// Copyright 2007-2008 Thiago H. de Paula Figueiredo
   //
   // Licensed under the Apache 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.apache.org/licenses/LICENSE-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 br.com.arsmachina.dao.hibernate;
  
  import java.io.Serializable;
  import java.util.List;
  
  import org.hibernate.Criteria;
  import org.hibernate.LockMode;
  import org.hibernate.SessionFactory;
  import org.hibernate.classic.Session;
  import org.hibernate.criterion.Example;
  import org.hibernate.criterion.MatchMode;
  import org.hibernate.criterion.Order;
  import org.hibernate.criterion.Projections;
  import org.hibernate.criterion.Restrictions;
  
  import br.com.arsmachina.dao.ReadableDAO;
  import br.com.arsmachina.dao.SortCriterion;
  
  /**
   * {@link ReadableDAO} implementation using Hibernate. All methods use {@link #getSession()} to get
   * {@link Session}.
   * 
   * @author Thiago H. de Paula Figueiredo
   * @param <T> the entity class related to this DAO.
   * @param <K> the type of the field that represents the entity class' primary key.
   */
  public abstract class ReadableDAOImpl<T, K extends Serializable> extends BaseHibernateDAO<T, K>
  		implements ReadableDAO<T, K> {
  
  	/**
  	 * A {@link SortCriterion} array with no elements.
  	 */
  	final public static SortCriterion[] EMPTY_SORTING_CRITERIA = new SortCriterion[0];
  
  	final private String defaultHqlOrderBy = toHqlOrderBy(getDefaultSortCriteria());
  
  	/**
  	 * Returns a HQL <code>order by</code> clause given some {@link SortCriterion}s.
  	 * 
  	 * @param sortCriteria {@link SortCriterion} instances.
  	 * @return a {@link String}.
  	 */
  	final public static String toHqlOrderBy(SortCriterion... sortCriteria) {
  
  		String string = "";
  
  		if (sortCriteria.length > 0) {
  
  			StringBuilder builder = new StringBuilder(" ORDER BY ");
  
  			for (int i = 0; i < sortCriteria.length - 1; i++) {
  				builder.append(sortCriteria.toString());
  				builder.append(", ");
  			}
  
  			builder.append(sortCriteria[sortCriteria.length - 1]);
  
  			string = builder.toString();
  
  		}
  
  		return string;
  
  	}
  
  	/**
  	 * Constructor that takes a {@link Class} and a {@link SessionFactory}.
  	 * 
  	 * @param clasz a {@link Class}.
  	 * @param sessionFactory a {@link SessionFactory}. It cannot be null.
  	 */
  	@SuppressWarnings("unchecked")
  	public ReadableDAOImpl(SessionFactory sessionFactory) {
  		super(null, sessionFactory);
  	}
  
  	/**
  	 * Constructor that takes a {@link Class} and a {@link SessionFactory}.
  	 * 
  	 * @param clasz a {@link Class}.
  	 * @param sessionFactory a {@link SessionFactory}. It cannot be null.
  	 */
  	@SuppressWarnings("unchecked")
  	public ReadableDAOImpl(Class<T> clasz, SessionFactory sessionFactory) {
  		super(clasz, sessionFactory);
 	}
 
 	/**
 	 * @see br.com.arsmachina.dao.ReadableDAO#countAll()
 	 */
 	public int countAll() {
 
 		final Criteria criteria = createCriteria();
 
 		criteria.setProjection(Projections.rowCount());
 
 		return (Integer) criteria.uniqueResult();
 
 	}
 
 	/**
 	 * Returns all the entity class' objects. They are sorted according to
 	 * {@link #getDefaultSortCriterions()}.
 	 * 
 	 * @see br.com.arsmachina.dao.ReadableDAO#findAll()
 	 * @see #getDefaultSortCriterions()
 	 */
 	@SuppressWarnings("unchecked")
 	public List<T> findAll() {
 
 		Criteria criteria = createCriteria();
 		addSortCriteria(criteria, getDefaultSortCriteria());
 		return criteria.list();
 
 	}
 
 	/**
 	 * @see br.com.arsmachina.dao.ReadableDAO#findById(java.io.Serializable)
 	 */
 	@SuppressWarnings("unchecked")
 	public T findById(K id) {
 		return (T) getSession().get(getEntityClass(), id);
 	}
 
 	/**
 	 * @see br.com.arsmachina.dao.ReadableDAO#findByIds(K[])
 	 */
 	@SuppressWarnings("unchecked")
 	public List<T> findByIds(K... ids) {
 
 		Criteria criteria = createCriteria();
 		criteria.add(Restrictions.in(getPrimaryKeyPropertyName(), ids));
 		return criteria.list();
 
 	}
 
 	/**
 	 * @see br.com.arsmachina.dao.ReadableDAO#findByExample(java.lang.Object)
 	 */
 	@SuppressWarnings("unchecked")
 	public List<T> findByExample(T example) {
 
 		Criteria criteria = createCriteria();
 
 		if (example != null) {
 			criteria.add(createExample(example));
 		}
 
 		return criteria.list();
 
 	}
 
 	/**
 	 * @see br.com.arsmachina.dao.WriteableDAO#refresh(java.lang.Object)
 	 */
 	public void refresh(T object) {
 		getSession().refresh(object);
 	}
 
