package com.dominikdorn.lyrix.dao;


import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceException;
import javax.persistence.Query;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Root;
import java.lang.reflect.ParameterizedType;
import java.util.List;


/**
 * Dominik Dorn
 * 0626165
 * dominik.dorn@tuwien.ac.at
 */
public abstract class AbstractJpaGenericDaoImpl<TYPE,KEY> implements GenericDao<TYPE,KEY> {
    @PersistenceContext(unitName = "lyrixPU")
    protected EntityManager em;

    protected Class entityClass;

    protected AbstractJpaGenericDaoImpl() {
        ParameterizedType genericSuperclass = (ParameterizedType) getClass().getGenericSuperclass();
        this.entityClass = (Class<TYPE>) genericSuperclass.getActualTypeArguments()[0];
    }

    @Override
    public TYPE create(TYPE object) {
        if(object == null)
            throw new PersistenceException("given object may not be null");
        em.persist(object);
        object = em.merge(object);
        return object;
    }

    @Override
    public TYPE edit(TYPE object) {
        if(object == null)
            throw new PersistenceException("given object may not be null");
        em.merge(object);
        return object;
    }

    @Override
    public void remove(TYPE object) {
        if(object == null)
            throw new PersistenceException("given object may not be null");
        em.refresh(object);
        em.remove(em.merge(object));
    }

    @Override
    public TYPE find(KEY id) {
        if(id == null)
            throw new PersistenceException("given object may not be null");
        return (TYPE) em.find(entityClass, id);
    }

    @Override
    public List<TYPE> findAll() {
        CriteriaQuery cq = em.getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        return em.createQuery(cq).getResultList();
    }

    @Override
    public List<TYPE> findRange(int[] range) {
        CriteriaQuery cq = em.getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        Query q = em.createQuery(cq);
        q.setMaxResults(range[1] - range[0]);
        q.setFirstResult(range[0]);
        return q.getResultList();
    }

    @Override
    public int count() {
        CriteriaQuery cq = em.getCriteriaBuilder().createQuery();
        Root<TYPE> rt = cq.from(entityClass);
        cq.select(em.getCriteriaBuilder().count(rt));
        Query q = em.createQuery(cq);
        return ((Long) q.getSingleResult()).intValue();
    }


    public EntityManager getEm() {
        return em;
    }

    public void setEm(EntityManager em) {
        this.em = em;
    }

    public Class getEntityClass() {
        return entityClass;
    }

    public void setEntityClass(Class entityClass) {
        this.entityClass = entityClass;
    }
}