/*
 * Copyright (c) 1998-2006 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 Software Foundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.db.table;

import java.util.ArrayList;

import java.io.IOException;

import java.sql.SQLException;

import com.caucho.util.L10N;

import com.caucho.sql.SQLExceptionWrapper;

import com.caucho.db.index.BTree;

import com.caucho.db.store.Transaction;

import com.caucho.db.sql.Expr;
import com.caucho.db.sql.QueryContext;

/**
 * Validity constraints.
 */
public class UniqueSingleColumnConstraint extends Constraint {
  private final static L10N L = new L10N(UniqueSingleColumnConstraint.class);
  private final Column _uniqueColumn;

  /**
   * Creates a uniqueness constraint.
   */
  public UniqueSingleColumnConstraint(Column column)
  {
    _uniqueColumn = column;
  }

  /**
   * validate the constraint.
   */
  public void validate(TableIterator []sourceRows,
		       QueryContext queryContext, Transaction xa)
    throws SQLException
  {
    Column column = _uniqueColumn;
    int columnOffset = column.getColumnOffset();

    BTree index = column.getIndex();

    if (index != null) {
      validateIndex(sourceRows, queryContext, xa);
      return;
    }
      
    TableIterator sourceRow = sourceRows[0];
    String value = null;

    Table table = sourceRow.getTable();
    TableIterator iter = table.createTableIterator();

    try {
      byte []sourceBuffer = sourceRow.getBuffer();
      int sourceOffset = sourceRow.getRowOffset();

      iter.init(queryContext);

      while (iter.next()) {
	byte []iterBuffer = iter.getBuffer();

	iter.prevRow();
	
	while (iter.nextRow()) {
	  int iterOffset = iter.getRowOffset();

	  if (iterBuffer == sourceBuffer && iterOffset == sourceOffset)
	    continue;

	  if (column.isEqual(iterBuffer, iterOffset,
			     sourceBuffer, sourceOffset)) 
	    throw new SQLException(L.l("`{0}' in {1}.{2} fails uniqueness constraint.",
				       column.getString(iterBuffer, iterOffset),
				       table.getName(),
				       column.getName()));
	}
      }
    } catch (IOException e) {
      throw new SQLExceptionWrapper(e);
    } finally {
      iter.free();
    }
  }

  /**
   * validate the constraint.
   */
  private void validateIndex(TableIterator []sourceRows,
			     QueryContext context, Transaction xa)
    throws SQLException
  {
    try {
      Column column = _uniqueColumn;
      TableIterator sourceRow = sourceRows[0];

      byte []sourceBuffer = sourceRow.getBuffer();
      int sourceOffset = sourceRow.getRowOffset();
      
      byte []buffer = context.getBuffer();

      BTree index = column.getIndex();

      /*
      int length = column.evalToBuffer(sourceBuffer, sourceOffset,
				       buffer, 0);

      if (length <= 0)
	return;

      long value = index.lookup(buffer, 0, length,
				context.getTransaction());
				
      */

      // currently this is a static length.  See StringColumn.
      int length = column.getLength();
      int offset = sourceOffset + _uniqueColumn.getColumnOffset();
      long value = index.lookup(sourceBuffer, offset, length,
				context.getTransaction());

      if (value != 0) {
	Table table = sourceRow.getTable();

	throw new SQLException(L.l("`{0}' in {1}.{2} fails uniqueness constraint.",
				   column.getString(sourceBuffer,
						    sourceOffset),
				   table.getName(),
				   column.getName()));
      }
    } catch (IOException e) {
      throw new SQLExceptionWrapper(e);
    }
  }
}
