/**
    * Copyright 2010 The Kuali Foundation Licensed under the
    * Educational Community License, Version 2.0 (the "License"); you may
    * not use this file except in compliance with the License. You may
    * obtain a copy of the License at
    *
    * http://www.osedu.org/licenses/ECL-2.0
    *
    * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an "AS IS"
   * BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
   * or implied. See the License for the specific language governing
   * permissions and limitations under the License.
   */
  
  package org.kuali.student.r1.common.dao.impl;
  
  import java.util.List;
  
  import javax.persistence.EntityManager;
  import javax.persistence.Query;
  
  import org.kuali.student.r1.common.dao.CrudDao;
  import org.kuali.student.r2.common.exceptions.DoesNotExistException;
  
  public abstract class AbstractCrudDaoImpl implements CrudDao {
  
  	protected EntityManager em;
  
  	public EntityManager getEm() {
  		return em;
  	}
  
  	public void setEm(EntityManager em) {
  		this.em = em;
  	}
  
  
  	@Override
  	public <T> T fetch(Class<T> clazz, String key) throws DoesNotExistException {
  		T entity = em.find(clazz, key);
  		if (entity == null) {
  			throw new DoesNotExistException("No entity for key '" + key + "' found for " + clazz);
  		}
  		return entity;
  	}
  
  	@SuppressWarnings("unchecked")
  	@Override
  	public <T> List<T> find(Class<T> clazz){
  
  		String className = clazz.getSimpleName();
  
  		Query q = em.createQuery("SELECT x FROM "+className+" x");
  		return (List<T>) q.getResultList();
  	}
  
  	@Override
  	public <T> T create(T entity) {
  		em.persist(entity);
  		return entity;
  	}
  
  	@Override
  	public <T> void delete(Class<T> clazz, String key) throws DoesNotExistException {
  		T entity = em.find(clazz, key);
  		if (entity == null) {
  			throw new DoesNotExistException("No such key '" + key + "' for " + clazz);
  		}
  		em.remove(entity);
  	}
  
  	@Override
  	public void delete(Object entity) {
  		em.remove(entity);
  	}
  
  	@Override
  	public <T> T update(T entity) {
  		T updated =  em.merge(entity);
  		//We need to flush here to make sure the version number is updated before we populate any messages that return the version
  		em.flush();
  		return updated;
  	}
  }