Developer Guide

• Acknowledgements
• Setting up, getting started
• Design
  • Architecture
  • UI component
  • Logic component
  • Model component
  • Storage component
  • Common classes
• Implementation
  • [Proposed] Undo/redo feature
    • Proposed Implementation
    • Design considerations:
  • [Proposed] Data archiving
• Documentation, logging, testing, configuration, dev-ops
• Appendix: Requirements
  • Product scope
  • User stories
  • Use cases
  • Non-Functional Requirements
  • Glossary
• Appendix: Instructions for manual testing
  • Launch and shutdown
  • Deleting a person
  • Saving data

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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 has two classes called Main and MainApp. It is responsible for,

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

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

The rest of the App consists of 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.

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:

How the Logic component works:

1. When Logic is called upon to execute a command, it uses the AddressBookParser class to parse the user command.
2. This results in a Command object (more precisely, an object of one of its subclasses e.g., AddCommand) which is executed by the LogicManager.
3. The command can communicate with the Model when it is executed (e.g. to add a person).
4. The result of the command execution is encapsulated as a CommandResult object which is returned back from Logic.

The Sequence Diagram below illustrates the interactions within the Logic component for the execute("delete 1") API call.

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.addressbook.commons package.

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Implementation

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

[Proposed] Undo/redo feature

Proposed Implementation

The proposed undo/redo mechanism is facilitated by VersionedAddressBook. It extends AddressBook with an undo/redo history, stored internally as an addressBookStateList and currentStatePointer. Additionally, it implements the following operations:

• VersionedAddressBook#commit() — Saves the current address book state in its history.
• VersionedAddressBook#undo() — Restores the previous address book state from its history.
• VersionedAddressBook#redo() — Restores a previously undone address book state from its history.

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

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

Step 1. The user launches the application for the first time. The VersionedAddressBook will be initialized with the initial address book state, and the currentStatePointer pointing to that single address book state.

Step 2. The user executes delete 5 command to delete the 5th person in the address book. The delete command calls Model#commitAddressBook(), causing the modified state of the address book after the delete 5 command executes to be saved in the addressBookStateList, and the currentStatePointer is shifted to the newly inserted address book state.

Step 3. The user executes add n/David …​ to add a new person. The add command also calls Model#commitAddressBook(), causing another modified address book state to be saved into the addressBookStateList.

Step 4. The user now decides that adding the person was a mistake, and decides to undo that action by executing the undo command. The undo command will call Model#undoAddressBook(), which will shift the currentStatePointer once to the left, pointing it to the previous address book state, and restores the address book to that state.

The following sequence diagram shows how the undo operation works:

The redo command does the opposite — it calls Model#redoAddressBook(), which shifts the currentStatePointer once to the right, pointing to the previously undone state, and restores the address book to that state.

Step 5. The user then decides to execute the command list. Commands that do not modify the address book, such as list, will usually not call Model#commitAddressBook(), Model#undoAddressBook() or Model#redoAddressBook(). Thus, the addressBookStateList remains unchanged.

Step 6. The user executes clear, which calls Model#commitAddressBook(). Since the currentStatePointer is not pointing at the end of the addressBookStateList, all address book states after the currentStatePointer will be purged. Reason: It no longer makes sense to redo the add n/David …​ command. This is the behavior that most modern desktop applications follow.

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

Design considerations:

Aspect: How undo & redo executes:

• Alternative 1 (current choice): Saves the entire address book.
  • Pros: Easy to implement.
  • Cons: May have performance issues in terms of memory usage.
• Alternative 2: Individual command knows how to undo/redo by itself.
  • Pros: Will use less memory (e.g. for delete, just save the person being deleted).
  • Cons: We must ensure that the implementation of each individual command are correct.

