jpa/org.eclipse.persistence.jpa.jpql/src/main/java/org/eclipse/persistence/jpa/jpql/tools/model/query/CollectionExpressionStateObject.java

/*
 * 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 java.io.IOException;
import java.util.List;
import org.eclipse.persistence.jpa.jpql.parser.CollectionExpression;

/**
 * This {@link StateObject} is a temporary object used to store a list of {@link StateObject
 * StateObjects}. Those objects are not parented. {@link StateObjectVisitor} is not aware of this
 * object either, to visit it, the visitor will be notified via reflection, see {@link
 * AbstractStateObject#acceptUnknownVisitor(StateObjectVisitor)}.
 *
 * @see CollectionExpression
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
public final class CollectionExpressionStateObject extends AbstractStateObject {

    /**
     * The list of children owned by this state object.
     */
    private List<? extends StateObject> items;

    /**
     * Creates a new <code>CollectionExpressionStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @param items The list of children owned by this state object
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    public CollectionExpressionStateObject(StateObject parent, List<? extends StateObject> items) {
        super(parent);
        this.items = items;
    }

    @Override
    public void accept(StateObjectVisitor visitor) {
        acceptUnknownVisitor(visitor);
    }

    @Override
    protected void addChildren(List<StateObject> children) {
        children.addAll(items);
    }

    /**
     * Determines whether the children of this {@link StateObject} are equivalent to the children
     * of the given one, i.e. the information of the {@link StateObject StateObjects} is the same.
     *
     * @param stateObject The {@link StateObject} to compare its children to this one's children
     * @return <code>true</code> if both have equivalent children; <code>false</code> otherwise
     */
    protected boolean areChildrenEquivalent(CollectionExpressionStateObject stateObject) {

        int size = items.size();

        if (size != stateObject.items.size()) {
            return false;
        }

        for (int index = size; --index >= 0; ) {

            StateObject child1 = items.get(index);
            StateObject child2 = stateObject.items.get(index);

            if (!child1.isEquivalent(child2)) {
                return false;
            }
        }

        return true;
    }

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

    @Override
    public boolean isEquivalent(StateObject stateObject) {

        if (super.isEquivalent(stateObject)) {
            CollectionExpressionStateObject collection = (CollectionExpressionStateObject) stateObject;
            return areChildrenEquivalent(collection);
        }

        return false;
    }

    /**
     * Keeps a reference of the {@link CollectionExpression 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 CollectionExpression parsed object} representing a collection
     * expression
     */
    public void setExpression(CollectionExpression expression) {
        super.setExpression(expression);
    }

    @Override
    protected void toTextInternal(Appendable writer) throws IOException {
        toStringItems(writer, items, true);
    }
}