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The eobjects.dk MetaModel is a common domain model, query-engine and optimizer for different kinds of datastores.
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/*
 * Copyright 2008 eobjects.dk
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package dk.eobjects.metamodel.query;

import org.apache.commons.lang.builder.EqualsBuilder;

/**
 * Represents an ORDER BY item. An OrderByItem sorts the resulting DataSet
 * according to a SelectItem that may or may not be a part of the query already.
 * 
 * @see OrderByClause
 * @see SelectItem
 */
public class OrderByItem implements IQueryItem, Cloneable {

	public enum Direction {
		ASC, DESC
	}

	private static final long serialVersionUID = -8397473619828484774L;
	private Direction _direction;
	private SelectItem _selectItem;
	private Query _query;

	/**
	 * Private constructor, used for cloning
	 */
	private OrderByItem() {
	}

	/**
	 * Creates an OrderByItem
	 * 
	 * @param selectItem
	 *            the select item to order
	 * @param direction
	 *            the direction to order the select item
	 */
	public OrderByItem(SelectItem selectItem, Direction direction) {
		if (selectItem == null) {
			throw new IllegalArgumentException("SelectItem cannot be null");
		}
		_selectItem = selectItem;
		_direction = direction;
	}

	/**
	 * Creates an OrderByItem
	 * 
	 * @param selectItem
	 * @param ascending
	 * @deprecated user OrderByItem(SelectItem, Direction) instead
	 */
	@Deprecated
	public OrderByItem(SelectItem selectItem, boolean ascending) {
		if (selectItem == null) {
			throw new IllegalArgumentException("SelectItem cannot be null");
		}
		_selectItem = selectItem;
		if (ascending) {
			_direction = Direction.ASC;
		} else {
			_direction = Direction.DESC;
		}
	}

	/**
	 * Creates an ascending OrderByItem
	 * 
	 * @param selectItem
	 */
	public OrderByItem(SelectItem selectItem) {
		this(selectItem, Direction.ASC);
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append(_selectItem.getSameQueryAlias() + ' ');
		sb.append(_direction);
		return sb.toString();
	}

	@Override
	public boolean equals(Object obj) {
		if (obj == this) {
			return true;
		}
		if (obj instanceof OrderByItem) {
			OrderByItem that = (OrderByItem) obj;
			EqualsBuilder eb = new EqualsBuilder();
			eb.append(this.getDirection(), that.getDirection());
			eb.append(this.getSelectItem(), that.getSelectItem());
			return eb.isEquals();
		}
		return false;
	}

	public boolean isAscending() {
		return (_direction == Direction.ASC);
	}

	public boolean isDescending() {
		return (_direction == Direction.DESC);
	}

	public Direction getDirection() {
		return _direction;
	}

	public OrderByItem setDirection(Direction direction) {
		_direction = direction;
		return this;
	}

	public SelectItem getSelectItem() {
		return _selectItem;
	}

	public Query getQuery() {
		return _query;
	}

	public OrderByItem setQuery(Query query) {
		_query = query;
		if (_selectItem != null) {
			_selectItem.setQuery(query);
		}
		return this;
	}

	@Override
	protected OrderByItem clone() {
		OrderByItem o = new OrderByItem();
		o._direction = _direction;
		o._selectItem = _selectItem.clone();
		return o;
	}
}