Merge branch 'develop' into f/new_ui

client/pom.xml

@@ -37,15 +37,6 @@
 				<directory>src/main/resources</directory>
 			</resource>
 		</resources>
-		<pluginManagement>
-			<plugins>
-				<plugin>
-					<groupId>org.apache.maven.plugins</groupId>
-					<artifactId>maven-compiler-plugin</artifactId>
-					<version>3.8.1</version>
-				</plugin>
-			</plugins>
-		</pluginManagement>
 		<plugins>
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>

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

@@ -7,8 +7,10 @@ import java.util.List;
 import java.util.Objects;
 
 import envoy.client.net.WriteProxy;
-import envoy.data.*;
+import envoy.data.Contact;
+import envoy.data.Message;
 import envoy.data.Message.MessageStatus;
+import envoy.data.User;
 import envoy.event.MessageStatusChange;
 
 /**
@@ -31,6 +33,11 @@ public class Chat implements Serializable {
 
 	protected int unreadAmount;
 
+	/**
+	 * Stores the last time an {@link envoy.event.IsTyping} event has been sent.
+	 */
+	protected transient long lastWritingEvent;
+
 	private static final long serialVersionUID = 1L;
 
 	/**
@@ -41,16 +48,14 @@ public class Chat implements Serializable {
 	 * @param recipient the user who receives the messages
 	 * @since Envoy Client v0.1-alpha
 	 */
-	public Chat(Contact recipient) {
-		this.recipient	= recipient;
-	}
+	public Chat(Contact recipient) { this.recipient = recipient; }
 
 	@Override
 	public String toString() { return String.format("Chat[recipient=%s,messages=%d]", recipient, messages.size()); }
 
 	/**
 	 * Generates a hash code based on the recipient.
-	 * 
+	 *
 	 * @since Envoy Client v0.1-beta
 	 */
 	@Override
@@ -58,14 +63,14 @@ public class Chat implements Serializable {
 
 	/**
 	 * Tests equality to another object based on the recipient.
-	 * 
+	 *
 	 * @since Envoy Client v0.1-beta
 	 */
 	@Override
 	public boolean equals(Object obj) {
 		if (this == obj) return true;
 		if (!(obj instanceof Chat)) return false;
-		Chat other = (Chat) obj;
+		final Chat other = (Chat) obj;
 		return Objects.equals(recipient, other.recipient);
 	}
 
@@ -101,7 +106,7 @@ public class Chat implements Serializable {
 
 	/**
 	 * Inserts a message at the correct place according to its creation date.
-	 * 
+	 *
 	 * @param message the message to insert
 	 * @since Envoy Client v0.1-beta
 	 */
@@ -116,13 +121,13 @@ public class Chat implements Serializable {
 
 	/**
 	 * Increments the amount of unread messages.
-	 * 
+	 *
 	 * @since Envoy Client v0.1-beta
 	 */
 	public void incrementUnreadAmount() { unreadAmount++; }
 
 	/**
-	 * @return the amount of unread mesages in this chat
+	 * @return the amount of unread messages in this chat
 	 * @since Envoy Client v0.1-beta
 	 */
 	public int getUnreadAmount() { return unreadAmount; }
@@ -140,14 +145,16 @@ public class Chat implements Serializable {
 	public Contact getRecipient() { return recipient; }
 
 	/**
-	 * @return whether this {@link Chat} points at a {@link User}
-	 * @since Envoy Client v0.1-beta
+	 * @return the last known time a {@link envoy.event.IsTyping} event has been
+	 *         sent
+	 * @since Envoy Client v0.2-beta
 	 */
-	public boolean isUserChat() { return recipient instanceof User; }
+	public long getLastWritingEvent() { return lastWritingEvent; }
 
 	/**
-	 * @return whether this {@link Chat} points at a {@link Group}
-	 * @since Envoy Client v0.1-beta
+	 * Sets the {@code lastWritingEvent} to {@code System#currentTimeMillis()}.
+	 *
+	 * @since Envoy Client v0.2-beta
 	 */
-	public boolean isGroupChat() { return recipient instanceof Group; }
+	public void lastWritingEventWasNow() { lastWritingEvent = System.currentTimeMillis(); }
 }

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

@@ -75,8 +75,12 @@ public class Settings {
 
 	private void supplementDefaults() {
 		items.putIfAbsent("enterToSend", new SettingsItem<>(true, "Enter to send", "Sends a message by pressing the enter key."));
-		items.putIfAbsent("onCloseMode", new SettingsItem<>(true, "Hide on close", "Hides the chat window when it is closed."));
+		items.putIfAbsent("hideOnClose", new SettingsItem<>(true, "Hide on close", "Hides the chat window when it is closed."));
 		items.putIfAbsent("currentTheme", new SettingsItem<>("dark", "Current Theme Name", "The name of the currently selected theme."));
+		items.putIfAbsent("downloadLocation",
+				new SettingsItem<>(new File(System.getProperty("user.home") + "/Downloads/"), "Download location",
+						"The location where files will be saved to"));
+		items.putIfAbsent("autoSaveDownloads", new SettingsItem<>(false, "Save without asking?", "Should downloads be saved without asking?"));
 	}
 
 	/**
@@ -120,19 +124,50 @@ public class Settings {
 	 */
 	public void setEnterToSend(boolean enterToSend) { ((SettingsItem<Boolean>) items.get("enterToSend")).set(enterToSend); }
 
+	/**
+	 * @return whether Envoy will prompt a dialogue before saving an
+	 *         {@link envoy.data.Attachment}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public Boolean isDownloadSavedWithoutAsking() { return (Boolean) items.get("autoSaveDownloads").get(); }
+
+	/**
+	 * Sets whether Envoy will prompt a dialogue before saving an
+	 * {@link envoy.data.Attachment}.
+	 *
+	 * @param autosaveDownload whether a download should be saved without asking
+	 *                         before
+	 * @since Envoy Client v0.2-beta
+	 */
+	public void setDownloadSavedWithoutAsking(boolean autosaveDownload) { ((SettingsItem<Boolean>) items.get("autoSaveDownloads")).set(autosaveDownload); }
+
+	/**
+	 * @return the path where downloads should be saved
+	 * @since Envoy Client v0.2-beta
+	 */
+	public File getDownloadLocation() { return (File) items.get("downloadLocation").get(); }
+
+	/**
+	 * Sets the path where downloads should be saved.
+	 *
+	 * @param downloadLocation the path to set
+	 * @since Envoy Client v0.2-beta
+	 */
+	public void setDownloadLocation(File downloadLocation) { ((SettingsItem<File>) items.get("downloadLocation")).set(downloadLocation); }
+
 	/**
 	 * @return the current on close mode.
 	 * @since Envoy Client v0.3-alpha
 	 */
-	public Boolean getCurrentOnCloseMode() { return (Boolean) items.get("onCloseMode").get(); }
+	public Boolean isHideOnClose() { return (Boolean) items.get("hideOnClose").get(); }
 
 	/**
 	 * Sets the current on close mode.
 	 *
-	 * @param currentOnCloseMode the on close mode that should be set.
+	 * @param hideOnClose whether the application should be minimized on close
 	 * @since Envoy Client v0.3-alpha
 	 */
-	public void setCurrentOnCloseMode(boolean currentOnCloseMode) { ((SettingsItem<Boolean>) items.get("onCloseMode")).set(currentOnCloseMode); }
+	public void setHideOnClose(boolean hideOnClose) { ((SettingsItem<Boolean>) items.get("hideOnClose")).set(hideOnClose); }
 
