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

@@ -121,6 +121,15 @@ public class Chat implements Serializable {
 		messages.add(0, message);
 	}
 
+	/**
+	 * Removes the message with the given ID
+	 *
+	 * @param messageID the ID of the message to remove
+	 * @return whether any message has been removed
+	 * @since Envoy Client v0.3-beta
+	 */
+	public boolean remove(long messageID) { return messages.removeIf(m -> m.getID() == messageID); }
+
 	/**
 	 * Increments the amount of unread messages.
 	 *

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

@@ -7,6 +7,7 @@ import java.time.Instant;
 import java.util.*;
 import java.util.logging.*;
 
+import javafx.application.Platform;
 import javafx.collections.*;
 
 import envoy.client.event.*;
@@ -235,7 +236,7 @@ public final class LocalDB implements EventListener {
 
 	@Event(priority = 150)
 	private void onUserStatusChange(UserStatusChange evt) {
-		this.getChat(evt.getID()).map(Chat::getRecipient).map(User.class::cast).ifPresent(u -> u.setStatus(evt.get()));
+		getChat(evt.getID()).map(Chat::getRecipient).map(User.class::cast).ifPresent(u -> u.setStatus(evt.get()));
 	}
 
 	@Event(priority = 150)
@@ -273,6 +274,24 @@ public final class LocalDB implements EventListener {
 		cacheMap.clear();
 	}
 
+	/**
+	 * Deletes the message with the given ID, if any is present.
+	 *
+	 * @param message the event that was
+	 * @since Envoy Client v0.3-beta
+	 */
+	@Event()
+	private void onMessageDeletion(MessageDeletion message) {
+		Platform.runLater(() -> {
+
+			// We suppose that messages have unique IDs, hence the search can be stopped
+			// once a message was removed
+			final var messageID = message.get();
+			for (final var chat : chats)
+				if (chat.remove(messageID)) break;
+		});
+	}
+
 	/**
 	 * @return a {@code Map<String, User>} of all users stored locally with their
 	 *         user names as keys

client/src/main/java/envoy/client/ui/control/MessageControl.java

@@ -15,12 +15,16 @@ import javafx.scene.layout.*;
 import javafx.stage.FileChooser;
 
 import envoy.client.data.*;
-import envoy.client.ui.*;
+import envoy.client.net.Client;
+import envoy.client.ui.SceneContext;
 import envoy.client.util.IconUtil;
 import envoy.data.*;
 import envoy.data.Message.MessageStatus;
+import envoy.event.MessageDeletion;
 import envoy.util.EnvoyLog;
 
+import dev.kske.eventbus.EventBus;
+
 /**
  * This class transforms a single {@link Message} into a UI component.
  *
@@ -32,9 +36,11 @@ public final class MessageControl extends Label {
 
 	private final boolean ownMessage;
 
-	private final LocalDB		localDB			= Context.getInstance().getLocalDB();
-	private final SceneContext	sceneContext	= Context.getInstance().getSceneContext();
+	private final LocalDB		localDB			= context.getLocalDB();
+	private final SceneContext	sceneContext	= context.getSceneContext();
+	private final Client		client			= context.getClient();
 
+	private static final Context					context			= Context.getInstance();
 	private static final DateTimeFormatter			dateFormat		= DateTimeFormatter.ofPattern("dd.MM.yyyy HH:mm:ss")
 		.withZone(ZoneId.systemDefault());
 	private static final Map<MessageStatus, Image>	statusImages	= IconUtil.loadByEnum(MessageStatus.class, 16);
@@ -47,6 +53,8 @@ public final class MessageControl extends Label {
 	 * @since Envoy Client v0.1-beta
 	 */
 	public MessageControl(Message message) {
+		ownMessage = message.getSenderID() == localDB.getUser().getID();
+
 		// Creating the underlying VBox and the dateLabel
 		final var hbox = new HBox();
 		if (message.getSenderID() != localDB.getUser().getID() && message instanceof GroupMessage) {
@@ -67,18 +75,40 @@ public final class MessageControl extends Label {
 		final var vbox = new VBox(hbox);
 
