People.connect - Developer Guide

By: Team SE-EDU Since: Jun 2016 Licence: MIT

1. Setting up
2. Design
3. Implementation
4. Documentation
5. Testing
6. Dev Ops
Appendix A: Suggested Programming Tasks to Get Started
- A.1. Improving each component
- A.2. Creating a new command: remark
Appendix B: User Stories
Appendix C: Use Cases
Appendix D: Non Functional Requirements
Appendix E: Glossary
Appendix F: Product Survey

1. Setting up

1.1. Prerequisites

JDK 1.8.0_60 or later

Having any Java 8 version is not enough.
This app will not work with earlier versions of Java 8.
IntelliJ IDE

IntelliJ by default has Gradle and JavaFx plugins installed.
Do not disable them. If you have disabled them, go to File > Settings > Plugins to re-enable them.

1.2. Setting up the project in your computer

Fork this repo, and clone the fork to your computer
Open IntelliJ (if you are not in the welcome screen, click File > Close Project to close the existing project dialog first)
Set up the correct JDK version for Gradle
1. Click Configure > Project Defaults > Project Structure
2. Click New… and find the directory of the JDK
Click Import Project
Locate the build.gradle file and select it. Click OK
Click Open as Project
Click OK to accept the default settings
Open a console and run the command gradlew processResources (Mac/Linux: ./gradlew processResources). It should finish with the BUILD SUCCESSFUL message.
This will generate all resources required by the application and tests.

1.3. Verifying the setup

Run the seedu.address.MainApp and try a few commands
Run the tests to ensure they all pass.

1.4. Configurations to do before writing code

1.4.1. Configuring the coding style

This project follows oss-generic coding standards. IntelliJ’s default style is mostly compliant with ours but it uses a different import order from ours. To rectify,

Go to File > Settings… (Windows/Linux), or IntelliJ IDEA > Preferences… (macOS)
Select Editor > Code Style > Java
Click on the Imports tab to set the order
- For Class count to use import with '*' and Names count to use static import with '*': Set to 999 to prevent IntelliJ from contracting the import statements
- For Import Layout: The order is import static all other imports, import java.*, import javax.*, import org.*, import com.*, import all other imports. Add a <blank line> between each import

Optionally, you can follow the UsingCheckstyle.adoc document to configure Intellij to check style-compliance as you write code.

1.4.2. Updating documentation to match your fork

After forking the repo, links in the documentation will still point to the se-edu/addressbook-level4 repo. If you plan to develop this as a separate product (i.e. instead of contributing to the se-edu/addressbook-level4) , you should replace the URL in the variable repoURL in DeveloperGuide.adoc and UserGuide.adoc with the URL of your fork.

1.4.3. Setting up CI

Set up Travis to perform Continuous Integration (CI) for your fork. See UsingTravis.adoc to learn how to set it up.

Optionally, you can set up AppVeyor as a second CI (see UsingAppVeyor.adoc).

Having both Travis and AppVeyor ensures your App works on both Unix-based platforms and Windows-based platforms (Travis is Unix-based and AppVeyor is Windows-based)

1.4.4. Getting started with coding

When you are ready to start coding,

Get some sense of the overall design by reading the Architecture section.
Take a look at the section Suggested Programming Tasks to Get Started.

2. Design

2.1. Architecture

Figure 2.1.1 : Architecture Diagram

The Architecture Diagram given above explains the high-level design of the App. Given below is a quick overview of each component.

The .pptx files used to create diagrams in this document can be found in the diagrams folder. To update a diagram, modify the diagram in the pptx file, select the objects of the diagram, and choose Save as picture.

Main has only one class called 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 method where necessary.

Commons represents a collection of classes used by multiple other components. Two of those classes play important roles at the architecture level.

EventsCenter : This class (written using Google’s Event Bus library) is used by components to communicate with other components using events (i.e. a form of Event Driven design)
LogsCenter : Used by many classes to write log messages to the App’s log file.

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.

Each of the four components

Defines its API in an interface with the same name as the Component.
Exposes its functionality using a {Component Name}Manager class.

For example, the Logic component (see the class diagram given below) defines it’s API in the Logic.java interface and exposes its functionality using the LogicManager.java class.

Figure 2.1.2 : Class Diagram of the Logic Component

Events-Driven nature of the design

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

Figure 2.1.3a : Component interactions for delete 1 command (part 1)

Note how the Model simply raises a AddressBookChangedEvent when the Address Book data are changed, instead of asking the Storage to save the updates to the hard disk.

The diagram below shows how the EventsCenter reacts to that event, which eventually results in the updates being saved to the hard disk and the status bar of the UI being updated to reflect the 'Last Updated' time.

