/*******************************************************************************
 * See the NOTICE file distributed with this work for additional information
 * regarding copyright ownership.
 *
 * 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 hr.fer.zemris.vhdllab.dao.impl;

import hr.fer.zemris.vhdllab.dao.EntityDao;

import java.util.List;

import org.apache.commons.lang.Validate;
import org.springframework.orm.jpa.support.JpaDaoSupport;

public abstract class AbstractEntityDao<T> extends JpaDaoSupport implements
        EntityDao<T> {

    /**
     * Class of an entity.
     */
    protected final Class<T> clazz;

    /**
     * Constructor.
     *
     * @param clazz
     *            class of an entity
     * @throws NullPointerException
     *             if <code>clazz</code> is <code>null</code>
     */
    public AbstractEntityDao(Class<T> clazz) {
        Validate.notNull(clazz, "Entity class can't be null");
        this.clazz = clazz;
    }

    /*
     * (non-Javadoc)
     *
     * @see hr.fer.zemris.vhdllab.dao.EntityDao#persist(java.lang.Object)
     */
    public void persist(T entity) {
        Validate.notNull(entity, "Entity can't be null");
        getJpaTemplate().persist(entity);
    }

    /*
     * (non-Javadoc)
     *
     * @see hr.fer.zemris.vhdllab.dao.EntityDao#merge(java.lang.Object)
     */
    public T merge(T entity) {
        Validate.notNull(entity, "Entity can't be null");
        return getJpaTemplate().merge(entity);
    }

    /*
     * (non-Javadoc)
     *
     * @see hr.fer.zemris.vhdllab.dao.EntityDao#load(java.lang.Integer)
     */
    @Override
    public T load(Integer id) {
        Validate.notNull(id, "Entity identifier can't be null");
        return getJpaTemplate().find(clazz, id);
    }

    /*
     * (non-Javadoc)
     *
     * @see hr.fer.zemris.vhdllab.dao.EntityDao#delete(java.lang.Object)
     */
    @Override
    public void delete(T entity) {
        Validate.notNull(entity, "Entity can't be null");
        getJpaTemplate().remove(entity);
    }

    /**
     * Returns a unique result for specified query string or <code>null</code>
     * if such entity doesn't exist.
     *
     * @param queryString
     *            a query to execute
     * @param values
     *            parameter values to a query
     * @return unique result returned by query
     * @throws IllegalStateException
     *             if query returns more then 1 result
     */
    @SuppressWarnings("unchecked")
    protected final T findUniqueResult(String queryString, Object... values) {
        List<T> list = getJpaTemplate().find(queryString, values);
        if (list.size() > 1) {
            throw new IllegalStateException(
                    "Found more matches for unique result for class "
                            + clazz.getCanonicalName());
        }
        return !list.isEmpty() ? list.get(0) : null;
    }

}