package envoy.client.data;

import java.util.*;

import envoy.data.*;
import envoy.event.GroupResize;
import envoy.event.MessageStatusChange;
import envoy.event.NameChange;

/**
 * Stores information about the current {@link User} and their {@link Chat}s.
 * For message ID generation a {@link IDGenerator} is stored as well.
 * <p>
 * Project: <strong>envoy-client</strong><br>
 * File: <strong>LocalDB.java</strong><br>
 * Created: <strong>3 Feb 2020</strong><br>
 *
 * @author Kai S. K. Engelbart
 * @since Envoy Client v0.3-alpha
 */
public abstract class LocalDB {

	protected User					user;
	protected Map<String, Contact>	users		= new HashMap<>();
	protected List<Chat>			chats		= new ArrayList<>();
	protected IDGenerator			idGenerator;
	protected CacheMap				cacheMap	= new CacheMap();

	{
		cacheMap.put(Message.class, new Cache<>());
		cacheMap.put(MessageStatusChange.class, new Cache<>());
	}

	/**
	 * Initializes a storage space for a user-specific list of chats.
	 *
	 * @since Envoy Client v0.3-alpha
	 */
	public void initializeUserStorage() {}

	/**
	 * Stores all users. If the client user is specified, their chats will be stored
	 * as well. The message id generator will also be saved if present.
	 *
	 * @throws Exception if the saving process failed
	 * @since Envoy Client v0.3-alpha
	 */
	public void save() throws Exception {}

	/**
	 * Loads all user data.
	 *
	 * @throws Exception if the loading process failed
	 * @since Envoy Client v0.3-alpha
	 */
	public void loadUsers() throws Exception {}

	/**
	 * Loads all data of the client user.
	 *
	 * @throws Exception if the loading process failed
	 * @since Envoy Client v0.3-alpha
	 */
	public void loadUserData() throws Exception {}

	/**
	 * Loads the ID generator. Any exception thrown during this process is ignored.
	 *
	 * @since Envoy Client v0.3-alpha
	 */
	public void loadIDGenerator() {}

	/**
	 * Synchronizes the contact list of the client user with the chat and user
	 * storage.
	 * 
	 * @since Envoy Client v0.1-beta
	 */
	public void synchronize() {
		user.getContacts().stream().filter(u -> u instanceof User && !users.containsKey(u.getName())).forEach(u -> users.put(u.getName(), u));
		users.put(user.getName(), user);

		// Synchronize user status data
		for (Contact contact : users.values())
			if (contact instanceof User)
				getChat(contact.getID()).ifPresent(chat -> { ((User) chat.getRecipient()).setStatus(((User) contact).getStatus()); });

		// Create missing chats
		user.getContacts()
			.stream()
			.filter(c -> !c.equals(user) && getChat(c.getID()).isEmpty())
			.map(c -> c instanceof User ? new Chat(c) : new GroupChat(user, c))
			.forEach(chats::add);
	}

	/**
	 * @return a {@code Map<String, User>} of all users stored locally with their
	 *         user names as keys
	 * @since Envoy Client v0.2-alpha
	 */
	public Map<String, Contact> getUsers() { return users; }

	/**
	 * @return all saved {@link Chat} objects that list the client user as the
	 *         sender
	 * @since Envoy Client v0.1-alpha
	 **/
	public List<Chat> getChats() { return chats; }

	/**
	 * @param chats the chats to set
	 */
	public void setChats(List<Chat> chats) { this.chats = chats; }

	/**
	 * @return the {@link User} who initialized the local database
	 * @since Envoy Client v0.2-alpha
	 */
	public User getUser() { return user; }

	/**
	 * @param user the user to set
	 * @since Envoy Client v0.2-alpha
	 */
	public void setUser(User user) { this.user = user; }

	/**
	 * @return the message ID generator
	 * @since Envoy Client v0.3-alpha
	 */
	public IDGenerator getIDGenerator() { return idGenerator; }

	/**
	 * @param idGenerator the message ID generator to set
	 * @since Envoy Client v0.3-alpha
	 */
	public void setIDGenerator(IDGenerator idGenerator) { this.idGenerator = idGenerator; }

	/**
	 * @return {@code true} if an {@link IDGenerator} is present
	 * @since Envoy Client v0.3-alpha
	 */
	public boolean hasIDGenerator() { return idGenerator != null; }

	/**
	 * @return the cache map for messages and message status changes
	 * @since Envoy Client v0.1-beta
	 */
	public CacheMap getCacheMap() { return cacheMap; }

	/**
	 * Searches for a message by ID.
	 *
	 * @param id the ID of the message to search for
	 * @return an optional containing the message
	 * @since Envoy Client v0.1-beta
	 */
	public Optional<Message> getMessage(long id) {
		return chats.stream().map(Chat::getMessages).flatMap(List::stream).filter(m -> m.getID() == id).findAny();
	}

	/**
	 * Searches for a chat by recipient ID.
	 * 
	 * @param recipientID the ID of the chat's recipient
	 * @return an optional containing the chat
	 * @since Envoy Client v0.1-beta
	 */
	public Optional<Chat> getChat(long recipientID) { return chats.stream().filter(c -> c.getRecipient().getID() == recipientID).findAny(); }

	/**
	 * Performs a contact name change if the corresponding contact is present.
	 *
	 * @param event the {@link NameChange} to process
	 * @since Envoy Client v0.1-beta
	 */
	public void replaceContactName(NameChange event) {
		chats.stream().map(Chat::getRecipient).filter(c -> c.getID() == event.getID()).findAny().ifPresent(c -> c.setName(event.get()));
	}

	/**
	 * Performs a group resize operation if the corresponding group is present.
	 *
	 * @param event the {@link GroupResize} to process
	 * @since Envoy Client v0.1-beta
	 */
	public void updateGroup(GroupResize event) {
		chats.stream()
			.map(Chat::getRecipient)
			.filter(Group.class::isInstance)
			.filter(g -> g.getID() == event.getGroupID() && g.getID() != user.getID())
			.map(Group.class::cast)
			.findAny()
			.ifPresent(group -> {
				switch (event.getOperation()) {
					case ADD:
						group.getContacts().add(event.get());
						break;
					case REMOVE:
						group.getContacts().remove(event.get());
						break;
				}
			});
	}
}