# Requirements Document
Generated: Tuesday, September 16, 2025

## Functional Requirements (Developer-Facing)

### FR-001: Project Initialization
- **Description:** The system shall provide a developer-ready Angular project that can be set up with minimal effort.
- **Acceptance Criteria:**
    - A developer shall be able to clone the project from a Git repository.
    - A developer shall be able to install all required dependencies using a single `npm install` command.
    - A developer shall be able to start the local development server using the `ng serve` command.
    - The boilerplate shall compile without errors and be viewable in a web browser.
- **Priority:** High

### FR-002: Modular Architecture
- **Description:** The system shall be structured with a scalable and maintainable modular architecture.
- **Acceptance Criteria:**
    - The project shall include a `CoreModule` for providing singleton services and one-time imports.
    - The project shall include a `SharedModule` for reusable components, directives, and pipes.
    - The architecture shall support the creation of lazy-loaded `FeatureModules` to encapsulate business domain logic.
- **Priority:** High

### FR-003: Clarity Design System Integration
- **Description:** The system shall be fully integrated with the VMware Clarity Design System for UI components and styling.
- **Acceptance Criteria:**
    - All necessary Clarity npm packages shall be included as dependencies.
    - Clarity's global stylesheets and assets shall be correctly configured and loaded.
    - The boilerplate shall use Clarity components for its core layout (header, sidebar, etc.).
    - Developers shall be able to use any Clarity component within their feature modules.
- **Priority:** High

### FR-004: Responsive Application Layout
- **Description:** The system shall provide a default, responsive application layout.
- **Acceptance Criteria:**
    - The boilerplate shall include a main application shell with a header, a collapsible sidebar for navigation, and a main content area.
    - The layout shall adapt correctly to various screen sizes, including desktop, tablet, and mobile.
- **Priority:** High

### FR-005: Routing and Navigation
- **Description:** The system shall include a pre-configured routing system for navigating between different views.
- **Acceptance Criteria:**
    - The project shall have a main `AppRoutingModule`.
    - The boilerplate shall provide an example of a lazy-loaded feature route.
    - Navigation links in the sidebar shall correctly navigate to their corresponding routes.
- **Priority:** Medium

## Non-Functional Requirements

### NFR-001: Performance (Developer Experience)
- **Description:** The boilerplate should be optimized for a fast and efficient development workflow.
- **Acceptance Criteria:**
    - The initial `ng serve` compilation time shall be reasonably fast.
    - Live-reloading times during development shall be minimal.
    - The production build (`ng build --prod`) shall be optimized, with tree-shaking and minification enabled.
- **Priority:** Medium

### NFR-002: Usability (Developer Experience)
- **Description:** The codebase should be intuitive and easy for an Angular developer to understand and extend.
- **Acceptance Criteria:**
    - The project structure shall be logical and follow established Angular best practices.
    - The code shall be clean, well-formatted, and include comments for complex or non-obvious sections.
    - A comprehensive `README.txt` file shall guide developers on setup, architecture, and usage.
- **Priority:** High

### NFR-003: Maintainability
- **Description:** The codebase should be structured to allow for easy updates, modifications, and extensions.
- **Acceptance Criteria:**
    - The modular architecture shall allow for independent development and testing of features.
    - Dependencies shall be clearly defined in `package.json` and easy to update.
    - The separation of concerns between modules should be strictly enforced.
- **Priority:** High

## Data Requirements (Client-Side)

### Entity Modeling:
- **Description:** The boilerplate will not have predefined data models but will require developers to define them using TypeScript.
- **Attributes:**
    - Data models shall be defined as **TypeScript interfaces or classes**.
    - These models will represent the structure of data consumed from and sent to a backend API.

## Interface Requirements

### UI/UX Requirements (Frontend Boilerplate):
- **Layout:** A clean, professional single-page application layout based on the Clarity Design System.
- **Header:** A top header bar, typically containing the application title/logo and user-related actions (e.g., profile, logout).
- **Sidebar:** A collapsible vertical navigation sidebar containing links to different feature areas of the application.
- **Content Area:** A main content area where the components for the currently active route are displayed.
- **Styling:** Adherence to the styles and design tokens provided by the Clarity Design System.

