/*
 * Copyright (C) 2010 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 android.database;

import java.io.File;
import java.util.List;

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.util.Log;
import android.util.Pair;

Default class used to define the action to take when database corruption is reported
by sqlite.
 An application can specify an implementation of DatabaseErrorHandler on the following: 

  
SQLiteDatabase.openOrCreateDatabase(String, CursorFactory, DatabaseErrorHandler)
  
SQLiteDatabase.openDatabase(String, CursorFactory, int, DatabaseErrorHandler)
 The specified DatabaseErrorHandler is used to handle database corruption errors, if they occur. 
 If null is specified for the DatabaseErrorHandler param in the above calls, this class is used as the default DatabaseErrorHandler. /**
 * Default class used to define the action to take when database corruption is reported
 * by sqlite.
 * <p>
 * An application can specify an implementation of {@link DatabaseErrorHandler} on the
 * following:
 * <ul>
 *   <li>{@link SQLiteDatabase#openOrCreateDatabase(String,
 *      android.database.sqlite.SQLiteDatabase.CursorFactory, DatabaseErrorHandler)}</li>
 *   <li>{@link SQLiteDatabase#openDatabase(String,
 *      android.database.sqlite.SQLiteDatabase.CursorFactory, int, DatabaseErrorHandler)}</li>
 * </ul>
 * The specified {@link DatabaseErrorHandler} is used to handle database corruption errors, if they
 * occur.
 * <p>
 * If null is specified for the DatabaseErrorHandler param in the above calls, this class is used
 * as the default {@link DatabaseErrorHandler}.
 */
public final class DefaultDatabaseErrorHandler implements DatabaseErrorHandler {

    private static final String TAG = "DefaultDatabaseErrorHandler";

    
defines the default method to be invoked when database corruption is detected.
Params:
dbObj – the SQLiteDatabase object representing the database on which corruption is detected./**
     * defines the default method to be invoked when database corruption is detected.
     * @param dbObj the {@link SQLiteDatabase} object representing the database on which corruption
     * is detected.
     */
    public void onCorruption(SQLiteDatabase dbObj) {
        Log.e(TAG, "Corruption reported by sqlite on database: " + dbObj.getPath());

        // is the corruption detected even before database could be 'opened'?
        if (!dbObj.isOpen()) {
            // database files are not even openable. delete this database file.
            // NOTE if the database has attached databases, then any of them could be corrupt.
            // and not deleting all of them could cause corrupted database file to remain and 
            // make the application crash on database open operation. To avoid this problem,
            // the application should provide its own {@link DatabaseErrorHandler} impl class
            // to delete ALL files of the database (including the attached databases).
            deleteDatabaseFile(dbObj.getPath());
            return;
        }

        List<Pair<String, String>> attachedDbs = null;
        try {
            // Close the database, which will cause subsequent operations to fail.
            // before that, get the attached database list first.
            try {
                attachedDbs = dbObj.getAttachedDbs();
            } catch (SQLiteException e) {
                /* ignore */
            }
            try {
                dbObj.close();
            } catch (SQLiteException e) {
                /* ignore */
            }
        } finally {
            // Delete all files of this corrupt database and/or attached databases
            if (attachedDbs != null) {
                for (Pair<String, String> p : attachedDbs) {
                    deleteDatabaseFile(p.second);
                }
            } else {
                // attachedDbs = null is possible when the database is so corrupt that even
                // "PRAGMA database_list;" also fails. delete the main database file
                deleteDatabaseFile(dbObj.getPath());
            }
        }
    }

    private void deleteDatabaseFile(String fileName) {
        if (fileName.equalsIgnoreCase(":memory:") || fileName.trim().length() == 0) {
            return;
        }
        Log.e(TAG, "deleting the database file: " + fileName);
        try {
            SQLiteDatabase.deleteDatabase(new File(fileName));
        } catch (Exception e) {
            /* print warning and ignore exception */
            Log.w(TAG, "delete failed: " + e.getMessage());
        }
    }
}