Figure 2.1.3b : Component interactions for delete 1 command (part 2)

Note how the event is propagated through the EventsCenter to the Storage and UI without Model having to be coupled to either of them. This is an example of how this Event Driven approach helps us reduce direct coupling between components.

The sections below give more details of each component.

2.2. UI component

Figure 2.2.1 : Structure of the UI Component

API : Ui.java

The UI consists of a MainWindow that is made up of parts e.g.CommandBox, ResultDisplay, PersonListPanel, StatusBarFooter, MapsPanel etc. All these, including the MainWindow, inherit from the abstract UiPart class.

The UI component uses 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.
Binds itself to some data in the Model so that the UI can auto-update when data in the Model change.
Responds to events raised from various parts of the App and updates the UI accordingly.

2.3. Logic component

Figure 2.3.1 : Structure of the Logic Component

Figure 2.3.2 : Structure of Commands in the Logic Component. This diagram shows finer details concerning XYZCommand and Command in Figure 2.3.1

API : Logic.java

Logic uses the AddressBookParser class to parse the user command.
This results in a Command object which is executed by the LogicManager.
The command execution can affect the Model (e.g. adding a person) and/or raise events.
The result of the command execution is encapsulated as a CommandResult object which is passed back to the Ui.

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

Figure 2.3.1 : Interactions Inside the Logic Component for the delete 1 Command

2.4. Model component

Figure 2.4.1 : Structure of the Model Component

API : Model.java

The Model,

stores a UserPref object that represents the user’s preferences.
stores the Address Book data.
exposes an unmodifiable ObservableList<ReadOnlyPerson> 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.
does not depend on any of the other three components.

2.5. Storage component

Figure 2.5.1 : Structure of the Storage Component

API : Storage.java

The Storage component,

can save UserPref objects in json format and read it back.
can save the Address Book data in xml format and read it back.

2.6. Common classes

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

3. Implementation

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

3.1. Undo/Redo mechanism

The undo/redo mechanism is facilitated by an UndoRedoStack, which resides inside LogicManager. It supports undoing and redoing of commands that modifies the state of the address book (e.g. add, edit). Such commands will inherit from UndoableCommand.

UndoRedoStack only deals with UndoableCommands. Commands that cannot be undone will inherit from Command instead. The following diagram shows the inheritance diagram for commands:

As you can see from the diagram, UndoableCommand adds an extra layer between the abstract Command class and concrete commands that can be undone, such as the DeleteCommand. Note that extra tasks need to be done when executing a command in an undoable way, such as saving the state of the address book before execution. UndoableCommand contains the high-level algorithm for those extra tasks while the child classes implements the details of how to execute the specific command. Note that this technique of putting the high-level algorithm in the parent class and lower-level steps of the algorithm in child classes is also known as the template pattern.

Commands that are not undoable are implemented this way:

public class ListCommand extends Command {
    @Override
    public CommandResult execute() {
        // ... list logic ...
    }
}

With the extra layer, the commands that are undoable are implemented this way:

public abstract class UndoableCommand extends Command {
    @Override
    public CommandResult execute() {
        // ... undo logic ...

        executeUndoableCommand();
    }
}

public class DeleteCommand extends UndoableCommand {
    @Override
    public CommandResult executeUndoableCommand() {
        // ... delete logic ...
    }
}

Suppose that the user has just launched the application. The UndoRedoStack will be empty at the beginning.

The user executes a new UndoableCommand, delete 5, to delete the 5th person in the address book. The current state of the address book is saved before the delete 5 command executes. The delete 5 command will then be pushed onto the undoStack (the current state is saved together with the command).

As the user continues to use the program, more commands are added into the undoStack. For example, the user may execute add n/David … to add a new person.

If a command fails its execution, it will not be pushed to the UndoRedoStack at all.

The user now decides that adding the person was a mistake, and decides to undo that action using undo.

We will pop the most recent command out of the undoStack and push it back to the redoStack. We will restore the address book to the state before the add command executed.

If the undoStack is empty, then there are no other commands left to be undone, and an Exception will be thrown when popping the undoStack.

The following sequence diagram shows how the undo operation works:

The redo does the exact opposite (pops from redoStack, push to undoStack, and restores the address book to the state after the command is executed).

If the redoStack is empty, then there are no other commands left to be redone, and an Exception will be thrown when popping the redoStack.

The user now decides to execute a new command, clear. As before, clear will be pushed into the undoStack. This time the redoStack is no longer empty. It will be purged as it no longer make sense to redo the add n/David command (this is the behavior that most modern desktop applications follow).

