/*
 * Copyright (c) 2006, 2020 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.internal.jpa.jpql;

import org.eclipse.persistence.jpa.jpql.parser.AbstractSelectClause;
import org.eclipse.persistence.jpa.jpql.parser.AbstractSelectStatement;
import org.eclipse.persistence.jpa.jpql.parser.CollectionExpression;
import org.eclipse.persistence.jpa.jpql.parser.EclipseLinkAnonymousExpressionVisitor;
import org.eclipse.persistence.jpa.jpql.parser.GroupByClause;
import org.eclipse.persistence.jpa.jpql.parser.HavingClause;
import org.eclipse.persistence.jpa.jpql.parser.IdentificationVariable;
import org.eclipse.persistence.queries.ReportQuery;

/**
 * This visitor is responsible to populate a {@link ReportQuery}.
 *
 * @version 2.4
 * @since 2.3
 * @author Pascal Filion
 * @author John Bracken
 */
final class ReportQueryVisitor extends ReadAllQueryVisitor {

    /**
     * This array is used to store the type of the select {@link org.eclipse.persistence.jpa.jpql
     * parser.Expression JPQL Expression} that is converted into an {@link org.eclipse.persistence.
     * expressions.Expression EclipseLink Expression}.
     */
    Class<?> type;

    /**
     * Creates a new <code>ReportQueryVisitor</code>.
     *
     * @param queryContext The context used to query information about the application metadata and
     * cached information
     * @param query The {@link ReportQuery} to populate by using this visitor to visit the parsed
     * tree representation of the JPQL query
     */
    ReportQueryVisitor(JPQLQueryContext queryContext, ReportQuery query) {
        super(queryContext, query);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(GroupByClause expression) {
        GroupByVisitor visitor = new GroupByVisitor();
        expression.accept(visitor);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(HavingClause expression) {
        ((ReportQuery) query).setHavingExpression(queryContext.buildExpression(expression));
    }

    /**
     * {@inheritDoc}
     */
    @Override
    void visitAbstractSelectClause(AbstractSelectClause expression) {

        // First set couple flags on the query
        super.visitAbstractSelectClause(expression);

        // Now visit the select expressions and create the corresponding EclipseLink Expressions
        ReportItemBuilder builder = new ReportItemBuilder(queryContext, (ReportQuery) query);
        expression.accept(builder);
        type = builder.type[0];
    }

    /**
     * {@inheritDoc}
     */
    @Override
    void visitAbstractSelectStatement(AbstractSelectStatement expression) {

        super.visitAbstractSelectStatement(expression);

        if (expression.hasHavingClause()) {
            expression.getHavingClause().accept(this);
        }

        if (expression.hasGroupByClause()) {
            expression.getGroupByClause().accept(this);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    void visitIdentificationVariable(IdentificationVariable expression) {
        // ReportQuery does not require it
    }

    /**
     * This visitor is responsible to add the {@link org.eclipse.persistence.jpa.jpql.parser.Expression
     * group items} by traversing the group items.
     */
    private class GroupByVisitor extends EclipseLinkAnonymousExpressionVisitor {

        /**
         * {@inheritDoc}
         */
        @Override
        public void visit(CollectionExpression expression) {
            expression.acceptChildren(this);
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public void visit(GroupByClause expression) {
            expression.getGroupByItems().accept(this);
        }

        /**
         * {@inheritDoc}
         */
        @Override
        protected void visit(org.eclipse.persistence.jpa.jpql.parser.Expression expression) {
            ((ReportQuery) query).addGrouping(queryContext.buildExpression(expression));
        }
    }
}