quality Language (CQL) expressions asynchronously via web workers or node worker threads.

import { parentPort } from "worker_threads";
import CqlProcessor from "./CqlProcessor.js";
var processor = {};

/**
 * TODO: Update this comment for node worker thread.
 * Define an event handler for when a message is sent to this web worker.
 * Three types of messages can be sent here.
 * 1. elmJson & valueSetJon - Logic and code libraries for initial setup
 * 2. patientBundle - An initial or updated patient bundle
 * 3. expression - A logical expression needing to be evaluated
 * It is assumed that at least initially messages are sent in that order. For
 * the third type, if an expression can be evaluated, the result is sent back
 * as a message.
 * @param {object} rx - The message object being sent
 */
parentPort.onmessage = async function (rx) {
  let elmJson;
  let valueSetJson;
  let patientBundle;
  let expression;
  let parameters;
  let elmJsonDependencies;

  // For efficiency, first check if this is an expression message, since that is
  // the type called most often.
  if ((expression = rx.data.expression) != null) {
    let tx, result;
    if (processor.patientSource._bundles.length > 0) {
      if (expression == "__evaluate_library__") {
        result = await processor.evaluateLibrary();
      } else {
         result = await processor.evaluateExpression(expression);
      }
      tx = {
        expression: expression,
        result: result,
      };
    } else {
      // If we don't have a bundle just send the expression back.
      tx = {
        expression: expression,
        result: "WAITING_FOR_PATIENT_BUNDLE",
      };
    }
    parentPort.postMessage(tx); // send the result back
  } else if ((patientBundle = rx.data.patientBundle) != null) {
    // If the message contains a patient bundle, load it.
    processor.loadBundle(patientBundle);
  } else if (
    (elmJson = rx.data.elmJson) != null &&
    (valueSetJson = rx.data.valueSetJson) != null
  ) {
    // TODO: Allow empty value sets and check elm dependencies
    // If the message contains translated CQL (ELM JSON), use it to create a new
    // CQL Processor object.
    parameters = rx.data.parameters;
    elmJsonDependencies = rx.data.elmJsonDependencies;
    processor = new CqlProcessor(
      elmJson,
      valueSetJson,
      parameters,
      elmJsonDependencies
    );
  }
};