Level 1. Greet, Echo, Exit

Implement a skeletal version of Duke that starts by greeting the user, simply echos commands entered by the user, and exits when the user types bye.
Example:

    ____________________________________________________________
     Hello! I'm Duke
     What can I do for you?
    ____________________________________________________________

list
    ____________________________________________________________
     list
    ____________________________________________________________

blah
    ____________________________________________________________
     blah
    ____________________________________________________________

bye
    ____________________________________________________________
     Bye. Hope to see you again soon!
    ____________________________________________________________

• The indentation and horizontal lines are optional.

Level 2. Add, List

Add the ability to store whatever text entered by the user and display them back to the user when requested.

Example:

    ____________________________________________________________
     Hello! I'm Duke
     What can I do for you?
    ____________________________________________________________

read book
    ____________________________________________________________
     added: read book
    ____________________________________________________________

return book
    ____________________________________________________________
     added: return book
    ____________________________________________________________

list
    ____________________________________________________________
     1. read book
     2. return book
    ____________________________________________________________
bye
    ____________________________________________________________
     Bye. Hope to see you again soon!
    ____________________________________________________________

• There is no need to save the data to the hard disk.
• Assume there will be no more than 100 tasks. If you wish, you may use a fixed size array (e.g., String[100]) to store the items.

Level 3. Mark as Done

Add the ability to mark tasks as done.

list
    ____________________________________________________________
     Here are the tasks in your list:
     1.[X] read book
     2.[ ] return book
     3.[ ] buy bread
    ____________________________________________________________

done 2
    ____________________________________________________________
     Nice! I've marked this task as done: 
       [X] return book
    ____________________________________________________________

public class Task {
    protected String description;
    protected boolean isDone;

    public Task(String description) {
        this.description = description;
        this.isDone = false;
    }

    public String getStatusIcon() {
        return (isDone ? "X" : " "); // mark done task with X
    }

    //...
}

Task t = new Task("read book");
t.markAsDone();

Level 4. ToDos, Events, Deadlines

Add support for tracking three types of tasks:

1. ToDos: tasks without any date/time attached to it e.g., visit new theme park
2. Deadlines: tasks that need to be done before a specific date/time e.g., submit report by 11/10/2019 5pm
3. Events: tasks that start at a specific time and ends at a specific time e.g., team project meeting on 2/10/2019 2-4pm

Example:

todo borrow book
    ____________________________________________________________
     Got it. I've added this task: 
       [T][ ] borrow book
     Now you have 5 tasks in the list.
    ____________________________________________________________

list
    ____________________________________________________________
     Here are the tasks in your list:
     1.[T][X] read book
     2.[D][ ] return book (by: June 6th)
     3.[E][ ] project meeting (at: Aug 6th 2-4pm)
     4.[T][X] join sports club
     5.[T][ ] borrow book
    ____________________________________________________________

deadline return book /by Sunday
    ____________________________________________________________
     Got it. I've added this task: 
       [D][ ] return book (by: Sunday)
     Now you have 6 tasks in the list.
    ____________________________________________________________

event project meeting /at Mon 2-4pm
    ____________________________________________________________
     Got it. I've added this task: 
       [E][ ] project meeting (at: Mon 2-4pm)
     Now you have 7 tasks in the list.
    ____________________________________________________________

At this point, dates/times can be treated as strings; there is no need to convert them to actual dates/times.

Example:

deadline do homework /by no idea :-p
    ____________________________________________________________
     Got it. I've added this task: 
       [D][ ] do homework (by: no idea :-p)
     Now you have 6 tasks in the list.
    ____________________________________________________________

public class Deadline extends Task {

    protected String by;

    public Deadline(String description, String by) {
        super(description);
        this.by = by;
    }

    @Override
    public String toString() {
        return "[D]" + super.toString() + " (by: " + by + ")";
    }
}

Task[] tasks = new Task[100];
task[0] = new Deadline("return book", "Monday");

Level 4. ToDos, Events, Deadlines

Add support for tracking three types of tasks:

1. ToDos: tasks without any date/time attached to it e.g., visit new theme park
2. Deadlines: tasks that need to be done before a specific date/time e.g., submit report by 11/10/2019 5pm
3. Events: tasks that start at a specific time and ends at a specific time e.g., team project meeting on 2/10/2019 2-4pm

Example:

todo borrow book
    ____________________________________________________________
     Got it. I've added this task: 
       [T][ ] borrow book
     Now you have 5 tasks in the list.
    ____________________________________________________________

list
    ____________________________________________________________
     Here are the tasks in your list:
     1.[T][X] read book
     2.[D][ ] return book (by: June 6th)
     3.[E][ ] project meeting (at: Aug 6th 2-4pm)
     4.[T][X] join sports club
     5.[T][ ] borrow book
    ____________________________________________________________

deadline return book /by Sunday
    ____________________________________________________________
     Got it. I've added this task: 
       [D][ ] return book (by: Sunday)
     Now you have 6 tasks in the list.
    ____________________________________________________________

event project meeting /at Mon 2-4pm
    ____________________________________________________________
     Got it. I've added this task: 
       [E][ ] project meeting (at: Mon 2-4pm)
     Now you have 7 tasks in the list.
    ____________________________________________________________

At this point, dates/times can be treated as strings; there is no need to convert them to actual dates/times.

