app-utils.js

const EventEmitter = require('events');
class Emitter extends EventEmitter {}
const events = new Emitter();

function getRandomBytes(numberOfBytes = 1) {
  /**
	 * can be done with crypto lib
	 * 
			var crypto = require("crypto");
			var id = crypto.randomBytes(20).toString('hex'); // "bb5dc8842ca31d4603d6aa11448d1654"
	 */
  let numberOfBytesx = numberOfBytes * 2;

  var byteString = '0x';
  var possible = 'ABCDEF0123456789';

  for (var i = 0; i < numberOfBytesx; i++) {
    byteString += possible.charAt(Math.floor(Math.random() * possible.length));
  }
  return byteString;
}
function getRandomRawValue(JSONValues) {
  if (JSONValues) {
    return JSONValues[Math.floor(Math.random() * JSONValues.length)] || null;
  } else {
    return null;
  }
}

function getJSONFile() {
  const JSONdataFileName = process.argv[2];
  if (!JSONdataFileName) {
    console.log(`
	Missing argument!
	
	example: 'npm start my-json-file.json'
		`);
    process.exit(-1);
  } else {
    return require('./' + JSONdataFileName);
  }
}

function getRandomInterval(min, max, charName) {
  if (min < max) {
    return Math.floor(Math.random() * max) + min;
  } else {
    return null;
  }
}
function setControlledinterval(interval, characteristic) {
  let int = setInterval(() => {
    let rawValue = getRandomRawValue(characteristic.notifyValues);
    events.emit(characteristic.characteristicName, {
      rawValue: Buffer.from(rawValue),
      characteristicName: characteristic.characteristicName,
    });

    let interval = getRandomInterval(
      characteristic.notifyIntervalMin,
      characteristic.notifyIntervalMax
    );
    clearInterval(int);
    setControlledinterval(interval * 1000, characteristic);
  }, interval);
}

function getNotifyValuesForChar(charUuid, JSONData) {
  // console.log('getNotifyValueForChar', charUuid, typeof JSONData)
  for (let service of JSONData.services) {
    for (let characteristic of service.characteristics) {
      if (characteristic.uuid.split('-').join('') === charUuid) {
        return characteristic.notifyValues || null;
      }
    }
    return null;
  }
}
module.exports = {
  getRandomBytes: getRandomBytes,
  getRandomRawValue: getRandomRawValue,
  // getRandomInterval: getRandomInterval,
  // setControlledinterval: setControlledinterval,
  getJSONFile: getJSONFile,
  getNotifyValuesForChar: getNotifyValuesForChar,
};