 	/**
 	 * @return the items

client/src/main/java/envoy/client/data/audio/AudioRecorder.java

@@ -27,6 +27,11 @@ public final class AudioRecorder {
 	 */
 	public static final AudioFormat DEFAULT_AUDIO_FORMAT = new AudioFormat(16000, 16, 1, true, false);
 
+	/**
+	 * The format in which audio files will be saved.
+	 */
+	public static final String FILE_FORMAT = "wav";
+
 	private final AudioFormat	format;
 	private final DataLine.Info	info;
 
@@ -78,7 +83,7 @@ public final class AudioRecorder {
 			line.start();
 
 			// Prepare temp file
-			tempFile = Files.createTempFile("recording", "wav");
+			tempFile = Files.createTempFile("recording", FILE_FORMAT);
 
 			// Start the recording
 			final var ais = new AudioInputStream(line);
@@ -117,6 +122,6 @@ public final class AudioRecorder {
 		line.close();
 		try {
 			Files.deleteIfExists(tempFile);
-		} catch (IOException e) {}
+		} catch (final IOException e) {}
 	}
 }

client/src/main/java/envoy/client/data/commands/OnCall.java

@@ -0,0 +1,34 @@
+package envoy.client.data.commands;
+
+import java.util.function.Supplier;
+
+/**
+ * This interface defines an action that should be performed when a system
+ * command gets called.
+ * <p>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>OnCall.java</strong><br>
+ * Created: <strong>23.07.2020</strong><br>
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Client v0.2-beta
+ */
+public interface OnCall {
+
+	/**
+	 * Performs class specific actions when a {@link SystemCommand} has been called.
+	 *
+	 * @since Envoy Client v0.2-beta
+	 */
+	void onCall();
+
+	/**
+	 * Performs actions that can only be performed by classes that are not
+	 * {@link SystemCommand}s when a SystemCommand has been called.
+	 *
+	 * @param consumer the action to perform when this {@link SystemCommand} has
+	 *                 been called
+	 * @since Envoy Client v0.2-beta
+	 */
+	void onCall(Supplier<Void> consumer);
+}

client/src/main/java/envoy/client/data/commands/SystemCommand.java

@@ -0,0 +1,135 @@
+package envoy.client.data.commands;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
+/**
+ * This class is the base class of all {@code SystemCommands} and contains an
+ * action and a number of arguments that should be used as input for this
+ * function.
+ * No {@code SystemCommand} can return anything.
+ * Every {@code SystemCommand} must have as argument type {@code List<String>} so
+ * that the words following the indicator String can be used as input of the
+ * function. This approach has one limitation:<br>
+ * <b>Order matters!</b> Changing the order of arguments will likely result in
+ * unexpected behavior.
+ * <p>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>SystemCommand.java</strong><br>
+ * Created: <strong>16.07.2020</strong><br>
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Client v0.2-beta
+ */
+public class SystemCommand implements OnCall {
+
+	protected int relevance;
+
+	/**
+	 * The argument count of the command.
+	 */
+	protected final int numberOfArguments;
+
+	/**
+	 * This function takes a {@code List<String>} as argument because automatically
+	 * {@code SystemCommand#numberOfArguments} words following the necessary command
+	 * will be put into this list.
+	 *
+	 * @see String#split(String)
+	 */
+	protected final Consumer<List<String>> action;
+
+	protected final String description;
+
+	protected final List<String> defaults;
+
+	/**
+	 * Constructs a new {@code SystemCommand}.
+	 *
+	 * @param action            the action performed by the command
+	 * @param numberOfArguments the argument count accepted by the action
+	 * @param defaults          the default values for the corresponding arguments
+	 * @param description       the description of this {@code SystemCommand}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommand(Consumer<List<String>> action, int numberOfArguments, List<String> defaults, String description) {
+		this.numberOfArguments	= numberOfArguments;
+		this.action				= action;
+		this.defaults			= defaults == null ? new ArrayList<>() : defaults;
+		this.description		= description;
+	}
+
+	/**
+	 * @return the action that should be performed
+	 * @since Envoy Client v0.2-beta
+	 */
+	public Consumer<List<String>> getAction() { return action; }
+
+	/**
+	 * @return the argument count of the command
+	 * @since Envoy Client v0.2-beta
+	 */
+	public int getNumberOfArguments() { return numberOfArguments; }
+
+	/**
+	 * @return the description
+	 * @since Envoy Client v0.2-beta
+	 */
+	public String getDescription() { return description; }
+
+	/**
+	 * @return the relevance
+	 * @since Envoy Client v0.2-beta
+	 */
+	public int getRelevance() { return relevance; }
+
+	/**
+	 * @param relevance the relevance to set
+	 * @since Envoy Client v0.2-beta
+	 */
+	public void setRelevance(int relevance) { this.relevance = relevance; }
+
+	/**
+	 * Increments the relevance of this {@code SystemCommand}.
+	 */
+	@Override
+	public void onCall() { relevance++; }
+
+	/**
+	 * Increments the relevance of this {@code SystemCommand} and executes the
+	 * supplier.
+	 */
+	@Override
+	public void onCall(Supplier<Void> consumer) {
+		onCall();
+		consumer.get();
+	}
+
+	/**
+	 * @return the defaults
+	 * @since Envoy Client v0.2-beta
+	 */
+	public List<String> getDefaults() { return defaults; }
+
+	@Override
+	public int hashCode() { return Objects.hash(action); }
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj) return true;
+		if (obj == null) return false;
+		if (getClass() != obj.getClass()) return false;
+		final SystemCommand other = (SystemCommand) obj;
+		return Objects.equals(action, other.action);
+	}
+
+	@Override
+	public String toString() {
+		return "SystemCommand [relevance=" + relevance + ", numberOfArguments=" + numberOfArguments + ", "
+				+ (action != null ? "action=" + action + ", " : "") + (description != null ? "description=" + description + ", " : "")
+				+ (defaults != null ? "defaults=" + defaults : "") + "]";
+	}
+}

