public class MeasureRepository {


private static MeasureRepository sInstance;
private final AppDataBase mDatabase;
private MediatorLiveData<List<Measure>> mObservableMeasures;
private MediatorLiveData<List<Measure>> mObservableMeasuresBySheet;
private MutableLiveData<List<Measure>> measuresBySheetMutable;
private LiveData<List<Measure>> mMeasuresOfSheet;

public AppExecutors appExecutors = new AppExecutors();

long mSheetId;


//private constructor
private MeasureRepository(final AppDataBase database, long sheetId) {

    mDatabase = database;

    mSheetId = sheetId;


    mObservableMeasures = new MediatorLiveData<>();
    mObservableMeasuresBySheet = new MediatorLiveData<>();

    //Here we are keeping this instance as class variable so we can remove it later from mObservableMeasuresBySheet source
    mMeasuresOfSheet=mDatabase.measureDao().getMeasuresOfSheet(sheetId);
    mObservableMeasuresBySheet.addSource(mMeasuresOfSheet, new Observer<List<Measure>>() {
        @Override
        public void onChanged(@Nullable List<Measure> measuresBySheet) {
            if (mDatabase.getDatabaseCreated().getValue() != null) {
                appExecutors.diskIO().execute(() ->
                        mObservableMeasuresBySheet.postValue(measuresBySheet));
            }
        }
    });


public static MeasureRepository getInstance(final AppDataBase database, long sheetId) {
    if (sInstance == null) {
        synchronized (MeasureRepository.class) {
            if (sInstance == null) {
                sInstance = new MeasureRepository(database, sheetId);
            }
        }
    }
    return sInstance;
}

/*****Room Measures DAO*****/

public void addNewMeasure(Measure measure, AtomicBoolean lock) {

    appExecutors.diskIO().execute(new Runnable() {
        @Override
        public void run() {

            if (!lock.get()) {
                lock.set(true);
                mDatabase.measureDao().newMeasure(measure);
            }
            lock.set(false);
        }


    });

    Log.d("ADD_MEASURE", "Added empty measure to database");

}


public void saveMeasures(List<Measure> measures) {
    appExecutors.diskIO().execute(() ->
            mDatabase.measureDao().insertAll(measures));
}

public LiveData<List<Measure>> getAllMeasures() {

    return mObservableMeasures;
}

public LiveData<List<Measure>> getMeasuresBySheet() {
    return mObservableMeasuresBySheet;
}

//Here we are updating the mObservableMeasuresBySheet with new source based on new sheetId
public void updateSheetId(long sheetId) {
      if(mMeasuresOfSheet!=null) {
          mObservableMeasuresBySheet.removeSource(mMeasuresOfSheet);
      }
      mMeasuresOfSheet=mDatabase.measureDao().getMeasuresOfSheet(sheetId);
      mObservableMeasuresBySheet.addSource(mMeasuresOfSheet, new Observer<List<Measure>>() {
          @Override
          public void onChanged(@Nullable List<Measure> measuresBySheet) {
              if (mDatabase.getDatabaseCreated().getValue() != null) {
                  appExecutors.diskIO().execute(() ->
                          mObservableMeasuresBySheet.postValue(measuresBySheet));
              }
          }
      });
  }