package envoy.server.database;

import java.util.Date;
import java.util.List;

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

import envoy.data.User.UserStatus;
import envoy.server.data.ConfigItem;
import envoy.server.data.Message;
import envoy.server.data.User;
import envoy.server.net.ConnectionManager;

/**
 * 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 final EntityManager		entityManager	= Persistence.createEntityManagerFactory("envoy").createEntityManager();
	private final EntityTransaction	transaction		= entityManager.getTransaction();

	private static final PersistenceManager persistenceManager = new PersistenceManager();

	/**
	 * Creates the singleton instance of the @link{PersistenceManager}.
	 *
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	private PersistenceManager() {
		transaction.begin();
		Runtime.getRuntime().addShutdownHook(new Thread(() -> {
			ConnectionManager.getInstance()
				.getOnlineUsers()
				.stream()
				.map(this::getUserById)
				.forEach(user -> { user.setStatus(UserStatus.OFFLINE); user.setLastSeen(new Date()); updateUser(user); });
			transaction.commit();
		}));
	}

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

	/**
	 * 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);
		entityManager.flush();
	}

	/**
	 * 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);
		entityManager.flush();
	}

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

	/**
	 * 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.merge(user);
		entityManager.flush();
	}

	/**
	 * 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.merge(message);
		entityManager.flush();
	}

	/**
	 * Updates a {@link ConfigItem} in the database.
	 *
	 * @param configItem the configItem to update
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void updateConfigItem(ConfigItem configItem) {
		entityManager.merge(configItem);
		entityManager.flush();
	}

	/**
	 * Deletes a {@link User} in the database.
	 *
	 * @param user the {@link User} to delete
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void deleteUser(User user) {
		entityManager.remove(user);
		entityManager.flush();
	}

	/**
	 * Deletes a {@link Message} in the database.
	 *
	 * @param message the {@link Message} to delete
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void deleteMessage(Message message) {
		entityManager.remove(message);
		entityManager.flush();
	}

	/**
	 * 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 entityManager.find(User.class, id); }

	/**
	 * Searched for a {@link User} with a specific name.
	 *
	 * @param name the name of the user
	 * @return the user with the specified name
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public User getUserByName(String name) {
		return (User) entityManager.createNamedQuery("getUserByName").setParameter("name", name).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 entityManager.find(Message.class, id); }

	/**
	 * @param key the name of this {@link ConfigItem}
	 * @return the {@link ConfigItem} with the given name
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public ConfigItem getConfigItemById(String key) { return entityManager.find(ConfigItem.class, key); }

	/**
	 * 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
	 */
	public List<Message> getUnreadMessages(User user) {
		return entityManager.createNamedQuery("getUnreadMessages").setParameter("recipient", user).getResultList();
	}

	/**
	 * Searches for users matching a search phrase. Contacts of the attached user
	 * and the attached user is ignored.
	 *
	 * @param searchPhrase the search phrase
	 * @param userId       the ID of the user in whose context the search is
	 *                     performed
	 * @return a list of all users who matched the criteria
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public List<User> searchUsers(String searchPhrase, long userId) {
		return entityManager.createNamedQuery("searchUsers")
			.setParameter("searchPhrase", searchPhrase + "%")
			.setParameter("context", getUserById(userId))
			.getResultList();
	}

	/**
	 * Adds a user to the contact list of another user and vice versa.
	 *
	 * @param userId1 the ID of the first user
	 * @param userId2 the ID of the second user
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void addContact(long userId1, long userId2) {
		User	u1	= getUserById(userId1);
		User	u2	= getUserById(userId2);
		u1.getContacts().add(u2);
		u2.getContacts().add(u1);
		updateUser(u1);
		updateUser(u2);
	}

	/**
	 * @param user the User whose contacts should be retrieved
	 * @return the contacts of this User
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public List<User> getContacts(User user) {
		return entityManager.createNamedQuery("getContactsOfUser").setParameter("user", user).getResultList();
	}
}