Commands that are not undoable are not added into the undoStack. For example, list, which inherits from Command rather than UndoableCommand, will not be added after execution:

The following activity diagram summarize what happens inside the UndoRedoStack when a user executes a new command:

3.1.1. Design Considerations

Aspect: Implementation of UndoableCommand
Alternative 1 (current choice): Add a new abstract method executeUndoableCommand()
Pros: We will not lose any undone/redone functionality as it is now part of the default behaviour. Classes that deal with Command do not have to know that executeUndoableCommand() exist.
Cons: Hard for new developers to understand the template pattern.
Alternative 2: Just override execute()
Pros: Does not involve the template pattern, easier for new developers to understand.
Cons: Classes that inherit from UndoableCommand must remember to call super.execute(), or lose the ability to undo/redo.

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.

Aspect: Type of commands that can be undone/redone
Alternative 1 (current choice): Only include commands that modifies the address book (add, clear, edit).
Pros: We only revert changes that are hard to change back (the view can easily be re-modified as no data are lost).
Cons: User might think that undo also applies when the list is modified (undoing filtering for example), only to realize that it does not do that, after executing undo.
Alternative 2: Include all commands.
Pros: Might be more intuitive for the user.
Cons: User have no way of skipping such commands if he or she just want to reset the state of the address book and not the view.
Additional Info: See our discussion here.

Aspect: Data structure to support the undo/redo commands
Alternative 1 (current choice): Use separate stack for undo and redo
Pros: Easy to understand for new Computer Science student undergraduates to understand, who are likely to be the new incoming developers of our project.
Cons: Logic is duplicated twice. For example, when a new command is executed, we must remember to update both HistoryManager and UndoRedoStack.
Alternative 2: Use HistoryManager for undo/redo
Pros: We do not need to maintain a separate stack, and just reuse what is already in the codebase.
Cons: Requires dealing with commands that have already been undone: We must remember to skip these commands. Violates Single Responsibility Principle and Separation of Concerns as HistoryManager now needs to do two different things.

3.2. Sort mechanism

The sort mechanism is facilitated the AddressBookParser where the sort command will be called.
When a sort command is executed, the sort command will conduct a sort on the current list in the address book based on the full name in alphabetical order.

The following sequence diagram shows how the sort operation works:

The following activity diagram summarize what happens inside the Sort Command when a user executes the command:

3.2.1. Design Considerations

Aspect: Implementation of SortCommand
Alternative 1 (current choice): Sort list by the sort command parser to sort the current ObservableList<ReadOnlyPerson> person list.
Pros: We will not make any changes to the current internalList thus will not affect any other commands that we have implemented.
Cons: Hard for new developers to understand the way we sort the read only person list.
Alternative 2: Just sort the internalList
Pros: Does not involve the ObservableList, easier for new developers to understand.
Cons: Changes made to the internalList might affect other existing commands.

3.3. List mechanism

The list mechanism is assisted by two classes ListCommandParser residing in parser and PersonContainsKeywordsPredicate residing in person.
It supports the listing of contacts which do not modify the addressbook(e.g. Exit, Find). Such commands inherit from Command, unlike commands inheriting from UndoableCommand which modify the state of the address book.

The following sequence diagram shows how the list operation works:

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

3.3.1. Design Considerations

Aspect: Implementation of ListCommand
Alternative 1 (current choice): Add a new class ListCommandParser
Pros: We will be able to provide arguments to list only certain types of contacts
Cons: Hard for new developers to understand why we used list command instead of find to get contacts with certain tags.
Alternative 2: No parser class
Pros: Easier for new developers to understand
Cons: All contacts are listed every time which may be an issue if user is trying to filter contacts by tags

3.4. Locate mechanism

The locate mechanism is facilitated by an PersonPanelSelectionChangedEvent which resides in Events.
It supports locating an address on Google maps based on the person selected based on the index chosen.

The following sequence diagram shows how the locate operation works:

3.4.1. Design Considerations

Aspect: Implementation of LocateCommand
Alternative 1 (current choice): Add a new class LocateCommandParser
Pros: We will be able to provide arguments to locate a specific person
Cons: Hard for new developers to understand why we used locate command instead of using mouse to select a specific person.
Alternative 2: No locate command parser class
Pros: Easier for new developers to understand
Cons: Increase mouse usage instead of making full use of the Command Line Interface(CLI)

3.5. Logging

We are using java.util.logging package for logging. The LogsCenter class is used to manage the logging levels and logging destinations.

The logging level can be controlled using the logLevel setting in the configuration file (See Configuration)
The Logger for a class can be obtained using LogsCenter.getLogger(Class) which will log messages according to the specified logging level
Currently log messages are output through: Console and to a .log file.