client/src/main/java/envoy/client/data/commands/SystemCommandBuilder.java

@@ -0,0 +1,144 @@
+package envoy.client.data.commands;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Consumer;
+
+/**
+ * This class acts as a builder for {@link SystemCommand}s.
+ * <p>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>SystemCommandBuilder.java</strong><br>
+ * Created: <strong>23.07.2020</strong><br>
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Client v0.2-beta
+ */
+public class SystemCommandBuilder {
+
+	private int						numberOfArguments;
+	private Consumer<List<String>>	action;
+	private List<String>			defaults;
+	private String					description;
+	private int						relevance;
+
+	/**
+	 * @param numberOfArguments the numberOfArguments to set
+	 * @return this {@code SystemCommandBuilder}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommandBuilder setNumberOfArguments(int numberOfArguments) {
+		this.numberOfArguments = numberOfArguments;
+		return this;
+	}
+
+	/**
+	 * @param action the action to set
+	 * @return this {@code SystemCommandBuilder}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommandBuilder setAction(Consumer<List<String>> action) {
+		this.action = action;
+		return this;
+	}
+
+	/**
+	 * @param description the description to set
+	 * @return this {@code SystemCommandBuilder}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommandBuilder setDescription(String description) {
+		this.description = description;
+		return this;
+	}
+
+	/**
+	 * @param relevance the relevance to set
+	 * @return this {@code SystemCommandBuilder}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommandBuilder setRelevance(int relevance) {
+		this.relevance = relevance;
+		return this;
+	}
+
+	/**
+	 * @param defaults the defaults to set
+	 * @return this {@code SystemCommandBuilder}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommandBuilder setDefaults(String... defaults) {
+		this.defaults = List.of(defaults);
+		return this;
+	}
+
+	/**
+	 * Resets all values stored.
+	 *
+	 * @return this {@code SystemCommandBuilder}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommandBuilder reset() {
+		numberOfArguments	= 0;
+		action				= null;
+		defaults			= new ArrayList<>();
+		description			= "";
+		relevance			= 0;
+		return this;
+	}
+
+	/**
+	 * Builds a {@code SystemCommand} based upon the previously entered data.
+	 *
+	 * @return the built {@code SystemCommand}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommand build() { return build(true); }
+
+	/**
+	 * Builds a {@code SystemCommand} based upon the previously entered data.<br>
+	 * {@code SystemCommand#numberOfArguments} will be set to 0, regardless of the
+	 * previous value.<br>
+	 * At the end, this {@code SystemCommandBuilder} will be reset.
+	 *
+	 * @return the built {@code SystemCommand}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommand buildNoArg() {
+		numberOfArguments = 0;
+		return build(true);
+	}
+
+	/**
+	 * Builds a {@code SystemCommand} based upon the previously entered data.<br>
+	 * {@code SystemCommand#numberOfArguments} will be set to use the rest of the
+	 * string as argument, regardless of the previous value.<br>
+	 * At the end, this {@code SystemCommandBuilder} will be reset.
+	 *
+	 * @return the built {@code SystemCommand}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommand buildRemainingArg() {
+		numberOfArguments = -1;
+		return build(true);
+	}
+
+	/**
+	 * Builds a {@code SystemCommand} based upon the previously entered data.<br>
+	 * At the end, this {@code SystemCommandBuilder} <b>can</b> be reset but must
+	 * not be.
+	 *
+	 * @param reset whether this {@code SystemCommandBuilder} should be reset
+	 *              afterwards.<br>
+	 *              This can be useful if another command wants to execute something
+	 *              similar
+	 * @return the built {@code SystemCommand}
+	 * @since Envoy Client v0.2-beta
+	 */
+	public SystemCommand build(boolean reset) {
+		final var sc = new SystemCommand(action, numberOfArguments, defaults, description);
+		sc.setRelevance(relevance);
+		if (reset) reset();
+		return sc;
+	}
+}

