/*
 * 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.FromClause;
import org.eclipse.persistence.jpa.jpql.parser.InternalFromClauseBNF;
import org.eclipse.persistence.jpa.jpql.tools.spi.IManagedType;

/**
 * The <code><b>FROM</b></code> clause of a query defines the domain of the query by declaring
 * identification variables. An identification variable is an identifier declared in the
 * <code><b>FROM</b></code> clause of a query. The domain of the query may be constrained by path
 * expressions. Identification variables designate instances of a particular entity abstract schema
 * type. The <code><b>FROM</b></code> clause can contain multiple identification variable
 * declarations separated by a comma (,).
 *
 * <pre><code>BNF: from_clause ::= FROM identification_variable_declaration {, {identification_variable_declaration | collection_member_declaration}}*</code></pre>
 *
 * @see CollectionMemberDeclarationStateObject
 * @see IdentificationVariableDeclarationStateObject
 * @see JoinStateObject
 * @see SelectStatementStateObject
 *
 * @see FromClause
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
public class FromClauseStateObject extends AbstractFromClauseStateObject {

    /**
     * Creates a new <code>FromClauseStateObject</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 FromClauseStateObject(SelectStatementStateObject parent) {
        super(parent);
    }

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

    @Override
    protected String declarationBNF() {
        return InternalFromClauseBNF.ID;
    }

    @Override
    public IManagedType findManagedType(StateObject stateObject) {
        // This is the declaration clause of the top-level query
        return getManagedType(stateObject);
    }

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

    @Override
    public SelectStatementStateObject getParent() {
        return (SelectStatementStateObject) super.getParent();
    }

    /**
     * Keeps a reference of the {@link FromClause 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 FromClause parsed object} representing a <code><b>FROM</b></code>
     * expression
     */
    public void setExpression(FromClause expression) {
        super.setExpression(expression);
    }
}