jpa/org.eclipse.persistence.jpa.jpql/src/main/java/org/eclipse/persistence/jpa/jpql/tools/model/query/AggregateFunctionStateObject.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 org.eclipse.persistence.jpa.jpql.parser.AggregateFunction;
import static org.eclipse.persistence.jpa.jpql.parser.AbstractExpression.*;

/**
 * In the <code><b>SELECT</b></code> clause the result of a query may be the result of an aggregate
 * function applied to a path expression.
 *
 * <pre><code>BNF: aggregate_expression ::= {AVG|MAX|MIN|SUM}([DISTINCT] state_field_path_expression) |
 *                              COUNT([DISTINCT] identification_variable | state_field_path_expression | single_valued_association_path_expression)</code></pre>
 *
 * @see org.eclipse.persistence.jpa.jpql.parser.AggregateFunction AggregateFunction
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
@SuppressWarnings({"nls", "unused"}) // unused used for the import statement: see bug 330740
public abstract class AggregateFunctionStateObject extends AbstractSingleEncapsulatedExpressionStateObject {

    /**
     * Determines whether the <code><b>DISTINCT</b></code> keyword is part of the query, which is
     * used to return only distinct (different) values.
     */
    private boolean distinct;

    /**
     * Notifies the visibility of the <code><b>DISTINCT</b></code> identifier has changed.
     */
    public static final String DISTINCT_PROPERTY = "distinct";

    /**
     * Creates a new <code>AggregateFunctionStateObject</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>
     */
    protected AggregateFunctionStateObject(StateObject parent) {
        super(parent);
    }

    /**
     * Creates a new <code>AggregateStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @param distinct <code>true</code> to add <code><b>DISTINCT</b></code> to the query in order to
     * have distinct values; <code>false</code> if it is not required
     * @param stateObject The {@link StateObject} representing the encapsulated expression
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    protected AggregateFunctionStateObject(StateObject parent,
                                           boolean distinct,
                                           StateObject stateObject) {

        super(parent, stateObject);
        this.distinct = distinct;
    }

    /**
     * Creates a new <code>AggregateFunctionStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @param distinct <code>true</code> to add <code><b>DISTINCT</b></code> to the query in order to
     * have distinct values; <code>false</code> if it is not required
     * @param path Either the identification variable or the state field path expression
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    protected AggregateFunctionStateObject(StateObject parent, boolean distinct, String path) {
        super(parent, path);
        this.distinct = distinct;
    }

    /**
     * Creates a new <code>AggregateStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @param stateObject The {@link StateObject} representing the encapsulated expression
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    protected AggregateFunctionStateObject(StateObject parent, StateObject stateObject) {
        this(parent, false, stateObject);
    }

    /**
     * Creates a new <code>AggregateFunctionStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @param path Either the identification variable or the state field path expression
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    protected AggregateFunctionStateObject(StateObject parent, String path) {
        super(parent, path);
    }

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

    /**
     * Sets whether the <code><b>DISTINCT</b></code> keyword should be part of the query, which is
     * used to return only distinct (different) values.
     *
     * @return <code>true</code> to add <code><b>DISTINCT</b></code> to the query in order to have
     * distinct values; <code>false</code> if it is not required
     */
    public boolean hasDistinct() {
        return distinct;
    }

    @Override
    public boolean isEquivalent(StateObject stateObject) {

        if (super.isEquivalent(stateObject)) {
            AggregateFunctionStateObject function = (AggregateFunctionStateObject) stateObject;
            return distinct == function.distinct;
        }

        return false;
    }

    /**
     * Sets whether the <code><b>DISTINCT</b></code> keyword should be part of the query, which is
     * used to return only distinct (different) values
     *
     * @param distinct <code>true</code> to add <code><b>DISTINCT</b></code> to the query in order to
     * have distinct values; <code>false</code> if it is not required
     */
    public void setDistinct(boolean distinct) {
        boolean oldDistinct = this.distinct;
        this.distinct = distinct;
        firePropertyChanged(DISTINCT_PROPERTY, oldDistinct, distinct);
    }

    @Override
    public void setStateObject(StateObject stateObject) {
        super.setStateObject(stateObject);
    }

    /**
     * Reverses the visibility of the <code><b>DISTINCT</b></code> identifier.
     */
    public void toggleDistinct() {
        setDistinct(!hasDistinct());
    }

    @Override
    protected void toTextEncapsulatedExpression(Appendable writer) throws IOException {

        if (hasDistinct()) {
            writer.append(DISTINCT);
            writer.append(SPACE);
        }

        super.toTextEncapsulatedExpression(writer);
    }
}