/*

 * Copyright (c) 2007-2008 Nokia Corporation and/or its subsidiary(-ies).

 * All rights reserved.

 * This component and the accompanying materials are made available

 * under the terms of the License "Eclipse Public License v1.0"

 * which accompanies this distribution, and is available

 * at the URL "http://www.eclipse.org/legal/epl-v10.html".

 *

 * Initial Contributors:

 * Nokia Corporation - initial contribution.

 *

 * Contributors:

 *

 * Description:  

 *

 */

package com.nokia.helium.metadata.fmpp;

import java.util.List;

import javax.persistence.EntityManager;

import javax.persistence.Query;

import freemarker.template.SimpleScalar;

import freemarker.template.TemplateModel;

import freemarker.template.TemplateModelIterator;

/**

 * Internal Iterator class which provides data as collection. 

 */

class ORMTemplateModelIterator implements TemplateModelIterator {

    private static final int PAGE_SIZE = 2000;

    private String queryString;

    private Query query;

    private int index;

    private String returnType;

    private boolean nativeQuery;

    private EntityManager entityManager;

    private List<Object> data;

    private int currentPage;

    private Object next;

    public ORMTemplateModelIterator(EntityManager entityManager, String queryString, String type, String retType) {

        this.entityManager = entityManager;

        this.queryString = queryString;

        returnType = retType;

        if (type.startsWith("native")) {

            nativeQuery = true;

        }

        index = 0;

    }

    /**

     * {@inheritDoc}

     */

    public TemplateModel next() {

        Object value = next;

        next = null;

        if (value != null) {

            if (nativeQuery && returnType.equals("java.lang.String")) {

                return new SimpleScalar((String)value);

            } else {

                return new ORMObjectModel(value);

            }

        }

        return null;

    }

    /**

     * {@inheritDoc}

     */

    @SuppressWarnings("unchecked")

    public boolean hasNext() {

        int page = index / PAGE_SIZE;

        if (query == null || page != currentPage) {

            if (nativeQuery) {

                query = entityManager.createNativeQuery(queryString);

            } else {

                query = entityManager.createQuery(queryString);

            }

            query.setFirstResult(page * PAGE_SIZE);

            query.setMaxResults(PAGE_SIZE);

            data = query.getResultList();

            currentPage = page;

        }

        if (next == null && index < data.size()) {

            next = data.get(index);

            index++;

        }

        return next != null;

    }

}