foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/internal/jpa/parsing/CaseNode.java

/*
 * Copyright (c) 1998, 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:
//     tware - initial implementation as part of JPA 2.0 RI
package org.eclipse.persistence.internal.jpa.parsing;

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import org.eclipse.persistence.expressions.Expression;
import org.eclipse.persistence.queries.ObjectLevelReadQuery;
import org.eclipse.persistence.queries.ReportQuery;

/**
 * INTERNAL
 * <p><b>Purpose</b>: Represent an CASE statement in EJBQL
 * <p><b>Responsibilities</b>:<ul>
 * <li> Generate the correct expression for an CASE in EJBQL
 * </ul>
 *    @author tware
 *    @since EclipseLink 1.2
 */
public class CaseNode extends Node implements AliasableNode {

    private List<Node> whenClauses = null;


    public CaseNode(){
        super();
    }

    /**
     * INTERNAL
     * Apply this node to the passed query
     */
    @Override
    public void applyToQuery(ObjectLevelReadQuery theQuery, GenerationContext generationContext) {
        if (theQuery instanceof ReportQuery) {
            ReportQuery reportQuery = (ReportQuery)theQuery;
            Expression expression = generateExpression(generationContext);
            reportQuery.addAttribute("Case", expression, (Class<?>)getType());
        }
    }

    /**
     * INTERNAL
     * Generate the a new EclipseLink TableEntryExpression for this node.
     */
    @Override
    public Expression generateExpression(GenerationContext context) {
        Map<Expression, Expression> whenClauseMap = new LinkedHashMap<>(whenClauses.size());
        Iterator<Node> i = whenClauses.iterator();
        while (i.hasNext()){
            WhenThenNode clause = (WhenThenNode)i.next();
            whenClauseMap.put(clause.generateExpressionForWhen(context), clause.generateExpressionForThen(context));
        }

        Expression whereClause = null;
        if (getLeft() == null){
            whereClause = context.getBaseExpression().caseStatement(whenClauseMap, getRight().generateExpression(context));
        } else {
            whereClause = getLeft().generateExpression(context).caseStatement(whenClauseMap, getRight().generateExpression(context));
        }
        return whereClause;
    }

    @Override
    public void validate(ParseTreeContext context) {
        TypeHelper typeHelper = context.getTypeHelper();
        if (left != null){
            left.validate(context);
        }
        right.validate(context);
        Iterator<Node> i = whenClauses.iterator();
        Object type = null;
        while (i.hasNext()){
            Node node = i.next();
            node.validate(context);
            if (type == null){
                type = node.getType();
            } else if (!type.equals(node.getType())){
                type = Object.class;
            }
        }
        if (getRight().getType() != type){
            type = typeHelper.getObjectType();
        }
        setType(type);
    }


    public List<Node> getWhenClauses() {
        return whenClauses;
    }

    public void setWhenClauses(List<Node> whenClauses) {
        this.whenClauses = whenClauses;
    }

    @Override
    public boolean isAliasableNode(){
        return true;
    }
}