Logging Levels

SEVERE : Critical problem detected which may possibly cause the termination of the application
WARNING : Can continue, but with caution
INFO : Information showing the noteworthy actions by the App
FINE : Details that is not usually noteworthy but may be useful in debugging e.g. print the actual list instead of just its size

3.6. Birthday attribute

Person class consists of five different attributes: Name, Address, Phone, Email and Birthday. Birthday class has a very similar implementation compared to the other attribute classes. New instance of Birthday is initialized by giving the constructor the parameter birthday in String format. The parameter is required to be non-null, and it is first validated before accepting it as a birthday value for the class.

Validation

The valid form for a birthday string is DD/MM/YYYY, where every character must be a digit except for the slashes. This validation is performed to prohibit the user from inputting something completely peculiar, for example a string of spaces or a long sequence of characters.

Examples for a valid birthday:

14/12/1993
22/02/2001
29/02/2008

The date of the birthday is validated using Java’s SimpleDateFormatter class. The formatter parses user’s input and if the parsing is successful, the date is valid. The parser also accounts for leap days.

3.7. Phone attribute

Person class consists of five different attributes: Name, Address, Phone, Email and Birthday. The Phone class
has implementation similar to other attribute classes. New instance of Phone is initialized through constructor. Important
thing to note here is the once the phone is validated to be only numbers, it is also followed by the conversion of phone
into the national convention format as well.

The conversion to national convention is done within the Phone class in the following way:

public Phone(String phone) throws IllegalValueException {
    // ... phone validation logic ...

    this.value = formatPhone(trimmedPhone);
}

public static String formatPhone(String trimmedPhone) {
    // ... variable declarations ...
    String formattedPhone = generateFormattedPhone(trimmedPhone, phoneLength);

    return formattedPhone;
}

Validation

The valid form of phone is xxxxxxxx with as many characters as the user want, but no less than 3. Every character must
be a digit and there should be no other character like +. This prevents the user to enter alphabets or other invalid
characters while entering phone numbers.

The example of valid phone numbers are:

6596631234
919911204422
15671237070

The example of invalid phone numbers are:

6596asd
+919911204422
12

The current validation allows the user to enter as many digits as he/she wants which is not the case in real life. The
numbers must be restricted to certain number of digits based on the country. Such validation will be performed in the future
version of the tool. The validation for number of digits will be quite extensive since different countries have different
number of digits in their phone numbers, which is the reason it is noe done yet.

3.8. Photo attribute

Person class consists of five different attributes: Name, Address, Phone, Email and Birthday. Photo class has a very similar implementation compared to the other attribute classes. New instance of Photo is initialized by giving the constructor the parameter photo in String format. The parameter is optional and if a file is not in the correct location, a default photo will be loaded on the address book.

Validation

The valid form for a birthday string is template.jpg, where both file name and file type must be valid. This validation is performed to prohibit the user from inputting something completely peculiar, for example a file name which only consists of numbers and a file type which is not an image.

Examples for a valid photo file name:

abc.jpg
JPG.png
EddyTan.jpg

Examples for a invalid photo file name:

.jpg
123.txt
EddyTan

3.9. Load command

Load command’s implementation is similar to other commands: LoadCommand class inherits UndoableCommand and load command’s parser implements Parser interface. The following sequence diagram shows the execution of command "load testbook.xml"

3.10. Configuration

Certain properties of the application can be controlled (e.g App name, logging level) through the configuration file (default: config.json).

4. Documentation

We use asciidoc for writing documentation.

We chose asciidoc over Markdown because asciidoc, although a bit more complex than Markdown, provides more flexibility in formatting.

4.1. Editing Documentation

See UsingGradle.adoc to learn how to render .adoc files locally to preview the end result of your edits. Alternatively, you can download the AsciiDoc plugin for IntelliJ, which allows you to preview the changes you have made to your .adoc files in real-time.

4.2. Publishing Documentation

See UsingTravis.adoc to learn how to deploy GitHub Pages using Travis.

4.3. Converting Documentation to PDF format

We use Google Chrome for converting documentation to PDF format, as Chrome’s PDF engine preserves hyperlinks used in webpages.

Here are the steps to convert the project documentation files to PDF format.

Follow the instructions in UsingGradle.adoc to convert the AsciiDoc files in the docs/ directory to HTML format.
Go to your generated HTML files in the build/docs folder, right click on them and select Open with → Google Chrome.
Within Chrome, click on the Print option in Chrome’s menu.
Set the destination to Save as PDF, then click Save to save a copy of the file in PDF format. For best results, use the settings indicated in the screenshot below.

Figure 5.6.1 : Saving documentation as PDF files in Chrome

5. Testing

5.1. Running Tests

There are three ways to run tests.

