LambdaLab Developer Guide

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Acknowledgements

{ list here sources of all reused/adapted ideas, code, documentation, and third-party libraries -- include links to the original source as well }

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Setting up, getting started

Refer to the guide Setting up and getting started.

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Design

Architecture

The Architecture Diagram given above explains the high-level design of the App.

Given below is a quick overview of main components and how they interact with each other.

Main components of the architecture

Main (consisting of classes Main and MainApp) is in charge of the app launch and shut down.

• At app launch, it initializes the other components in the correct sequence, and connects them up with each other.
• At shut down, it shuts down the other components and invokes cleanup methods where necessary.

The bulk of the app's work is done by the following four components:

• UI: The UI of the App.
• Logic: The command executor.
• Model: Holds the data of the App in memory.
• Storage: Reads data from, and writes data to, the hard disk.

Commons represents a collection of classes used by multiple other components.

How the architecture components interact with each other

The Sequence Diagram below shows how the components interact with each other for the scenario where the user issues the command delete 1.

Each of the four main components (also shown in the diagram above),

• defines its API in an interface with the same name as the Component.
• implements its functionality using a concrete {Component Name}Manager class (which follows the corresponding API interface mentioned in the previous point.

For example, the Logic component defines its API in the Logic.java interface and implements its functionality using the LogicManager.java class which follows the Logic interface. Other components interact with a given component through its interface rather than the concrete class (reason: to prevent outside component's being coupled to the implementation of a component), as illustrated in the (partial) class diagram below.

The sections below give more details of each component.

UI component

The API of this component is specified in Ui.java

The UI consists of a MainWindow that is made up of parts e.g.CommandBox, ResultDisplay, PersonListPanel, StatusBarFooter etc. All these, including the MainWindow, inherit from the abstract UiPart class which captures the commonalities between classes that represent parts of the visible GUI.

The UI component uses the JavaFx UI framework. The layout of these UI parts are defined in matching .fxml files that are in the src/main/resources/view folder. For example, the layout of the MainWindow is specified in MainWindow.fxml

The UI component,

• executes user commands using the Logic component.
• listens for changes to Model data so that the UI can be updated with the modified data.
• keeps a reference to the Logic component, because the UI relies on the Logic to execute commands.
• depends on some classes in the Model component, as it displays Person object residing in the Model.

Logic component

API : Logic.java

Here's a (partial) class diagram of the Logic component:

The sequence diagram below illustrates the interactions within the Logic component, taking execute("delete 1") API call as an example.

How the Logic component works:

1. When Logic is called upon to execute a command, it is passed to an AddressBookParser object which in turn creates a parser that matches the command (e.g., DeleteCommandParser) and uses it to parse the command.
2. This results in a Command object (more precisely, an object of one of its subclasses e.g., DeleteCommand) which is executed by the LogicManager.
3. The command can communicate with the Model when it is executed (e.g. to delete a person).
   Note that although this is shown as a single step in the diagram above (for simplicity), in the code it can take several interactions (between the command object and the Model) to achieve.
4. The result of the command execution is encapsulated as a CommandResult object which is returned back from Logic.

Here are the other classes in Logic (omitted from the class diagram above) that are used for parsing a user command:

How the parsing works:

• When called upon to parse a user command, the AddressBookParser class creates an XYZCommandParser (XYZ is a placeholder for the specific command name e.g., AddCommandParser) which uses the other classes shown above to parse the user command and create a XYZCommand object (e.g., AddCommand) which the AddressBookParser returns back as a Command object.
• All XYZCommandParser classes (e.g., AddCommandParser, DeleteCommandParser, ...) inherit from the Parser interface so that they can be treated similarly where possible e.g, during testing.

