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LocalUserDataSource.java

/*
 * 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 static com.example.android.persistence.migrations.UserPersistenceContract.UserEntry
        .COLUMN_NAME_ENTRY_ID;
import static com.example.android.persistence.migrations.UserPersistenceContract.UserEntry
        .COLUMN_NAME_USERNAME;
import static com.example.android.persistence.migrations.UserPersistenceContract.UserEntry
        .TABLE_NAME;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.annotation.NonNull;

/**
 * Concrete implementation of the UserDataSource, working directly with SQLite APIs.
 */
public class LocalUserDataSource implements UserDataSource {

private static LocalUserDataSource INSTANCE;

private UsersDbHelper mDbHelper;

// Prevent direct instantiation.
    private LocalUserDataSource(@NonNull Context context) {
        mDbHelper = new UsersDbHelper(context);
    }

public static LocalUserDataSource getInstance(@NonNull Context context) {
        if (INSTANCE == null) {
            INSTANCE = new LocalUserDataSource(context);
        }
        return INSTANCE;
    }

@Override
    public User getUser() {
        User user = null;

SQLiteDatabase db = mDbHelper.getReadableDatabase();

String[] projection = {
                COLUMN_NAME_ENTRY_ID,
                COLUMN_NAME_USERNAME
        };

// Get the user from the table. Since, for simplicity we only have one user in the database,
        // this query gets all users from the table, but limits the result to just the 1st user
        Cursor c = db.query(TABLE_NAME, projection, null, null,
                null, null, null, "1");

if (c != null && c.getCount() > 0) {
            if (c.moveToNext()) {
                int itemId = c.getInt(c.getColumnIndexOrThrow(COLUMN_NAME_ENTRY_ID));
                String title = c.getString(c.getColumnIndexOrThrow(COLUMN_NAME_USERNAME));
                user = new User(itemId, title);
            }
        }
        if (c != null) {
            c.close();
        }
        db.close();

return user;
    }

@Override
    public void insertOrUpdateUser(User user) {
        SQLiteDatabase db = mDbHelper.getWritableDatabase();

ContentValues values = new ContentValues();
        values.put(COLUMN_NAME_ENTRY_ID, user.getId());
        values.put(COLUMN_NAME_USERNAME, user.getUserName());

db.insertWithOnConflict(TABLE_NAME, null, values,
                SQLiteDatabase.CONFLICT_REPLACE);

db.close();
    }

@Override
    public void deleteAllUsers() {
        SQLiteDatabase db = mDbHelper.getWritableDatabase();

db.delete(TABLE_NAME, null, null);

db.close();
    }
}