package at.gv.egovernment.moa.id.process.dao;

import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.criterion.Restrictions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import at.gv.egovernment.moa.id.commons.db.MOASessionDBUtils;
import at.gv.egovernment.moa.id.commons.db.ex.MOADatabaseException;

/**
 * Database backed implementation of the {@link ProcessInstanceStoreDAO}
 * interface.
 */
public class ProcessInstanceStoreDAOImpl implements ProcessInstanceStoreDAO {

	private Logger log = LoggerFactory.getLogger(getClass());

	private static ProcessInstanceStoreDAO instance = new ProcessInstanceStoreDAOImpl();

	public static ProcessInstanceStoreDAO getInstance() {
		return instance;
	}

	@Override
	public void saveOrUpdate(ProcessInstanceStore pIStore) throws MOADatabaseException {
		try {
			MOASessionDBUtils.saveOrUpdate(pIStore);
			log.debug("Store process instance with='{}' in the database.", pIStore.getProcessInstanceId());
		} catch (MOADatabaseException e) {
			log.warn("ProcessInstanceStore could not be persisted to the database.");
			throw e;
		}
	}

	@Override
	public ProcessInstanceStore load(String processInstanceId) throws MOADatabaseException {

		log.debug("Retrieve the ProcessInstanceStore for id='{}' from the database.", processInstanceId);
		Session session = MOASessionDBUtils.getCurrentSession();

		ProcessInstanceStore result = null;
		Transaction tx = null;
		synchronized (session) {
			try {

				tx = session.beginTransaction();
				// select all where processInstanceId equals processInstanceId
				Criteria criteria = session.createCriteria(ProcessInstanceStore.class);
				criteria.add(Restrictions.eq("processInstanceId", processInstanceId));
				result = (ProcessInstanceStore) criteria.uniqueResult();
				tx.commit();

			} catch (Exception e) {
				log.error("There are multiple persisted processes with the same process instance id '{}'",
						processInstanceId);
				if (tx != null) {
					tx.rollback();
				}
				throw e;
			} finally {
				MOASessionDBUtils.closeSession();
			}
		}
		if (result != null) {
			log.debug("Found process instance store for instance '{}'.", processInstanceId);
		} else {
			log.debug("Unable to find process instance store for instance '{}'.", processInstanceId);
		}
		return result;
	}

	@Override
	public void remove(String processInstanceId) throws MOADatabaseException {

		log.debug("Delete the ProcessInstanceStore for id='{}' from the database.", processInstanceId);
		ProcessInstanceStore toBeDeleted = load(processInstanceId);
		if (toBeDeleted != null) {
			if (!MOASessionDBUtils.delete(toBeDeleted)) {
				log.warn("Could not delete the ProcessInstanceStore with process instance id '{}'", processInstanceId);
				throw new MOADatabaseException("Could not delete the ProcessInstanceStore with process instance id '"
						+ processInstanceId + "'.");
			}
		} else 
			log.trace("ProcessInstanceStore for id='{}' was not found and could therefore not be deleted.", processInstanceId);
	}

}