pomoLights.js

const noble = require('noble');
const { EventEmitter } = require('events');

class PomoLight extends EventEmitter {
  constructor(prefix, serviceUUID, writeUUID) {
    super();

    this.prefix = prefix;
    this.serviceUUID = serviceUUID;
    this.writeUUID = writeUUID;
    this.foundDevices = {};
    this.connected = false;
    this.stream = null;
    this.peripheral = null;
    this.state = null;
    this.foundDevice = false;

    noble.on('discover', (peripheral) => {
      this.onDiscover(peripheral);
    });
  }

  start() {
    noble.on('stateChange', (state) => {
      this.onStateChange(state);
    });

    if (this.state === 'poweredOn') {
      console.log('Scanning');
      noble.startScanning([], true);
    }
  }

  onDiscover(peripheral) {
    const name = peripheral.advertisement.localName || '';

    if (name.startsWith(this.prefix)) {
      this.foundDevices[name] = peripheral;
    }

    this.emit('foundNewDevice', this.foundDevices);
  }

  onStateChange(state) {
    this.state = state;
    if (state === 'poweredOn') {
      console.log('Scanning');
      noble.startScanning([], true);
    }
  }

  connect(peripheral) {
    if (this.foundDevice) {
      return;
    }

    this.foundDevice = true;
    noble.stopScanning();
    peripheral.connect();

    peripheral.once('disconnect', () => {
      console.log('Disconnect');
      this.disconnect();
      this.start();
    });

    peripheral.once('connect', () => {
      console.log('Connect');
      this.peripheral = peripheral;
      this.connected = true;

      peripheral.discoverSomeServicesAndCharacteristics([this.serviceUUID], [this.writeUUID], (err, services, characteristics) => {
        if (characteristics.length === 1) {
          console.log('Connected');
          this.stream = characteristics[0];
          this.emit('connected');
        }
      });
    });
  }

  disconnect() {
    this.connected = false;
    this.stream = null;
    this.foundDevice = false;
  }

  changeColor(red, green, blue) {
    if (this.connected) {
      this.stream.write(Buffer.from([0, red, green, blue]));

      return true;
    }

    return false;
  }
}

const a = new PomoLight('Pomo Light', '6e400001b5a3f393e0a9e50e24dcca9e', '6e400002b5a3f393e0a9e50e24dcca9e');

a.on('foundNewDevice', (devices) => {
  const b = devices['Pomo Light #1'];
  if (b) {
    a.connect(b);
  }
});

const sleep = ms => new Promise(res => setTimeout(res, ms));

a.on('connected', async () => {
  while (true) {
    a.changeColor(255, 0, 0);
    await sleep(500);
    a.changeColor(0, 255, 0);
    await sleep(500);
    a.changeColor(0, 0, 255);
    await sleep(500);
  }
});

a.start();