{more aspects and alternatives to be added}

[Proposed] Data archiving

{Explain here how the data archiving feature will be 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:

University students

• whose first language is English
• who are learning a new language

Value proposition:

• Fast way to generate flashcards to learn new languages
• Help students memorise words when learning a new language
• Gamified features such as recording of scores and tracking of improvements to make learning engaging and encourage continued usage

User stories

Categories: Usage pattern, user behaviours, general user, multiple language user, user learning style, user learning ‘rate’, level of experience, user collaboration Priorities: High (must have) - * * *, Medium (nice to have) - * *, Low (unlikely to have) - *

Priority	Category	As a/an…	I want to…	So that I…
*	Usage patterns	active user with hundred of cards already made	be automatically given a list of cards to test my memory	can efficiently expand my vocabulary
*	Usage patterns	frequent user	be able to jumble up my flashcards	am really testing my vocabulary instead of just memorising without really knowing the vocabulary
*	Usage patterns	forgetful user (who forgets about LingoGO!)	be reminded about using flashcards	can be actively learning new vocabularies instead of just cramming them at the last minute
*	Usage patterns	frequent user	be able to load up cards done x days ago	can test my memory retention of the words I learned that day
***	User behaviours	lazy user	automatically generate cards by typing in the vocabulary	don’t have to spend time manually creating cards
*	User behaviours	user who seeks improvement	see the progress made in terms of scores	can visualize my improvement
*	User behaviours	organised user (who prepares flashcards based on languages)	I want to be able to combine different decks of flashcards	can prepare for my major exams (eg. mid-terms, finals)
*	User behaviours	mobile user	be able to access my cards wherever I am, on the go
*	User behaviours	user who learns better when things are in hardcopy	have a convenient way to print out the flashcards	do not have to manually format the card design
*	General user	user	use the app in another language
*	General user	user	see the summary statistics over a period of time	can track my progress
*	General user	user	be able to tag my flashcards under the categories I specify (e.g. easy, medium, for fun, nouns, etc.)	organise my flashcards easily
***	General user	user	be able to add new flash cards
***	General user	user	be able to list my flashcards
***	General user	user	be able to test myself and view my performance using flashcards
***	General user	user	be able to delete my flashcards
***	General user	user	be able to update my flashcards
*	Multiple language user	user who is learning multiple languages	be able to load different question sets and store my questions in different files
*	Multiple language user	user who is learning multiple languages	be able to combine flashcards of the same question in different languages	can test myself in all the languages that I have learnt in one go
*	User learning style	auditory user	hear the vocabulary that I stored in the flashcard	can better memorize the words by sound
*	User learning style	visual learner	use pictures instead of words as the question part of my flashcard	can remember the vocabulary easier
*	User learning style	visual learner	color code my flashcards	can better memorize the words by category
*	User learning ‘rate’	slow/fast learner	adjust the frequency at which the cards will be tested	can better suit my pace of learning
*	User learning ‘rate’	slow learner	have cards with words I don’t remember to be shown more often to reinforce my learning
*	Level of experience	long-time user	be able to delete flashcards that have not been used for over a year	only have the flashcards that are relevant to me
***	Level of experience	new user	be guided through the set-up process of a flashcard	can use LingoGo! Properly
*	Level of experience	new user	have intuitive UI and commands	can get started easily
*	Level of experience	new user	have a basic set of questions available from the get go	can reduce the setup time or reduce the need for setup
*	Level of experience	long-time user	be able to archive my flashcards that I may not have used for a long time	can retrieve them in future should I want to use them
*	Level of experience	long-time user	be able to quickly search through my large library of cards easily and quickly
*	Level of experience	expert user	be able to set up questions in batches	can prepare flashcards faster
*	Level of experience	experienced user	be able to delete multiple flashcards that are no longer relevant to me (multi-delete function)
*	User collaboration	helpful user	be able to export and share my flashcards with my friends	can help them save time in generating their own set of flashcards (and they can help me too!)
*	User collaboration	competitive user	be able to compete with my friends based on how fast and how mnay flashcards we can get correct	will be more motivated to learn

Use cases

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

Use case: Add a flashcard

Guarantees

• A flashcard is added only if all of its information is provided.

MSS

1. User requests to add a new flashcard.
2. User provides information regarding the flashcard they want to add.

3. LingoGO! creates and adds a new flashcard.

   Use case ends.

Extensions

• 2a. Flashcard that the user wants to add is a duplicate of a flashcard already present in LingoGO!