The most reliable way to run tests is the 3rd one. The first two methods might fail some GUI tests due to platform/resolution-specific idiosyncrasies.

Method 1: Using IntelliJ JUnit test runner

To run all tests, right-click on the src/test/java folder and choose Run 'All Tests'
To run a subset of tests, you can right-click on a test package, test class, or a test and choose Run 'ABC'

Method 2: Using Gradle

Open a console and run the command gradlew clean allTests (Mac/Linux: ./gradlew clean allTests)

See UsingGradle.adoc for more info on how to run tests using Gradle.

Method 3: Using Gradle (headless)

Thanks to the TestFX library we use, our GUI tests can be run in the headless mode. In the headless mode, GUI tests do not show up on the screen. That means the developer can do other things on the Computer while the tests are running.

To run tests in headless mode, open a console and run the command gradlew clean headless allTests (Mac/Linux: ./gradlew clean headless allTests)

5.2. Types of tests

We have two types of tests:

GUI Tests - These are tests involving the GUI. They include,
1. System Tests that test the entire App by simulating user actions on the GUI. These are in the systemtests package.
2. Unit tests that test the individual components. These are in seedu.address.ui package.
Non-GUI Tests - These are tests not involving the GUI. They include,
1. Unit tests targeting the lowest level methods/classes.
  e.g. seedu.address.commons.StringUtilTest
2. Integration tests that are checking the integration of multiple code units (those code units are assumed to be working).
  e.g. seedu.address.storage.StorageManagerTest
3. Hybrids of unit and integration tests. These test are checking multiple code units as well as how the are connected together.
  e.g. seedu.address.logic.LogicManagerTest

5.3. Troubleshooting Testing

Problem: HelpWindowTest fails with a NullPointerException.

Reason: One of its dependencies, UserGuide.html in src/main/resources/docs is missing.
Solution: Execute Gradle task processResources.

6. Dev Ops

6.1. Build Automation

See UsingGradle.adoc to learn how to use Gradle for build automation.

6.2. Continuous Integration

We use Travis CI and AppVeyor to perform Continuous Integration on our projects. See UsingTravis.adoc and UsingAppVeyor.adoc for more details.

6.3. Making a Release

Here are the steps to create a new release.

Update the version number in MainApp.java.
Generate a JAR file using Gradle.
Tag the repo with the version number. e.g. v0.1
Create a new release using GitHub and upload the JAR file you created.

6.4. Managing Dependencies

A project often depends on third-party libraries. For example, Address Book depends on the Jackson library for XML parsing. Managing these dependencies can be automated using Gradle. For example, Gradle can download the dependencies automatically, which is better than these alternatives.
a. Include those libraries in the repo (this bloats the repo size)
b. Require developers to download those libraries manually (this creates extra work for developers)

Appendix A: Suggested Programming Tasks to Get Started

Suggested path for new programmers:

First, add small local-impact (i.e. the impact of the change does not go beyond the component) enhancements to one component at a time. Some suggestions are given in this section Improving a Component.
Next, add a feature that touches multiple components to learn how to implement an end-to-end feature across all components. The section Creating a new command: remark explains how to go about adding such a feature.

A.1. Improving each component

Each individual exercise in this section is component-based (i.e. you would not need to modify the other components to get it to work).

`Logic` component

Do take a look at the Design: Logic Component section before attempting to modify the Logic component.

Add a shorthand equivalent alias for each of the individual commands. For example, besides typing clear, the user can also type c to remove all persons in the list.
- Hints
  
  Just like we store each individual command word constant COMMAND_WORD inside *Command.java (e.g. FindCommand#COMMAND_WORD, DeleteCommand#COMMAND_WORD), you need a new constant for aliases as well (e.g. FindCommand#COMMAND_ALIAS).
  
  AddressBookParser is responsible for analyzing command words.
- Solution
  
  Modify the switch statement in AddressBookParser#parseCommand(String) such that both the proper command word and alias can be used to execute the same intended command.
  
  See this PR for the full solution.

`Model` component

Do take a look at the Design: Model Component section before attempting to modify the Model component.

Add a removeTag(Tag) method. The specified tag will be removed from everyone in the address book.
- Hints
  
  The Model API needs to be updated.
  
  Find out which of the existing API methods in AddressBook and Person classes can be used to implement the tag removal logic. AddressBook allows you to update a person, and Person allows you to update the tags.
- Solution
  
  Add the implementation of deleteTag(Tag) method in ModelManager. Loop through each person, and remove the tag from each person.
  
  See this PR for the full solution.

`Ui` component

Do take a look at the Design: UI Component section before attempting to modify the UI component.

