Update GUI and files for handling errors

TodoException, DeadlineException, and EventException classes were
removed. Handling of errors in several files were modified.

Parser.java was edited significantly to separate methods for parsing.

GUI was improved to display full text.

src/main/java/gbot/DialogBox.java

@@ -9,7 +9,7 @@
 import javafx.fxml.FXMLLoader;
 import javafx.geometry.Pos;
 import javafx.scene.Node;
-import javafx.scene.control.Label;
+import javafx.scene.text.Text;
 import javafx.scene.image.Image;
 import javafx.scene.image.ImageView;
 import javafx.scene.layout.HBox;
@@ -20,7 +20,7 @@
  */
 public class DialogBox extends HBox {
     @FXML
-    private Label dialog;
+    private Text dialog;
     @FXML
     private ImageView displayPicture;
 

src/main/java/gbot/GBot.java

@@ -33,9 +33,6 @@ private void run() {
                 inputScanner.close();
                 Ui.displayExitMessage();
                 return;
-            } else if (message.strip().equals("help")) {
-                Ui.displayHelpMessage();
-                continue;
             }
             try {
                 Ui.print(Parser.parse(message, tasks));

src/main/java/gbot/Parser.java

@@ -14,14 +14,18 @@
  * @author Gallen Ong
  */
 public class Parser {
+    private static final String INVALIDTASK = "Although you might not be wrong, I simply do not understand...\n" +
+                                              "Kindly enter a valid task number.";
     /**
      * Returns corresponding methods after parsing user inputs.
      *
      * @param message The user input.
      * @param tasks The TaskList object that stores tasks.
      */
     public static String parse(String message, TaskList tasks) throws GBotException {
-        assert !message.isBlank() : "Please enter a valid command.";
+        if (message.isBlank()) {
+            throw new GBotException("Please enter a command.");
+        }
         switch (message.strip()) {
         case "list":
             return tasks.listTasks();
@@ -44,27 +48,168 @@ public static String parse(String message, TaskList tasks) throws GBotException
      * @param tasks The TaskList object that stores tasks.
      * @throws GBotException If user command is invalid.
      */
-    private static String checkPrefix(String message, TaskList tasks) {
+    private static String checkPrefix(String message, TaskList tasks) throws RuntimeException {
         String prefix = message.split(" ")[0];
-        String remainingInput = message.substring(prefix.length() + 1);
+        String response;
         switch (prefix) {
+        case "help":
+            return Ui.getHelpMessage();
         case "mark":
-            return tasks.markTask(remainingInput);
+            response = parseMark(message, tasks);
+            break;
         case "unmark":
-            return tasks.unmarkTask(remainingInput);
+            response = parseUnmark(message, tasks);
+            break;
         case "todo":
-            return tasks.addTodo(remainingInput);
+            response = parseTodo(message, tasks);
+            break;
         case "deadline":
-            return tasks.addDeadline(remainingInput);
+            response = parseDeadline(message, tasks);
+            break;
         case "event":
-            return tasks.addEvent(remainingInput);
+            response = parseEvent(message, tasks);
+            break;
         case "delete":
-            return tasks.deleteTask(remainingInput);
+            response = parseDelete(message, tasks);
+            break;
         case "find":
-            return tasks.find(remainingInput);
-        default:
+            response = parseFind(message, tasks);
+            break;
+        default: // if invalid command provided
             throw new GBotException();
         }
+        assert !response.isBlank();
+        return response;
+    }
+
+    /**
+     * Returns response for Mark after parsing input.
+     *
+     * @param message The user input.
+     * @param tasks The TaskList object that stores tasks.
+     */
+    private static String parseMark(String message, TaskList tasks) {
+        String[] words = message.split(" ");
+        if (words.length != 2) {
+            return INVALIDTASK;
+        }
+        try {