### API Requirements (Backend Interaction):
- **Backend Agnostic:** The boilerplate is a frontend application and makes no assumptions about the backend technology stack.
- **Communication Protocol:** The boilerplate shall use Angular's `HttpClient` module to communicate with a backend over HTTP/HTTPS.
- **API Endpoint Configuration:** The base URL for the backend API shall be configurable via the `environments` files (e.g., `environment.ts`, `environment.prod.ts`).
- **Data Format:** The boilerplate is designed to work with APIs that transact data in **JSON** format.
- **Error Handling:** The architecture shall support a centralized way to handle API errors, typically through an `HttpInterceptor` provided in the `CoreModule`.

---

## REQUIREMENTS UPDATE - 2025-10-10 04:17:44


# Requirements Document
Generated: 2025-10-10T[timestamp]

## Functional Requirements

### FR-001: User Registration
-   **Description:** Allows new users to create an account by providing a unique username, email, and password.
-   **Acceptance Criteria:**
    -   Given I am on the registration page, When I input a unique username, valid email, and strong password (min 8 chars, alphanumeric), Then my account is successfully created, and I am automatically logged in.
    -   Given I am on the registration page, When I input a username or email that already exists, Then the system provides an error message indicating the conflict.
-   **Priority:** High

### FR-002: User Login/Logout
-   **Description:** Enables registered users to securely log into and out of the application.
-   **Acceptance Criteria:**
    -   Given I am on the login page, When I input my registered username/email and correct password, Then I am authenticated and granted access to the application.
    -   Given I am logged in, When I select the logout option, Then my session is terminated, and I am redirected to the login page.
    -   Given I input incorrect credentials, Then the system displays an "Invalid credentials" error.
-   **Priority:** High

### FR-003: User Profile Management
-   **Description:** Users can view and update their profile information (e.g., username, profile picture, status).
-   **Acceptance Criteria:**
    -   Given I am logged in, When I navigate to my profile, Then I can see my current profile details.
    -   Given I am viewing my profile, When I update my username or profile picture, Then the changes are saved and reflected across the application.
-   **Priority:** Medium

### FR-004: User Presence Status
-   **Description:** Displays the online/offline status of users to their contacts.
-   **Acceptance Criteria:**
    -   Given a user is logged in and active, When other users view their contact list, Then the user's status is displayed as "Online".
    -   Given a user logs out or becomes inactive for a configured period, When other users view their contact list, Then the user's status changes to "Offline".
-   **Priority:** High

### FR-005: User Search
-   **Description:** Allows users to search for other registered users within the application to initiate new conversations.
-   **Acceptance Criteria:**
    -   Given I am logged in, When I use the search bar, Then I can type a username or email fragment.
    -   Given I have typed a search query, When matching users exist, Then a list of matching registered users is displayed.
-   **Priority:** Medium

### FR-006: Send Text Message (1:1)
-   **Description:** Enables a user to send a text message to another specific user.
-   **Acceptance Criteria:**
    -   Given I am in a 1:1 chat window, When I type a message into the input field and click 'Send' or press 'Enter', Then the message is sent to the recipient and displayed in my chat history.
    -   Given the message is sent, When the recipient is online, Then they receive the message in real-time.
-   **Priority:** High

### FR-007: Receive Text Message (1:1)
-   **Description:** Enables a user to receive real-time text messages from another specific user.
-   **Acceptance Criteria:**
    -   Given I am in a 1:1 chat window with an active sender, When the sender sends a message, Then the message instantly appears in my chat window.
    -   Given I am not in the chat window or offline, When I receive a message, Then a notification is triggered (as per FR-015).
-   **Priority:** High

### FR-008: View Message History (1:1)
-   **Description:** Displays the chronological history of messages between two users.
-   **Acceptance Criteria:**
    -   Given I open an existing 1:1 chat, When the chat window loads, Then the most recent messages are displayed, and older messages can be loaded by scrolling up.
-   **Priority:** High

### FR-009: Real-time Message Delivery (1:1)
-   **Description:** Ensures immediate transmission and display of 1:1 messages between online users.
-   **Acceptance Criteria:**
    -   Given both sender and receiver are online and in the respective chat windows, When a message is sent, Then the message appears in both chat windows within 500ms.
-   **Priority:** High

### FR-010: Create Group Chat
-   **Description:** Allows a user to initiate a new group conversation and invite other users.
-   **Acceptance Criteria:**
    -   Given I am logged in, When I select the "Create Group Chat" option, Then I can provide a group name and select at least one other user to invite.
    -   Given a group chat is created, Then I am automatically added as a member and administrator.
-   **Priority:** Medium

