/*
 Copyright (C) 2002-2004 MySQL AB

 This program is free software; you can redistribute it and/or modify
 it under the terms of version 2 of the GNU General Public License as
 published by the Free Software Foundation.
 

 There are special exceptions to the terms and conditions of the GPL 
 as it is applied to this software. View the full text of the 
 exception exception in file EXCEPTIONS-CONNECTOR-J in the directory of this 
 software distribution.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */
package com.mysql.jdbc;

import java.io.IOException;
import java.sql.SQLException;


/**
 * Allows streaming of MySQL data.
 *
 * @author dgan
 * @version $Id: RowDataDynamic.java,v 1.8.2.9 2004/08/09 22:15:10 mmatthew Exp $
 */
public class RowDataDynamic implements RowData {
    private MysqlIO io;
    private byte[][] nextRow;
    private boolean isAfterEnd = false;
    private boolean isAtEnd = false;
    private boolean streamerClosed = false;
    private int columnCount;
    private int index = -1;
    private long lastSuccessfulReadTimeMs = 0;
    private long netWriteTimeoutMs = 0;
    private ResultSet owner;

    /**
     * Creates a new RowDataDynamic object.
     *
     * @param io DOCUMENT ME!
     * @param colCount DOCUMENT ME!
     *
     * @throws SQLException DOCUMENT ME!
     */
    public RowDataDynamic(MysqlIO io, int colCount) throws SQLException {
        this.io = io;
        this.columnCount = colCount;
        nextRecord();
    }

    /**
     * Returns true if we got the last element.
     *
     * @return true if after last row
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isAfterLast() throws SQLException {
        return isAfterEnd;
    }

    /**
     * Only works on non dynamic result sets.
     *
     * @param index row number to get at
     *
     * @return row data at index
     *
     * @throws SQLException if a database error occurs
     */
    public byte[][] getAt(int index) throws SQLException {
        notSupported();

        return null;
    }

    /**
     * Returns if iteration has not occured yet.
     *
     * @return true if before first row
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isBeforeFirst() throws SQLException {
        return index < 0;
    }

    /**
     * Moves the current position in the result set to the given row number.
     *
     * @param rowNumber row to move to
     *
     * @throws SQLException if a database error occurs
     */
    public void setCurrentRow(int rowNumber) throws SQLException {
        notSupported();
    }
    
	/**
	 * @see com.mysql.jdbc.RowData#setOwner(com.mysql.jdbc.ResultSet)
	 */
	public void setOwner(ResultSet rs) {
		this.owner = rs;
	}
	
	/**
	 * @see com.mysql.jdbc.RowData#getOwner()
	 */
	public ResultSet getOwner() {
		return this.owner;
	}

    /**
     * Returns the current position in the result set as a row number.
     *
     * @return the current row number
     *
     * @throws SQLException if a database error occurs
     */
    public int getCurrentRowNumber() throws SQLException {
        notSupported();

        return -1;
    }

    /**
     * Returns true if the result set is dynamic. This means that move back and
     * move forward won't work because we do not hold on to the records.
     *
     * @return true if this result set is streaming from the server
     */
    public boolean isDynamic() {
        return true;
    }

    /**
     * Has no records.
     *
     * @return true if no records
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isEmpty() throws SQLException {
        notSupported();

        return false;
    }

    /**
     * Are we on the first row of the result set?
     *
     * @return true if on first row
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isFirst() throws SQLException {
        notSupported();

        return false;
    }

    /**
     * Are we on the last row of the result set?
     *
     * @return true if on last row
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isLast() throws SQLException {
        notSupported();

        return false;
    }

    /**
     * Adds a row to this row data.
     *
     * @param row the row to add
     *
     * @throws SQLException if a database error occurs
     */
    public void addRow(byte[][] row) throws SQLException {
        notSupported();
    }

    /**
     * Moves to after last.
     *
     * @throws SQLException if a database error occurs
     */
    public void afterLast() throws SQLException {
        notSupported();
    }

