content: /*
   * Copyright (C) 2018 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.google.android.exoplayer2.database;
  
  import android.content.Context;
  import android.database.Cursor;
  import android.database.SQLException;
  import android.database.sqlite.SQLiteDatabase;
  import android.database.sqlite.SQLiteOpenHelper;
  import com.google.android.exoplayer2.util.Log;
  
  /**
   * An {@link SQLiteOpenHelper} that provides instances of a standalone database.
   *
   * <p>Suitable for use by applications that do not already have their own database, or that would
   * prefer to keep tables used by media library components isolated in their own database. Other
   * applications should prefer to use {@link DefaultDatabaseProvider} with their own {@link
   * SQLiteOpenHelper}.
   */
  // TODO: Make this class final when ExoDatabaseProvider is removed.
  public class StandaloneDatabaseProvider extends SQLiteOpenHelper implements DatabaseProvider {
  
    /** The file name used for the standalone database. */
    public static final String DATABASE_NAME = "exoplayer_internal.db";
  
    private static final int VERSION = 1;
    private static final String TAG = "SADatabaseProvider";
  
    /**
     * Provides instances of the database located by passing {@link #DATABASE_NAME} to {@link
     * Context#getDatabasePath(String)}.
     *
     * @param context Any context.
     */
    public StandaloneDatabaseProvider(Context context) {
      super(context.getApplicationContext(), DATABASE_NAME, /* factory= */ null, VERSION);
    }
  
    @Override
    public void onCreate(SQLiteDatabase db) {
      // Features create their own tables.
    }
  
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
      // Features handle their own upgrades.
    }
  
    @Override
    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
      wipeDatabase(db);
    }
  
    /**
     * Makes a best effort to wipe the existing database. The wipe may be incomplete if the database
     * contains foreign key constraints.
     */
    private static void wipeDatabase(SQLiteDatabase db) {
      String[] columns = {"type", "name"};
      try (Cursor cursor =
          db.query(
              "sqlite_master",
              columns,
              /* selection= */ null,
              /* selectionArgs= */ null,
              /* groupBy= */ null,
              /* having= */ null,
              /* orderBy= */ null)) {
        while (cursor.moveToNext()) {
          String type = cursor.getString(0);
          String name = cursor.getString(1);
          if (!"sqlite_sequence".equals(name)) {
            // If it's not an SQL-controlled entity, drop it
            String sql = "DROP " + type + " IF EXISTS " + name;
            try {
              db.execSQL(sql);
            } catch (SQLException e) {
              Log.e(TAG, "Error executing " + sql, e);
            }
          }
        }
      }
    }
  }
  