### FR-011: Add/Remove Members from Group
-   **Description:** Group administrators can manage the membership of a group chat.
-   **Acceptance Criteria:**
    -   Given I am a group administrator, When I access group settings, Then I can view current members and search for new users to invite.
    -   Given I select a user to add/remove, When I confirm the action, Then the user is added/removed from the group, and other members are notified (optional, but good for UX).
-   **Priority:** Medium

### FR-012: Send Text Message (Group)
-   **Description:** Enables a user to send a text message to all members of a group chat.
-   **Acceptance Criteria:**
    -   Given I am in a group chat, When I type a message and press send, Then the message is sent to all active group members and displayed in the group chat history.
-   **Priority:** Medium

### FR-013: Receive Text Message (Group)
-   **Description:** Enables a user to receive real-time text messages from other members in a group chat.
-   **Acceptance Criteria:**
    -   Given I am in a group chat, When another member sends a message, Then the message instantly appears in my group chat window.
-   **Priority:** Medium

### FR-014: View Message History (Group)
-   **Description:** Displays the chronological history of messages within a group chat.
-   **Acceptance Criteria:**
    -   Given I open an existing group chat, When the chat window loads, Then the most recent messages are displayed, and older messages can be loaded by scrolling up.
-   **Priority:** Medium

### FR-015: New Message Notification
-   **Description:** Notifies the user of new messages when they are not actively viewing the conversation.
-   **Acceptance Criteria:**
    -   Given I receive a new message in a conversation I am not currently viewing, When I am online, Then I receive an in-app notification (e.g., badge count, toast message).
-   **Priority:** Medium

### FR-016: User Online/Offline Status Notification
-   **Description:** Notifies users when a contact comes online or goes offline.
-   **Acceptance Criteria:**
    -   Given I am online, When one of my contacts comes online/goes offline, Then I receive an in-app notification of their status change (configurable).
-   **Priority:** Low

### FR-017: Send Image/File in Chat
-   **Description:** Allows users to attach and send image or file attachments within a chat.
-   **Acceptance Criteria:**
    -   Given I am in a chat window, When I select the "Attach File" option and choose an image/file (up to 10MB), Then the file is uploaded and sent as part of the message.
-   **Priority:** Low (for MVP, but crucial for enhancement)

### FR-018: View Shared Image/File in Chat
-   **Description:** Allows users to view or download shared image/file attachments within a chat.
-   **Acceptance Criteria:**
    -   Given I receive a message with an attached image/file, When I view the message, Then I can see a preview of the image or a link to download the file.
-   **Priority:** Low (for MVP, but crucial for enhancement)

## Non-Functional Requirements

### NFR-001: Performance (Message Latency)
-   **Description:** Messages between active, online users should be delivered with minimal delay.
-   **Acceptance Criteria:** 95% of real-time messages shall be delivered from sender to receiver within 500 milliseconds under typical load (up to 1,000 concurrent users).

### NFR-002: Performance (Concurrent Users)
-   **Description:** The system must be able to handle a specified number of users actively using the chat features simultaneously.
-   **Acceptance Criteria:** The system shall support at least 1,000 concurrently active users, sending/receiving messages without significant degradation in performance (NFR-001).

### NFR-003: Security (Authentication)
-   **Description:** All user access to the application and its features must be securely authenticated.
-   **Acceptance Criteria:** User authentication shall be implemented using JSON Web Tokens (JWT) for API access, ensuring token expiration and refresh mechanisms are in place.

### NFR-004: Security (Authorization)
-   **Description:** Users must only be able to access data and perform actions for which they have explicit permission.
-   **Acceptance Criteria:**
    -   A user shall only be able to retrieve their own messages and messages from conversations they are a part of.
    -   Only group administrators can perform administrative actions (e.g., add/remove members).

### NFR-005: Security (Data Encryption)
-   **Description:** Communication between the client and server must be encrypted to protect sensitive data.
-   **Acceptance Criteria:** All network communication (HTTP and WebSocket) shall use TLS/SSL encryption (HTTPS/WSS).

### NFR-006: Scalability (Horizontal Scaling)
-   **Description:** The backend services should be designed to scale horizontally to handle increased user load and data volume.
-   **Acceptance Criteria:** Backend services (API, WebSocket server) shall be stateless and deployable as multiple instances behind a load balancer without requiring session affinity.

