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Chat Overview

1. Overall Feature Overview​

The Chat feature enables real-time text-based communication between users within the application, primarily facilitating interaction between tutors and students. It allows users to:

  • View a list of their ongoing conversations.
  • Initiate new chats with other users.
  • Send and receive messages within a dedicated chat screen.

The feature is primarily composed of three main UI components: MessagesPage for listing existing chats, NewChatPage for starting new conversations, and ChatScreen for the actual messaging interface. Data persistence and real-time updates are handled by Firebase Firestore, accessed through the ChatRepository (from the core module) and direct Firestore SDK calls in the UI components.

2. Chat List Sub-Feature (MessagesPage)​

2.1. Overview​

The MessagesPage displays a list of all chat conversations the current user is a part of. Each item in the list typically shows the name of the other participant and the last message exchanged. Tapping on a conversation navigates the user to the ChatScreen for that specific chat. This page also includes basic internet connectivity checking.

2.2. Class Diagram (MessagesPage)​

Key Relationships:​

  • MessagesPage is a StatefulWidget managing _MessagesPageState.
  • _MessagesPageState uses StreamBuilder to listen to chat data from FirebaseFirestore.
  • For each chat, it uses a FutureBuilder to fetch the other participant's name from FirebaseFirestore.
  • It uses FirebaseAuth to get the current user's ID.
  • It uses the connectivity_plus package to check and monitor network status.
  • Tapping a chat item navigates to the ChatScreen.

2.3. Sequence Diagram: Loading and Displaying Chats​

2.4. State Management​

The MessagesPage primarily uses:

  • Local StatefulWidget state (isConnected).
  • StreamBuilder to reactively display the list of chats based on real-time data from FirebaseFirestore.
  • FutureBuilder nested within the StreamBuilder's item builder to asynchronously fetch and display the names of other participants in each chat.
  • The connectivity_plus package stream to update the isConnected state.

No dedicated BLoC is used for this page; state is managed through Flutter's built-in mechanisms for handling asynchronous data and local UI state.

3. Start New Chat Sub-Feature (NewChatPage)​

3.1. Overview​

The NewChatPage allows the current user to browse a list of other registered users and initiate a new private chat conversation with any of them. If a chat already exists between the two users, it navigates to the existing ChatScreen; otherwise, it creates a new chat document in Firestore before navigating.

3.2. Class Diagram (NewChatPage)​

Key Relationships:​

  • NewChatPage is a StatelessWidget.
  • It uses a StreamBuilder to fetch and display a list of users from FirebaseFirestore, excluding the current user.
  • FirebaseAuth is used to get the currentUserId.
  • The _startChat method handles the logic of finding an existing chat or creating a new one in FirebaseFirestore.
  • Tapping a user navigates to the ChatScreen.

3.3. Sequence Diagram: Starting a New Chat​

3.4. State Management​

NewChatPage is a StatelessWidget.

  • It uses StreamBuilder to display the list of users reactively from FirebaseFirestore.
  • The logic for finding or creating a chat room is encapsulated within the _startChat method, which is called directly upon user interaction.

No dedicated BLoC or complex local state management is employed for this page.

4. Chat Screen Sub-Feature (ChatScreen)​

4.1. Overview​

The ChatScreen is the core messaging interface where users exchange text messages in real-time. It displays the history of messages in a conversation, ordered by time, and provides an input field for composing and sending new messages. User names for messages are fetched dynamically.

4.2. Class Diagram (ChatScreen)​

Key Relationships:​

  • ChatScreen is a StatefulWidget managing _ChatScreenState.
  • _ChatScreenState holds a TextEditingController for message input and references to FirebaseAuth and FirebaseFirestore.
  • It uses a StreamBuilder to listen for real-time messages from the specified chat's messages subcollection in Firestore.
  • Within the message list, it uses FutureBuilder to fetch the sender's name for each message (note: this could be optimized).
  • The sendMessage method handles adding new messages to Firestore and updating the main chat document's lastMessage field.

4.3. Sequence Diagram: Sending a Message​

4.4. Sequence Diagram: Receiving Messages​

4.5. State Management​

ChatScreen uses:

  • Local StatefulWidget state to manage the TextEditingController for the message input field (_messageController), the other user's name (otherUserName), and potentially loading states for fetching otherUserName.
  • StreamBuilder to reactively display the list of messages in real-time from FirebaseFirestore.
  • FutureBuilder within the message list item builder to fetch and display the sender's name for each message.

Similar to other chat components, it does not use a dedicated BLoC, relying on Flutter's built-in state management widgets for handling asynchronous data and UI updates.

5. External Dependencies for Chat Feature​

The Chat feature relies on the following key external packages:

  • cloud_firestore:
    • Purpose: Provides access to Google Cloud Firestore database.
    • Usage: Used extensively across MessagesPage, NewChatPage, and ChatScreen for storing, retrieving, and listening to real-time updates for chat rooms and messages. Also used to fetch user details (names).
  • firebase_auth:
    • Purpose: Handles user authentication with Firebase.
    • Usage: Used in all chat components to get the currentUserId for querying relevant chats/messages and identifying message senders.
  • connectivity_plus:
    • Purpose: Allows checking the network connectivity status of the device.
    • Usage: Used in MessagesPage to display an offline message if the user has no internet connection, preventing attempts to load chats.

These packages are fundamental to the chat feature's ability to provide real-time, persistent messaging.