  • 2a1. LingoGO! shows an error message.

    Use case resumes at step 1.

• 2b. Information provided by the user in incomplete.

  • 2b1. LingoGO! shows an error message.

    Use case resumes at step 1.

Use case: Delete a flashcard

MSS

1. User requests to list out all flashcards.
2. LingoGO! shows a list of flashcards.
3. User requests to delete a specific flashcard from the list.

4. LingoGO! deletes the flashcard.

   Use case ends.

Extensions

• 2a. The list is empty.

  Use case ends.

• 3a. The given index is invalid.

  • 3a1. LingoGO! shows an error message.

    Use case resumes at step 2.

Use case: Edit a flashcard

Guarantees

• A flashcard will be edited only if the edited information provided is valid.

MSS

1. User requests to list out all flashcards.
2. LingoGO! shows a list of flashcards.
3. User requests to edit a specific flashcard from the list.
4. User provides the updated information for the flashcard.

5. LingoGO! updates the flashcard with the information.

   Use case ends.

Extensions

• 2a. The list is empty.

  Use case ends.

• 3a. The given index is invalid.

  • 3a1. LingoGO! shows an error message.

    Use case resumes at step 2.

• 4a. The user does not provide any information.

  • 4a1. LingoGO! shows an error message.

    Use case resumes at step 2.

• 4b. The user provides information that causes the flashcard to become a duplicate of another flashcard in LingoGO!

  • 4b1. LingoGO! shows an error message.

    Use case resumes at step 2.

Use case: Flip a flashcard

MSS

1. User requests to toggle whether a flashcard’s answer can be seen.

2. LingoGO! toggles the visibility of the flashcard’s answer.

   Use case ends.

Extensions

• 1a. The given index is invalid.

  • 1a1. LingoGO! shows an error message.

    Use case resumes at step 1.

Use case: Test a user

Preconditions: Flashcard tested is not showing its answer.

MSS

1. User provides an answer to a flashcard.

2. LingoGO! shows the user whether their answer is correct or not.

   Use case ends.

Extensions

• 1a. The given index is invalid.

  • 1a1. LingoGO! shows an error message.

    Use case resumes at step 1.

• 1b. The user does not provide an answer.

  • 1b1. LingoGO! shows an error message.

    Use case resumes at step 1.

Use case: Import flashcards

Guarantees

• Flashcards will only be imported if the information provided is complete.

MSS

1. User creates a file containing information about flashcard questions and their corresponding answers.
2. User requests to import the information in the file into LingoGO!

3. LingoGO! creates and adds new flashcards to the current list of flashcards according to the information provided in the file.

   Use case ends.

Extensions

• 2a. Information provided in the file is incomplete.
  • 2a1. LingoGO! shows an error message.

  • 2a2. User checks and edits the file to fill in any missing information.

    Steps 2a1-2a2 are repeated until the data in the file is complete.

    Use case resumes from step 3.

• 2b. One or more flashcards in the file are duplicates of flashcards currently in LingoGO!

  • 2b1. LingoGO! shows a warning message.

    Use case resumes from step 3, with LingoGO! skipping the creation and addition of the duplicate flashcards.

Use case: Export flashcards

MSS

1. User requests to export all flashcards.

2. LingoGO! creates a file containing all information on each flashcard.

   Use case ends.

Extensions

• 1a. There are no flashcards present.

  • 1a1. LingoGO! shows a warning message.

    Use case ends.

• 1b. The file name and file path is not specified.

  • 1b1. LingoGO! creates a file with a default name in a default directory that will contain all information on each flashcard.

    Use case ends.

Use case: Request for help

MSS

1. User requests for help.

2. LingoGO! shows user a help message.

   Use case ends.

Non-Functional Requirements

1. Should work on any mainstream OS as long as it has Java 11 or above installed.
2. Should be able to hold up to 1000 flashcards 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. Should be usable to someone who has never used flashcards before.

Glossary

• Mainstream OS: Windows, Linux, Unix, OS-X
• Flashcard: A memory aid that users can use to input a phrase or word in the language that they are learning along with a hidden translation

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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 …​ }