package envoy.client.ui;

import java.io.*;
import java.time.Instant;
import java.util.concurrent.TimeoutException;
import java.util.logging.*;

import javafx.application.Application;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.stage.Stage;

import envoy.data.*;
import envoy.data.User.UserStatus;
import envoy.event.UserStatusChange;
import envoy.exception.EnvoyException;
import envoy.util.EnvoyLog;

import envoy.client.data.*;
import envoy.client.data.shortcuts.EnvoyShortcutConfig;
import envoy.client.helper.ShutdownHelper;
import envoy.client.net.Client;
import envoy.client.ui.controller.LoginScene;
import envoy.client.util.IconUtil;

/**
 * Handles application startup.
 *
 * @author Kai S. K. Engelbart
 * @author Maximilian Käfer
 * @since Envoy Client v0.1-beta
 */
public final class Startup extends Application {

	/**
	 * The version of this client. Used to verify compatibility with the server.
	 *
	 * @since Envoy Client v0.1-beta
	 */
	public static final String VERSION = "0.2-beta";

	private static LocalDB localDB;

	private static final Context		context	= Context.getInstance();
	private static final Client			client	= context.getClient();
	private static final ClientConfig	config	= ClientConfig.getInstance();
	private static final Logger			logger	= EnvoyLog.getLogger(Startup.class);

	/**
	 * Loads the configuration, initializes the client and the local database and delegates the rest
	 * of the startup process to {@link LoginScene}.
	 *
	 * @since Envoy Client v0.1-beta
	 */
	@Override
	public void start(Stage stage) throws Exception {

		// Initialize config and logger
		try {
			config.loadAll(Startup.class, "client.properties",
				getParameters().getRaw().toArray(new String[0]));
			EnvoyLog.initialize(config);
		} catch (final IllegalStateException e) {
			new Alert(AlertType.ERROR, "Error loading configuration values:\n" + e);
			logger.log(Level.SEVERE, "Error loading configuration values: ", e);
			System.exit(1);
		}
		logger.log(Level.INFO, "Envoy starting...");

		// Initialize the local database
		try {
			final var localDBFile = new File(config.getHomeDirectory(), config.getServer());
			logger.info("Initializing LocalDB at " + localDBFile);
			localDB = new LocalDB(localDBFile);
		} catch (IOException | EnvoyException e) {
			logger.log(Level.SEVERE, "Could not initialize local database: ", e);
			new Alert(AlertType.ERROR, "Could not initialize local database!\n" + e).showAndWait();
			System.exit(1);
			return;
		}

		// Prepare handshake
		context.setLocalDB(localDB);

		// Configure stage
		stage.setTitle("Envoy");
		stage.getIcons().add(IconUtil.loadIcon("envoy_logo"));

		// Configure global shortcuts
		EnvoyShortcutConfig.initializeEnvoyShortcuts();

		// Create scene context
		final var sceneContext = new SceneContext(stage);
		context.setSceneContext(sceneContext);

		// Authenticate with token if present or load login scene
		if (localDB.getAuthToken() != null) {
			logger.info("Attempting authentication with token...");
			localDB.loadUserData();
			if (!performHandshake(
				LoginCredentials.loginWithToken(localDB.getUser().getName(), localDB.getAuthToken(),
					VERSION, localDB.getLastSync())))
				sceneContext.load(SceneInfo.LOGIN_SCENE);
		} else
			sceneContext.load(SceneInfo.LOGIN_SCENE);

		stage.show();
	}

	/**
	 * Tries to perform a Handshake with the server.
	 *
	 * @param credentials the credentials to use for the handshake
	 * @return whether the handshake was successful or offline mode could be entered
	 * @since Envoy Client v0.2-beta
	 */
	public static boolean performHandshake(LoginCredentials credentials) {
		final var originalStatus =
			localDB.getUser() == null ? UserStatus.ONLINE : localDB.getUser().getStatus();
		try {
			client.performHandshake(credentials);
			if (client.isOnline()) {