 		// Creating the actions for the MenuItems
-		final var	contextMenu		= new ContextMenu();
-		final var	copyMenuItem	= new MenuItem("Copy");
-		final var	deleteMenuItem	= new MenuItem("Delete");
-		final var	forwardMenuItem	= new MenuItem("Forward");
-		final var	quoteMenuItem	= new MenuItem("Quote");
-		final var	infoMenuItem	= new MenuItem("Info");
-		copyMenuItem.setOnAction(e -> copyMessage(message));
-		deleteMenuItem.setOnAction(e -> deleteMessage(message));
-		forwardMenuItem.setOnAction(e -> forwardMessage(message));
-		quoteMenuItem.setOnAction(e -> quoteMessage(message));
+		final var	contextMenu	= new ContextMenu();
+		final var	items		= contextMenu.getItems();
+
+		// Copy message action
+		final var copyMenuItem = new MenuItem("Copy Text");
+		copyMenuItem.setOnAction(e -> copyMessageText(message.getText()));
+		items.add(copyMenuItem);
+
+		// Delete message - if own message - action
+		if (ownMessage && client.isOnline()) {
+			final var deleteMenuItem = new MenuItem("Delete");
+			deleteMenuItem.setOnAction(e -> deleteMessage(message));
+			items.add(deleteMenuItem);
+		}
+
+		// As long as these types of messages are not implemented and no caches are
+		// defined for them, we only want them to appear when being online
+		if (client.isOnline()) {
+
+			// Forward menu item
+			final var forwardMenuItem = new MenuItem("Forward");
+			forwardMenuItem.setOnAction(e -> forwardMessage(message));
+			items.add(forwardMenuItem);
+
+			// Quote menu item
+			final var quoteMenuItem = new MenuItem("Quote");
+			quoteMenuItem.setOnAction(e -> quoteMessage(message));
+			items.add(quoteMenuItem);
+		}
+
+		// Info actions
+		final var infoMenuItem = new MenuItem("Info");
 		infoMenuItem.setOnAction(e -> loadMessageInfoScene(message));
-		contextMenu.getItems().addAll(copyMenuItem, deleteMenuItem, forwardMenuItem, quoteMenuItem, infoMenuItem);
+		items.add(infoMenuItem);
 
 		// Handling message attachment display
 		// TODO: Add missing attachment types
@@ -98,7 +128,7 @@ public final class MessageControl extends Label {
 			}
 			final var saveAttachment = new MenuItem("Save attachment");
 			saveAttachment.setOnAction(e -> saveAttachment(message));
-			contextMenu.getItems().add(saveAttachment);
+			items.add(saveAttachment);
 		}
 		// Creating the textLabel
 		final var textLabel = new Label(message.getText());
@@ -116,12 +146,8 @@ public final class MessageControl extends Label {
 			hBoxBottom.getChildren().add(statusIcon);
 			hBoxBottom.setAlignment(Pos.BOTTOM_RIGHT);
 			getStyleClass().add("own-message");
-			ownMessage = true;
 			hbox.setAlignment(Pos.CENTER_RIGHT);
-		} else {
-			getStyleClass().add("received-message");
-			ownMessage = false;
-		}
+		} else getStyleClass().add("received-message");
 		vbox.getChildren().add(hBoxBottom);
 		// Adjusting height and weight of the cell to the corresponding ListView
 		paddingProperty().setValue(new Insets(5, 20, 5, 20));
@@ -131,11 +157,22 @@ public final class MessageControl extends Label {
 
 	// Context Menu actions
 
-	private void copyMessage(Message message) {
-		Toolkit.getDefaultToolkit().getSystemClipboard().setContents(new StringSelection(message.getText()), null);
+	private void copyMessageText(String text) {
+		logger.log(Level.FINEST, "A copy of message text \"" + text + "\" was requested");
+		Toolkit.getDefaultToolkit().getSystemClipboard().setContents(new StringSelection(text), null);
 	}
 
-	private void deleteMessage(Message message) { logger.log(Level.FINEST, "message deletion was requested for " + message); }
+	private void deleteMessage(Message message) {
+		final var messageDeletionEvent = new MessageDeletion(message.getID());
+		messageDeletionEvent.setOwnEvent();
+
+		// Removing the message locally
+		EventBus.getInstance().dispatch(messageDeletionEvent);
+
+		// Removing the message on the server and this chat's recipients
+		Context.getInstance().getClient().send(messageDeletionEvent);
+		logger.log(Level.FINEST, "message deletion was requested for " + message);
+	}
 
 	private void forwardMessage(Message message) { logger.log(Level.FINEST, "message forwarding was requested for " + message); }
 

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

@@ -308,6 +308,15 @@ public final class ChatScene implements EventListener, Restorable {
 	@Event(eventType = Logout.class, priority = 200)
 	private void onLogout() { eventBus.removeListener(this); }
 
