/*

 * Copyright (c) 2007-2008 Nokia Corporation and/or its subsidiary(-ies).

 * All rights reserved.

 * This component and the accompanying materials are made available

 * under the terms of the License "Eclipse Public License v1.0"

 * which accompanies this distribution, and is available

 * at the URL "http://www.eclipse.org/legal/epl-v10.html".

 *

 * Initial Contributors:

 * Nokia Corporation - initial contribution.

 *

 * Contributors:

 *

 * Description:  

 *

 */

package com.nokia.helium.metadata;

import java.io.File;

import java.io.OutputStream;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Hashtable;

import javax.persistence.EntityManager;

import javax.persistence.EntityManagerFactory;

import javax.persistence.Persistence;

import org.apache.commons.io.FileUtils;

import org.eclipse.persistence.config.PersistenceUnitProperties;

import com.nokia.helium.metadata.ant.types.SeverityEnum;

import com.nokia.helium.metadata.model.Version;

import com.nokia.helium.metadata.model.metadata.Severity;

/**

 * Class implementing a EntityManagerFactoryCreator for the derby database.

 * This will be used to create new EntityManagerFactory for each database. It also

 * handles the driver management, and basic factory settings. 

 *

 */

public class DerbyFactoryManagerCreator implements EntityManagerFactoryCreator {

    public static final OutputStream DEV_NULL = new OutputStream() {         

        public void write(int b) { }     

    };

    public synchronized EntityManagerFactory create(File database) throws MetadataException {

        EntityManagerFactory factory;

        String name = "metadata";

        Hashtable<String, String> persistProperties = new Hashtable<String, String>();

        persistProperties.put("javax.persistence.jdbc.driver", "org.apache.derby.jdbc.EmbeddedDriver");

        // This swallow all the output log from derby.

        System.setProperty("derby.stream.error.field", "com.nokia.helium.metadata.DerbyFactoryManagerCreator.DEV_NULL");

        persistProperties.put("javax.persistence.jdbc.url",

               "jdbc:derby:" + database.getAbsolutePath());

        persistProperties.put(

                PersistenceUnitProperties.PERSISTENCE_CONTEXT_CLOSE_ON_COMMIT,

                "false");

        persistProperties.put(

                PersistenceUnitProperties.PERSISTENCE_CONTEXT_REFERENCE_MODE,

                "WEAK");

        persistProperties.put(PersistenceUnitProperties.BATCH_WRITING,

                "JDBC");

        persistProperties.put("eclipselink.read-only", "true");

        persistProperties.put(PersistenceUnitProperties.LOGGING_LEVEL, "warning");

        if (database.exists()) {

            if (!checkDatabaseIntegrity(database)) {

                try {

                    FileUtils.forceDelete(database);

                } catch (java.io.IOException iex) {

                    throw new MetadataException("Failed deleting corrupted db: " + iex, iex);

                }

            } else {

                return

                    Persistence.createEntityManagerFactory(

                        name,

                        persistProperties);

            }

        }

        persistProperties.put("javax.persistence.jdbc.url",

               "jdbc:derby:" + database + ";create=true");

        persistProperties.put(PersistenceUnitProperties.DDL_GENERATION,

                "create-tables");

        persistProperties.put(

                PersistenceUnitProperties.DDL_GENERATION_MODE,

                "database");

        persistProperties.put(

                PersistenceUnitProperties.PERSISTENCE_CONTEXT_CLOSE_ON_COMMIT,

                "false");

        persistProperties.put(

                PersistenceUnitProperties.PERSISTENCE_CONTEXT_REFERENCE_MODE,

                "WEAK");

        persistProperties.put(PersistenceUnitProperties.BATCH_WRITING,

                "JDBC");

        persistProperties.put("eclipselink.read-only", "true");

        factory = Persistence.createEntityManagerFactory(

                name,

                persistProperties);

        EntityManager entityManager = factory.createEntityManager();

        // Pushing default data into the current schema

        try {

            entityManager.getTransaction().begin();

            // Version of the schema is pushed.

            entityManager.persist(new Version());

            // Default set of severity is pushed.

            for (SeverityEnum.Severity severity : SeverityEnum.Severity.values()) {

                Severity pData = new Severity();

                pData.setSeverity(severity.toString());

                entityManager.persist(pData);

            }

            entityManager.getTransaction().commit();

        } finally {

            if (entityManager.getTransaction().isActive()) {

                entityManager.getTransaction().rollback();

                entityManager.clear();

            }

            entityManager.close();

        }

        return factory;

    }

    /**

     * Checks the database integrity.

     * @param urlPath - database path to be connected to.

     * @return boolean - true if db is valid false otherwise.

     */

    private static boolean checkDatabaseIntegrity(File database) throws MetadataException {

        boolean result = false;

        Connection connection = null;

        try {

            connection = DriverManager.getConnection("jdbc:derby:" + database);

            if (connection != null) {

                Statement stmt = connection.createStatement();

                ResultSet rs = stmt.executeQuery("select version from version");

                int version = -1;

                if ( rs.next()) {

                    version = rs.getInt(1);

                }

                rs.close();

                stmt.close();

                connection.close();

                connection = null;

                result = version == Version.DB_VERSION; 

            }

        } catch (SQLException ex) {

            try {

                DriverManager.getConnection("jdbc:derby:;shutdown=true");

            } catch (java.sql.SQLException sex) {

                // normal exception during database shutdown

                connection = null;

            }

            return false;

        } finally {

            try {            

                if (connection != null) {

                    connection.close();

                }

            } catch (java.sql.SQLException sex) {

                // normal exception during database shutdown

                connection = null;

            }

            connection = null;

            if (!result) {

                try {

                    DriverManager.getConnection("jdbc:derby:;shutdown=true");

                } catch (java.sql.SQLException sex) {

                    // normal exception during database shutdown

                    connection = null;

                }

            }

        }

        //shutdown unloads the driver, driver need to be loaded again.

        return result;

    }

    public synchronized void unload(File database) {

        try {

            DriverManager.getConnection("jdbc:derby:" + database + ";shutdown=true");

        } catch (SQLException e) {

            // normal exception during database shutdown

            e = null;

        }        

    }

    public synchronized void initialize() throws MetadataException {

        try {

            Class.forName("org.apache.derby.jdbc.EmbeddedDriver");

        } catch (java.lang.ClassNotFoundException e) {

            throw new MetadataException("JDBC Driver could not be found", e);

        }

    }

}