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 com.vaadin.ui.Notification;

import com.vaadin.ui.UI;

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

import eu.etaxonomy.cdm.api.conversation.ConversationHolder;

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;

/**

 * @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 tx = null;

    ConversationHolder conversationHolder = 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;

    }

    public TransactionStatus startConversationalTransaction() {

        checkExistingTransaction();

        getConversationHolder().bind();

        tx = getConversationHolder().startTransaction();

        return tx;

    }

    /**

     * @return

     */

    protected ConversationHolder getConversationHolder() {

        if(conversationHolder == null){

            conversationHolder = (ConversationHolder) repo.getBean("conversationHolder");

        }

        return conversationHolder;

    }

    /**

     * @return

     *

     */

    private TransactionStatus startTransaction(boolean readOnly) {

        checkExistingTransaction();

        return repo.startTransaction(readOnly);

    }

    /**

     *

     */

    protected void checkExistingTransaction() {

        if (tx != 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("Can't process a second save operation while another one is in progress.");

        }

    }

    /**

     * 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) {

        Session session = getSession();

        // session.clear();

        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

     */

    public 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

     * @param tx2

     * @param presaveSession

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

     *         persistent storage.

     */

    public EntityChangeEvent saveBean(T bean) {

        Type changeEventType;

        if(bean.getId() > 1){

            changeEventType = Type.MODIFIED;

        } else {

            changeEventType = Type.CREATED;

        }

        Session session = getSession();

        if(tx == null){

            startTransaction(false);

        }

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

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

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

        T mergedBean = mergedBean(bean);

        repo.getCommonService().saveOrUpdate(mergedBean);

        flushCommitAndCloseConversationTransaction();

        return new EntityChangeEvent(mergedBean.getClass(), mergedBean.getId(), changeEventType);

    }

    /**

     *

     * @param bean

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

     */

    public final EntityChangeEvent deleteBean(T bean) {

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

        startTransaction(false);

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

        DeleteResult result = service.delete(bean);

        if (result.isOk()) {

            flushCommitAndClose();

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

            return new EntityChangeEvent(bean.getClass(), bean.getId(), Type.REMOVED);

        } else {

            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>");

            }

            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());

            tx = null;

        }

        return null;

    }

    /**

     * @param session

     */

    protected void flushCommitAndClose() {

        Session session = getSession();

        session.flush();

        logger.trace(this._toString() + "session flushed");

        repo.commitTransaction(tx);

        tx = null;

        if(session.isOpen()){

            session.close();

        }

        session = null;

        logger.trace(this._toString() + "transaction comitted and session closed");

    }

    protected void flushCommitAndCloseConversationTransaction() {

        getConversationHolder().getSession().flush();

        logger.trace(this._toString() + "conversational session flushed");

        getConversationHolder().commit();

        getConversationHolder().close();

        tx = null;

        logger.trace(this._toString() + "conversational transaction comitted and session closed");

    }

}