Notify user about unsuccessful system command execution

Additionally added error system command.
Fixes #75

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

@@ -1,11 +1,16 @@
 package envoy.client.data.commands;
 
 import java.util.*;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Consumer;
 import java.util.logging.*;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
+import javafx.application.Platform;
+import javafx.scene.control.Alert;
+import javafx.scene.control.Alert.AlertType;
+
 import envoy.util.EnvoyLog;
 
 /**
@@ -27,26 +32,9 @@ public final class SystemCommandMap {
 	private static final Logger logger = EnvoyLog.getLogger(SystemCommandMap.class);
 
 	/**
-	 * The default char to be used as activator.
+	 * Creates a new {@code SystemCommandMap} with the given char as activator.
-	 * <p>
+	 * If this Character is null, any text used as input will be treated as a system
-	 * Value: '/'.
+	 * command.
-	 *
-	 * @since Envoy Client v0.3-beta
-	 */
-	public static final char defaultActivator = '/';
-
-	/**
-	 * The Character to use if every String should be considered as a possible
-	 * {@link SystemCommand}.
-	 * <p>
-	 * Value: null.
-	 *
-	 * @since Envoy Client v0.3-beta
-	 */
-	public static final Character noActivator = null;
-
-	/**
-	 * Creates a new {@link SystemCommandMap} with the given activator.
 	 *
 	 * @param activator the char to use as activator for commands
 	 * @since Envoy Client v0.3-beta
@@ -54,11 +42,11 @@ public final class SystemCommandMap {
 	public SystemCommandMap(Character activator) { this.activator = activator; }
 
 	/**
-	 * Creates a new {@link SystemCommandMap} with default activator.
+	 * Creates a new {@code SystemCommandMap} with '/' as activator.
 	 *
 	 * @since Envoy Client v0.3-beta
 	 */
-	public SystemCommandMap() { activator = defaultActivator; }
+	public SystemCommandMap() { activator = '/'; }
 
 	/**
 	 * Adds a new command to the map if the command name is valid.
@@ -101,7 +89,7 @@ public final class SystemCommandMap {
 	 * input.
 	 * It returns the command as (most likely) entered as key in the map for the
 	 * first word of the text.<br>
-	 * Activators in the middle of the wod will be disregarded.
+	 * Activators in the middle of the word will be disregarded.
 	 *
 	 * @param raw the input
 	 * @return the command as entered in the map
@@ -149,7 +137,7 @@ public final class SystemCommandMap {
 	 * activator. If that is the case, it will be executed.
 	 *
 	 * @param raw the raw input string
-	 * @return whether a command could be found
+	 * @return whether a command could be found and successfully executed
 	 * @since Envoy Client v0.2-beta
 	 */
 	public boolean executeIfPresent(String raw) {
@@ -204,12 +192,13 @@ public final class SystemCommandMap {
 	 * result: {@code button.getText()=="xyz"}
 	 *
 	 * @param input the input string given by the user
-	 * @return whether a command could be found
+	 * @return whether a command could be found and successfully executed
 	 * @since Envoy Client v0.2-beta
 	 */
 	private boolean executeAvailableCommand(String input) {
 		final var	command			= getCommand(input);
 		final var	value			= get(command);
+		final var	commandExecuted	= new AtomicBoolean(value.isPresent());
 		value.ifPresent(systemCommand -> {
 
 			// Splitting the String so that the leading command including the first " " is
@@ -225,11 +214,23 @@ public final class SystemCommandMap {
 						String.format(
 								"System command %s could not be performed correctly because the user is a dumbass and could not write a parseable number.",
 								command));
+				Platform.runLater(() -> {
+					final var alert = new Alert(AlertType.ERROR);
+					alert.setContentText("Please enter a readable number as argument.");
+					alert.showAndWait();
+				});
+				commandExecuted.set(false);
 			} catch (final Exception e) {
 				logger.log(Level.WARNING, "System command " + command + " threw an exception: ", e);
+				Platform.runLater(() -> {
+					final var alert = new Alert(AlertType.ERROR);
+					alert.setContentText("Could not execute system command: Internal error. Please insult the responsible programmer.");
+					alert.showAndWait();
+				});
+				commandExecuted.set(false);
 			}
 		});
-		return value.isPresent();
+		return commandExecuted.get();
 	}
 
 	/**

client/src/main/java/envoy/client/ui/chatscene/ChatSceneCommands.java

@@ -40,6 +40,9 @@ public final class ChatSceneCommands {
 	public ChatSceneCommands(ListView<Message> messageList, ChatScene chatScene) {
 		this.messageList = messageList;
 
+		// Error message initialization
+		builder.setAction(text -> { throw new RuntimeException(); }).setDescription("Shows an error message.").buildNoArg("error");
+
 		// Do A Barrel roll initialization
 		final var random = new Random();
 		builder.setAction(text -> chatScene.doABarrelRoll(Integer.parseInt(text.get(0)), Double.parseDouble(text.get(1))))