+	@Event(priority = 200)
+	private void onMessageDeletion(MessageDeletion message) {
+		
+		// Clearing the selection if the own user was the sender of this event
+		if (message.isOwnEvent()) Platform.runLater(() -> {
+			messageList.getSelectionModel().clearSelection();
+		});
+	}
+
 	/**
 	 * Initializes all {@code SystemCommands} used in {@code ChatScene}.
 	 *

common/src/main/java/envoy/event/MessageDeletion.java

@@ -0,0 +1,34 @@
+package envoy.event;
+
+/**
+ * Conveys the deletion of a message between clients and server.
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Common v0.3-beta
+ */
+public class MessageDeletion extends Event<Long> {
+
+	private static final long serialVersionUID = 1L;
+
+	private transient boolean ownEvent;
+
+	/**
+	 * @param messageID the ID of the deleted message
+	 * @since Envoy Common v0.3-beta
+	 */
+	public MessageDeletion(long messageID) { super(messageID); }
+
+	/**
+	 * @return whether the current user was the creator of this event.
+	 * @since Envoy Common v0.3-beta
+	 */
+	public boolean isOwnEvent() { return ownEvent; }
+
+	/**
+	 * Marks this event as being sent by this user. Is needed for a bug free
+	 * and efficient selection clearing.
+	 *
+	 * @since Envoy Common v0.3-beta
+	 */
+	public void setOwnEvent() { ownEvent = true; }
+}

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

@@ -56,7 +56,8 @@ public final class Startup {
 						new NameChangeProcessor(),
 						new ProfilePicChangeProcessor(),
 						new PasswordChangeRequestProcessor(),
-						new IssueProposalProcessor())));
+						new IssueProposalProcessor(),
+						new MessageDeletionProcessor())));
 
 		// Initialize the current message ID
 		final var persistenceManager = PersistenceManager.getInstance();

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

@@ -1,7 +1,7 @@
 package envoy.server.data;
 
 import java.time.Instant;
-import java.util.Set;
+import java.util.*;
 
 import javax.persistence.*;
 
@@ -98,6 +98,34 @@ public abstract class Contact {
 	 */
 	public void setCreationDate(Instant creationDate) { this.creationDate = creationDate; }
 
+	/**
+	 * Shortcut to convert a {@code Contact} into a {@code User}.
+	 *
+	 * @param contact the contact to convert
+	 * @return the casted contact
+	 * @throws IllegalStateException if the given contact is not a User
+	 * @since Envoy Server v0.3-beta
+	 */
+	public static User toUser(Contact contact) {
+		if (!(contact instanceof User)) throw new IllegalStateException("Cannot cast a non user to a user");
+		return (User) contact;
+	}
+
+	/**
+	 * Shortcut to convert a set of {@code Contact}s into a set of {@code User}s.
+	 *
+	 * @param contacts the contacts to convert
+	 * @return the casted contacts
+	 * @throws IllegalStateException if one of the given contacts is not a User
+	 * @since Envoy Server v0.3-beta
+	 */
+	public static Set<User> toUser(Set<Contact> contacts) {
+		final var newSet = new HashSet<User>();
+		for (final var contact : contacts)
+			newSet.add(toUser(contact));
+		return newSet;
+	}
+
 	@Override
 	public String toString() { return String.format("%s[id=%d,name=%s,%d contact(s)]", getClass().getSimpleName(), id, name, contacts.size()); }
 }