Example:

deadline do homework /by no idea :-p
    ____________________________________________________________
     Got it. I've added this task: 
       [D][ ] do homework (by: no idea :-p)
     Now you have 6 tasks in the list.
    ____________________________________________________________

public class Deadline extends Task {

    protected String by;

    public Deadline(String description, String by) {
        super(description);
        this.by = by;
    }

    @Override
    public String toString() {
        return "[D]" + super.toString() + " (by: " + by + ")";
    }
}

Task[] tasks = new Task[100];
task[0] = new Deadline("return book", "Monday");

Level 5. Handle Errors

Teach Duke to deal with errors such as incorrect inputs entered by the user.

Example:

todo
    ____________________________________________________________
     ☹ OOPS!!! The description of a todo cannot be empty.
    ____________________________________________________________

blah
    ____________________________________________________________
     ☹ OOPS!!! I'm sorry, but I don't know what that means :-(
    ____________________________________________________________

• Minimal: handle at least the two types of errors shown in the example above.
• Stretch goal: handle all possible errors in the current version. As you evolve Duke, continue to handle errors related to the new features added.

Level 6. Delete

Add support for deleting tasks from the list.

Example:

list
    ____________________________________________________________
     Here are the tasks in your list:
     1.[T][X] read book
     2.[D][X] return book (by: June 6th)
     3.[E][ ] project meeting (at: Aug 6th 2-4pm)
     4.[T][X] join sports club
     5.[T][ ] borrow book
    ____________________________________________________________

delete 3
    ____________________________________________________________
     Noted. I've removed this task: 
       [E][ ] project meeting (at: Aug 6th 2-4pm)
     Now you have 4 tasks in the list.
    ____________________________________________________________

Level 7. Save

Save the tasks in the hard disk automatically whenever the task list changes. Load the data from the hard disk when Duke starts up. You may hard-code the file name and location e.g., [project_root]/data/duke.txt

The format of the file is up to you. Example:

T | 1 | read book
D | 0 | return book | June 6th
E | 0 | project meeting | Aug 6th 2-4pm
T | 1 | join sports club

If you use file paths in your code,

• remember to use relative paths rather than absolute paths such as C:\data. If not, your app can cause unpredictable results when used in another computer.
• remember to specify file paths in an OS-independent way. If not, your app might not work when used on a different OS.

Your code must i.e., if the file is missing, your code must creat ithandle the case where the data file doesn't exist at the start. Reason: when someone else takes your Duke and runs it for the first time, the required file might not exist in their computer. Similarly, if you expect the data file to be in as specific folder (e.g., ./data/), you must also handle the folder-does-not-exist-yet case.

Level 9. Find

Give users a way to find a task by searching for a keyword.

Example:

find book
    ____________________________________________________________
     Here are the matching tasks in your list:
     1.[T][X] read book
     2.[D][X] return book (by: June 6th)
    ____________________________________________________________

Make the Task class an abstract class. If applicable, use abstract methods as well.

Refactor the code to extract out closely related code as classes.

• Minimal: Extract the following classes:
  • Ui: deals with interactions with the user
  • Storage: deals with loading tasks from the file and saving tasks in the file
  • Parser: deals with making sense of the user command
  • TaskList: contains the task list e.g., it has operations to add/delete tasks in the list

public class Duke {

    private Storage storage;
    private TaskList tasks;
    private Ui ui;

    public Duke(String filePath) {
        ui = new Ui();
        storage = new Storage(filePath);
        try {
            tasks = new TaskList(storage.load());
        } catch (DukeException e) {
            ui.showLoadingError();
            tasks = new TaskList();
        }
    }

    public void run() {
        //...
    }

    public static void main(String[] args) {
        new Duke("data/tasks.txt").run();
    }
}

• Stretch Goal: Consider extracting more classes. e.g., *Command classes (i.e., AddCommand, DeleteCommand, ExitCommand etc.) that inherits from an abstract Command class, so that you can write the main logic of the App as follows:

  public void run() {
      ui.showWelcome();
      boolean isExit = false;
      while (!isExit) {
          try {
              String fullCommand = ui.readCommand();
              ui.showLine(); // show the divider line ("_______")
              Command c = Parser.parse(fullCommand);
              c.execute(tasks, ui, storage);
              isExit = c.isExit();
          } catch (DukeException e) {
              ui.showError(e.getMessage());
          } finally {
              ui.showLine();
          }
      }
  }
  

  You can get some inspiration from how the code of the addressbook-level2 is organized.

Organize the classes into suitable java packages.

• Minimal: put all classes in one package e.g., duke
• Stretch goal: divide into multiple packages as the number of classes increase e.g., duke.task, duke.command

Add JavaDoc comments to the code.

• Minimal: Add header comments to at least half of the non-private classes/methods.
• Stretch goal: Add header comments to all non-private classes/methods, and non-trivial private methods.

Add JUnit tests to test the behavior of the code.

Requirements:

• Minimum: More than two test methods, preferably targeting more than one class (if you have multiple classes)
• Stretch goal: test methods to target all public methods of all classes

Refer to the JUnit tutorial @se-edu/guides to find how to use JUnit.

Use checkStyle to detect coding style violations.

Refer the tutorial Using Checkstyle @SE-EDU/guides to learn how to use Checkstyle.