/*
 * Copyright (c) 2008, 2009 Sun Microsystems. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Linda DeMichiel - Java Persistence 2.0 - Version 2.0 (October 1, 2009)
 *     Specification available from http://jcp.org/en/jsr/detail?id=317
 */

// $Id: Subquery.java 20957 2011-06-13 09:58:51Z stliu $

package javax.persistence.criteria;

import java.util.List;
import java.util.Set;

/**
 * The <code>Subquery</code> interface defines functionality that is
 * specific to subqueries.
 *
 * A subquery has an expression as its selection item.
 *
 * @param <T> the type of the selection item.
 * @since Java Persistence 2.0
 */
public interface Subquery<T> extends AbstractQuery<T>, Expression<T> {
	/**
	 * Specify the item that is to be returned as the subquery
	 * result.
	 * Replaces the previously specified selection, if any.
	 *
	 * @param expression expression specifying the item that
	 * is to be returned as the subquery result
	 *
	 * @return the modified subquery
	 */
	Subquery<T> select(Expression<T> expression);

	/**
	 * Modify the subquery to restrict the result according
	 * to the specified boolean expression.
	 * Replaces the previously added restriction(s), if any.
	 * This method only overrides the return type of the
	 * corresponding <code>AbstractQuery</code> method.
	 *
	 * @param restriction a simple or compound boolean expression
	 *
	 * @return the modified subquery
	 */
	Subquery<T> where(Expression<Boolean> restriction);

	/**
	 * Modify the subquery to restrict the result according
	 * to the conjunction of the specified restriction predicates.
	 * Replaces the previously added restriction(s), if any.
	 * If no restrictions are specified, any previously added
	 * restrictions are simply removed.
	 * This method only overrides the return type of the
	 * corresponding <code>AbstractQuery</code> method.
	 *
	 * @param restrictions zero or more restriction predicates
	 *
	 * @return the modified subquery
	 */
	Subquery<T> where(Predicate... restrictions);

	/**
	 * Specify the expressions that are used to form groups over
	 * the subquery results.
	 * Replaces the previous specified grouping expressions, if any.
	 * If no grouping expressions are specified, any previously
	 * added grouping expressions are simply removed.
	 * This method only overrides the return type of the
	 * corresponding <code>AbstractQuery</code> method.
	 *
	 * @param grouping zero or more grouping expressions
	 *
	 * @return the modified subquery
	 */
	Subquery<T> groupBy(Expression<?>... grouping);

	/**
	 * Specify the expressions that are used to form groups over
	 * the subquery results.
	 * Replaces the previous specified grouping expressions, if any.
	 * If no grouping expressions are specified, any previously
	 * added grouping expressions are simply removed.
	 * This method only overrides the return type of the
	 * corresponding <code>AbstractQuery</code> method.
	 *
	 * @param grouping list of zero or more grouping expressions
	 *
	 * @return the modified subquery
	 */
	Subquery<T> groupBy(List<Expression<?>> grouping);

	/**
	 * Specify a restriction over the groups of the subquery.
	 * Replaces the previous having restriction(s), if any.
	 * This method only overrides the return type of the
	 * corresponding <code>AbstractQuery</code> method.
	 *
	 * @param restriction a simple or compound boolean expression
	 *
	 * @return the modified subquery
	 */
	Subquery<T> having(Expression<Boolean> restriction);

	/**
	 * Specify restrictions over the groups of the subquery
	 * according the conjunction of the specified restriction
	 * predicates.
	 * Replaces the previously added having restriction(s), if any.
	 * If no restrictions are specified, any previously added
	 * restrictions are simply removed.
	 * This method only overrides the return type of the
	 * corresponding <code>AbstractQuery</code> method.
	 *
	 * @param restrictions zero or more restriction predicates
	 *
	 * @return the modified subquery
	 */
	Subquery<T> having(Predicate... restrictions);

	/**
	 * Specify whether duplicate query results will be eliminated.
	 * A true value will cause duplicates to be eliminated.
	 * A false value will cause duplicates to be retained.
	 * If distinct has not been specified, duplicate results must
	 * be retained.
	 * This method only overrides the return type of the
	 * corresponding <code>AbstractQuery</code> method.
	 *
	 * @param distinct boolean value specifying whether duplicate
	 * results must be eliminated from the subquery result or
	 * whether they must be retained
	 *
	 * @return the modified subquery.
	 */
	Subquery<T> distinct(boolean distinct);

	/**
	 * Create a subquery root correlated to a root of the
	 * enclosing query.
	 *
	 * @param parentRoot a root of the containing query
	 *
	 * @return subquery root
	 */
	<Y> Root<Y> correlate(Root<Y> parentRoot);

	/**
	 * Create a subquery join object correlated to a join object
	 * of the enclosing query.
	 *
	 * @param parentJoin join object of the containing query
	 *
	 * @return subquery join
	 */
	<X, Y> Join<X, Y> correlate(Join<X, Y> parentJoin);

	/**
	 * Create a subquery collection join object correlated to a
	 * collection join object of the enclosing query.
	 *
	 * @param parentCollection join object of the containing query
	 *
	 * @return subquery join
	 */
	<X, Y> CollectionJoin<X, Y> correlate(CollectionJoin<X, Y> parentCollection);

	/**
	 * Create a subquery set join object correlated to a set join
	 * object of the enclosing query.
	 *
	 * @param parentSet join object of the containing query
	 *
	 * @return subquery join
	 */
	<X, Y> SetJoin<X, Y> correlate(SetJoin<X, Y> parentSet);

	/**
	 * Create a subquery list join object correlated to a list join
	 * object of the enclosing query.
	 *
	 * @param parentList join object of the containing query
	 *
	 * @return subquery join
	 */
	<X, Y> ListJoin<X, Y> correlate(ListJoin<X, Y> parentList);

	/**
	 * Create a subquery map join object correlated to a map join
	 * object of the enclosing query.
	 *
	 * @param parentMap join object of the containing query
	 *
	 * @return subquery join
	 */
	<X, K, V> MapJoin<X, K, V> correlate(MapJoin<X, K, V> parentMap);

	/**
	 * Return the query of which this is a subquery.
	 *
	 * @return the enclosing query or subquery
	 */
	AbstractQuery<?> getParent();

	/**
	 * Return the selection expression.
	 *
	 * @return the item to be returned in the subquery result
	 */
	Expression<T> getSelection();

	/**
	 * Return the correlated joins of the subquery.
	 * Returns empty set if the subquery has no correlated
	 * joins.
	 * Modifications to the set do not affect the query.
	 *
	 * @return the correlated joins of the subquery
	 */
	Set<Join<?, ?>> getCorrelatedJoins();
}