package envoy.server.database;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.Persistence;

import org.hibernate.Session;

import envoy.server.data.Message;
import envoy.server.data.User;

/**
 * Project: <strong>envoy-server-standalone</strong><br>
 * File: <strong>PersistenceManager.java</strong><br>
 * Created: <strong>1 Jan 2020</strong><br>
 *
 * @author Leon Hofmeister
 * @since Envoy Server Standalone v0.1-alpha
 */
public class PersistenceManager {

	private static final PersistenceManager persistenceManager = new PersistenceManager();

	/**
	 * Creates the singleton instance of the @link{PersistenceManager}.
	 *
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	private PersistenceManager() {}

	/**
	 * @return the {@link PersistenceManager} singleton
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public static PersistenceManager getPersistenceManager() { return persistenceManager; }

	private EntityManager entityManager = Persistence.createEntityManagerFactory("envoy").createEntityManager();

	/**
	 * Adds a {@link User} to the database.
	 *
	 * @param User the {@link User} to add to the database
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void addUser(User User) { entityManager.persist(User); }

	/**
	 * Adds a {@link Message} to the database.
	 *
	 * @param message the {@link Message} to add to the database
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void addMessage(Message message) { entityManager.persist(message); }

	/**
	 * Updates a {@link User} in the database
	 *
	 * @param user the {@link User} to add to the database
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void updateUser(User user) { entityManager.unwrap(Session.class).merge(user); }

	/**
	 * Updates a {@link Message} in the database.
	 *
	 * @param message the message to update
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void updateMessage(Message message) { entityManager.unwrap(Session.class).merge(message); }

	/**
	 * Searches for a {@link User} with a specific id.
	 *
	 * @param id - the id to search for
	 * @return the user with the specified id
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public User getUserById(long id) { return (User) entityManager.createNamedQuery("getUserById").setParameter("id", id).getSingleResult(); }

	/**
	 * Searches for a {@link Message} with a specific id.
	 *
	 * @param id - the id to search for
	 * @return the message with the specified id
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public Message getMessageById(long id) {
		return (Message) entityManager.createNamedQuery("getMessageById").setParameter("id", id).getSingleResult();
	}

	/**
	 * Returns all messages received while being offline.
	 *
	 * @param user - the user who wants to receive his unread messages
	 * @return all messages that the client does not yet have (unread messages)
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	@SuppressWarnings("unchecked")
	public List<Message> getUnreadMessages(User user) {
		return entityManager.createNamedQuery("getUnreadMessages").setParameter("recipient", user).getResultList();
	}

	/**
	 * @param user the User whose contacts should be retrieved
	 * @return the contacts of this User - currently everyone using Envoy
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	@SuppressWarnings("unchecked")
	public List<User> getContacts(User user) { return entityManager.createQuery("FROM User").getResultList(); }
	// TODO current solution gets all users, not just contacts. Should be changed to
	// entityManager.createNamedQuery("getContactsOfUser").setParameter("user",
	// user).getResultList();
}