/*
 * Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
 * and the EPL 1.0 (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.DriverPropertyInfo;
import java.sql.SQLException;
import java.util.Properties;
import java.util.logging.Logger;
import org.h2.engine.Constants;
import org.h2.jdbc.JdbcConnection;
import org.h2.message.DbException;
import org.h2.upgrade.DbUpgrade;

The database driver. An application should not use this class directly. The
only thing the application needs to do is load the driver. This can be done
using Class.forName. To load the driver and open a database connection, use
the following code:
Class.forName("org.h2.Driver");
Connection conn = DriverManager.getConnection(
     "jdbc:h2:˜/test", "sa", "sa");

/**
 * The database driver. An application should not use this class directly. The
 * only thing the application needs to do is load the driver. This can be done
 * using Class.forName. To load the driver and open a database connection, use
 * the following code:
 *
 * <pre>
 * Class.forName(&quot;org.h2.Driver&quot;);
 * Connection conn = DriverManager.getConnection(
 *      &quot;jdbc:h2:&tilde;/test&quot;, &quot;sa&quot;, &quot;sa&quot;);
 * </pre>
 */
public class Driver implements java.sql.Driver, JdbcDriverBackwardsCompat {

    private static final Driver INSTANCE = new Driver();
    private static final String DEFAULT_URL = "jdbc:default:connection";
    private static final ThreadLocal<Connection> DEFAULT_CONNECTION =
            new ThreadLocal<>();

    private static boolean registered;

    static {
        load();
    }

    
Open a database connection.
This method should not be called by an application.
Instead, the method DriverManager.getConnection should be used.
Params:
url – the database URL
info – the connection properties
Returns:
the new connection or null if the URL is not supported/**
     * Open a database connection.
     * This method should not be called by an application.
     * Instead, the method DriverManager.getConnection should be used.
     *
     * @param url the database URL
     * @param info the connection properties
     * @return the new connection or null if the URL is not supported
     */
    @Override
    public Connection connect(String url, Properties info) throws SQLException {
        try {
            if (info == null) {
                info = new Properties();
            }
            if (!acceptsURL(url)) {
                return null;
            }
            if (url.equals(DEFAULT_URL)) {
                return DEFAULT_CONNECTION.get();
            }
            Connection c = DbUpgrade.connectOrUpgrade(url, info);
            if (c != null) {
                return c;
            }
            return new JdbcConnection(url, info);
        } catch (Exception e) {
            throw DbException.toSQLException(e);
        }
    }

    
Check if the driver understands this URL.
This method should not be called by an application.
Params:
url – the database URL
Returns:
if the driver understands the URL/**
     * Check if the driver understands this URL.
     * This method should not be called by an application.
     *
     * @param url the database URL
     * @return if the driver understands the URL
     */
    @Override
    public boolean acceptsURL(String url) {
        if (url != null) {
            if (url.startsWith(Constants.START_URL)) {
                return true;
            } else if (url.equals(DEFAULT_URL)) {
                return DEFAULT_CONNECTION.get() != null;
            }
        }
        return false;
    }

    
Get the major version number of the driver.
This method should not be called by an application.
Returns:
the major version number/**
     * Get the major version number of the driver.
     * This method should not be called by an application.
     *
     * @return the major version number
     */
    @Override
    public int getMajorVersion() {
        return Constants.VERSION_MAJOR;
    }

    
Get the minor version number of the driver.
This method should not be called by an application.
Returns:
the minor version number/**
     * Get the minor version number of the driver.
     * This method should not be called by an application.
     *
     * @return the minor version number
     */
    @Override
    public int getMinorVersion() {
        return Constants.VERSION_MINOR;
    }

    
Get the list of supported properties.
This method should not be called by an application.
Params:
url – the database URL
info – the connection properties
Returns:
a zero length array/**
     * Get the list of supported properties.
     * This method should not be called by an application.
     *
     * @param url the database URL
     * @param info the connection properties
     * @return a zero length array
     */
    @Override
    public DriverPropertyInfo[] getPropertyInfo(String url, Properties info) {
        return new DriverPropertyInfo[0];
    }

    
Check if this driver is compliant to the JDBC specification.
This method should not be called by an application.
Returns:
true/**
     * Check if this driver is compliant to the JDBC specification.
     * This method should not be called by an application.
     *
     * @return true
     */
    @Override
    public boolean jdbcCompliant() {
        return true;
    }

    
[Not supported]
/**
     * [Not supported]
     */
    @Override
    public Logger getParentLogger() {
        return null;
    }

    
INTERNAL
/**
     * INTERNAL
     */
    public static synchronized Driver load() {
        try {
            if (!registered) {
                registered = true;
                DriverManager.registerDriver(INSTANCE);
            }
        } catch (SQLException e) {
            DbException.traceThrowable(e);
        }
        return INSTANCE;
    }

    
INTERNAL
/**
     * INTERNAL
     */
    public static synchronized void unload() {
        try {
            if (registered) {
                registered = false;
                DriverManager.deregisterDriver(INSTANCE);
            }
        } catch (SQLException e) {
            DbException.traceThrowable(e);
        }
    }

    
INTERNAL
Sets, on a per-thread basis, the default-connection for
user-defined functions.
/**
     * INTERNAL
     * Sets, on a per-thread basis, the default-connection for
     * user-defined functions.
     */
    public static void setDefaultConnection(Connection c) {
        if (c == null) {
            DEFAULT_CONNECTION.remove();
        } else {
            DEFAULT_CONNECTION.set(c);
        }
    }

    
INTERNAL
/**
     * INTERNAL
     */
    public static void setThreadContextClassLoader(Thread thread) {
        // Apache Tomcat: use the classloader of the driver to avoid the
        // following log message:
        // org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
        // SEVERE: The web application appears to have started a thread named
        // ... but has failed to stop it.
        // This is very likely to create a memory leak.
        try {
            thread.setContextClassLoader(Driver.class.getClassLoader());
        } catch (Throwable t) {
            // ignore
        }
    }

}