client/src/main/java/envoy/client/data/Chat.java

@@ -22,20 +22,21 @@ import envoy.client.net.WriteProxy;
  */
 public class Chat implements Serializable {
 
+	protected transient ObservableList<Message> messages = FXCollections.observableArrayList();
+
+	protected final Contact recipient;
+
 	protected boolean	disabled;
+	protected boolean	underlyingContactDeleted;
 
 	/**
 	 * Stores the last time an {@link envoy.event.IsTyping} event has been sent.
 	 */
 	protected transient long lastWritingEvent;
 
-	protected transient ObservableList<Message> messages = FXCollections.observableArrayList();
-
 	protected int						unreadAmount;
 	protected static IntegerProperty	totalUnreadAmount	= new SimpleIntegerProperty();
 
-	protected final Contact recipient;
-
 	private static final long serialVersionUID = 2L;
 
 	/**

client/src/main/java/envoy/client/data/LocalDB.java

@@ -248,6 +248,10 @@ public final class LocalDB implements EventListener {
 	 */
 	@Event(eventType = EnvoyCloseEvent.class, priority = 500)
 	private synchronized void save() {
+
+		// Stop saving if this account has been deleted
+		if (userFile == null)
+			return;
 		EnvoyLog.getLogger(LocalDB.class).log(Level.FINER, "Saving local database...");
 
 		// Save users
@@ -273,6 +277,20 @@ public final class LocalDB implements EventListener {
 		}
 	}
 
+	/**
+	 * Deletes any local remnant of this user.
+	 *
+	 * @since Envoy Client v0.3-beta
+	 */
+	public void delete() {
+		if (lastLoginFile != null)
+			lastLoginFile.delete();
+		userFile.delete();
+		users.remove(user.getName());
+		userFile = null;
+		onLogout();
+	}
+
 	@Event(priority = 500)
 	private void onMessage(Message msg) {
 		if (msg.getStatus() == MessageStatus.SENT)
@@ -404,6 +422,17 @@ public final class LocalDB implements EventListener {
 		getChat(event.get().getID()).ifPresent(chat -> chat.setDisabled(true));
 	}
 
+	@Event(priority = 500)
+	private void onAccountDeletion(AccountDeletion deletion) {
+		if (user.getID() == deletion.get())
+			logger.log(Level.WARNING,
+				"I have been informed by the server that I have been deleted without even knowing it...");
+		getChat(deletion.get()).ifPresent(chat -> {
+			chat.setDisabled(true);
+			chat.setUnderlyingContactDeleted(true);
+		});
+	}
+
 	/**
 	 * @return a {@code Map<String, User>} of all users stored locally with their user names as keys
 	 * @since Envoy Client v0.2-alpha

client/src/main/java/envoy/client/ui/controller/ChatScene.java

@@ -6,7 +6,7 @@ import java.io.*;
 import java.nio.file.Files;
 import java.time.LocalDateTime;
 import java.time.format.DateTimeFormatter;
-import java.util.*;
+import java.util.Map;
 import java.util.logging.*;
 
 import javafx.animation.RotateTransition;
@@ -25,9 +25,8 @@ import javafx.scene.shape.Rectangle;
 import javafx.stage.FileChooser;
 import javafx.util.Duration;
 
+import dev.kske.eventbus.*;
 import dev.kske.eventbus.Event;
-import dev.kske.eventbus.EventBus;
-import dev.kske.eventbus.EventListener;
 
 import envoy.data.*;
 import envoy.data.Attachment.AttachmentType;
@@ -882,24 +881,22 @@ public final class ChatScene implements EventListener, Restorable, KeyboardMappi
 
 	@Override
 	public Map<KeyCombination, Runnable> getKeyboardShortcuts() {
-		final var map = new HashMap<KeyCombination, Runnable>();
+		return Map.<KeyCombination, Runnable>of(
 
 			// Delete text before the caret with "Control" + U
-		map.put(new KeyCodeCombination(KeyCode.U, KeyCombination.CONTROL_DOWN), () -> {
+			new KeyCodeCombination(KeyCode.U, KeyCombination.CONTROL_DOWN), () -> {
 				messageTextArea
-				.setText(messageTextArea.getText().substring(messageTextArea.getCaretPosition()));
+					.setText(
+						messageTextArea.getText().substring(messageTextArea.getCaretPosition()));
 				checkPostConditions(false);
-		});
 