client/src/main/java/envoy/client/data/commands/SystemCommandsMap.java

@@ -0,0 +1,263 @@
+package envoy.client.data.commands;
+
+import java.util.*;
+import java.util.function.Function;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+import envoy.util.EnvoyLog;
+
+/**
+ * This class stores all {@link SystemCommand}s used.
+ * <p>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>SystemCommandsMap.java</strong><br>
+ * Created: <strong>17.07.2020</strong><br>
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Client v0.2-beta
+ */
+public final class SystemCommandsMap {
+
+	private final Map<String, SystemCommand> systemCommands = new HashMap<>();
+
+	private final Pattern commandPattern = Pattern.compile("^[a-zA-Z0-9_:!\\(\\)\\?\\.\\,\\;\\-]+$");
+
+	private static final Logger logger = EnvoyLog.getLogger(SystemCommandsMap.class);
+
+	/**
+	 * Adds a new command to the map if the command name is valid.
+	 *
+	 * @param command       the input string to execute the
+	 *                      given action
+	 * @param systemCommand the command to add - can be built using
+	 *                      {@link SystemCommandBuilder}
+	 * @see SystemCommandsMap#isValidKey(String)
+	 * @since Envoy Client v0.2-beta
+	 */
+	public void add(String command, SystemCommand systemCommand) { if (isValidKey(command)) systemCommands.put(command, systemCommand); }
+
+	/**
+	 * This method checks if the input String is a key in the map and returns the
+	 * wrapped System command if present.
+	 * It will return an empty optional if the value after the slash is not a key in
+	 * the map, which is a valid case (i.e. input="3/4" and "4" is not a key in the
+	 * map).
+	 * <p>
+	 * Usage example:<br>
+	 * {@code SystemCommandsMap systemCommands = new SystemCommandsMap();}<br>
+	 * {@code Button button = new  Button();}
+	 * {@code systemCommands.add("example", text -> button.setText(text.get(0), 1);}<br>
+	 * {@code ....}<br>
+	 * user input: {@code "/example xyz ..."}<br>
+	 * {@code systemCommands.get("example xyz ...")} or
+	 * {@code systemCommands.get("/example xyz ...")}
+	 * result: {@code Optional<SystemCommand>}
+	 *
+	 * @param input the input string given by the user
+	 * @return the wrapped system command, if present
+	 * @since Envoy Client v0.2-beta
+	 */
+	public Optional<SystemCommand> get(String input) { return Optional.ofNullable(systemCommands.get(getCommand(input))); }
+
+	/**
+	 * This method ensures that the "/" of a {@link SystemCommand} is stripped.<br>
+	 * It returns the command as (most likely) entered as key in the map for the
+	 * first word of the text.<br>
+	 * It should only be called on strings that contain a "/" at position 0/-1.
+	 *
+	 * @param raw the input
+	 * @return the command as entered in the map
+	 * @since Envoy Client v0.2-beta
+	 * @apiNote this method will (most likely) not return anything useful if
+	 *          whatever is entered after the slash is not a system command. Only
+	 *          exception: for recommendation purposes.
+	 */
+	public String getCommand(String raw) {
+		final var	trimmed	= raw.stripLeading();
+		final var	index	= trimmed.indexOf(' ');
+		return trimmed.substring(trimmed.charAt(0) == '/' ? 1 : 0, index < 1 ? trimmed.length() : index);
+	}
+
+	/**
+	 * Examines whether a key can be put in the map and logs it with
+	 * {@code Level.WARNING} if that key violates API constrictions.<br>
+	 * (allowed chars are <b>a-zA-Z0-9_:!()?.,;-</b>)
+	 * <p>
+	 * The approach to not throw an exception was taken so that an ugly try-catch
+	 * block for every addition to the system commands map could be avoided, an
+	 * error that should only occur during implementation and not in production.
+	 *
+	 * @param command the key to examine
+	 * @return whether this key can be used in the map
+	 * @since Envoy Client v0.2-beta
+	 */
+	public boolean isValidKey(String command) {
+		final boolean valid = commandPattern.matcher(command).matches();
+		if (!valid) logger.log(Level.WARNING,
+				"The command \"" + command
+						+ "\" is not valid. As it will cause problems in execution, it will not be entered into the map. Only the characters "
+						+ commandPattern + "are allowed");
+		return valid;
+	}
+
+	/**
+	 * Takes a 'raw' string (the whole input) and checks if "/" is the first visible
+	 * character and then checks if a command is present after that "/". If that is
+	 * the case, it will be executed.
+	 * <p>
+	 *
+	 * @param raw the raw input string
+	 * @return whether a command could be found
+	 * @since Envoy Client v0.2-beta
+	 */
+	public boolean executeIfAnyPresent(String raw) {
+		// possibly a command was detected and could be executed
+		final var	raw2			= raw.stripLeading();
+		final var	commandFound	= raw2.startsWith("/") ? executeIfPresent(raw2) : false;
+		// the command was executed successfully - no further checking needed
+		if (commandFound) logger.log(Level.FINE, "executed system command " + getCommand(raw2));
+		return commandFound;
+	}
+
+	/**
+	 * This method checks if the input String is a key in the map and executes the
+	 * wrapped System command if present.
+	 * Its intended usage is after a "/" has been detected in the input String.
+	 * It will do nothing if the value after the slash is not a key in
+	 * the map, which is a valid case (i.e. input="3/4" and "4" is not a key in the
+	 * map).
+	 * <p>
+	 * Usage example:<br>
+	 * {@code SystemCommandsMap systemCommands = new SystemCommandsMap();}<br>
+	 * {@code Button button = new Button();}<br>
+	 * {@code systemCommands.add("example", (words)-> button.setText(words.get(0), 1);}<br>
+	 * {@code ....}<br>
+	 * user input: {@code "/example xyz ..."}<br>
+	 * {@code systemCommands.executeIfPresent("example xyz ...")}
+	 * result: {@code button.getText()=="xyz"}
+	 *
+	 * @param input the input string given by the user
+	 * @return whether a command could be found
+	 * @since Envoy Client v0.2-beta
+	 */
+	public boolean executeIfPresent(String input) {
+		final var	command	= getCommand(input);
+		final var	value	= get(command);
+		value.ifPresent(systemCommand -> {
+			// Splitting the String so that the leading command including the first " " is
+			// removed and only as many following words as allowed by the system command
+			// persist
+			final var arguments = extractArguments(input, systemCommand);
+			// Executing the function
+			try {
+				systemCommand.getAction().accept(arguments);
+				systemCommand.onCall();
+			} catch (final Exception e) {
+				logger.log(Level.WARNING, "The system command " + command + " threw an exception: ", e);
+			}
+		});
+		return value.isPresent();
+	}
+
+	/**
+	 * Supplies missing values with default values.
+	 *
+	 * @param input         the input String
+	 * @param systemCommand the command that is expected
+	 * @return the list of arguments that can be used to parse the systemCommand
+	 * @since Envoy Client v0.2-beta
+	 */
+	private List<String> extractArguments(String input, SystemCommand systemCommand) {
+		// no more arguments follow after the command (e.g. text = "/DABR")
+		final var indexOfSpace = input.indexOf(" ");
+		if (indexOfSpace < 0) return supplementDefaults(new String[] {}, systemCommand);
+		// the arguments behind a system command
+		final var	remainingString		= input.substring(indexOfSpace + 1);
+		final var	numberOfArguments	= systemCommand.getNumberOfArguments();
+		// splitting those arguments and supplying default values
+		final var	textArguments		= remainingString.split(" ", -1);
+		final var	originalArguments	= numberOfArguments >= 0 ? Arrays.copyOfRange(textArguments, 0, numberOfArguments) : textArguments;
+		final var	arguments			= supplementDefaults(originalArguments, systemCommand);
+		return arguments;
+	}
+
+	/**
+	 * Retrieves the recommendations based on the current input entered.<br>
+	 * The first word is used for the recommendations and
+	 * it does not matter if the "/" is at its beginning or not.<br>
+	 * If none are present, nothing will be done.<br>
+	 * Otherwise the given function will be executed on the recommendations.<br>
+	 *
+	 * @param input  the input string
+	 * @param action the action that should be taken for the recommendations, if any
+	 *               are present
+	 * @since Envoy Client v0.2-beta
+	 */
+	public void requestRecommendations(String input, Function<Set<String>, Void> action) {
+		final var partialCommand = getCommand(input);
+		// Get the expected commands
+		final var recommendations = recommendCommands(partialCommand);
+		if (recommendations.isEmpty()) return;
+		// Execute the given action
+		else action.apply(recommendations);
+	}
+
+	/**
+	 * Recommends commands based upon the currently entered input.<br>
+	 * In the current implementation, all we check is whether a key contains this
+	 * input. This might be updated later on.
+	 *
+	 * @param partialCommand the partially entered command
+	 * @return a set of all commands that match this input
+	 * @since Envoy Client v0.2-beta
+	 */
+	private Set<String> recommendCommands(String partialCommand) {
+		// current implementation only looks if input is contained within a command,
+		// might be updated
+		return systemCommands.keySet()
+			.stream()
+			.filter(command -> command.contains(partialCommand))
+			.sorted((command1, command2) -> Integer.compare(systemCommands.get(command1).getRelevance(), systemCommands.get(command2).getRelevance()))
+			.collect(Collectors.toSet());
+	}
+
+	/**
+	 *
+	 * Supplies the default values for arguments if none are present in the text for
+	 * any argument. <br>
+	 * Will only work for {@code SystemCommand}s whose argument counter is bigger
+	 * than 1.
+	 *
+	 * @param textArguments the arguments that were parsed from the text
+	 * @param toEvaluate    the system command whose default values should be used
+	 * @return the final argument list
+	 * @since Envoy Client v0.2-beta
+	 * @apiNote this method will insert an empty String if the size of the list
+	 *          given to the {@code SystemCommand} is smaller than its argument
+	 *          counter and no more text arguments could be found.
+	 */
+	private List<String> supplementDefaults(String[] textArguments, SystemCommand toEvaluate) {
+		final var			defaults			= toEvaluate.getDefaults();
+		final var			numberOfArguments	= toEvaluate.getNumberOfArguments();
+		final List<String>	result				= new ArrayList<>();
+
+		if (toEvaluate.getNumberOfArguments() > 0) for (int index = 0; index < numberOfArguments; index++) {
+			String textArg = null;
+			if (index < textArguments.length) textArg = textArguments[index];
+			// Set the argument at position index to the current argument of the text, if it
+			// is present. Otherwise the default for that argument will be taken if present.
+			// In the worst case, an empty String will be used.
+			result.add(!(textArg == null) && !textArg.isBlank() ? textArg : index < defaults.size() ? defaults.get(index) : "");
+		}
+		return result;
+	}
+
+	/**
+	 * @return all {@link SystemCommand}s used with the underlying command as key
+	 * @since Envoy Client v0.2-beta
+	 */
+	public Map<String, SystemCommand> getSystemCommands() { return systemCommands; }
+}

client/src/main/java/envoy/client/data/commands/package-info.java

@@ -0,0 +1,12 @@
+/**
+ * This package contains all classes that can be used as system commands.<br>
+ * Every system command can be called using a specific syntax:"/&lt;command&gt;"
+ * <p>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>package-info.java</strong><br>
+ * Created: <strong>16.07.2020</strong><br>
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Client v0.2-beta
+ */
+package envoy.client.data.commands;

client/src/main/java/envoy/client/net/Client.java

@@ -155,6 +155,9 @@ public class Client implements Closeable {
 		// Process group size changes
 		receiver.registerProcessor(GroupResize.class, evt -> { localDB.updateGroup(evt); eventBus.dispatch(evt); });
 
+		// Process IsTyping events
+		receiver.registerProcessor(IsTyping.class, eventBus::dispatch);
+
 		// Send event
 		eventBus.register(SendEvent.class, evt -> {
 			try {

client/src/main/java/envoy/client/net/Receiver.java

@@ -1,8 +1,6 @@
 package envoy.client.net;
 
-import java.io.ByteArrayInputStream;
-import java.io.InputStream;
-import java.io.ObjectInputStream;
+import java.io.*;
 import java.net.SocketException;
 import java.util.HashMap;
 import java.util.Map;
@@ -82,8 +80,9 @@ public class Receiver extends Thread {
 						logger.log(Level.WARNING, String.format("The received object has the %s for which no processor is defined.", obj.getClass()));
 					else processor.accept(obj);
 				}
-			} catch (final SocketException e) {
+			} catch (final SocketException | EOFException e) {
 				// Connection probably closed by client.
+				logger.log(Level.FINER, "Exiting receiver...");
 				return;
 			} catch (final Exception e) {
 				logger.log(Level.SEVERE, "Error on receiver thread", e);

client/src/main/java/envoy/client/ui/IconUtil.java

@@ -1,9 +1,13 @@
 package envoy.client.ui;
 