				// Restore the original status as the server automatically returns status ONLINE
				client.getSender().setStatus(originalStatus);
				loadChatScene();

				// Request an ID generator if none is present or the existing one is consumed
				if (!localDB.hasIDGenerator() || !localDB.getIDGenerator().hasNext())
					client.requestIDGenerator();

				return true;
			} else
				return false;
		} catch (IOException | InterruptedException | TimeoutException e) {
			logger.log(Level.INFO, "Could not connect to server. Entering offline mode...");
			return attemptOfflineMode(credentials.getIdentifier());
		}
	}

	/**
	 * Attempts to load {@link envoy.client.ui.controller.ChatScene} in offline mode for a given
	 * user.
	 *
	 * @param identifier the identifier of the user - currently his username
	 * @return whether the offline mode could be entered
	 * @since Envoy Client v0.2-beta
	 */
	public static boolean attemptOfflineMode(String identifier) {
		try {
			// Try entering offline mode
			final User clientUser = localDB.getUsers().get(identifier);
			if (clientUser == null)
				throw new EnvoyException("Could not enter offline mode: user name unknown");
			client.setSender(clientUser);
			loadChatScene();
			return true;
		} catch (final Exception e) {
			new Alert(AlertType.ERROR, "Client error: " + e).showAndWait();
			logger.log(Level.SEVERE, "Offline mode could not be loaded: ", e);
			System.exit(1);
			return false;
		}
	}

	/**
	 * Loads the last known time a user has been online.
	 *
	 * @param identifier the identifier of this user - currently his name
	 * @return the last {@code Instant} at which he has been online
	 * @since Envoy Client v0.2-beta
	 */
	public static Instant loadLastSync(String identifier) {
		try {
			localDB.setUser(localDB.getUsers().get(identifier));
			localDB.loadUserData();
		} catch (final Exception e) {
			// User storage empty, wrong user name etc. -> default lastSync
		}
		return localDB.getLastSync();
	}

	private static void loadChatScene() {

		// Set client user in local database
		final var user = client.getSender();
		localDB.setUser(user);

		// Initialize chats in local database
		try {
			localDB.loadUserData();
		} catch (final FileNotFoundException e) {
			// The local database file has not yet been created, probably first login
		} catch (final Exception e) {
			new Alert(AlertType.ERROR,
				"Error while loading local database: " + e + "\nChats will not be stored locally.")
					.showAndWait();
			logger.log(Level.WARNING, "Could not load local database: ", e);
		}

		context.initWriteProxy();

		if (client.isOnline()) {
			context.getWriteProxy().flushCache();

			// Inform the server that this user has a different user status than expected
			if (!user.getStatus().equals(UserStatus.ONLINE))
				client.send(new UserStatusChange(user));
		} else

			// Set all contacts to offline mode
			localDB.getChats()
				.stream()
				.map(Chat::getRecipient)
				.filter(User.class::isInstance)
				.map(User.class::cast)
				.forEach(u -> u.setStatus(UserStatus.OFFLINE));

		final var stage = context.getStage();

		// Pop LoginScene if present
		if (!context.getSceneContext().isEmpty())
			context.getSceneContext().pop();

		// Load ChatScene
		stage.setMinHeight(400);
		stage.setMinWidth(843);
		context.getSceneContext().load(SceneInfo.CHAT_SCENE);
		stage.centerOnScreen();

		// Exit or minimize the stage when a close request occurs
		stage.setOnCloseRequest(
			e -> {
				ShutdownHelper.exit();
				if (Settings.getInstance().isHideOnClose() && StatusTrayIcon.isSupported())
					e.consume();
			});

		// Initialize status tray icon
		if (StatusTrayIcon.isSupported())
			new StatusTrayIcon(stage).show();

		// Start auto save thread
		localDB.initAutoSave();
	}
}