 				// Delete text after the caret with "Control" + K
-		map.put(new KeyCodeCombination(KeyCode.K, KeyCombination.CONTROL_DOWN), () -> {
+			}, new KeyCodeCombination(KeyCode.K, KeyCombination.CONTROL_DOWN), () -> {
 				messageTextArea
 					.setText(
 						messageTextArea.getText().substring(0, messageTextArea.getCaretPosition()));
 				checkPostConditions(false);
 				messageTextArea.positionCaret(messageTextArea.getText().length());
 			});
-
-		return map;
 	}
 }

client/src/main/java/envoy/client/ui/controller/GroupCreationTab.java

@@ -14,7 +14,7 @@ import dev.kske.eventbus.*;
 
 import envoy.data.*;
 import envoy.event.GroupCreation;
-import envoy.event.contact.UserOperation;
+import envoy.event.contact.*;
 import envoy.util.Bounds;
 
 import envoy.client.data.*;
@@ -252,4 +252,10 @@ public class GroupCreationTab implements EventListener {
 			}
 		});
 	}
+
+	@Event
+	private void onAccountDeletion(AccountDeletion deletion) {
+		final var deletedID = deletion.get();
+		Platform.runLater(() -> userList.getItems().removeIf(user -> (user.getID() == deletedID)));
+	}
 }

client/src/main/java/envoy/client/ui/settings/UserSettingsPane.java

@@ -20,7 +20,7 @@ import envoy.event.*;
 import envoy.util.*;
 
 import envoy.client.ui.control.ProfilePicImageView;
-import envoy.client.util.IconUtil;
+import envoy.client.util.*;
 
 /**
  * @author Leon Hofmeister
@@ -38,6 +38,7 @@ public final class UserSettingsPane extends OnlineOnlySettingsPane {
 	private final PasswordField	newPasswordField		= new PasswordField();
 	private final PasswordField	repeatNewPasswordField	= new PasswordField();
 	private final Button		saveButton				= new Button("Save");
+	private final Button		deleteAccountButton		= new Button("Delete Account");
 
 	private static final EventBus	eventBus	= EventBus.getInstance();
 	private static final Logger		logger		= EnvoyLog.getLogger(UserSettingsPane.class);
@@ -112,15 +113,18 @@ public final class UserSettingsPane extends OnlineOnlySettingsPane {
 
 		final PasswordField[]					passwordFields	=
 			{ currentPasswordField, newPasswordField, repeatNewPasswordField };
-		final EventHandler<? super InputEvent>	passwordEntered	= e -> {
+		final EventHandler<? super InputEvent>	passwordEntered	=
+			e -> {
 																		newPassword	=
-																		newPasswordField.getText();
-																	validPassword	= newPassword
-																		.equals(
+																			newPasswordField
+																				.getText();
+																		validPassword =
+																			newPassword.equals(
 																				repeatNewPasswordField
 																					.getText())
 																				&& !newPasswordField
-																			.getText().isBlank();
+																					.getText()
+																					.isBlank();
 																	};
 		newPasswordField.setOnInputMethodTextChanged(passwordEntered);
 		newPasswordField.setOnKeyTyped(passwordEntered);
@@ -140,6 +144,11 @@ public final class UserSettingsPane extends OnlineOnlySettingsPane {
 			.setOnAction(e -> save(currentPasswordField.getText()));
 		saveButton.setAlignment(Pos.BOTTOM_RIGHT);
 		getChildren().add(saveButton);
+
+		// Displaying the delete account button
+		deleteAccountButton.setAlignment(Pos.BASELINE_CENTER);
+		deleteAccountButton.setOnAction(e -> UserUtil.deleteAccount());
+		getChildren().add(deleteAccountButton);
 	}
 
 	/**

client/src/main/java/envoy/client/util/UserUtil.java

@@ -2,7 +2,7 @@ package envoy.client.util;
 
 import java.util.logging.*;
 
-import javafx.scene.control.Alert;
+import javafx.scene.control.*;
 import javafx.scene.control.Alert.AlertType;
 
 import dev.kske.eventbus.EventBus;
@@ -10,7 +10,7 @@ import dev.kske.eventbus.EventBus;
 import envoy.data.*;
 import envoy.data.User.UserStatus;
 import envoy.event.*;
-import envoy.event.contact.UserOperation;
+import envoy.event.contact.*;
 import envoy.util.EnvoyLog;
 