+import java.awt.image.BufferedImage;
+import java.io.IOException;
 import java.util.EnumMap;
 import java.util.EnumSet;
 import java.util.logging.Level;
 
+import javax.imageio.ImageIO;
+
 import javafx.scene.image.Image;
 
 import envoy.client.data.Settings;
@@ -145,6 +149,23 @@ public class IconUtil {
 		return icons;
 	}
 
+	/**
+	 * Loads a buffered image from the resource folder which is compatible with AWT.
+	 *
+	 * @param path the path to the icon inside the resource folder
+	 * @return the loaded image
+	 * @since Envoy Client v0.2-beta
+	 */
+	public static BufferedImage loadAWTCompatible(String path) {
+		BufferedImage image = null;
+		try {
+			image = ImageIO.read(IconUtil.class.getResource(path));
+		} catch (IOException e) {
+			EnvoyLog.getLogger(IconUtil.class).log(Level.WARNING, String.format("Could not load image at path %s: ", path), e);
+		}
+		return image;
+	}
+
 	/**
 	 * This method should be called if the display of an image depends upon the
 	 * currently active theme.<br>
@@ -154,7 +175,7 @@ public class IconUtil {
 	 * @return the theme specific folder
 	 * @since Envoy Client v0.1-beta
 	 */
-	public static String themeSpecificSubFolder() {
+	private static String themeSpecificSubFolder() {
 		return Settings.getInstance().isUsingDefaultTheme() ? Settings.getInstance().getCurrentTheme() + "/" : "";
 	}
 }

client/src/main/java/envoy/client/ui/StatusTrayIcon.java

@@ -2,15 +2,13 @@ package envoy.client.ui;
 
 import java.awt.*;
 import java.awt.TrayIcon.MessageType;
-import java.awt.event.WindowAdapter;
-import java.awt.event.WindowEvent;
-import java.util.logging.Level;
+
+import javafx.application.Platform;
+import javafx.stage.Stage;
 
 import envoy.client.event.MessageCreationEvent;
 import envoy.data.Message;
 import envoy.event.EventBus;
-import envoy.exception.EnvoyException;
-import envoy.util.EnvoyLog;
 
 /**
  * Project: <strong>envoy-client</strong><br>
@@ -35,66 +33,65 @@ public class StatusTrayIcon {
 	 */
 	private boolean displayMessages = false;
 
+	/**
+	 * @return {@code true} if the status tray icon is supported on this platform
+	 * @since Envoy Client v0.2-beta
+	 */
+	public static boolean isSupported() { return SystemTray.isSupported(); }
+
 	/**
 	 * Creates a {@link StatusTrayIcon} with the Envoy logo, a tool tip and a pop-up
 	 * menu.
 	 *
-	 * @param focusTarget the {@link Window} which focus determines if message
-	 *                    notifications are displayed
-	 * @throws EnvoyException if the currently used OS does not support the System
-	 *                        Tray API
-	 * @since Envoy Client v0.2-alpha
+	 * @param stage the stage whose focus determines if message
+	 *              notifications are displayed
+	 * @since Envoy Client v0.2-beta
 	 */
-	public StatusTrayIcon(Window focusTarget) throws EnvoyException {
-		if (!SystemTray.isSupported()) throw new EnvoyException("The Envoy tray icon is not supported.");
-
-		final ClassLoader	loader	= Thread.currentThread().getContextClassLoader();
-		final Image			img		= Toolkit.getDefaultToolkit().createImage(loader.getResource("envoy_logo.png"));
-		trayIcon = new TrayIcon(img, "Envoy Client");
+	public StatusTrayIcon(Stage stage) {
+		trayIcon = new TrayIcon(IconUtil.loadAWTCompatible("/icons/envoy_logo.png"), "Envoy");
 		trayIcon.setImageAutoSize(true);
 		trayIcon.setToolTip("You are notified if you have unread messages.");
 
 		final PopupMenu popup = new PopupMenu();
 
 		final MenuItem exitMenuItem = new MenuItem("Exit");
-		exitMenuItem.addActionListener(evt -> System.exit(0));
+		exitMenuItem.addActionListener(evt -> { Platform.exit(); System.exit(0); });
 		popup.add(exitMenuItem);
 
 		trayIcon.setPopupMenu(popup);
 
-		// Only display messages if the chat window is not focused
-		focusTarget.addWindowFocusListener(new WindowAdapter() {
-
-			@Override
-			public void windowGainedFocus(WindowEvent e) { displayMessages = false; }
-
-			@Override
-			public void windowLostFocus(WindowEvent e) { displayMessages = true; }
-		});
+		// Only display messages if the stage is not focused
+		stage.focusedProperty().addListener((ov, onHidden, onShown) -> displayMessages = !ov.getValue());
 
 		// Show the window if the user clicks on the icon
-		trayIcon.addActionListener(evt -> { focusTarget.setVisible(true); focusTarget.requestFocus(); });
+		trayIcon.addActionListener(evt -> Platform.runLater(() -> { stage.setIconified(false); stage.toFront(); stage.requestFocus(); }));
 
 		// Start processing message events
-		// TODO: Handle other message types
-		EventBus.getInstance()
-			.register(MessageCreationEvent.class,
-					evt -> { if (displayMessages) trayIcon.displayMessage("New message received", evt.get().getText(), MessageType.INFO); });
+		EventBus.getInstance().register(MessageCreationEvent.class, evt -> {
+			if (displayMessages) trayIcon
+				.displayMessage(
+						evt.get().hasAttachment() ? "New " + evt.get().getAttachment().getType().toString().toLowerCase() + " message received"
+								: "New message received",
+						evt.get().getText(),
+						MessageType.INFO);
+		});
 	}
 
 	/**
-	 * Makes this {@link StatusTrayIcon} appear in the system tray.
+	 * Makes the icon appear in the system tray.
 	 *
-	 * @throws EnvoyException if the status icon could not be attaches to the system
-	 *                        tray for system-internal reasons
 	 * @since Envoy Client v0.2-alpha
 	 */
-	public void show() throws EnvoyException {
+	public void show() {
 		try {
 			SystemTray.getSystemTray().add(trayIcon);
-		} catch (final AWTException e) {
-			EnvoyLog.getLogger(StatusTrayIcon.class).log(Level.INFO, "Could not display StatusTrayIcon: ", e);
-			throw new EnvoyException("Could not attach Envoy tray icon to system tray.", e);
-		}
+		} catch (AWTException e) {}
 	}
+
+	/**
+	 * Removes the icon from the system tray.
+	 * 
+	 * @since Envoy Client v0.2-beta
+	 */
+	public void hide() { SystemTray.getSystemTray().remove(trayIcon); }
 }

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

@@ -8,6 +8,8 @@ import java.io.ByteArrayInputStream;
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Files;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
 import java.util.Random;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -33,7 +35,10 @@ import javafx.util.Duration;
 
 import envoy.client.data.*;
 import envoy.client.data.audio.AudioRecorder;
+import envoy.client.data.commands.SystemCommandBuilder;
+import envoy.client.data.commands.SystemCommandsMap;
 import envoy.client.event.MessageCreationEvent;
+import envoy.client.event.SendEvent;
 import envoy.client.net.Client;
 import envoy.client.net.WriteProxy;
 import envoy.client.ui.*;
@@ -126,6 +131,8 @@ public final class ChatScene implements Restorable {
 	private Attachment		pendingAttachment;
 	private boolean			postingPermanentlyDisabled;
 