Use different colors for different tags inside person cards. For example, friends tags can be all in grey, and colleagues tags can be all in red.

Before

After
- Hints
  
  The tag labels are created inside PersonCard#initTags(ReadOnlyPerson) (new Label(tag.tagName)). JavaFX’s Label class allows you to modify the style of each Label, such as changing its color.
  
  Use the .css attribute -fx-background-color to add a color.
- Solution
  
  See this PR for the full solution.
Modify NewResultAvailableEvent such that ResultDisplay can show a different style on error (currently it shows the same regardless of errors).

Before

After
- Hints
  
  NewResultAvailableEvent is raised by CommandBox which also knows whether the result is a success or failure, and is caught by ResultDisplay which is where we want to change the style to.
  
  Refer to CommandBox for an example on how to display an error.
- Solution
  
  Modify NewResultAvailableEvent 's constructor so that users of the event can indicate whether an error has occurred.
  
  Modify ResultDisplay#handleNewResultAvailableEvent(event) to react to this event appropriately.
  
  See this PR for the full solution.
Modify the StatusBarFooter to show the total number of people in the address book.

Before

After
- Hints
  
  StatusBarFooter.fxml will need a new StatusBar. Be sure to set the GridPane.columnIndex properly for each StatusBar to avoid misalignment!
  
  StatusBarFooter needs to initialize the status bar on application start, and to update it accordingly whenever the address book is updated.
- Solution
  
  Modify the constructor of StatusBarFooter to take in the number of persons when the application just started.
  
  Use StatusBarFooter#handleAddressBookChangedEvent(AddressBookChangedEvent) to update the number of persons whenever there are new changes to the addressbook.
  
  See this PR for the full solution.

`Storage` component

Do take a look at the Design: Storage Component section before attempting to modify the Storage component.

Add a new method backupAddressBook(ReadOnlyAddressBook), so that the address book can be saved in a fixed temporary location.
- Hint
  
  Add the API method in AddressBookStorage interface.
  
  Implement the logic in StorageManager class.
- Solution
  
  See this PR for the full solution.

A.2. Creating a new command: `remark`

By creating this command, you will get a chance to learn how to implement a feature end-to-end, touching all major components of the app.

A.2.1. Description

Edits the remark for a person specified in the INDEX.
Format: remark INDEX r/[REMARK]

Examples:

remark 1 r/Likes to drink coffee.
Edits the remark for the first person to Likes to drink coffee.
remark 1 r/
Removes the remark for the first person.

A.2.2. Step-by-step Instructions

[Step 1] Logic: Teach the app to accept 'remark' which does nothing

Let’s start by teaching the application how to parse a remark command. We will add the logic of remark later.

Main:

Add a RemarkCommand that extends UndoableCommand. Upon execution, it should just throw an Exception.
Modify AddressBookParser to accept a RemarkCommand.

Tests:

Add RemarkCommandTest that tests that executeUndoableCommand() throws an Exception.
Add new test method to AddressBookParserTest, which tests that typing "remark" returns an instance of RemarkCommand.

[Step 2] Logic: Teach the app to accept 'remark' arguments

Let’s teach the application to parse arguments that our remark command will accept. E.g. 1 r/Likes to drink coffee.

Main:

Modify RemarkCommand to take in an Index and String and print those two parameters as the error message.
Add RemarkCommandParser that knows how to parse two arguments, one index and one with prefix 'r/'.
Modify AddressBookParser to use the newly implemented RemarkCommandParser.

Tests:

Modify RemarkCommandTest to test the RemarkCommand#equals() method.
Add RemarkCommandParserTest that tests different boundary values for RemarkCommandParser.
Modify AddressBookParserTest to test that the correct command is generated according to the user input.

[Step 3] Ui: Add a placeholder for remark in `PersonCard`

Let’s add a placeholder on all our PersonCard s to display a remark for each person later.

Main:

Add a Label with any random text inside PersonListCard.fxml.
Add FXML annotation in PersonCard to tie the variable to the actual label.

Tests:

Modify PersonCardHandle so that future tests can read the contents of the remark label.

[Step 4] Model: Add `Remark` class

We have to properly encapsulate the remark in our ReadOnlyPerson class. Instead of just using a String, let’s follow the conventional class structure that the codebase already uses by adding a Remark class.

Main:

Add Remark to model component (you can copy from Address, remove the regex and change the names accordingly).
Modify RemarkCommand to now take in a Remark instead of a String.

Tests:

Add test for Remark, to test the Remark#equals() method.

[Step 5] Model: Modify `ReadOnlyPerson` to support a `Remark` field

Now we have the Remark class, we need to actually use it inside ReadOnlyPerson.

