EDIT

/**

* Copyright (C) 2017 EDIT

* European Distributed Institute of Taxonomy

* http://www.e-taxonomy.eu

*

* The contents of this file are subject to the Mozilla Public License Version 1.1

* See LICENSE.TXT at the top of this package for the full license terms.

*/

package eu.etaxonomy.cdm.service;

import org.apache.log4j.Logger;

import org.hibernate.Session;

import org.hibernate.engine.spi.SessionImplementor;

import org.springframework.transaction.TransactionStatus;

import org.springframework.transaction.support.DefaultTransactionDefinition;

import com.vaadin.ui.Notification;

import com.vaadin.ui.UI;

import eu.etaxonomy.cdm.api.application.CdmRepository;

import eu.etaxonomy.cdm.api.service.DeleteResult;

import eu.etaxonomy.cdm.api.service.IService;

import eu.etaxonomy.cdm.model.common.CdmBase;

import eu.etaxonomy.cdm.model.common.IdentifiableEntity;

import eu.etaxonomy.cdm.vaadin.event.EntityChangeEvent;

import eu.etaxonomy.cdm.vaadin.event.EntityChangeEvent.Type;

import eu.etaxonomy.vaadin.mvp.AbstractView;

/**

 * @author a.kohlbecker

 * @since Jun 26, 2017

 *

 * TODO better naming of this class, ServiceWrapper, ServiceOperator, ...?

 *

 */

public class CdmStore<T extends CdmBase, S extends IService<T>> {

    private static final Logger logger = Logger.getLogger(CdmStore.class);

    private CdmRepository repo;

    private S service;

    TransactionStatus txStatus = null;

    protected DefaultTransactionDefinition txDefinition = null;

    /**

     *

     * @param repo

     * @param service

     *            may be <code>null</code>, but delete operations will fail with

     *            a NullPointerException in this case.

     */

    public CdmStore(CdmRepository repo, S service) {

        this.repo = repo;

        this.service = service;

    }

    /**

     * @return

     *

     */

    public TransactionStatus startTransaction() {

        checkExistingTransaction();

        txStatus = repo.startTransaction();

        return txStatus;

    }

    /**

     *

     */

    protected void checkExistingTransaction() {

        if (txStatus != null) {

            // @formatter:off

            // holding the TransactionStatus as state is not good design. we

            // should change the save operation

            // in the EditorView so that the presenter can process the save in

            // one method call.

            // Problems:

            // 1. the fieldGroup needs a open session and read transaction

            // during the validation, otherwise

            // LazyInitialisationExceptions occur.

            // 2. passing the TransactionState to the view also doesn't seem

            // like a good idea.

            // @formatter:on

            throw new RuntimeException("Opening a second transaction in the same" + this.getClass().getSimpleName() + " is not supported");

        }

    }

    /**

     * If the bean is contained in the session it is being updated by doing an

     * evict and merge. The fieldGroup is updated with the merged bean.

     *

     *

     * @param bean

     * @return The bean merged to the session or original bean in case a merge

     *         was not necessary.

     */

    public T mergedBean(T bean) throws IllegalStateException {

        Session session = getSession();

        if (session.contains(bean)) {

            // evict bean before merge to avoid duplicate beans in same session

            logger.trace(this._toString() + ".mergedBean() - evict " + bean.toString());

            session.evict(bean);

        }

        logger.trace(this._toString() + ".mergedBean() - doing merge of" + bean.toString());

        // to avoid merge problems as described in https://dev.e-taxonomy.eu/redmine/issues/6687

        // we are set the hibernate property hibernate.event.merge.entity_copy_observer=allow

        @SuppressWarnings("unchecked")

        T mergedBean = (T) session.merge(bean);

        logger.trace(this._toString() + ".mergedBean() - bean after merge " + bean.toString());

        return mergedBean;

    }

    /**

     * @return

     */

    private Session getSession() {

        Session session = repo.getSession();

        logger.trace(this._toString() + ".getSession() - session:" + session.hashCode() + ", persistenceContext: "

                + ((SessionImplementor) session).getPersistenceContext() + " - " + session.toString());

        return session;

    }

    protected String _toString() {

        return this.getClass().getSimpleName() + "@" + this.hashCode();

    }

    /**

     *

     * @param bean

     *

     * @return the merged bean, this bean is <b>not reloaded</b> from the

     *         persistent storage.

