/*
 * Copyright (c) 1998-2011 Caucho Technology -- all rights reserved
 *
 * This file is part of Resin(R) Open Source
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Resin Open Source is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Resin Open Source 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, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Resin Open Source; if not, write to the
 *   Free SoftwareFoundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.db.sql;

import java.sql.SQLException;

import com.caucho.db.block.BlockStore;
import com.caucho.db.jdbc.GeneratedKeysResultSet;
import com.caucho.db.table.Column;
import com.caucho.db.table.Table;
import com.caucho.db.table.TableIterator;

class IdentityExpr extends Expr {
  private Table _table;
  private Column _column;

  IdentityExpr(Table table, Column column)
  {
    _table = table;
    _column = column;
  }

  /**
   * Returns the type of the expression.
   */
  @Override
  public Class<?> getType()
  {
    return long.class;
  }

  /**
   * Evaluates the expression as a long
   *
   * @param row the current data tuple
   *
   * @return the long value
   */
  @Override
  public long evalLong(QueryContext context)
    throws SQLException
  {
    GeneratedKeysResultSet keysRS = context.getGeneratedKeysResultSet();

    final TableIterator []rows = context.getTableIterators();
    final TableIterator row = rows[0];
    
    long value = (row.getBlockId() & BlockStore.BLOCK_MASK) + row.getRowOffset();

    if (keysRS != null) {
      keysRS.setColumn(1, _column);
      keysRS.setLong(1, value);
    }

    return value;
  }

  /**
   * Evaluates the expression as a double
   *
   * @param row the current data tuple
   *
   * @return the double value
   */
  @Override
  public double evalDouble(QueryContext context)
    throws SQLException
  {
    return evalLong(context);
  }

  /**
   * Evaluates the expression as a string
   *
   * @param row the current data tuple
   *
   * @return the string value
   */
  @Override
  public String evalString(QueryContext context)
    throws SQLException
  {
    return String.valueOf(evalLong(context));
  }

  @Override
  public String toString()
  {
    return "identity()";
  }
}