AB-3 Developer Guide

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Acknowledgements

• This project evolved from the AddressBook-Level3 project created by the SE-EDU initiative.

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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, 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.

The sequence diagram below illustrates the interactions within the UI component when the window is resized, to dynamically change the number of displayed columns of contacts.

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 both address book data and user preference data in JSON format, and read them back into corresponding objects.
• inherits from both AddressBookStorage and UserPrefStorage, 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)

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

The undo mechanism is implemented within ModelManager. It allows the user to restore the address book to its immediate previous state after a data-modifying command, but only once.

Implementation

The undo mechanism is facilitated by ModelManager storing a ReadOnlyAddressBook named previousAddressBook. It implements the following operations:

• ModelManager#commitAddressBook() — Saves a copy of the current address book state before a data-modifying command executes.
• ModelManager#undoAddressBook() — Restores the address book state from the stored backup and clears the backup to ensure only one undo is possible.
• ModelManager#canUndo() — Checks if a backup state exists.

These operations are exposed in the Model interface as Model#commitAddressBook(), Model#undoAddressBook() and Model#canUndo() 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 is initialized with the initial address book state. previousAddressBook is null.

Step 2. The user executes the delete 5 command. The command calls Model#commitAddressBook(), which saves the state before the deletion into previousAddressBook. The command then deletes the person.

Step 3. The user executes add n/David …​ to add a new person. The add command also calls Model#commitAddressBook(), overwriting previousAddressBook with the state that included everyone except the 5th person. The command then adds David.

Step 4. The user decides adding David was a mistake and executes undo. The UndoCommand calls Model#undoAddressBook(), which restores the Model to the state saved in previousAddressBook (the state after the deletion but before the add). previousAddressBook is then set back to null.

The following sequence diagram shows how an undo operation goes through the Logic and Model components:

[Proposed] Multiple Undo Feature

The current single-state backup in ModelManager can only support undoing a maximum of one command. To support a multiple undo feature, the current single-state backup in ModelManager would need to be upgraded to a state history list (similar to the original AB3 proposal). This would involve:

1. Replacing previousAddressBook with an addressBookStateList and a currentStatePointer.
2. Changing the implementation of Model#undoAddressBook(), to move the pointer backward in the history list to restore a previous state.
3. Updating the "Purge" logic: If a new data-modifying command is executed after an undo, all "redoable" states at the end of the list must be deleted.

Design considerations:

Aspect: How undo executes:

• Alternative 1 (current choice): Saves the entire address book.

  • Pros: Easy to implement and less prone to bugs when complex fields (like certificates) are modified.
  • Cons: Higher memory usage since a full snapshot is taken for every modifying command

• Alternative 2: Individual commands know how to reverse themselves (eg an AddCommand does undo by performing a delete).

  • Pros: Very memory efficient.
  • Cons: Highly complex to implement correctly, especially for commands that modify multiple internal states simultaneously.

Due to time constraints, Alternative 1 was implemented.

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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:

• are HR/Admin personnel of a small startup
• manages a significant number of employee information (~50 employees)
• prefer desktop apps over other types
• can type fast
• prefers typing to mouse interactions
• is reasonably comfortable using CLI apps

Value proposition: manage critical employee information faster than a typical mouse/GUI driven app

The app does not support managing larger workgroups beyond the average startup size (~50 people) and will only manage critical employee-related information such as contact details, departments, team structures and salaries.

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 Big Brother and the Actor is the user, unless specified otherwise)

Use case: UC1 Add a person

MSS

1. User requests to add a person

2. Big Brother indicates that a person is added

   Use case ends.

Extensions

• 1a. User inputs an invalid command

  • 1a1. Big Brother shows an error message

    Use case resumes at step 1.

Use case: UC2 Add a tag to a person

MSS

1. User requests to list persons

2. Big Brother shows a list of persons

3. User requests to add a tag to a specific person in the list

4. Big Brother adds the tag to the person

   Use case ends.

Extensions

• 1a. The list is empty

  Use case ends.

• 3a. The given person's index is invalid

  • 3a1. Big Brother shows an error message

    Use case resumes at step 2.

Use case: UC3 Delete a person

MSS

1. User requests to list persons

2. Big Brother shows a list of persons

3. User requests to delete a specific person in the list

4. Big Brother deletes the person

   Use case ends.

Extensions

• 1a. The list is empty

  Use case ends.

• 3a. The given person's index is invalid

  • 3a1. Big Brother shows an error message

    Use case resumes at step 2.

Use case: UC4 Delete a tag

MSS

1. User requests to list persons

2. Big Brother shows a list of persons

3. User requests to delete a tag from a specific person in the list

4. Big Brother deletes the tag from the person

   Use case ends.

Extensions

• 1a. The list is empty

  Use case ends.

• 3a. The given person's index is invalid

  • 3a1. Big Brother shows an error message

    Use case resumes at step 2.

• 3b. The tag specified cannot be found

  • 3b1. Big Brother shows an error message

    Use case resumes at step 2.

Use case: UC5 Find a person

MSS

1. User requests to find a specific person

2. Big Brother displays the details of the specific person

   Use case ends.

Extensions

• 1a. Person specified does not exist

  • 1a1. Big Brother shows an error message

    Use case ends.

{More to be added}

Non-Functional Requirements

Environment

1. Should work on any mainstream OS as long as it has Java 17 installed.
2. Should be fully usable offline, without remote services nor servers.
3. Should offer sufficient in-built support for fully offline use.

App Format

1. Should work without requiring an installer.
2. Should be packaged as a single jar or zip file.
3. Should not exceed 100MB in size for the file.

Visual Performance

1. GUI should work well for:

• standard screen resolutions 1920x1080 and higher
• for screen scales 100% and 125%

2. GUI should work for:

• resolutions 1280x720 and higher
• for screen scales 150%

Functional Performance

1. Should be able to hold up to 100 persons without a noticeable sluggishness in performance for typical usage.
2. 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.
3. Should respond in at most 2 seconds for any command.

Data

1. Should not rely on database management systems.
2. Should be formatted in human-readable format.
3. Should be saved locally in human-editable text file.
4. Should be recoverable in the event of corruption.

Glossary

• Mainstream OS: Windows, Linux, Unix, MacOS
• Private contact detail: A contact detail that is not meant to be shared with others
• Employee profile: Grouped information about an employee's name, phone number, email, address, associated tags (if any), salary and certificates (if any)
• Invalid command: A command that is not supported by the application
• Above average typing speed: An average typing speed > 80 WPM

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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 …​ }