/*
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is the Kowari Metadata Store.
 *
 * The Initial Developer of the Original Code is Plugged In Software Pty
 * Ltd (http://www.pisoftware.com, mailto:info@pisoftware.com). Portions
 * created by Plugged In Software Pty Ltd are Copyright (C) 2001,2002
 * Plugged In Software Pty Ltd. All Rights Reserved.
 *
 * Contributor(s): N/A.
 *
 * [NOTE: The text of this Exhibit A may differ slightly from the text
 * of the notices in the Source Code files of the Original Code. You
 * should use the text of this Exhibit A rather than the text found in the
 * Original Code Source Code for Your Modifications.]
 *
 */

package org.mulgara.store.tuples;

import java.util.Collections;
import java.util.List;

// Locally written packages
import org.mulgara.query.TuplesException;

/**
 * A tuples representing an uncontrained version of tuples.
 *
 * @created 2003-11-27
 *
 * @author Andrew Newman
 *
 * @version $Revision: 1.9 $
 *
 * @modified $Date: 2005/01/05 04:59:10 $
 *
 * @maintenanceAuthor $Author: newmana $
 *
 * @company <A href="mailto:info@PIsoftware.com">Plugged In Software</A>
 *
 * @copyright © 2003 <A href="http://www.PIsoftware.com/">Plugged In
 *      Software Pty Ltd</A>
 *
 * @licence <a href="{@docRoot}/../../LICENCE">Mozilla Public License v1.1</a>
 */
public class UnconstrainedTuples extends AbstractTuples implements StoreTuples {

  /**
   * The current row number.
   */
  private int rowNumber = 0;

  /**
   * The singleton version of the unconstrained tuples.
   */
  private static final UnconstrainedTuples tuples = new UnconstrainedTuples();

  private static final int[] columnOrder = new int[0];

  /**
   * Returns the singleton of this class.
   *
   * @return the singleton of this class.
   */
  public static UnconstrainedTuples getInstance() {
    return tuples;
  }

  /**
   * Generate an unconstrained expression.
   */
  private UnconstrainedTuples() {
  }

  //
  // Methods implementing Tuples interface
  //

  /**
   * METHOD TO DO
   *
   * @param prefix PARAMETER TO DO
   * @param suffixTruncation PARAMETER TO DO
   * @throws TuplesException EXCEPTION TO DO
   */
  public void beforeFirst(long[] prefix, int suffixTruncation)
      throws TuplesException {
    rowNumber = 0;
  }

  /**
   * METHOD TO DO
   *
   * @return RETURNED VALUE TO DO
   * @throws TuplesException EXCEPTION TO DO
   */
  public boolean next() throws TuplesException {
    boolean hasNext = (rowNumber == 0);
    rowNumber++;
    return hasNext;
  }

  /**
   * Gets the ColumnValue attribute of the MemoryTuples object
   *
   * @param column PARAMETER TO DO
   * @return The ColumnValue value
   * @throws TuplesException EXCEPTION TO DO
   */
  public long getColumnValue(int column) throws TuplesException {
    return Tuples.UNBOUND;
  }

  /**
   * Unconstrained tuples always returns 1.
   *
   * @return The RowCount value
   */
  public long getRowCount() {
    return 1;
  }

  public long getRowUpperBound() {
    return getRowCount();
  }

  public long getRowExpectedCount() {
    return getRowCount();
  }

  public boolean isEmpty() throws TuplesException {
    return false;
  }

  /**
   * Unconstrained has no columns that can be unbound.
   *
   * @throws TuplesException always, because there's no possible valid value
   *   for the <var>column</var> parameter
   */
  public boolean isColumnEverUnbound(int column) throws TuplesException {
    throw new TuplesException("No such column " + column);
  }

  public boolean hasNoDuplicates() {
    return true;
  }

  /**
   * Always returns true - unconstrained is always materialized.
   *
   * @return return true - unconstrained is always materialized.
   */
  public boolean isMaterialized() {
    return true;
  }

  public List<Tuples> getOperands() {
    return Collections.emptyList();
  }

  /**
   * Returns an array which maps from column index to triple node index
   * (Subject=0, Predicate=1, Object=2, Meta=3).
   *
   * @return the array describing the column mapping.
   * @throws TuplesException EXCEPTION TO DO
   */
  public int[] getColumnOrder() {
    return columnOrder;
  }


  //
  // Methods overriding the Object class
  //

  /**
   * METHOD TO DO
   *
   * @param object PARAMETER TO DO
   * @return RETURNED VALUE TO DO
   */
  public boolean equals(Object object) {
    return (object == this);
  }

  /**
   * Added to match {@link #equals(Object)}.
   */
  public int hashCode() {
    return super.hashCode();
  }

  /**
   * Returns itself.
   *
   * @return itself.
   */
  public Object clone() {
    return tuples;
  }

  /**
   * METHOD TO DO
   */
  public void close() {
    // NO-OP
  }
}