     */

    public EntityChangeEvent saveBean(T bean, AbstractView view) {

        Type changeEventType;

        if(bean.isPersited()){

            changeEventType = Type.MODIFIED;

        } else {

            changeEventType = Type.CREATED;

        }

        Session session = getSession();

        try {

            logger.trace(this._toString() + ".onEditorSaveEvent - session: " + session.hashCode());

            if(txStatus == null){

                // no running transaction, start one ...

                startTransaction();

            }

            logger.trace(this._toString() + ".onEditorSaveEvent - merging bean into session");

            // merge the changes into the session, ...

            T mergedBean = mergedBean(bean);

            session.flush();

            commitTransaction();

            return new EntityChangeEvent(mergedBean, changeEventType, view);

        } finally {

            session.clear(); // #7559

        }

    }

    /**

     *

     * @param bean

     * @return a EntityChangeEvent in case the deletion was successful otherwise <code>null</code>.

     */

    public final EntityChangeEvent deleteBean(T bean, AbstractView view) {

        logger.trace(this._toString() + ".onEditorPreSaveEvent - starting transaction");

        Session session = getSession();

        try {

            startTransaction();

            logger.trace(this._toString() + ".deleteBean - deleting" + bean.toString());

            DeleteResult result = service.delete(bean);

            if (result.isOk()) {

                session.flush();

                commitTransaction();

                logger.trace(this._toString() + ".deleteBean - transaction comitted");

                return new EntityChangeEvent(bean, Type.REMOVED, view);

            } else {

                handleDeleteresultInError(result, session);

                txStatus = null;

            }

        } finally {

            session.clear(); // #7559

        }

        return null;

    }

    /**

     * @param result

     */

    public static void handleDeleteresultInError(DeleteResult result, Session session) {

        String notificationTitle;

        StringBuffer messageBody = new StringBuffer();

        if (result.isAbort()) {

            notificationTitle = "The delete operation as abborded by the system.";

        } else {

            notificationTitle = "An error occured during the delete operation.";

        }

        if (!result.getExceptions().isEmpty()) {

            messageBody.append("<h3>").append("Exceptions:").append("</h3>").append("<ul>");

            result.getExceptions().forEach(e -> messageBody.append("<li>").append(e.getMessage()).append("</li>"));

            messageBody.append("</ul>");

            /*

             * not needed since covered by clear() in finally clause

            if(result.getExceptions().stream().anyMatch(e -> HibernateException.class.isAssignableFrom(e.getClass()))){

                session.clear(); // #7559

            }

            */

        }

        if (!result.getRelatedObjects().isEmpty()) {

            messageBody.append("<h3>").append("Related objects exist:").append("</h3>").append("<ul>");

            result.getRelatedObjects().forEach(e -> {

                messageBody.append("<li>");

                if (IdentifiableEntity.class.isAssignableFrom(e.getClass())) {

                    messageBody.append(((IdentifiableEntity) e).getTitleCache());

                } else {

                    messageBody.append(e.toString());

                }

                messageBody.append("</li>");

            });

            messageBody.append("</ul>");

        }

        Notification notification = new Notification(notificationTitle, messageBody.toString(),

                com.vaadin.ui.Notification.Type.ERROR_MESSAGE, true);

        notification.show(UI.getCurrent().getPage());

    }

    protected void commitTransaction() {

        repo.commitTransaction(txStatus);

        txStatus = null;

    }

    /**

     * @param entityId

     */

    public T loadBean(int entityId) {

        return service.find(entityId);

    }

    public S getService() {

        return service;

    }

}