+	private final SystemCommandsMap messageTextAreaCommands = new SystemCommandsMap();
+
 	private static final Settings	settings	= Settings.getInstance();
 	private static final EventBus	eventBus	= EventBus.getInstance();
 	private static final Logger		logger		= EnvoyLog.getLogger(ChatScene.class);
@@ -221,7 +228,7 @@ public final class ChatScene implements Restorable {
 			switch (e.getOperationType()) {
 				case ADD:
 					if (contact instanceof User) localDB.getUsers().put(contact.getName(), (User) contact);
-					Chat chat = contact instanceof User ? new Chat(contact) : new GroupChat(client.getSender(), contact);
+					final Chat chat = contact instanceof User ? new Chat(contact) : new GroupChat(client.getSender(), contact);
 					Platform.runLater(() -> chatList.getItems().add(chat));
 					break;
 				case REMOVE:
@@ -231,6 +238,22 @@ public final class ChatScene implements Restorable {
 		});
 	}
 
+	/**
+	 * Initializes all {@code SystemCommands} used in {@code ChatScene}.
+	 *
+	 * @since Envoy Client v0.2-beta
+	 */
+	private void initializeSystemCommandsMap() {
+		final var builder = new SystemCommandBuilder();
+		// Do A Barrel roll initialization
+		final var random = new Random();
+		builder.setAction(text -> doABarrelRoll(Integer.parseInt(text.get(0)), Double.parseDouble(text.get(1))))
+			.setDefaults(Integer.toString(random.nextInt(3) + 1), Double.toString(random.nextDouble() * 3 + 1))
+			.setDescription("See for yourself :)")
+			.setNumberOfArguments(2);
+		messageTextAreaCommands.add("DABR", builder.build());
+	}
+
 	/**
 	 * Initializes all necessary data via dependency injection-
 	 *
@@ -251,9 +274,12 @@ public final class ChatScene implements Restorable {
 		chatList.setItems(chats);
 		contactLabel.setText(localDB.getUser().getName());
 		MessageControl.setLocalDB(localDB);
+    MessageControl.setSceneContext(sceneContext);
+
 		if (!client.isOnline()) updateInfoLabel("You are offline", "infoLabel-info");
 
 		recorder = new AudioRecorder();
+		initializeSystemCommandsMap();
 	}
 
 	@Override
@@ -362,7 +388,9 @@ public final class ChatScene implements Restorable {
 					});
 					recorder.start();
 				} else {
-					pendingAttachment	= new Attachment(recorder.finish(), AttachmentType.VOICE);
+					pendingAttachment	= new Attachment(recorder.finish(), "Voice_recording_"
+							+ DateTimeFormatter.ofPattern("yyyy_MM_dd-HH_mm_ss").format(LocalDateTime.now()) + "." + AudioRecorder.FILE_FORMAT,
+							AttachmentType.VOICE);
 					recording			= false;
 					Platform.runLater(() -> {
 						voiceButton.setGraphic(new ImageView(IconUtil.loadIconThemeSensitive("microphone", DEFAULT_ICON_SIZE)));
@@ -413,7 +441,7 @@ public final class ChatScene implements Restorable {
 			// Create the pending attachment
 			try {
 				final var fileBytes = Files.readAllBytes(file.toPath());
-				pendingAttachment = new Attachment(fileBytes, type);
+				pendingAttachment = new Attachment(fileBytes, file.getName(), type);
 				checkPostConditions(false);
 				// Setting the preview image as image of the attachmentView
 				if (type == AttachmentType.PICTURE)
@@ -426,20 +454,34 @@ public final class ChatScene implements Restorable {
 	}
 
 	/**
-	 * Rotates every element in our application by 360° in at most 2.75s.
+	 * Rotates every element in our application by (at most 4 *) 360° in at most
+	 * 2.75s.
 	 *
 	 * @since Envoy Client v0.1-beta
 	 */
 	@FXML
 	private void doABarrelRoll() {
+		final var random = new Random();
+		doABarrelRoll(random.nextInt(3) + 1, random.nextDouble() * 3 + 1);
+	}
+
+	/**
+	 * Rotates every element in our application by {@code rotations}*360° in
+	 * {@code an}.
+	 *
+	 * @param rotations     the amount of times the scene is rotated by 360°
+	 * @param animationTime the time in seconds that this animation lasts
+	 * @since Envoy Client v0.1-beta
+	 */
+	private void doABarrelRoll(int rotations, double animationTime) {
 		// contains all Node objects in ChatScene in alphabetical order
-		final var	rotatableNodes	= new Node[] { attachmentButton, attachmentView, contactLabel, infoLabel, messageList, messageTextArea,
-				postButton, remainingChars, rotateButton, scene, settingsButton, chatList, voiceButton };
-		final var	random			= new Random();
+		final var rotatableNodes = new Node[] { attachmentButton, attachmentView, contactLabel, infoLabel, messageList, messageTextArea, postButton,
+				remainingChars, rotateButton, scene, settingsButton, chatList, voiceButton };
 		for (final var node : rotatableNodes) {
-			// Defines at most four whole rotation in at most 4s
-			final var rotateTransition = new RotateTransition(Duration.seconds(random.nextDouble() * 3 + 1), node);
-			rotateTransition.setByAngle((random.nextInt(3) + 1) * 360);
+			// Sets the animation duration to {animationTime}
+			final var rotateTransition = new RotateTransition(Duration.seconds(animationTime), node);
+			// rotates every element {rotations} times
+			rotateTransition.setByAngle(rotations * 360);
 			rotateTransition.play();
 			// This is needed as for some strange reason objects could stop before being
 			// rotated back to 0°
@@ -459,10 +501,28 @@ public final class ChatScene implements Restorable {
 	private void checkKeyCombination(KeyEvent e) {
 		// Checks whether the text is too long
 		messageTextUpdated();
+		// Sending an IsTyping event if none has been sent for
+		// IsTyping#millisecondsActive
+		if (client.isOnline() && currentChat.getLastWritingEvent() + IsTyping.millisecondsActive <= System.currentTimeMillis()) {
+			eventBus.dispatch(new SendEvent(new IsTyping(getChatID(), currentChat.getRecipient().getID())));
+			currentChat.lastWritingEventWasNow();
+		}
 		// Automatic sending of messages via (ctrl +) enter
 		checkPostConditions(e);
 	}
 
