IMessenger

IMessenger is a modern Android messaging application designed for school environments, facilitating communication between students, alumni, and administration.

Features

• User Authentication: Secure login and registration using Firebase Authentication (Email/Password & Google Sign-In).
• Real-time Messaging: Instant messaging with individuals and groups using Firebase Firestore.
• Group Chats:
  • Class Groups: Automatically added based on student level.
  • Club Groups: Join clubs and societies.
  • Alumni Network: Dedicated channel for alumni.
  • Public Channels: General school announcements.
  • Event Channels: Discussions for upcoming events.
• Profile Management: Edit profile details, view other users' profiles.
• Dark Mode: Fully supported dark theme for comfortable viewing at night.
• Push Notifications: Receive alerts for new messages (FCM).
• Modern UI: Clean, responsive interface built with Material Design components.

Architecture

The application follows the MVVM (Model-View-ViewModel) architectural pattern combined with the Single Activity Architecture recommended by Google. This ensures a robust, testable, and maintainable codebase.

• Single Activity: MainActivity serves as the entry point and container for the entire application, hosting various Fragments via the Navigation Component.
• Navigation Component: Manages app navigation, including the back stack, deep linking, and fragment transitions with animations.
• Model: Represents the data and business logic (e.g., User, ChatMessage, Group).
• View: UI components (Fragments) that observe the ViewModel and update the UI.
• ViewModel: Acts as a bridge between the View and the Repository, holding UI-related data and handling logic.
• Repository: Manages data operations, abstracting the data sources (Firebase Firestore, Auth). Implemented as Singletons to ensure a single source of truth and efficient resource management.
• AppExecutors: A centralized thread pool manager to handle background operations (disk, network) efficiently, preventing thread explosion and UI jank.

Key Components

• Repositories: AuthRepository, ChatRepository, UserRepository (Singleton Pattern).
• ViewModels: LoginViewModel, RegisterViewModel, ChatListViewModel, ChatViewModel, ProfileViewModel.
• Fragments: LoginFragment, ChatListFragment, ChatFragment, ProfileFragment, SettingsFragment, etc.
• Navigation: nav_graph.xml defines the application flow and transitions.

Tech Stack

• Language: Java
• Backend: Firebase (Authentication, Firestore, Storage, Cloud Messaging)
• UI: XML Layouts, Material Design Components (Material 3 recommended), AndroidX
• Navigation: Android Jetpack Navigation Component
• Image Loading: Glide
• Architecture: MVVM, Single Activity, Android Jetpack (ViewModel, LiveData, ViewBinding)

Setup

1. Clone the repository.
2. Open the project in Android Studio.
3. Connect the project to your Firebase Console project.
   • Add google-services.json to the app/ directory.
   • Enable Authentication (Email/Password, Google).
   • Enable Firestore Database.
   • Enable Cloud Messaging.
4. Build and run the application.

Roadmap

See roadmap.md for future plans.

Security & Maintenance

Security Enhancements

• End-to-End Encryption: Implemented AES-256 GCM (Galois/Counter Mode) with NoPadding for secure message encryption.
  • Messages are encrypted before being sent to Firestore.
  • Prevents plain-text data leakage in the database.
  • Includes integrity checks (Auth Tag) and random IVs for each message.
• Safety Checks: The application now strictly prevents sending messages if encryption fails, ensuring no plain-text messages are ever stored.

Code Maintenance

• Cleanup: Removed unused test boilerplate (ExampleUnitTest, ExampleInstrumentedTest) to keep the codebase clean.
• Optimization: Improved ChatRepository listener management to prevent memory leaks and duplicate message handling.