/**
 * 
 */
package ecologylab.sql;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * Wraps a java.sql.Connection object, keeping track of all of the statements it produces. On close,
 * automatically closes all open connections and releases them for garbage collection.
 * 
 * TODO Ultimately, this class should implement java.sql.Connection, but for now, it only implements
 * a few select methods; adding others as needed should be straightforward.
 * 
 * @author Zachary O. Toups (zach@ecologylab.net)
 */
public class ConnectionWithAutoClose
{
	Connection										conn;

	List<StatementWithAutoClose>	stmts	= null;

	public ConnectionWithAutoClose(Connection conn)
	{
		this.conn = conn;
	}

	public PreparedStatementWithAutoClose prepareStatement(String sql) throws SQLException
	{
		PreparedStatement ps = conn.prepareStatement(sql);
		PreparedStatementWithAutoClose psac = new PreparedStatementWithAutoClose(ps);
		stmts().add(psac);

		return psac;
	}

	public PreparedStatementWithAutoClose prepareStatement(String sql, int autoGeneratedKeys) throws SQLException
	{
		PreparedStatement ps = conn.prepareStatement(sql, autoGeneratedKeys);
		PreparedStatementWithAutoClose psac = new PreparedStatementWithAutoClose(ps);
		stmts().add(psac);

		return psac;
	}

	public StatementWithAutoClose<Statement> createStatement() throws SQLException
	{
		StatementWithAutoClose sac = new StatementWithAutoClose(conn.createStatement());
		stmts().add(sac);

		return sac;
	}

	private List<StatementWithAutoClose> stmts()
	{
		if (stmts == null)
		{
			synchronized (this)
			{
				if (stmts == null)
				{
					stmts = new LinkedList<StatementWithAutoClose>();
				}
			}
		}

		return stmts;
	}

	/**
	 * Wraps PreparedStatement.close() and eats its exceptions. Before invoking stmt.close(), closes
	 * all open ResultSets that were returned by this.
	 */
	public void close()
	{
		if (stmts != null)
		{
			Iterator<StatementWithAutoClose> stmtIter = stmts.iterator();

			while (stmtIter.hasNext())
			{
				StatementWithAutoClose stmt = stmtIter.next();
				stmtIter.remove();

				stmt.close();
			}
		}

		try
		{
			conn.close();
		}
		catch (SQLException e)
		{
		}

		conn = null;
	}
}