Parser.js

const { Transform } = require('stream');

function ParseChannels(str) {
  const fdatLine = str.match(/FDAT: (.*)/);
  const bvalLine = str.match(/BVAL: (.*)/);
  const diffLine = str.match(/DIFF: (.*)/);
  const touchLine = str.match(/TOUCH: (.*)/);

  const valuesRegex = /(-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+) (-?\d+)/;
  const fdatValues = fdatLine[0].match(valuesRegex);
  const bvalValues = bvalLine[0].match(valuesRegex);
  const diffValues = diffLine[0].match(valuesRegex);
  const touchValues = touchLine[0].match(valuesRegex);

  const channels = [];
  for (let i = 0; i < fdatValues.length - 1; i += 1) {
    const obj = {
      fdat: fdatValues[i + 1],
      bval: bvalValues[i + 1],
      diff: diffValues[i + 1],
      touch: touchValues[i + 1],
    };
    // console.log(obj);
    channels.push(obj);
  }

  return channels;
}

const frameRegex = /RTHS:[\s\S]*?TTHS:/gm;

class ElectrodeParser extends Transform {
  constructor() {
    super({ objectMode: true });
    this.buffer = Buffer.alloc(0);
  }

  static EatFrame(buf) {
    const str = buf.toString();
    const match = str.match(frameRegex);
    if (match == null) {
    // no frame detected, leave buffer unmodified
      return [null, buf];
    }
    // strip buffer up to and including the packet
    if (match.index === undefined) match.index = 0;
    const strippedBuf = buf.slice(match.index + match[0].length);

    const channels = ParseChannels(match[0]);
    return [channels, strippedBuf];
  }

  _transform(chunk, encoding, cb) { // eslint-disable-line no-underscore-dangle
    let data = Buffer.concat([this.buffer, chunk]);
    let channels;
    [channels, data] = ElectrodeParser.EatFrame(data);
    while (channels != null) {
      this.push(channels);
      [channels, data] = ElectrodeParser.EatFrame(data);
    }
    this.buffer = data;
    cb();
  }
}

module.exports = ElectrodeParser;