 import envoy.client.data.Context;
@@ -121,4 +121,40 @@ public final class UserUtil {
 			});
 		}
 	}
+
+	/**
+	 * Deletes anything pointing to this user, independent of client or server. Will do nothing if
+	 * the client is currently offline.
+	 *
+	 * @since Envoy Client v0.3-beta
+	 */
+	public static void deleteAccount() {
+		if (!context.getClient().isOnline())
+			return;
+		else {
+
+			// Show the first wall of defense, if not disabled by the user
+			final var outerAlert = new Alert(AlertType.CONFIRMATION);
+			outerAlert.setContentText(
+				"Are you sure you want to delete your account entirely? This action can seriously not be undone.");
+			outerAlert.setTitle("Delete Account?");
+			AlertHelper.confirmAction(outerAlert, () -> {
+
+				// Show the final wall of defense in every case
+				final var lastAlert = new Alert(AlertType.WARNING,
+					"Do you REALLY want to delete your account? Last Warning. Proceed?",
+					ButtonType.CANCEL, ButtonType.OK);
+				lastAlert.setTitle("Delete Account?");
+				lastAlert.showAndWait().filter(ButtonType.OK::equals).ifPresent(b2 -> {
+
+					// Delete the account
+					context.getClient()
+						.send(new AccountDeletion(context.getLocalDB().getUser().getID()));
+					context.getLocalDB().delete();
+					logger.log(Level.INFO, "The user just deleted his account. Goodbye.");
+					ShutdownHelper.exit(true);
+				});
+			});
+		}
+	}
 }

common/src/main/java/envoy/event/contact/AccountDeletion.java

@@ -0,0 +1,22 @@
+package envoy.event.contact;
+
+import envoy.event.Event;
+
+/**
+ * Signifies the deletion of an account.
+ * 
+ * @author Leon Hofmeister
+ * @since Envoy Common v0.3-beta
+ */
+public class AccountDeletion extends Event<Long> {
+
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * @param value the ID of the contact that was deleted
+	 * @since Envoy Common v0.3-beta
+	 */
+	public AccountDeletion(Long value) {
+		super(value);
+	}
+}

server/src/main/java/envoy/server/Startup.java

@@ -59,7 +59,8 @@ public final class Startup {
 				new NameChangeProcessor(),
 				new ProfilePicChangeProcessor(),
 				new PasswordChangeRequestProcessor(),
-				new IssueProposalProcessor())));
+				new IssueProposalProcessor(),
+				new AccountDeletionProcessor())));
 
 		// Initialize the current message ID
 		final var persistenceManager = PersistenceManager.getInstance();

server/src/main/java/envoy/server/data/Message.java

@@ -27,14 +27,18 @@ import envoy.data.Message.MessageStatus;
 @Entity
 @Table(name = "messages")
 @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
-@NamedQuery(name = Message.getPending, query = "SELECT m FROM Message m WHERE "
+@NamedQueries({
+				@NamedQuery(name = Message.getPending, query = "SELECT m FROM Message m WHERE "
 					// Send to or by the user before last seen
 					+ "(m.sender = :user OR m.recipient = :user) AND m.creationDate > :lastSeen "
 					// SENT to the user
 					+ "OR m.recipient = :user AND m.status = envoy.data.Message$MessageStatus.SENT "
 					// Sent by the user and RECEIVED / READ after last seen
 					+ "OR m.sender = :user AND (m.status = envoy.data.Message$MessageStatus.RECEIVED AND m.receivedDate > :lastSeen "
-	+ "OR m.status = envoy.data.Message$MessageStatus.READ AND m.readDate > :lastSeen)")
+					+ "OR m.status = envoy.data.Message$MessageStatus.READ AND m.readDate > :lastSeen)"),
+				@NamedQuery(name = Message.deleteByRecipient, query = "DELETE FROM Message m WHERE m.recipient = :deleted OR m.sender = :deleted")
+
+})
 public class Message {
 
 	/**
@@ -45,6 +49,13 @@ public class Message {
 	 */
 	public static final String getPending = "Message.getPending";
 
+	/**
+	 * Named query deleting all messages of a user (parameter {@code :deleted}).
+	 *
+	 * @since Envoy Server v0.3-beta
+	 */
+	public static final String deleteByRecipient = "Message.deleteByRecipient";
+
 	@Id
 	protected long id;
 

server/src/main/java/envoy/server/data/PersistenceManager.java

@@ -123,6 +123,10 @@ public final class PersistenceManager {
 			// Remove this contact from the contact list of his contacts
 			for (final var remainingContact : contact.getContacts())
 				remainingContact.getContacts().remove(contact);
+
+			entityManager
+				.createNamedQuery(Message.deleteByRecipient).setParameter("deleted", contact)
+				.executeUpdate();
 		});
 		remove(contact);
 	}

server/src/main/java/envoy/server/net/ConnectionManager.java

@@ -49,8 +49,10 @@ public final class ConnectionManager implements ISocketIdListener {
 			// Notify contacts of this users offline-going
 			final envoy.server.data.User user =
 				PersistenceManager.getInstance().getUserByID(getUserIDBySocketID(socketID));
+			if (user != null) {
 				user.setLastSeen(Instant.now());
 				UserStatusChangeProcessor.updateUserStatus(user, UserStatus.OFFLINE);
+			}
 