Model component

API : Model.java

The Model component,

• stores the address book data i.e., all Person objects (which are contained in a UniquePersonList object).
• stores the currently 'selected' Person objects (e.g., results of a search query) as a separate filtered list which is exposed to outsiders as an unmodifiable ObservableList<Person> that can be 'observed' e.g. the UI can be bound to this list so that the UI automatically updates when the data in the list change.
• stores a UserPref object that represents the user’s preferences. This is exposed to the outside as a ReadOnlyUserPref objects.
• does not depend on any of the other three components (as the Model represents data entities of the domain, they should make sense on their own without depending on other components)

Storage component

API : Storage.java

The Storage component,

• can save address book data, user preferences, and timeslot data in JSON format and read them back into model objects.
• inherits from AddressBookStorage, UserPrefsStorage, and TimeslotsStorage, which means it can be treated as either one (if only the functionality of only one is needed).
• depends on some classes in the Model component (because the Storage component's job is to save/retrieve objects that belong to the Model)
• delegates JSON conversion to classes such as JsonSerializableAddressBook / JsonAdaptedPerson for the address book and JsonSerializableTimeslots / JsonAdaptedTimeslot for timeslots.
• provides concrete implementations like JsonAddressBookStorage, JsonUserPrefsStorage, and JsonTimeslotsStorage which read/write files on disk.

The StorageManager class,

• composes the individual storage providers (address book, prefs, timeslots)
• exposes unified operations so MainApp, Logic, and other components access persistence through a single entry point

The timeslots file location is configurable via UserPrefs and the application will create or populate the file with sample timeslots when none is present.

Common classes

Classes used by multiple components are in the seedu.address.commons package.

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Implementation

This section describes some noteworthy details on how certain features are implemented.

Undo feature

Implementation

The undo mechanism is facilitated by ModelManager. It stores a single previous state of the address book and timeslots, stored internally as previousAddressBookState and previousTimeslotsState. Additionally, it implements the following operations:

• Model#saveAddressBook() — Saves the current address book and timeslots state before modification.
• Model#undoAddressBook() — Restores the previous address book and timeslots state.
• Model#canUndoAddressBook() — Checks if there is a previous state available to undo to.

These operations are exposed in the Model interface as Model#saveAddressBook(), Model#undoAddressBook() and Model#canUndoAddressBook() respectively.

Given below is an example usage scenario and how the undo mechanism behaves at each step.

Step 1. The user launches the application for the first time. The ModelManager will be initialized with the initial address book and timeslots state, with previousAddressBookState and previousTimeslotsState set to null (no previous state to undo to).

Step 2. The user executes delete 5 command to delete the 5th person in the address book. The delete command calls Model#saveAddressBook() before deleting, saving the current state. After the deletion, the current state is modified but the previous state preserves the state before deletion.

Step 3. The user executes add n/John Doe …​ to add a new student. The add command also calls Model#saveAddressBook() before adding, which replaces the previous state with the current state (ab1), then adds the new student.

Step 4. The user now decides that adding the student was a mistake, and decides to undo that action by executing the undo command. The undo command will call Model#undoAddressBook(), which restores the address book to the previous state (ab1) and sets both previousAddressBookState and previousTimeslotsState to null.

The following sequence diagram shows how an undo operation goes through the Logic component:

Similarly, how an undo operation goes through the Model component is shown below:

Step 5. The user then decides to execute the command list. Commands that do not modify the address book, such as list, find, or get-timeslots, will not call Model#saveAddressBook(). Thus, the previous state remains null.

Step 6. The user executes clear, which calls Model#saveAddressBook() before clearing. The current state (ab1) is saved as the previous state, then all persons are deleted, creating a new current state.

