code quality and exception changes

data/tasks.txt

@@ -1,2 +1,4 @@
 D|0|return book|Sunday
 E|1|project meeting|Mon 2pm|4pm
+T|1|submit report
+T|0|return book

src/main/java/opus/Main.java

@@ -10,6 +10,7 @@
 import javafx.scene.layout.Region;
 import javafx.stage.Stage;
 import javafx.scene.image.Image;
+import opus.commands.CommandResult;
 
 
 
@@ -97,14 +98,15 @@ public void start(Stage stage) {
 
     private void handleUserInput() {
         String userText = userInput.getText();
-        String opusText = opus.getResponse(userInput.getText());
+        CommandResult commandResult = opus.getResponse(userText);
+        String opusText = commandResult.getFeedbackToUser();
         dialogContainer.getChildren().addAll(
                 DialogBox.getUserDialog(userText, userImage),
                 DialogBox.getOpusDialog(opusText, opusImage)
         );
         userInput.clear();
 
-        if (opus.isExit()) {
+        if (commandResult.isExit()) {
             Platform.exit();
         }
     }

src/main/java/opus/Opus.java

@@ -1,166 +1,41 @@
 package opus;
 
+import opus.exceptions.OpusException;
+import opus.commands.Command;
+import opus.commands.CommandResult;
+
 /**
- * The Opus class is the main entry point of the Duke task manager application.
- * It initializes the necessary components (UI, storage, task list) and runs
- * the main loop to interact with the user, handle commands, and manage tasks.
+ * Represents the main class of the program.
  */
 public class Opus {
 
     private Storage storage;
     private TaskList taskList;
-    private boolean isExit = false;
 
     /**
-     * Initializes the Opus application with the specified file path for storage.
-     * Loads tasks from storage and sets up UI and task list.
+     * Creates a new instance of Opus.
      *
-     * @param filePath Path to the file where tasks are stored.
+     * @param filePath The file path of the storage file.
      */
     public Opus(String filePath) {
         storage = new Storage(filePath);
         taskList = new TaskList(storage.load());
     }
 
     /**
-     * Handles the bye command by saving tasks to storage and setting the exit flag.
+     * Gets the response to the user input.
      *
-     * @return The response message indicating the application will exit.
-     * @throws OpusException If an error occurs while saving tasks.
+     * @param input The user input.
+     * @return The response to the user.
      */
-    private String handleByeCommand() throws OpusException {
-        storage.save(taskList.getTasks());
-        isExit = true; // Set the exit flag
-        return "Bye. Hope to see you again soon!";
-    }
-
-    /**
-     * Returns whether the application should exit.
-     *
-     * @return True if the application should exit, false otherwise.
-     */
-    public boolean isExit() {
-        return isExit;
-    }
-
-    /**
-     * Handles the list command by displaying all tasks in the task list.
-     *
-     * @return The response message containing all tasks in the list.
-     */
-    private String handleListCommand() {
-        String response = "";
-        for (Task task : taskList.getTasks()) {
-            response += task.toString() + "\n";
-        }
-        return response;
-    }
-    /**
-     * Handles the mark command by marking a task as done.
-     *
-     * @param words The command split into words.
-     * @return The response message indicating the task has been marked as done.
-     * @throws OpusException If the task number is not specified or is invalid.
-     */
-    private String handleMarkCommand(String[] words) throws OpusException {
-        if (words.length < 2) {
-            throw new OpusException("Please specify the task number to mark.");
-        }
-        int i = Integer.parseInt(words[1]) - 1;
-        assert i >= 0 && i < taskList.getSize() : "Index out of bounds: " + i;
-        taskList.getTask(i).markAsDone();
-        return "Nice! I've marked this task as done:\n" + taskList.getTask(i).toString();
-    }
-    /**
-     * Handles the delete command by removing a task from the list.
-     *
-     * @param words The command split into words.
-     * @return The response message indicating the task has been deleted.
-     * @throws OpusException If the task number is not specified or is invalid.
-     */
-    private String handleDeleteCommand(String[] words) throws OpusException {
-        String response = "";
-        if (words.length < 2) {
-            throw new OpusException("Please specify the task number to delete.");
-        }
-        int i = Integer.parseInt(words[1]) - 1;
-        assert i >= 0 && i < taskList.getSize() : "Index out of bounds: " + i;
-        response = "Noted. I've removed this task:\n" + taskList.getTask(i).toString() + "\n";
-        taskList.removeTask(i);
-        response += "Now you have " + taskList.getSize() + " tasks in the list.";
-        return response;
-    }
-    /**
-     * Handles the help command by displaying a list of available commands.
-     *
-     * @return The response message containing the list of commands.
-     */
-    private String handleHelpCommand() {
-        String response = "Here are the commands you can use:\n";
-        response += "1. list - List all tasks\n";
-        response += "2. mark <index> - Mark a task as done\n";
-        response += "3. delete <index> - Delete a task\n";
-        response += "4. deadline <task> /by <end-date> - Add a deadline by the end date\n";
-        response += "5. event <task> /from <start-date> /to <end-date>";
-        response += " - Add an event with start and end dates\n";
-        response += "6. todotask <> - Add a Todo\n";
-        response += "7. bye - Exit the application";
-        return response;
-    }
-
-
-    /**
-     * Main method to launch the Opus application.
-     * @param args Command-line arguments, not used.
-     */
-    public static void main(String[] args) {
-        new Opus("data/tasks.txt");
-    }
-
-    public String getResponse(String input) {
-        String[] words = Parser.parse(input);
-        String response = "";
+    public CommandResult getResponse(String input) {
         try {
-            assert words.length > 0 : "Command cannot be empty";
-            if (words[0].equals("bye")) {
-                response = handleByeCommand();
-            } else if (words[0].equals("list")) {
-                response = handleListCommand();
-            } else if (words[0].equals("mark")) {
-                response = handleMarkCommand(words);
-            } else if (words[0].equals("delete")) {
-                response = handleDeleteCommand(words);
-            } else if (words[0].equals("help")) {
-                response = handleHelpCommand();
-            } else {
-                if (words[0].equals("todo")) {
-                    assert words.length > 1 : "The description of a todo cannot be empty";
-                    if (words.length <= 1) {
-                        throw new OpusEmptyDescriptionException("The description of a todo cannot be empty.");
-                    }
-                    Task todo = new ToDo(words[1]);
-                    taskList.addTask(todo);
-                } else if (words[0].equals("deadline")) {
-                    assert words.length > 1 : "Deadline details are missing";
-                    String[] parts = Parser.parseDeadlineDetails(words[1]);
-                    Task deadline = new Deadline(parts[0], parts[1]);
-                    taskList.addTask(deadline);
-                } else if (words[0].equals("event")) {
-                    assert words.length > 1 : "Event details are missing";
-                    String[] parts = Parser.parseEventDetails(words[1]);
-                    Task event = new Event(parts[0], parts[1], parts[2]);
-                    taskList.addTask(event);
-                } else {
-                    throw new OpusUnknownCommandException("I'm sorry, but I don't know what that means.");
-                }
-                response = "Got it. I've added this task:\n";
-                response += taskList.getTask(taskList.getSize() - 1).toString() + "\n";
-                response += "Now you have " + taskList.getSize() + " tasks in the list.";
-                return response;
-            }
+            Command command = Parser.parse(input);
+            String response = command.execute(taskList, storage);
+            boolean isExit = command.isExit();
+            return new CommandResult(response, isExit);
         } catch (OpusException e) {
-            return e.getMessage();
+            return new CommandResult(e.getMessage(), false);
         }
-        return response;
     }
 }