 			// Remove the socket
 			sockets.entrySet().removeIf(e -> e.getValue() == socketID);

server/src/main/java/envoy/server/processors/AccountDeletionProcessor.java

@@ -0,0 +1,33 @@
+package envoy.server.processors;
+
+import java.io.IOException;
+import java.time.Instant;
+
+import envoy.event.contact.AccountDeletion;
+
+import envoy.server.data.*;
+import envoy.server.net.ObjectWriteProxy;
+
+/**
+ * @author Leon Hofmeister
+ * @since Envoy Server v0.3-beta
+ */
+public class AccountDeletionProcessor implements ObjectProcessor<AccountDeletion> {
+
+	private static final PersistenceManager persistenceManager = PersistenceManager.getInstance();
+
+	@Override
+	public void process(AccountDeletion input, long socketID, ObjectWriteProxy writeProxy)
+		throws IOException {
+		final var contact = persistenceManager.getContactByID(input.get());
+
+		contact.getContacts().forEach(c -> {
+			persistenceManager.removeContactBidirectional(contact, c);
+			if (c instanceof User)
+				((User) c).setLatestContactDeletion(Instant.now());
+		});
+
+		writeProxy.writeToOnlineContacts(contact.getContacts(), input);
+		persistenceManager.deleteContact(contact);
+	}
+}

server/src/main/java/envoy/server/processors/GroupResizeProcessor.java

@@ -4,6 +4,7 @@ import java.time.Instant;
 import java.util.logging.Level;
 
 import envoy.event.GroupResize;
+import envoy.event.contact.AccountDeletion;
 import envoy.util.EnvoyLog;
 
 import envoy.server.data.*;
@@ -24,6 +25,12 @@ public final class GroupResizeProcessor implements ObjectProcessor<GroupResize>
 		final var	group	= persistenceManager.getGroupByID(groupResize.getGroupID());
 		final var	sender	= persistenceManager.getUserByID(groupResize.get().getID());
 
+		// Inform the sender that this group has already been deleted
+		if (group == null) {
+			writeProxy.write(socketID, new AccountDeletion(groupResize.getGroupID()));
+			return;
+		}
+
 		// Perform the desired operation
 		switch (groupResize.getOperation()) {
 			case ADD:

server/src/main/java/envoy/server/processors/UserOperationProcessor.java

@@ -4,7 +4,7 @@ import java.time.Instant;
 import java.util.logging.*;
 
 import envoy.event.ElementOperation;
-import envoy.event.contact.UserOperation;
+import envoy.event.contact.*;
 import envoy.util.EnvoyLog;
 
 import envoy.server.data.PersistenceManager;
@@ -22,9 +22,17 @@ public final class UserOperationProcessor implements ObjectProcessor<UserOperati
 	private static final PersistenceManager	persistenceManager	= PersistenceManager.getInstance();
 
 	@Override
-	public void process(UserOperation evt, long socketId, ObjectWriteProxy writeProxy) {
-		final long	userID		= ConnectionManager.getInstance().getUserIDBySocketID(socketId);
+	public void process(UserOperation evt, long socketID, ObjectWriteProxy writeProxy) {
+		final long	userID		= ConnectionManager.getInstance().getUserIDBySocketID(socketID);
 		final long	contactID	= evt.get().getID();
+		final var	recipient	= persistenceManager.getUserByID(contactID);
+
+		// Inform the sender if the requested contact has already been deleted
+		if (recipient == null) {
+			writeProxy.write(socketID, new AccountDeletion(contactID));
+			return;
+		}
+
 		final var sender = persistenceManager.getUserByID(userID);
 		switch (evt.getOperationType()) {
 			case ADD:
@@ -45,7 +53,7 @@ public final class UserOperationProcessor implements ObjectProcessor<UserOperati
 				sender.setLatestContactDeletion(Instant.now());
 
 				// Notify the removed contact on next startup(s) of this deletion
-				persistenceManager.getUserByID(contactID).setLatestContactDeletion(Instant.now());
+				recipient.setLatestContactDeletion(Instant.now());
 
 				// Notify the removed contact if online
 				if (connectionManager.isOnline(contactID))