The following activity diagram summarises what happens when a user executes a new command:

Commands that support undo

The following commands call Model#saveAddressBook() and thus support undo:

• add - Adds a student
• delete - Deletes a student
• edit - Edits a student
• clear - Clears all students
• marke - Marks an exercise
• marka - Marks attendance
• grade - Marks grade of an assessment
• block-timeslot - Adds a timeslot
• clear-timeslots - Clears all timeslots

The following commands do NOT support undo (read-only commands):

• list - Lists all students
• find - Finds students
• filter - Filters students
• sort - Sorts students base on some criteria
• get-timeslots - Displays timeslots
• help - Shows help
• exit - Exits the application

Design considerations

Aspect: How undo executes:

• Alternative 1 (current choice): Saves only one previous state (address book + timeslots).

  • Pros:
    • Simple to implement and understand.
    • Minimal memory usage (only doubles the data size at most).
    • No complex state management or pointer tracking.
  • Cons:
    • Cannot undo multiple commands in sequence.
    • Cannot undo a command once a new data-modifying command is executed.
    • No redo functionality.

• Alternative 2: Save entire history in a list with pointer.

  • Pros:
    • Can undo multiple commands in sequence.
    • Supports redo functionality.
  • Cons:
    • More complex to implement and maintain.
    • Higher memory usage (stores multiple states in a list).
    • Need to carefully manage state pointer and list boundaries.

• Alternative 3: Individual command knows how to undo itself (Command Pattern with undo).

  • Pros:
    • Memory efficient (only store minimal data needed to reverse each command).
    • Can undo multiple commands.
    • Each command encapsulates its own undo logic.
  • Cons:
    • Much more complex - every command must implement its own undo logic.
    • Must ensure correctness of each command's undo implementation.
    • Harder to maintain and test.
    • Increased development time for new commands.

Rationale for Alternative 1: For the scope of this project, a simple single-level undo is sufficient for most use cases. Users typically need to undo only their most recent action, and the simplicity of implementation outweighs the benefits of a full undo/redo stack. The minimal memory overhead and straightforward logic make this approach ideal for a student project with limited development time.

Future enhancements

• Multiple undo levels: Implement a full history stack (Alternative 2) to support undoing multiple commands in sequence. This would involve storing a list of states and maintaining a current state pointer.

• Redo functionality: Allow users to redo commands that were undone. This would require preserving the "future" states after an undo operation until a new modifying command is executed.

• Selective undo: Allow undoing specific commands in history rather than just the most recent one. This would require implementing Alternative 3 with command-specific undo logic.

• Undo command confirmation: For destructive commands like clear, prompt the user to confirm before executing, reducing the need for undo in the first place.

[Proposed] Data archiving

{Explain here how the data archiving feature will be implemented}

Find Feature:

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Documentation, logging, testing, configuration, dev-ops

• Documentation guide
• Testing guide
• Logging guide
• Configuration guide
• DevOps guide

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Appendix: Requirements

Product scope

Target user profile:

• Undergraduate Teaching Assistants of CS2030S
• need to manage a significant number of students
• prefer desktop apps for reliability during labs/consultations
• can type fast and are comfortable with keyboard shortcuts (Vim)
• prefer typing over mouse interactions
• comfortable using CLI apps

Value proposition: manage students, submissions, attendance, and resources faster and more efficiently than traditional spreadsheets or GUI-based systems

User stories

Priorities: High (must have) - * * *, Medium (nice to have) - * *, Low (unlikely to have) - *

Use cases

(For all use cases below, the System is the LambdaLab and the Actor is the user, unless specified otherwise)

Use case: Grade an exercise

Precondition: A student has submitted their programming exercise

MSS

1. User receives notification that a student has submitted the exercise
2. User navigates to student's submission on GitHub via notification
3. User returns after grading student's submission on GitHub
4. User marks exercise as graded in LambdaLab
5. LambdaLab updates statistics Use case ends.

Extensions

• 1a. User doesn't want to grade student's exercise now
  • 1a1. User dismisses the notification Use case ends.
• 1b. User accidentally dismisses notification
  • 1b1. User goes to student's profile
  • 1b2. User navigates to student's submission on GitHub via link in student's profile Use case resumes at Step 3

Use case: Mark student attendance

MSS

1. User wants to mark attendance, enters student name and lab number using the command format
2. LambdaLab validates the student name and lab number
3. LambdaLab marks the student’s attendance for the specified lab
4. LambdaLab confirms: “Attendance for marked for lab number ” Use case ends.

