java/src/com/android/textclassifier/ulp/database/LanguageProfileDatabase.java

/*
 * Copyright (C) 2019 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.android.textclassifier.ulp.database;

import android.content.Context;

import androidx.annotation.GuardedBy;
import androidx.room.Database;
import androidx.room.Room;
import androidx.room.RoomDatabase;

/**
 * Represents user language profile database.
 *
 * <p>Needed for Room database to work. Allows to create a database instance (or get an already
 * existing if there is one) and use it.
 */
@Database(
        entities = {LanguageSignalInfo.class},
        version = 1,
        exportSchema = false)
public abstract class LanguageProfileDatabase extends RoomDatabase {
    private static final Object sLock = new Object();

    @GuardedBy("sLock")
    private static LanguageProfileDatabase sINSTANCE;

    /**
     * Returns {@link LanguageSignalInfoDao} object belonging to the {@link LanguageProfileDatabase}
     * with which we can call database queries.
     */
    public abstract LanguageSignalInfoDao languageInfoDao();

    /**
     * Create an instance of {@link LanguageProfileDatabase} for chosen context or existing one if
     * it was already created.
     */
    public static LanguageProfileDatabase getInstance(final Context context) {
        synchronized (sLock) {
            if (sINSTANCE == null) {
                sINSTANCE =
                        Room.databaseBuilder(
                                        context.getApplicationContext(),
                                        LanguageProfileDatabase.class,
                                        "language_profile")
                                .build();
            }
            return sINSTANCE;
        }
    }
}