/*
 * Copyright (C) 2017 LibreCCM Foundation.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301  USA
 */
package org.libreccm.admin.ui;

import com.vaadin.cdi.ViewScoped;
import com.vaadin.data.provider.AbstractDataProvider;
import com.vaadin.data.provider.Query;
import org.libreccm.security.Party;
import org.libreccm.security.Role;
import org.libreccm.security.RoleMembership;

import javax.inject.Inject;
import javax.persistence.EntityManager;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Join;
import javax.persistence.criteria.Root;
import java.util.Objects;
import java.util.stream.Stream;

/**
 *
 * @author <a href="mailto:jens.pelzetter@googlemail.com">Jens Pelzetter</a>
 */
@ViewScoped
public class RolePartiesDataProvider extends AbstractDataProvider<Party, String> {

    private static final long serialVersionUID = -2770993810657270285L;
    
    @Inject
    private EntityManager entityManager;
    
    private Role role;

    @Override
    public boolean isInMemory() {
        return false;
    }

    @Override
    public int size(final Query<Party, String> query) {
        
        Objects.requireNonNull(role,
                               "This data provider needs to be initalized "
                                   + "by calling setRole(Role) before calling "
                                   + "the count method.");
        
        final CriteriaBuilder builder = entityManager.getCriteriaBuilder();
        final CriteriaQuery<Long> criteriaQuery = builder
        .createQuery(Long.class);
        
        final Root<RoleMembership> from = criteriaQuery
        .from(RoleMembership.class);
        
        criteriaQuery
            .select(builder.count(from))
            .where(builder.equal(from.get("role"), role));
        
        return entityManager
            .createQuery(criteriaQuery)
            .getSingleResult()
            .intValue();
    }

    @Override
    public Stream<Party> fetch(final Query<Party, String> query) {

        Objects.requireNonNull(role,
                               "This data provider needs to be initalized "
                                   + "by calling setRole(Role) before calling "
                                   + "the count method.");
        
        final CriteriaBuilder builder = entityManager.getCriteriaBuilder();
        final CriteriaQuery<RoleMembership> criteriaQuery  =builder
        .createQuery(RoleMembership.class);
        final Root<RoleMembership> from = criteriaQuery
        .from(RoleMembership.class);
        final Join<?, ?> join = from.join("role");
        criteriaQuery
            .where(builder.equal(from.get("role"), role))
            .orderBy(builder.asc(join.get("name")));
        
        
        return entityManager
            .createQuery(criteriaQuery)
            .setMaxResults(query.getLimit())
            .setFirstResult(query.getOffset())
            .getResultList()
            .stream()
            .map(RoleMembership::getMember);
    }
    
    public void setRole(final Role role) {
        this.role = role;
    }
    
}
