/*
 * 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 org.mozilla.thirdparty.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 org.mozilla.thirdparty.com.google.android.exoplayer2.util.Log;

/**
 * An {@link SQLiteOpenHelper} that provides instances of a standalone ExoPlayer database.
 *
 * <p>Suitable for use by applications that do not already have their own database, or that would
 * prefer to keep ExoPlayer tables isolated in their own database. Other applications should prefer
 * to use {@link DefaultDatabaseProvider} with their own {@link SQLiteOpenHelper}.
 */
public final class ExoDatabaseProvider extends SQLiteOpenHelper implements DatabaseProvider {

  /** The file name used for the standalone ExoPlayer database. */
  public static final String DATABASE_NAME = "exoplayer_internal.db";

  private static final int VERSION = 1;
  private static final String TAG = "ExoDatabaseProvider";

  /**
   * Provides instances of the database located by passing {@link #DATABASE_NAME} to {@link
   * Context#getDatabasePath(String)}.
   *
   * @param context Any context.
   */
  public ExoDatabaseProvider(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);
          }
        }
      }
    }
  }
}