+	/**
+	 * Returns the id that should be used to send things to the server:
+	 * the id of 'our' {@link User} if the recipient of that object is another User,
+	 * else the id of the {@link Group} 'our' user is sending to.
+	 *
+	 * @return an id that can be sent to the server
+	 * @since Envoy Client v0.2-beta
+	 */
+	private long getChatID() {
+		return currentChat.getRecipient() instanceof User ? client.getSender().getID() : currentChat.getRecipient().getID();
+	}
+
 	/**
 	 * @param e the keys that have been pressed
 	 * @since Envoy Client v0.1-beta
@@ -531,7 +591,7 @@ public final class ChatScene implements Restorable {
 			return;
 		}
 		final var text = messageTextArea.getText().strip();
-		try {
+		if (!messageTextAreaCommands.executeIfAnyPresent(text)) try {
 			// Creating the message and its metadata
 			final var builder = new MessageBuilder(localDB.getUser().getID(), currentChat.getRecipient().getID(), localDB.getIDGenerator())
 				.setText(text);
@@ -619,10 +679,15 @@ public final class ChatScene implements Restorable {
 	private void copyAndPostMessage() {
 		final var messageText = messageTextArea.getText();
 		Toolkit.getDefaultToolkit().getSystemClipboard().setContents(new StringSelection(messageText), null);
+		final var	image				= attachmentView.getImage();
+		final var	messageAttachment	= pendingAttachment;
 		postMessage();
 		messageTextArea.setText(messageText);
 		updateRemainingCharsLabel();
 		postButton.setDisable(messageText.isBlank());
+		attachmentView.setImage(image);
+		if (attachmentView.getImage() != null) attachmentView.setVisible(true);
+		pendingAttachment = messageAttachment;
 	}
 
 	@FXML

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

@@ -1,5 +1,6 @@
 package envoy.client.ui.controller;
 
+import java.util.function.Consumer;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -53,8 +54,20 @@ public class ContactSearchScene {
 
 	private LocalDB localDB;
 
-	private static EventBus		eventBus	= EventBus.getInstance();
-	private static final Logger	logger		= EnvoyLog.getLogger(ChatScene.class);
+	private Alert alert = new Alert(AlertType.CONFIRMATION);
+
+	private User currentlySelectedUser;
+
+	private final Consumer<ContactOperation> handler = e -> {
+		final var contact = e.get();
+		if (e.getOperationType() == ElementOperation.ADD) Platform.runLater(() -> {
+			userList.getItems().remove(contact);
+			if (currentlySelectedUser != null && currentlySelectedUser.equals(contact) && alert.isShowing()) alert.close();
+		});
+	};
+
+	private static final EventBus	eventBus	= EventBus.getInstance();
+	private static final Logger		logger		= EnvoyLog.getLogger(ChatScene.class);
 
 	/**
 	 * @param sceneContext enables the user to return to the chat scene
@@ -72,6 +85,7 @@ public class ContactSearchScene {
 		searchBar.setClearButtonListener(e -> { searchBar.getTextField().clear(); userList.getItems().clear(); });
 		eventBus.register(UserSearchResult.class,
 				response -> Platform.runLater(() -> { userList.getItems().clear(); userList.getItems().addAll(response.get()); }));
+		eventBus.register(ContactOperation.class, handler);
 	}
 
 	/**
@@ -108,20 +122,21 @@ public class ContactSearchScene {
 	private void userListClicked() {
 		final var user = userList.getSelectionModel().getSelectedItem();
 		if (user != null) {
-			final var alert = new Alert(AlertType.CONFIRMATION);
-			alert.setTitle("Add Contact to Contact List");
-			alert.setHeaderText("Add the user " + user.getName() + " to your contact list?");
+			currentlySelectedUser	= user;
+			alert					= new Alert(AlertType.CONFIRMATION);
+			alert.setTitle("Add User to Contact List");
+			alert.setHeaderText("Add the user " + currentlySelectedUser.getName() + " to your contact list?");
 			// Normally, this would be total BS (we are already on the FX Thread), however
 			// it could be proven that the creation of this dialog wrapped in
 			// Platform.runLater is less error-prone than without it
 			Platform.runLater(() -> alert.showAndWait().filter(btn -> btn == ButtonType.OK).ifPresent(btn -> {
-				final var event = new ContactOperation(user, ElementOperation.ADD);
+				final var event = new ContactOperation(currentlySelectedUser, ElementOperation.ADD);
 				// Sends the event to the server
 				eventBus.dispatch(new SendEvent(event));
 				// Removes the chosen user and updates the UI
-				userList.getItems().remove(user);
+				userList.getItems().remove(currentlySelectedUser);
 				eventBus.dispatch(event);
-				logger.log(Level.INFO, "Added user " + user);
+				logger.log(Level.INFO, "Added user " + currentlySelectedUser);
 			}));
 		}
 	}

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

@@ -17,9 +17,7 @@ import javafx.scene.image.ImageView;
 import envoy.client.data.*;
 import envoy.client.net.Client;
 import envoy.client.net.WriteProxy;
-import envoy.client.ui.IconUtil;
-import envoy.client.ui.SceneContext;
-import envoy.client.ui.Startup;
+import envoy.client.ui.*;
 import envoy.data.LoginCredentials;
 import envoy.data.User;
 import envoy.data.User.UserStatus;
@@ -77,6 +75,7 @@ public final class LoginScene {
 	private static final Logger			logger		= EnvoyLog.getLogger(LoginScene.class);
 	private static final EventBus		eventBus	= EventBus.getInstance();
 	private static final ClientConfig	config		= ClientConfig.getInstance();
+	private static final Settings		settings	= Settings.getInstance();
 
 	@FXML
 	private void initialize() {
@@ -239,5 +238,23 @@ public final class LoginScene {
 		sceneContext.load(SceneContext.SceneInfo.CHAT_SCENE);
 		sceneContext.<ChatScene>getController().initializeData(sceneContext, localDB, client, writeProxy);
 		sceneContext.getStage().centerOnScreen();
+
+		if (StatusTrayIcon.isSupported()) {
+
+			// Configure hide on close
+			sceneContext.getStage().setOnCloseRequest(e -> {
+				if (settings.isHideOnClose()) {
+					sceneContext.getStage().setIconified(true);
+					e.consume();
+				}
+			});
+
+			// Initialize status tray icon
+			final var trayIcon = new StatusTrayIcon(sceneContext.getStage());
+			settings.getItems().get("hideOnClose").setChangeHandler(c -> {
+				if ((Boolean) c) trayIcon.show();
+				else trayIcon.hide();
+			});
+		}
 	}
 }

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

@@ -4,6 +4,7 @@ import javafx.fxml.FXML;
 import javafx.scene.control.*;
 
 import envoy.client.ui.SceneContext;
+import envoy.client.ui.settings.DownloadSettingsPane;
 import envoy.client.ui.settings.GeneralSettingsPane;
 import envoy.client.ui.settings.SettingsPane;
 
@@ -29,7 +30,10 @@ public class SettingsScene {
 	 * @param sceneContext enables the user to return to the chat scene
 	 * @since Envoy Client v0.1-beta
 	 */
-	public void initializeData(SceneContext sceneContext) { this.sceneContext = sceneContext; }
+	public void initializeData(SceneContext sceneContext) {
+		this.sceneContext = sceneContext;
+		settingsList.getItems().add(new DownloadSettingsPane(sceneContext));
+	}
 
 	@FXML
 	private void initialize() {

client/src/main/java/envoy/client/ui/listcell/ChatControl.java

@@ -53,12 +53,12 @@ public class ChatControl extends HBox {
 		getChildren().add(new ContactControl(chat.getRecipient()));
 		// Unread messages
 		if (chat.getUnreadAmount() != 0) {
-			Region spacing = new Region();
+			final var spacing = new Region();
 			setHgrow(spacing, Priority.ALWAYS);
 			getChildren().add(spacing);
 			final var unreadMessagesLabel = new Label(Integer.toString(chat.getUnreadAmount()));
 			unreadMessagesLabel.setMinSize(15, 15);
-			var vBox2 = new VBox();
+			final var vBox2 = new VBox();
 			vBox2.setAlignment(Pos.CENTER_RIGHT);
 			unreadMessagesLabel.setAlignment(Pos.CENTER);
 			unreadMessagesLabel.getStyleClass().add("unreadMessagesAmount");