Main:

Add three methods setRemark(Remark), getRemark() and remarkProperty(). Be sure to implement these newly created methods in Person, which implements the ReadOnlyPerson interface.
You may assume that the user will not be able to use the add and edit commands to modify the remarks field (i.e. the person will be created without a remark).
Modify SampleDataUtil to add remarks for the sample data (delete your addressBook.xml so that the application will load the sample data when you launch it.)

[Step 6] Storage: Add `Remark` field to `XmlAdaptedPerson` class

We now have Remark s for Person s, but they will be gone when we exit the application. Let’s modify XmlAdaptedPerson to include a Remark field so that it will be saved.

Main:

Add a new Xml field for Remark.
Be sure to modify the logic of the constructor and toModelType(), which handles the conversion to/from ReadOnlyPerson.

Tests:

Fix validAddressBook.xml such that the XML tests will not fail due to a missing <remark> element.

[Step 7] Ui: Connect `Remark` field to `PersonCard`

Our remark label in PersonCard is still a placeholder. Let’s bring it to life by binding it with the actual remark field.

Main:

Modify PersonCard#bindListeners() to add the binding for remark.

Tests:

Modify GuiTestAssert#assertCardDisplaysPerson(…) so that it will compare the remark label.
In PersonCardTest, call personWithTags.setRemark(ALICE.getRemark()) to test that changes in the Person 's remark correctly updates the corresponding PersonCard.

[Step 8] Logic: Implement `RemarkCommand#execute()` logic

We now have everything set up… but we still can’t modify the remarks. Let’s finish it up by adding in actual logic for our remark command.

Main:

Replace the logic in RemarkCommand#execute() (that currently just throws an Exception), with the actual logic to modify the remarks of a person.

Tests:

Update RemarkCommandTest to test that the execute() logic works.

A.2.3. Full Solution

See this PR for the step-by-step solution.

Appendix B: User Stories

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

Priority As a … I want to … So that I can…

Priority	As a …	I want to …	So that I can…
`* * *`	new user	see usage instructions	refer to instructions when I forget how to use the App
`* * *`	user	add a new person
`* * *`	user	delete a person	remove entries that I no longer need
`* * *`	user	find a person by name	locate details of persons without having to go through the entire list
`* * *`	user	add birth dates	wish people on their birthdays
`* * *`	user with many persons in the address book	sort persons by name	locate a person easily
`* * *`	user with many persons in the address book	list people by tags	locate a person easily
`* * *`	user with many persons in the address book	have different colored tags	easily differentiate people based on different tags
`* *`	user	hide private contact details by default	minimize chance of someone else seeing them by accident
`* *`	user	add contacts from pre-existing address book	save time without entering the same contacts again
`* *`	user	auto-format phone number	easily figure out the country code or phone number
`* *`	user	add a picture of the person	make it easier for myself to identify the person
`* *`	user	find contacts in runtime	find contacts without typing the entire name
`* *`	user with many persons in the address book	set password to the address book	keep my contacts safe from others
`* *`	user with many persons in the address book	find a person by phone	locate details of a person without having to go through the entire list
`* *`	user with many persons in the address book	make groups of contacts	group relevant contacts together
`*`	user	add a picture of the person	make it easier for myself to identify the person
`* *`	user with many persons in the address book	see the contact details in grid view	find information faster
`*`	user	sync contacts from online services like facebook,google etc	add contacts directly without entering them
`*`	user	add prefix to name	assign proper designation to each name
`*`	user	add deadlines	so that I can finish tasks on time
`*`	user	use google maps to show me the address of person	navigate to that address
`*`	user	add homepage for the person	see the persons further details or publications if need be
`*`	user	add notes to a person	add extra information about that person
`*`	user	add twitter id	remain updated with their twitter posts
`*`	user	add multiple phone numbers to a person	know multiple ways to contact a person
`*`	user	enter the location for storage file	store my contacts anywhere I want
`*`	user	see the emails or messages exchanged with person	see the history of interaction with the person
`*`	user	receive notification for birthday	call or text the person to wish him/her
`*`	user	have alternate themes for the app	change look of the app if I get bored with one theme
`*`	user with many persons in the address book	add job title and department to a person	know the profession of each entry
`*`	user with many persons in the address book	find persons by group	locate details of persons belonging to particular group
`*`	user with many persons in the address book	see the number of searches performed on a person	see the people I search for the most
`*`	user with many persons in the address book	add connections to a person	connect different people in the list
`*`	user with many persons in the address book	see the number of connections made by person	see the people with most connections
`*`	user	add a person with incomplete details	add a person and fill incomplete entries later