+            return tasks.markTask(Integer.parseInt(words[1]));
+        } catch (NumberFormatException e) {
+            throw new GBotException(INVALIDTASK);
+        }
+    }
+
+    /**
+     * Returns response for Unmark after parsing input.
+     *
+     * @param message The user input.
+     * @param tasks The TaskList object that stores tasks.
+     */
+    private static String parseUnmark(String message, TaskList tasks) {
+        String[] words = message.split(" ");
+        if (words.length != 2) {
+            return INVALIDTASK;
+        }
+        try {
+            return tasks.unmarkTask(Integer.parseInt(words[1]));
+        } catch (NumberFormatException e) {
+            throw new GBotException(INVALIDTASK);
+        }
+    }
+
+    /**
+     * Returns response for adding a Todo task after parsing input.
+     *
+     * @param message The user input.
+     * @param tasks The TaskList object that stores tasks.
+     */
+    private static String parseTodo(String message, TaskList tasks) {
+        String desc = message.substring(4);
+        if (desc.isBlank()) {
+            return "I apologise. Kindly input a task description.";
+        }
+        return tasks.addTodo(desc);
+    }
+
+    /**
+     * Returns response for adding a Deadline task after parsing input.
+     *
+     * @param message The user input.
+     * @param tasks The TaskList object that stores tasks.
+     */
+    private static String parseDeadline(String message, TaskList tasks) {
+        String[] taskDesc = message.split(" /by ");
+        if (taskDesc.length != 2) {
+            return "I apologise for correcting you. Kindly follow the following:\n" +
+                   "deadline (task) /by (deadline in YYYY-MM-DD)\n" +
+                   "eg. deadline return book /by 2023-09-21";
+        }
+        return tasks.addDeadline(taskDesc[0].substring(8), taskDesc[1]);
+    }
+
+    /**
+     * Returns response for adding an Event task after parsing input.
+     *
+     * @param message The user input.
+     * @param tasks The TaskList object that stores tasks.
+     */
+    private static String parseEvent(String message, TaskList tasks) {
+        String[] inputSplitByFrom = message.split(" /from ");
+        String[] inputSplitByTo = message.split(" /to ");
+        if (inputSplitByFrom.length != 2 || inputSplitByTo.length != 2) {
+            return "I apologise for correcting you. Kindly follow the following:\n" +
+                    "event (task) /from (start in YYYY-MM-DD) /to (end in YYYY-MM-DD)\n" +
+                    "eg. event attend meeting /from 2023-09-21 /to 2023-09-22";
+        }
+
+        String[] inputAfterFrom = inputSplitByFrom[1].split(" /to ");
+        String desc;
+        String fromDate;
+        String toDate;
+
+        if (inputAfterFrom.length == 2) {
+            desc = inputSplitByFrom[0];
+            fromDate = inputAfterFrom[0];
+            toDate = inputAfterFrom[1];
+        } else {
+            desc = inputSplitByTo[0];
+            fromDate = inputSplitByTo[1].split(" /from ")[1];
+            toDate = inputSplitByTo[1].split(" /from ")[0];
+        }
+        return tasks.addEvent(desc, fromDate, toDate);
+    }
+
+    /**
+     * Returns response for deleting a task after parsing input.
+     *
+     * @param message The user input.
+     * @param tasks The TaskList object that stores tasks.
+     */
+    private static String parseDelete(String message, TaskList tasks) {
+        String[] words = message.split(" ");
+        if (words.length != 2) {
+            return INVALIDTASK;
+        }
+        try {
+            return tasks.deleteTask(Integer.parseInt(words[1]));
+        } catch (NumberFormatException e) {
+            throw new GBotException(INVALIDTASK);
+        }
+    }
+
+    /**
+     * Returns response for finding a task based on keyword after parsing input.
+     *
+     * @param message The user input.
+     * @param tasks The TaskList object that stores tasks.
+     */
+    private static String parseFind(String message, TaskList tasks) {
+        String[] words = message.split(" ");
+        if (words.length != 2) {
+            return "I wish I could read minds like you. Do kindly enter a keyword though.";
+        }
+        return tasks.find(message.substring(4));
     }
 
     /**