    /**
     * Moves to before first.
     *
     * @throws SQLException if a database error occurs
     */
    public void beforeFirst() throws SQLException {
        notSupported();
    }

    /**
     * Moves to before last so next el is the last el.
     *
     * @throws SQLException if a database error occurs
     */
    public void beforeLast() throws SQLException {
        notSupported();
    }

    /**
     * We're done.
     *
     * @throws SQLException if a database error occurs
     */
    public void close() throws SQLException {
        //drain the rest of the records.
        int count = 0;
        
        while (this.hasNext()) {
            this.next();
            
            count++;
            
            if (count == 100) {
            	Thread.yield();
            	count = 0;
            }
        }
    }

    /**
     * Returns true if another row exsists.
     *
     * @return true if more rows
     *
     * @throws SQLException if a database error occurs
     */
    public boolean hasNext() throws SQLException {
        boolean hasNext = (nextRow != null);

        if (!hasNext && !streamerClosed) {
            io.closeStreamer(this);
            streamerClosed = true;
        }

        return hasNext;
    }

    /**
     * Moves the current position relative 'rows' from the current position.
     *
     * @param rows the relative number of rows to move
     *
     * @throws SQLException if a database error occurs
     */
    public void moveRowRelative(int rows) throws SQLException {
        notSupported();
    }

    /**
     * Returns the next row.
     *
     * @return the next row value
     *
     * @throws SQLException if a database error occurs
     */
    public byte[][] next() throws SQLException {
        index++;

        byte[][] ret = nextRow;
        nextRecord();

        return ret;
    }

    /**
     * Removes the row at the given index.
     *
     * @param index the row to move to
     *
     * @throws SQLException if a database error occurs
     */
    public void removeRow(int index) throws SQLException {
        notSupported();
    }

    /**
     * Only works on non dynamic result sets.
     *
     * @return the size of this row data
     */
    public int size() {
        return RESULT_SET_SIZE_UNKNOWN;
    }

    private void nextRecord() throws SQLException {
        try {
            if (!isAtEnd) {
                nextRow = io.nextRow((int) columnCount);

                if (nextRow == null) {
                    isAtEnd = true;
                }
                
                this.lastSuccessfulReadTimeMs = System.currentTimeMillis();
            } else {
                isAfterEnd = true;
            }
        } catch (SQLException sqlEx) {
            // don't wrap SQLExceptions
            throw sqlEx;
        } catch (IOException ioEx) {
        	long timeSinceLastReadMs = System.currentTimeMillis() - this.lastSuccessfulReadTimeMs;
        	
            String exceptionType = ioEx.getClass().getName();
            String exceptionMessage = ioEx.getMessage();

            exceptionMessage += "\n\nNested Stack Trace:\n";
            exceptionMessage += Util.stackTraceToString(ioEx);

            throw new java.sql.SQLException(
                "IOException while retrieving next record in streaming result set."
                + "(Check for deadlock "
                + " or retrieval exceeding 'net_write_timeout' seconds. Last "
                + "successful record read was " + timeSinceLastReadMs + " ms ago, and"
                + "'net_write_timeout' is configured in the server as " + this.netWriteTimeoutMs 
                + " ms.) : "
                + exceptionType + " message given: " + exceptionMessage, SQLError.SQL_STATE_GENERAL_ERROR);
        } catch (Exception ex) {
            String exceptionType = ex.getClass().getName();
            String exceptionMessage = ex.getMessage();

            exceptionMessage += "\n\nNested Stack Trace:\n";
            exceptionMessage += Util.stackTraceToString(ex);

            throw new java.sql.SQLException(
                "Error retrieving record: Unexpected Exception: "
                + exceptionType + " message given: " + exceptionMessage, SQLError.SQL_STATE_GENERAL_ERROR);
        }
    }

    private void notSupported() throws SQLException {
        throw new OperationNotSupportedException();
    }

    class OperationNotSupportedException extends SQLException {
        OperationNotSupportedException() {
            super("Operation not supported for streaming result sets", SQLError.SQL_STATE_ILLEGAL_ARGUMENT);
        }
    }
}
