elm-review/lib/parse-elm-worker.js

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/**
 * This code was very much inspired by
 * <https://blog.logrocket.com/complete-guide-threads-node-js/>.
 */

/**
 * @import {MessagePort} from 'worker_threads';
 * @import {ElmFile} from './types/content';
 * @import {ParserApp, ParseJob, ParserModule} from './types/parse-elm';
 */
const {parentPort} = require('node:worker_threads');
const promisifyPort = require('./promisify-port');

const appForElmModule = Object.create(null);

if (parentPort) {
  subscribe(parentPort);
}

/**
 * @param {MessagePort} parentPort
 * @returns {void}
 */
function subscribe(parentPort) {
  parentPort.on('message', async (queueItem) => {
    const result = await workerParseElm(queueItem);
    parentPort.postMessage(result);
  });
}

/**
 * @param {ParseJob} queueItem
 * @returns {PromiseLike<ElmFile>}
 */
function workerParseElm({source, elmParserPath}) {
  /** @type {ParserApp} */
  let app = appForElmModule[elmParserPath];
  if (!app) {
    /** @type {ParserModule} */
    const elmParser = require(elmParserPath);
    app = elmParser.Elm.ParseMain.init();
    appForElmModule[elmParserPath] = app;
  }

  return promisifyPort({
    subscribeTo: app.ports.parseResult,
    sendThrough: app.ports.requestParsing,
    data: source
  });
}