package org.apache.torque.util;

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import java.util.Iterator;
import java.util.NoSuchElementException;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import com.workingdogs.village.Value;

import org.apache.torque.TorqueException;

/**
 * This is the base class, for fetching object one-by-one from a
 * java.sql.ResultSet.
 * @author <a href="mailto:deepspace@mailbox.hu">Zsombor Gegesy</a>
 */
public abstract class BaseIterator implements Iterator {

    ResultSetMetaData metadata;
    ResultSet resultSet;
    boolean closed=false;

    boolean hasNextRow;

    public BaseIterator (ResultSet resultset)
        throws TorqueException
    {
        try {
            this.resultSet  = resultset;
            this.metadata= resultSet.getMetaData();

            this.hasNextRow = resultSet.next();
        } catch (SQLException sql) {
            throw new TorqueException("SQL Error:"+sql.getMessage(),sql);
        }
    }

    /**
     * explicitly close the statement
     */
    public synchronized void close() {
        if (!closed) {
            closed= true;
            hasNextRow = false;
            try {
                resultSet.close();
            } catch (SQLException sql) {
                // silently ignore ...
            }
        }
    }

    /**
     * return the next Object, and when it's reach the end, close the statement with close()
     */
    public Object next() {
        try {
            Object result = null;
            if (hasNextRow) {
                Value[] values = new Value[ metadata.getColumnCount() ];
                for(int i=0; i<values.length;i++) {
                    values[i] = new Value( resultSet,i+1, metadata.getColumnType( i+1 ));
                }
                result = convert( values );
                hasNextRow = resultSet.next();
            }
            if (!hasNextRow) {
                close();
            }
            return result;
        } catch (TorqueException te) {
            close();
            throw new NoSuchElementException("Object creation broken, torque throwed an exception:"+te.getMessage());
        } catch (SQLException sql) {
            close();
            throw new NoSuchElementException("Object creation broken, sql exception:"+sql.getMessage());
        }
    }

    public boolean hasNext() {
        return hasNextRow;
    }

    public void remove() {
        throw new UnsupportedOperationException("Remove not supported on BaseIterator");
    }

    public abstract Object convert(Value[] values) throws TorqueException;
}