package nu.xss.jpa.dao;

import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import javax.persistence.EntityManager;
import javax.persistence.NoResultException;
import javax.persistence.NonUniqueResultException;
import javax.persistence.PersistenceContext;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import nu.xss.jpa.entity.TypedEntity;
import nu.xss.jpa.query.Pagination;
import nu.xss.jpa.query.Sort;
import nu.xss.jpa.query.filter.Filter;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public abstract class GenericJpaDao<E extends TypedEntity<K>, K> implements
		Dao<E, K>, Serializable {

	private static final long serialVersionUID = 4998055731089977476L;
	protected final Logger logger = LoggerFactory.getLogger(this.getClass());

	@PersistenceContext
	protected EntityManager entityManager;

	protected Class<E> entity;

	@SuppressWarnings("unchecked")
	public GenericJpaDao() {
		ParameterizedType genericSuperclass = (ParameterizedType) getClass()
				.getGenericSuperclass();
	    Type type = genericSuperclass.getActualTypeArguments()[0];
	    
	    
	    if (type instanceof Class) {
	      this.entity = (Class<E>) type;
	    } else if (type instanceof ParameterizedType) {
	      this.entity = (Class<E>) ((ParameterizedType)type).getRawType();
	    }
	}

	public void save(E entity) {
		entityManager.persist(entity);
		logger.info("Saved entity: {}.", entity.toString());
	}

	public void merge(E entity) {
		entityManager.merge(entity);
		logger.info("Updated unmanaged entity: {}.", entity.toString());
	}

	public void delete(E entity) {
		final E persistentEntity = findById(entity.getId());
		if (persistentEntity != null) {
			entityManager.remove(persistentEntity);
		}
		logger.info("Deleted entity: {}.", entity.toString());
	}

	public E findById(K id) {
		return entityManager.find(entity, id);
	}

	@Override
	public int count() {
		// TODO Auto-generated method stub
		return 0;
	}

	@Override
	public int count(Filter... filter) {
		// TODO Auto-generated method stub
		return 0;
	}

	@Override
	public List<E> findAll() {
		return find(null, null, null);
	}

	@Override
	public List<E> findAll(Sort sort) {
		return find(null, sort, null);
	}

	@Override
	public List<E> findAll(Pagination pagination) {
		return find(null, null, pagination);
	}

	@Override
	public List<E> findAll(Sort sort, Pagination pagination) {
		return find(null, sort, pagination);
	}

	@Override
	public List<E> findAll(Filter... filter) {
		return find(null, null, null, filter);
	}

	@Override
	public List<E> findAll(Sort sort, Filter... filter) {
		return find(null, sort, null, filter);
	}

	@Override
	public List<E> findAll(Pagination pagination, Filter... filter) {
		return find(null, null, pagination, filter);
	}

	@Override
	public List<E> findAll(Sort sort, Pagination pagination, Filter... filter) {
		return find(null, sort, pagination, filter);
	}

	protected List<E> find(CriteriaQuery<E> query) {
		return find(query, null, null);
	}

	protected List<E> find(CriteriaQuery<E> query, Pagination pagination) {
		return find(query, null, pagination);
	}

	protected List<E> find(CriteriaQuery<E> query, Sort sort) {
		return find(query, sort, null);
	}

	protected List<E> find(CriteriaQuery<E> query, Sort sort, Pagination pagination, Filter... filter) {
		Root<E> root;
		
		// check if we have a 'simple' query
		if (query == null) {
			query = createQuery();
		}

		root = query.from(this.entity);
		query.select(root);
		
		if (filter != null) {
			Set<Predicate> predicates = new HashSet<Predicate>();
			for (final Filter f: filter) {
				f.buildFilters(getCriteriaBuilder(), root);
				for (Predicate p : f.getPredicates()) {
					predicates.add(p);
				}
			}
			if (predicates.size() > 0) {
				query.where((Predicate[]) predicates.toArray());
			}
		}
		
		
		// Result Sorting
		// TODO: Multcolum sort
		if (sort != null) {
			if (sort.isAsc()) {
				query.orderBy(getCriteriaBuilder().asc(root.get(sort.getColumn())));
			} else {
				query.orderBy(getCriteriaBuilder().desc(root.get(sort.getColumn())));
			}
		}
		
		// Result pagination
		TypedQuery<E> q = entityManager.createQuery(query);
		if (pagination != null) {
			if ( pagination.getCount() > 0 ) {
				q.setFirstResult(pagination.getCount());
			}
			if ( pagination.getOffset() > 0) {
				q.setMaxResults(pagination.getOffset());
			}
		}
		
		return q.getResultList();
	}
	
	protected E findSingle(CriteriaQuery<E> query) {
		return entityManager.createQuery(query).getSingleResult();
	}

	protected E findSingleOrNull(CriteriaQuery<E> query) {
		try {
			return findSingle(query);
		} catch (final NoResultException e) {
			return null;
		} catch (final NonUniqueResultException e) {
			logger.error("Found more than one result.. return first one");
			return null;
		}
	}

	protected E findSingleFirstOrNull(CriteriaQuery<E> query) {
		try {
			return findSingle(query);
		} catch (final NoResultException e) {
			return null;
		} catch (final NonUniqueResultException e) {
			logger.warn("Found more than one result.. return first one");
			return find(query).get(0);
		}
	}
	

	protected CriteriaBuilder getCriteriaBuilder() {
		return entityManager.getCriteriaBuilder();
	}

	protected CriteriaQuery<E> createQuery() {
		CriteriaQuery<E> c = getCriteriaBuilder().createQuery(this.entity);
		return c;
	}

}