 	/**
 	 * If <code>sortingConstraints</code> is <code>null</code> or empty, this implementation
 	 * sort the results by the {@link SortCriterion}s returned by
 	 * {@link #getDefaultSortCriterions()}.
 	 * 
 	 * @see br.com.arsmachina.dao.ReadableDAO#findAll(int, int,
 	 * br.com.arsmachina.dao.SortCriterion[])
 	 */
 	@SuppressWarnings("unchecked")
 	public List<T> findAll(int firstResult, int maximumResults, SortCriterion... sortingConstraints) {
 
 		Criteria criteria = createCriteria();
 		criteria.setFirstResult(firstResult);
 		criteria.setMaxResults(maximumResults);
 
 		if (sortingConstraints == null || sortingConstraints.length == 0) {
 			sortingConstraints = getDefaultSortCriteria();
 		}
 
 		addSortCriteria(criteria, sortingConstraints);
 
 		return criteria.list();
 
 	}
 
 	/**
 	 * Reattaches the object to the current {@link org.hibernate.Session} using
 	 * <code>Session.lock(object, LockMode.NONE)</code> and then returns the object.
 	 * 
 	 * @param a <code>T</code>.
 	 * @return <code>object</code>.
 	 * @see br.com.arsmachina.dao.ReadableDAO#reattach(java.lang.Object)
 	 */
 	public T reattach(T object) {
 		
 		getSession().lock(object, LockMode.NONE);
 		return object;
 		
 	}
 	
 	/**
 	 * Adds <code>sortCriteria</code> to a {@link Criteria} instance.
 	 * 
 	 * @param criteria a {@link Criteria}. It cannot be null.
 	 * @param sortCriteria a {@link SortCriterion}<code>...</code>. It cannot be null.
 	 * @todo Support for property paths, not just property names.
 	 */
 	final public void addSortCriteria(Criteria criteria, SortCriterion... sortCriteria) {
 
 		assert criteria != null;
 		
 		if (sortCriteria == null || sortCriteria.length == 0) {
 			sortCriteria = getDefaultSortCriteria();
 		}
 		
 		for (SortCriterion sortingConstraint : sortCriteria) {
 
 			final String property = sortingConstraint.getProperty();
 			final boolean ascending = sortingConstraint.isAscending();
 			final Order order = ascending ? Order.asc(property) : Order.desc(property);
 			criteria.addOrder(order);
 
 		}
 
 	}
 
 	/**
 	 * Adds the default sort criteria to a {@link Criteria} instance. This method just does
 	 * <code>addSortCriteria(criteria, getDefaultSortCriteria());</code>.
 	 * 
 	 * @param criteria a {@link Criteria}. It cannot be null.
 	 */
 	protected void addSortCriteria(Criteria criteria) {
 		addSortCriteria(criteria, getDefaultSortCriteria());
 	}
 
 	/**
 	 * Returns the default {@link SortCriterion}s to be used to sort the objects lists returned by
 	 * methods like {@link #findAll()} and {@link #findAll(int, int, SortCriterion...)} when no
 	 * sorting constraints are given. This implementation returns {@link #EMPTY_SORTING_CRITERIA}.
 	 * 
 	 * @return a {@link SortCriterion} array. It cannot be <code>null</code>.
 	 */
 	public SortCriterion[] getDefaultSortCriteria() {
 		return EMPTY_SORTING_CRITERIA;
 	}
 
 	/**
 	 * Creates a {@link Criteria} for this entity class.
 	 * 
 	 * @return a {@link Criteria}.
 	 */
 	public Criteria createCriteria() {
 		return getSession().createCriteria(getEntityClass());
 	}
 
 	/**
 	 * Creates a {@link Criteria} for this entity class with given sort criteria.
 	 * 
 	 * @return a {@link Criteria}.
 	 */
 	public Criteria createCriteria(SortCriterion ... sortCriteria) {
 		
 		Criteria criteria = createCriteria();
 		addSortCriteria(criteria, sortCriteria);
 		return criteria;
 		
 	}
 
 	/**
 	 * Creates a {@link Criteria} for this entity class with given sort criteria,
 	 * first result index and maximum number of results. 
 	 * 
 	 * @return a {@link Criteria}.
 	 */
 	public Criteria createCriteria(int firstIndex, int maximumResults, SortCriterion ... sortCriteria) {
 		
 		Criteria criteria = createCriteria(sortCriteria);
 		criteria.setFirstResult(firstIndex);
 		criteria.setMaxResults(maximumResults);
 		return criteria;
 		
 	}
 
 	/**
 	 * Used by {@link #findByExample(Object)} to create an {@link Example} instance.
 	 * 
 	 * @todo add criteria for property types not handled by Example (primary keys, associations,
 	 * etc)
 	 * @return an {@link Example}.
 	 */
 	public Example createExample(T entity) {
 
 		Example example = Example.create(entity);
 		example.enableLike(MatchMode.ANYWHERE);
 		example.excludeZeroes();
 		example.ignoreCase();
 
 		return example;
 
 	}
 
 	/**
 	 * Returns the value of the <code>defaultHqlOrderBy</code> property.
 	 * 
 	 * @return a {@link String}.
 	 */
 	public final String getDefaultHqlOrderBy() {
 		return defaultHqlOrderBy;
 	}
 
 }