/*
 * Copyright (c) 2011, 2021 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle - initial API and implementation
//
package org.eclipse.persistence.jpa.jpql.tools.model.query;

import org.eclipse.persistence.jpa.jpql.parser.SimpleSelectStatement;
import org.eclipse.persistence.jpa.jpql.tools.model.ISimpleSelectExpressionStateObjectBuilder;

/**
 * This state object represents a subquery, which has at least a <code><b>SELECT</b></code> clause
 * and a <code><b>FROM</b></code> clause. The other clauses are optional.
 * <p>
 * <b>BNF:</b> <code>subquery ::= simple_select_clause subquery_from_clause [where_clause] [groupby_clause] [having_clause]</code><p>
 *
 * @see SimpleSelectStatement
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
public class SimpleSelectStatementStateObject extends AbstractSelectStatementStateObject {

    /**
     * Creates a new <code>SimpleSelectStatementStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    public SimpleSelectStatementStateObject(StateObject parent) {
        super(parent);
    }

    @Override
    public void accept(StateObjectVisitor visitor) {
        visitor.visit(this);
    }

    /**
     * Adds a new derived collection declaration to the <code><b>FROM</b></code> clause.
     *
     * @return The {@link CollectionMemberDeclarationStateObject} representing the collection
     * declaration
     */
    public CollectionMemberDeclarationStateObject addDerivedCollectionDeclaration() {
        return getFromClause().addDerivedCollectionDeclaration();
    }

    /**
     * Adds a new derived collection declaration to the <code><b>FROM</b></code> clause.
     *
     * @param collectionValuedPath The collection-valued path expression
     * @return The {@link CollectionMemberDeclarationStateObject} representing the collection
     * declaration
     */
    public CollectionMemberDeclarationStateObject addDerivedCollectionDeclaration(String collectionValuedPath) {
        return getFromClause().addDerivedCollectionDeclaration(collectionValuedPath);
    }

    /**
     * Adds a new derived identification variable declaration to the <code><b>FROM</b></code> clause.
     *
     * @return The {@link DerivedPathIdentificationVariableDeclarationStateObject} representing the collection
     * declaration
     */
    public DerivedPathIdentificationVariableDeclarationStateObject addDerivedPathDeclaration() {
        return getFromClause().addDerivedPathDeclaration();
    }

    /**
     * Adds a new derived identification variable declaration to the <code><b>FROM</b></code> clause.
     *
     * @param path Either the derived singled-valued object field or the collection-valued path expression
     * @param identificationVariable The identification variable defining the given path
     * @return The {@link DerivedPathIdentificationVariableDeclarationStateObject} representing the
     * path declaration
     */
    public DerivedPathIdentificationVariableDeclarationStateObject addDerivedPathDeclaration(String path,
                                                                                             String identificationVariable) {

        return getFromClause().addDerivedPathDeclaration(path, identificationVariable);
    }

    @Override
    protected AbstractFromClauseStateObject buildFromClause() {
        return new SimpleFromClauseStateObject(this);
    }

    @Override
    protected AbstractSelectClauseStateObject buildSelectClause() {
        return new SimpleSelectClauseStateObject(this);
    }

    @Override
    public SimpleSelectStatement getExpression() {
        return (SimpleSelectStatement) super.getExpression();
    }

    @Override
    public SimpleFromClauseStateObject getFromClause() {
        return (SimpleFromClauseStateObject) super.getFromClause();
    }

    /**
     * Creates and returns a new {@link ISimpleSelectExpressionStateObjectBuilder} that can be used
     * to programmatically create a single select expression and once the expression is complete,
     * {@link ISimpleSelectExpressionStateObjectBuilder#commit()} will push the {@link StateObject}
     * representation of that expression as this clause's select expression.
     *
     * @return A new builder that can be used to quickly create a select expression
     */
    public ISimpleSelectExpressionStateObjectBuilder getSelectBuilder() {
        return getSelectClause().getBuilder();
    }

    @Override
    public SimpleSelectClauseStateObject getSelectClause() {
        return (SimpleSelectClauseStateObject) super.getSelectClause();
    }

    /**
     * Keeps a reference of the {@link SimpleSelectStatement parsed object} object, which should only
     * be done when this object is instantiated during the conversion of a parsed JPQL query into
     * {@link StateObject StateObjects}.
     *
     * @param expression The {@link SimpleSelectStatement parsed object} representing a subquery
     * <code><b>SELECT</b></code> statement
     */
    public void setExpression(SimpleSelectStatement expression) {
        super.setExpression(expression);
    }

    /**
     * Sets the given {@link StateObject} as the <code><b>SELECT</b></code> clause's select item.
     *
     * @param stateObject The {@link StateObject} representing the single select item
     */
    public void setSelectItem(StateObject stateObject) {
        getSelectClause().setSelectItem(stateObject);
    }

    /**
     * Parses the given JPQL fragment and create the select item. For the top-level query, the
     * fragment can contain several select items but for a subquery, it can represent only one.
     *
     * @param jpqlFragment The portion of the query representing one or several select items
     */
    public void setSelectItem(String jpqlFragment) {
        getSelectClause().parse(jpqlFragment);
    }
}