Extensions

• 1a. User provides an empty name or a name with invalid characters
  • 1a1. LambdaLab displays error message: “Invalid name”
  • 1a2. User re-enters a valid name Use case resumes at Step 2
• 1b. User provides an invalid lab number (non-numeric, zero, negative, or out-of-range)
  • 1b1. System displays error message: “Invalid lab number”
  • 1b2. User re-enters a valid lab number Use case resumes at Step 2
• 3a. Attendance for the student in that lab number has already been marked
  • 3a1. LambdaLab displays: “Attendance already marked for in lab number ” Use case ends.

Use case: Schedule a consultation

Precondition: User has uploaded his schedule

Actor:User

MSS

1. User views all the periods of available time he has
2. User inputs a desired consultation time slot
3. Time slot is saved into his schedule
4. A day before the consultation, the user will be reminded of it

Extensions

• 2a. User inputs an invalid consultation slot
  • 1a1. User is prompted to enter a valid consultation slot Use case resumes at step 2.
• 3a.
  • 3a1. User requests to reschedule or delete the consultation.
  • 3a2. System allows modification or cancellation. Use case ends.

{More to be added}

Non-Functional Requirements

1. Should work on any mainstream OS as long as it has Java 17 or above installed.
2. Should be able to hold up to 1000 persons without a noticeable sluggishness in performance for typical usage.
3. A user with above average typing speed for regular English text (i.e. not code, not system admin commands) should be able to accomplish most of the tasks faster using commands than using the mouse.
4. The system should respond to any command within 1 second.
5. Core functionalities should be covered by automated tests to ensure that future changes do not break the existing features
6. Users should be able to run the application simply by executing a JAR file, without needing to run an installer.
7. Should be able to function fully offline.
8. Date persistence should not depend on an external database system. Storage should be file-based and embedded.
9. User data should not be lost due to unexpected situations (e.g., unexpected shutdowns).
10. Should be able to support multiple screen resolutions (e.g., 1280×720 and above) without layout issues.

Glossary

• Assignment: Weekly coding homework that is submitted through GitHub
• Auto-link: Automatically add a link to the students GitHub repo
• Consultation: Scheduled meeting between a TA and student
• Exercise: Weekly coding homework that is submitted through GitHub
• Mainstream OS: Windows, Linux, Unix, MacOS
• Students' performance: Grades that students receive for their weekly exercises and labs
• TA: Teaching Assistant

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Appendix: Instructions for manual testing

Given below are instructions to test the app manually.

Launch and shutdown

1. Initial launch

   1. Download the jar file and copy into an empty folder

   2. Double-click the jar file Expected: Shows the GUI with a set of sample contacts. The window size may not be optimum.

2. Saving window preferences

   1. Resize the window to an optimum size. Move the window to a different location. Close the window.

   2. Re-launch the app by double-clicking the jar file.
      Expected: The most recent window size and location is retained.

3. { more test cases …​ }

Deleting a person

1. Deleting a person while all persons are being shown

   1. Prerequisites: List all persons using the list command. Multiple persons in the list.

   2. Test case: delete 1
      Expected: First contact is deleted from the list. Details of the deleted contact shown in the status message. Timestamp in the status bar is updated.

   3. Test case: delete 0
      Expected: No person is deleted. Error details shown in the status message. Status bar remains the same.

   4. Other incorrect delete commands to try: delete, delete x, ... (where x is larger than the list size)
      Expected: Similar to previous.

2. { more test cases …​ }

Saving data

1. Dealing with missing/corrupted data files

   1. {explain how to simulate a missing/corrupted file, and the expected behavior}

2. { more test cases …​ }