* * *

new user

see usage instructions

refer to instructions when I forget how to use the App

* * *

user

add a new person

* * *

user

delete a person

remove entries that I no longer need

* * *

user

find a person by name

locate details of persons without having to go through the entire list

* * *

user

add birth dates

wish people on their birthdays

* * *

user with many persons in the address book

sort persons by name

locate a person easily

* * *

user with many persons in the address book

list people by tags

locate a person easily

* * *

user with many persons in the address book

have different colored tags

easily differentiate people based on different tags

* *

user

hide private contact details by default

minimize chance of someone else seeing them by accident

* *

user

add contacts from pre-existing address book

save time without entering the same contacts again

* *

user

auto-format phone number

easily figure out the country code or phone number

* *

user

add a picture of the person

make it easier for myself to identify the person

* *

user

find contacts in runtime

find contacts without typing the entire name

* *

user with many persons in the address book

set password to the address book

keep my contacts safe from others

* *

user with many persons in the address book

find a person by phone

locate details of a person without having to go through the entire list

* *

user with many persons in the address book

make groups of contacts

group relevant contacts together

*

user

add a picture of the person

make it easier for myself to identify the person

* *

user with many persons in the address book

see the contact details in grid view

find information faster

*

user

sync contacts from online services like facebook,google etc

add contacts directly without entering them

*

user

add prefix to name

assign proper designation to each name

*

user

add deadlines

so that I can finish tasks on time

*

user

use google maps to show me the address of person

navigate to that address

*

user

add homepage for the person

see the persons further details or publications if need be

*

user

add notes to a person

add extra information about that person

*

user

add twitter id

remain updated with their twitter posts

*

user

add multiple phone numbers to a person

know multiple ways to contact a person

*

user

enter the location for storage file

store my contacts anywhere I want

*

user

see the emails or messages exchanged with person

see the history of interaction with the person

*

user

receive notification for birthday

call or text the person to wish him/her

*

user

have alternate themes for the app

change look of the app if I get bored with one theme

*

user with many persons in the address book

add job title and department to a person

know the profession of each entry

*

user with many persons in the address book

find persons by group

locate details of persons belonging to particular group

*

user with many persons in the address book

see the number of searches performed on a person

see the people I search for the most

*

user with many persons in the address book

add connections to a person

connect different people in the list

*

user with many persons in the address book

see the number of connections made by person

see the people with most connections

*

user

add a person with incomplete details

add a person and fill incomplete entries later

{More to be added}

Appendix C: Use Cases

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

Use case: Delete person

MSS

User requests to list persons
AddressBook shows a list of persons
User requests to delete a specific person in the list
AddressBook deletes the person

Use case ends.

Extensions

2a. The list is empty.

Use case ends.
3a. The given index is invalid.
- 3a1. AddressBook shows an error message.
  
  Use case resumes at step 2.

C.1. Use case: Find contact’s birthday

MSS

User searches for specific person.
AddressBook shows the person for the user.
User checks person’s birthday.

Use case ends.

Extensions

1a. The searched person is not in the AddressBook.

Use case ends.

C.2. Use case: List people with a specific tag

MSS

User specifies the tag she wants to be searched.
The AddressBook shows the contacts with the searched tag.

Use case ends.

Extensions

1a. No contacts are found.

Use case ends.

C.3. Use case: Sort contacts by name

MSS

User lists all the contacts.
AddressBook shows the contacts in the order they were added to the AddressBook.
User sorts the contacts.
AddressBook lists all the contacts sorted by the their name.

Use case ends.

Extensions

2a. There are no contacts.

Use case ends.

{More to be added}

Appendix D: Non Functional Requirements

Should work on any mainstream OS as long as it has Java 1.8.0_60 or higher installed.
Should be able to hold up to 1000 persons without a noticeable sluggishness in performance for typical usage.
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.
Should not use more than 5 sec as a start up time.
Should respond within 1 sec of giving a command.
Should use at most 4 mb of memory.
Should not take more than 10 minutes for user to learn to use the system.
Should not use more than 30 % of CPU resources during command execution.
Should display all entries in a list perfectly correctly on every command.
Should not have any unhandled exceptions from wrong user input.
Should be easy to install by user without any assistance.
Should have consistent display formats for all commands.

{More to be added}

Appendix E: Glossary

Mainstream OS

Windows, Linux, Unix, OS-X

Private contact detail

A contact detail that is not meant to be shared with others

Appendix F: Product Survey

Product Name

Author: …

Pros:

Cons:

People.connect - Developer Guide

Events-Driven nature of the design

Logic component

Model component

Ui component

Storage component

Use case: Delete person

`Logic` component

`Model` component

`Ui` component

`Storage` component