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

@@ -0,0 +1,81 @@
+package envoy.server.data;
+
+import java.util.*;
+
+import javax.persistence.*;
+
+/**
+ * Defines a message that has been deleted.
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Server v0.3-beta
+ */
+@Entity
+@Table(name = "deletionEvents")
+@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
+public final class MessageDeletion {
+
+	@Id
+	@GeneratedValue
+	protected long messageID;
+
+	@ManyToOne(targetEntity = User.class)
+	protected Set<User> recipientsToInform;
+
+	/**
+	 * Creates an instance of {@code DeletionEvent}.
+	 *
+	 * @since Envoy Server v0.3-beta
+	 */
+	public MessageDeletion() {}
+
+	/**
+	 * Creates an instance of {@code MessageDeletion}.
+	 *
+	 * @param messageID          the ID of the message
+	 * @param recipientsToInform the recipientsToInform of the message<br>
+	 *                           <strong>that have not yet been notified of its
+	 *                           deletion</strong>
+	 * @since Envoy Server v0.3-beta
+	 */
+	public MessageDeletion(long messageID, Set<User> recipientsToInform) {
+		this.messageID			= messageID;
+		this.recipientsToInform	= recipientsToInform;
+	}
+
+	/**
+	 * @return the messageID
+	 * @since Envoy Server v0.3-beta
+	 */
+	public long getMessageID() { return messageID; }
+
+	/**
+	 * @param messageID the messageID to set
+	 * @since Envoy Server v0.3-beta
+	 */
+	public void setMessageID(long messageID) { this.messageID = messageID; }
+
+	/**
+	 * @return the recipients that have yet to be informed
+	 * @since Envoy Server v0.3-beta
+	 */
+	public Set<User> getRecipientsToInform() { return recipientsToInform; }
+
+	/**
+	 * @param recipientsToInform the recipients that have yet to be informed
+	 * @since Envoy Server v0.3-beta
+	 */
+	public void setRecipientsToInform(Set<User> recipientsToInform) { this.recipientsToInform = recipientsToInform; }
+
+	/**
+	 * @param user the user who has been informed of the message deletion
+	 * @since Envoy Server v0.3-beta
+	 */
+	public void recipientInformed(User user) { recipientsToInform.remove(user); }
+
+	/**
+	 * @param users the users that have been informed of the message deletion
+	 * @since Envoy Server v0.3-beta
+	 */
+	public void recipientInformed(Collection<User> users) { recipientsToInform.removeAll(users); }
+}

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

@@ -1,7 +1,7 @@
 package envoy.server.data;
 
 import java.time.Instant;
-import java.util.List;
+import java.util.*;
 
 import javax.persistence.*;
 
@@ -100,12 +100,35 @@ public final class PersistenceManager {
 	public void deleteContact(Contact contact) { remove(contact); }
 
 	/**
-	 * Deletes a {@link Message} in the database.
+	 * Deletes a {@link Message} in the database and creates a new
+	 * {@link MessageDeletion} object for <strong>all</strong> recipients of the
+	 * message.
 	 *
 	 * @param message the {@link Message} to delete
-	 * @since Envoy Server Standalone v0.1-alpha
+	 * @return the created {@link MessageDeletion} object
+	 * @since Envoy Server v0.3-beta
 	 */
-	public void deleteMessage(Message message) { remove(message); }
+	public MessageDeletion deleteMessage(Message message) {
+		final var recipient = message.getRecipient();
+		return deleteMessage(message,
+				recipient instanceof Group ? Contact.toUser(getGroupByID(recipient.id).getContacts()) : Set.of(Contact.toUser(recipient)));
+	}
+
+	/**
+	 * Deletes a {@link Message} in the database and creates a new
+	 * {@link MessageDeletion} object for the given recipients of the message.
+	 *
+	 * @param message               the {@link Message} to delete
+	 * @param recipientsYetToInform the (sub)set of all recipients of that message
+	 * @return the created {@link MessageDeletion} object
+	 * @since Envoy Server v0.3-beta
+	 */
+	public MessageDeletion deleteMessage(Message message, Set<User> recipientsYetToInform) {
+		final MessageDeletion deletion = new MessageDeletion(message.id, recipientsYetToInform);
+		persist(deletion);
+		remove(message);
+		return deletion;
+	}
 
 	/**
 	 * Searches for a {@link User} with a specific ID.
@@ -172,6 +195,16 @@ public final class PersistenceManager {
 	 */
 	public ConfigItem getConfigItemByID(String key) { return entityManager.find(ConfigItem.class, key); }
 
+	/**
+	 * Searches for a {@link MessageDeletion} with the given message id.
+	 *
+	 * @param id the id of the message to search for
+	 * @return the message deletion object with the specified ID or {@code null} if
+	 *         none is found
+	 * @since Envoy Server v0.3-beta
+	 */
+	public MessageDeletion getMessageDeletionByID(long id) { return entityManager.find(MessageDeletion.class, id); }
+
 	/**
 	 * Returns all messages received while being offline or the ones that have
 	 * changed.

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

@@ -0,0 +1,18 @@
+package envoy.server.processors;
+
+import java.io.IOException;
+
+import envoy.event.MessageDeletion;
+import envoy.server.net.ObjectWriteProxy;
+
+/**
+ * Listens for and handles incoming {@link MessageDeletion}s.
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Server v0.3-beta
+ */
+public class MessageDeletionProcessor implements ObjectProcessor<MessageDeletion> {
+
+	@Override
+	public void process(MessageDeletion message, long socketID, ObjectWriteProxy writeProxy) throws IOException {}
+}