content: /*
   * Copyright (C) 2017 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.example.android.persistence.migrations;
  
  import android.content.Context;
  import androidx.annotation.NonNull;
  import androidx.annotation.VisibleForTesting;
  
  /**
   * Concrete implementation of the {@link LocalUserDataSource} that works with Room.
   */
  public class LocalUserDataSource implements UserDataSource {
  
      private static volatile LocalUserDataSource INSTANCE;
  
      private final UserDao mUserDao;
  
      @VisibleForTesting
      LocalUserDataSource(UserDao userDao) {
          mUserDao = userDao;
      }
  
      public static LocalUserDataSource getInstance(@NonNull Context context) {
          if (INSTANCE == null) {
              synchronized (LocalUserDataSource.class) {
                  if (INSTANCE == null) {
                      UsersDatabase database = UsersDatabase.getInstance(context);
                      INSTANCE = new LocalUserDataSource(database.userDao());
                  }
              }
          }
          return INSTANCE;
      }
  
      @Override
      public User getUser() {
          return mUserDao.getUser();
      }
  
      @Override
      public void insertOrUpdateUser(User user) {
          mUserDao.insertUser(user);
      }
  
      @Override
      public void deleteAllUsers() {
          mUserDao.deleteAllUsers();
      }
  }
  