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

@@ -2,7 +2,7 @@ package envoy.client.ui.listcell;
 
 import java.awt.Toolkit;
 import java.awt.datatransfer.StringSelection;
-import java.io.ByteArrayInputStream;
+import java.io.*;
 import java.time.ZoneId;
 import java.time.format.DateTimeFormatter;
 import java.util.Map;
@@ -17,10 +17,14 @@ import javafx.scene.control.MenuItem;
 import javafx.scene.image.Image;
 import javafx.scene.image.ImageView;
 import javafx.scene.layout.*;
+import javafx.stage.FileChooser;
 
 import envoy.client.data.LocalDB;
+import envoy.client.data.Settings;
 import envoy.client.ui.AudioControl;
 import envoy.client.ui.IconUtil;
+import envoy.client.ui.SceneContext;
+
 import envoy.data.GroupMessage;
 import envoy.data.Message;
 import envoy.data.Message.MessageStatus;
@@ -44,9 +48,12 @@ public class MessageControl extends Label {
 
 	private static LocalDB localDB;
 
+	private static SceneContext sceneContext;
+
 	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);
+	private static final Settings					settings		= Settings.getInstance();
 	private static final Logger						logger			= EnvoyLog.getLogger(MessageControl.class);
 
 	/**
@@ -149,7 +156,26 @@ public class MessageControl extends Label {
 
 	private void loadMessageInfoScene(Message message) { logger.log(Level.FINEST, "message info scene was requested for " + message); }
 
-	private void saveAttachment(Message message) { logger.log(Level.FINEST, "attachment saving was requested for " + message); }
+	private void saveAttachment(Message message) {
+		File		file;
+		final var	fileName			= message.getAttachment().getName();
+		final var	downloadLocation	= settings.getDownloadLocation();
+		// Show save file dialog, if the user did not opt-out
+		if (!settings.isDownloadSavedWithoutAsking()) {
+			final var fileChooser = new FileChooser();
+			fileChooser.setInitialFileName(fileName);
+			fileChooser.setInitialDirectory(downloadLocation);
+			file = fileChooser.showSaveDialog(sceneContext.getStage());
+		} else file = new File(downloadLocation, fileName);
+
+		// A file was selected
+		if (file != null) try (FileOutputStream fos = new FileOutputStream(file)) {
+			fos.write(message.getAttachment().getData());
+			logger.log(Level.FINE, "Attachment of message was saved at " + file.getAbsolutePath());
+		} catch (final IOException e) {
+			logger.log(Level.WARNING, "Could not save attachment of " + message + ": ", e);
+		}
+	}
 
 	/**
 	 * @param localDB the localDB
@@ -163,4 +189,10 @@ public class MessageControl extends Label {
 	 * @since Envoy Client v0.1-beta
 	 */
 	public boolean isOwnMessage() { return ownMessage; }
+
+	/**
+	 * @param sceneContext the scene context storing the stage used in Envoy
+	 * @since Envoy Client v0.1-beta
+	 */
+	public static void setSceneContext(SceneContext sceneContext) { MessageControl.sceneContext = sceneContext; }
 }

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

@@ -0,0 +1,65 @@
+package envoy.client.ui.settings;
+
+import javafx.geometry.Insets;
+import javafx.scene.control.Button;
+import javafx.scene.control.CheckBox;
+import javafx.scene.control.Label;
+import javafx.scene.layout.HBox;
+import javafx.scene.layout.VBox;
+import javafx.stage.DirectoryChooser;
+
+import envoy.client.ui.SceneContext;
+
+/**
+ * Displays options for downloading {@link envoy.data.Attachment}s.
+ * <p>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>DownloadSettingsPane.java</strong><br>
+ * Created: <strong>27.07.2020</strong><br>
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Client v0.2-beta
+ */
+public class DownloadSettingsPane extends SettingsPane {
+
+	/**
+	 * Constructs a new {@code DownloadSettingsPane}.
+	 *
+	 * @param sceneContext the {@code SceneContext} used to block input to the
+	 *                     {@link javafx.stage.Stage} used in Envoy
+	 * @since Envoy Client v0.2-beta
+	 */
+	public DownloadSettingsPane(SceneContext sceneContext) {
+		super("Download");
+		final var vbox = new VBox(15);
+		vbox.setPadding(new Insets(15));
+		// checkbox to disable asking
+		final var checkBox = new CheckBox(settings.getItems().get("autoSaveDownloads").getUserFriendlyName());
+		checkBox.setSelected(settings.isDownloadSavedWithoutAsking());
+		checkBox.setOnAction(e -> settings.setDownloadSavedWithoutAsking(checkBox.isSelected()));
+		vbox.getChildren().add(checkBox);
+
+		// Displaying the default path to save to
+		vbox.getChildren().add(new Label(settings.getItems().get("downloadLocation").getDescription() + ":"));
+		final var	hbox		= new HBox(20);
+		final var	currentPath	= new Label(settings.getDownloadLocation().getAbsolutePath());
+		hbox.getChildren().add(currentPath);
+
+		// Setting the default path
+		final var button = new Button("Select");
+		button.setOnAction(e -> {
+			final var directoryChooser = new DirectoryChooser();
+			directoryChooser.setTitle("Select the directory where attachments should be saved to");
+			directoryChooser.setInitialDirectory(settings.getDownloadLocation());
+			final var selectedDirectory = directoryChooser.showDialog(sceneContext.getStage());
+
+			if (selectedDirectory != null) {
+				currentPath.setText(selectedDirectory.getAbsolutePath());
+				settings.setDownloadLocation(selectedDirectory);
+			}
+		});
+		hbox.getChildren().add(button);
+		vbox.getChildren().add(hbox);
+		getChildren().add(vbox);
+	}
+}

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

@@ -5,7 +5,6 @@ import java.util.List;
 import javafx.scene.control.ComboBox;
 import javafx.scene.layout.VBox;
 
-import envoy.client.data.Settings;
 import envoy.client.data.SettingsItem;
 import envoy.client.event.ThemeChangeEvent;
 import envoy.data.User.UserStatus;
@@ -21,8 +20,6 @@ import envoy.event.EventBus;
  */
 public class GeneralSettingsPane extends SettingsPane {
 
-	private static final Settings settings = Settings.getInstance();
-
 	/**
 	 * @since Envoy Client v0.1-beta
 	 */
@@ -31,7 +28,7 @@ public class GeneralSettingsPane extends SettingsPane {
 		final var vbox = new VBox();
 
 		// TODO: Support other value types
-		List.of("onCloseMode", "enterToSend")
+		List.of("hideOnClose", "enterToSend")
 			.stream()
 			.map(settings.getItems()::get)
 			.map(i -> new SettingsCheckbox((SettingsItem<Boolean>) i))

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

@@ -2,11 +2,13 @@ package envoy.client.ui.settings;
 
 import javafx.scene.layout.Pane;
 
+import envoy.client.data.Settings;
+
 /**
  * Project: <strong>envoy-client</strong><br>
  * File: <strong>SettingsPane.java</strong><br>
  * Created: <strong>18.04.2020</strong><br>
- * 
+ *
  * @author Kai S. K. Engelbart
  * @since Envoy Client v0.1-beta
  */
@@ -14,6 +16,8 @@ public abstract class SettingsPane extends Pane {
 
 	protected String title;
 
+	protected static final Settings settings = Settings.getInstance();
+
 	protected SettingsPane(String title) { this.title = title; }
 
 	/**