mpd-avr-client/src/services/govee-service.js

AVR as a MPD client

const { readFile } = require('fs');
const { Observable, of } = require('rxjs');
const { take, shareReplay, switchMap, catchError } = require('rxjs/operators');
const {
  getInstance: getBluetoothClient,
} = require('../clients/bluetooth-client');

const GoveeService = function (_ledLaunchProfilePath) {
  return ((ledLaunchProfilePath) => {
    const ledLaunchProfile$ =
      /** @type Observable<LedLaunchProfile> */ new Observable((subscriber) => {
        readFile(ledLaunchProfilePath, (err, data) => {
          if (err) {
            return subscriber.error(err);
          }

          try {
            subscriber.next(JSON.parse(data.toString()));
            subscriber.complete();
          } catch (err) {
            subscriber.error(err);
            subscriber.complete();
          }
        });

        return () => {};
      }).pipe(shareReplay());

    /**
     * Generates a Govee BLE payload with the correct checksum.
     * @param {boolean} ledOn - Desired power state
     * @returns {string} 40-character (i.e. 20 Bytes) long hex string
     */
    function generateGoveePowerPayload(ledOn) {
      const payload = Buffer.alloc(20, 0x00);

      payload[0] = 0x33; // Command header
      payload[1] = 0x01; // Command: Power
      payload[2] = ledOn ? 0x01 : 0x00;
      payload[19] = payload.reduce((acc, item) => acc ^ item, 0);

      return payload.toString('hex');
    }

    const wake = () =>
      ledLaunchProfile$
        .pipe(
          switchMap(({ macAddress, rowNumberHex }) =>
            getBluetoothClient().write(
              macAddress,
              rowNumberHex,
              generateGoveePowerPayload(true)
            )
          ),
          catchError(() => of(null)),
          take(1)
        )
        .subscribe();

    const standBy = () =>
      ledLaunchProfile$
        .pipe(
          switchMap(({ macAddress, rowNumberHex }) =>
            getBluetoothClient().write(
              macAddress,
              rowNumberHex,
              generateGoveePowerPayload(false)
            )
          ),
          catchError(() => of(null)),
          take(1)
        )
        .subscribe();

    return {
      wake,
      standBy,
    };
  })(_ledLaunchProfilePath);
};

let instance;

module.exports = {
  getInstance: (ledLaunchProfilePath) => {
    if (!instance) {
      instance = new GoveeService(ledLaunchProfilePath);
    }

    return /** @type {LedService} */ instance;
  },
};