### NFR-007: Usability (Responsive UI)
-   **Description:** The application's user interface must adapt to different screen sizes and devices.
-   **Acceptance Criteria:** The frontend, leveraging Angular Clarity, shall provide a fully responsive layout that is usable on desktop, tablet, and mobile browsers.

### NFR-008: Reliability (Message Persistence)
-   **Description:** All sent messages must be reliably stored and retrievable.
-   **Acceptance Criteria:** Every successfully sent message shall be persisted in the database and accessible in chat history, even after application restarts or user logouts.

## Data Requirements

### Entities:

1.  **User:**
    *   `id` (Primary Key, UUID)
    *   `username` (String, Unique, Not Null)
    *   `email` (String, Unique, Not Null)
    *   `password_hash` (String, Not Null)
    *   `profile_picture_url` (String, Optional)
    *   `status` (Enum: 'online', 'offline', 'away', Default: 'offline')
    *   `created_at` (Timestamp, Not Null)
    *   `updated_at` (Timestamp, Not Null)

2.  **Conversation:** (Represents a 1:1 or Group Chat instance)
    *   `id` (Primary Key, UUID)
    *   `type` (Enum: 'one_to_one', 'group', Not Null)
    *   `name` (String, Optional, for Group Chats)
    *   `created_at` (Timestamp, Not Null)
    *   `updated_at` (Timestamp, Not Null)

3.  **ConversationParticipant:** (Junction table for Users and Conversations)
    *   `conversation_id` (Foreign Key to Conversation.id)
    *   `user_id` (Foreign Key to User.id)
    *   `role` (Enum: 'member', 'admin', Optional, for Group Chats)
    *   `joined_at` (Timestamp, Not Null)
    *   `last_read_message_id` (Foreign Key to Message.id, Optional, tracks read status)
    *   `is_active` (Boolean, Default: true, for leaving groups/1:1s)

4.  **Message:**
    *   `id` (Primary Key, UUID)
    *   `conversation_id` (Foreign Key to Conversation.id, Not Null)
    *   `sender_id` (Foreign Key to User.id, Not Null)
    *   `content` (Text, Not Null)
    *   `type` (Enum: 'text', 'image', 'file', Default: 'text')
    *   `attachment_url` (String, Optional, for image/file)
    *   `sent_at` (Timestamp, Not Null)
    *   `edited_at` (Timestamp, Optional)
    *   `deleted_at` (Timestamp, Optional)

### Relationships:
*   User 1:N ConversationParticipant (A user can participate in many conversations)
*   Conversation 1:N ConversationParticipant (A conversation has many participants)
*   Conversation 1:N Message (A conversation has many messages)
*   User 1:N Message (A user can send many messages)

## Interface Requirements

### General UI/UX:
*   **Clarity Design System Adherence:** The frontend UI must strictly follow the guidelines and component library of the Clarity Design System for consistency and accessibility.
*   **Responsive Layout:** The main layout (header, sidebar, content area) must be responsive, adapting to different screen sizes as per the base boilerplate.

### Specific Components (Leveraging Angular Clarity):
*   **Login/Registration Forms:** Use Clarity form controls (input, password, button) with validation feedback.
*   **Chat List/Sidebar:** Implement a Clarity-style navigable list (`clr-vertical-nav` or similar) to display active conversations with user names/group names and unread indicators.
*   **Chat Window:**
    *   **Header:** Display current chat partner's name/group name, presence status (for 1:1).
    *   **Message Display Area:** Use Clarity cards or lists to display individual messages. Messages from current user should be visually distinct from others. Display sender name/picture, message content, and timestamp.
    *   **Message Input:** Clarity input field with a send button and optional attachment icon.
    *   **Scroll Behavior:** Auto-scroll to the latest message on load and new message receipt.
*   **User Profile Page:** Display user details using Clarity forms and cards.
*   **Notifications:** Use Clarity alerts or toast messages for in-app notifications.

### API Requirements:
*   **RESTful API (Backend):**
    *   `POST /api/auth/register`: User registration.
    *   `POST /api/auth/login`: User login, returns JWT.
    *   `GET /api/users/me`: Retrieve current user profile.
    *   `PUT /api/users/me`: Update current user profile.
    *   `GET /api/users/search?query=...`: Search for users.
    *   `GET /api/conversations`: Retrieve list of user's conversations.
    *   `GET /api/conversations/{id}/messages`: Retrieve messages for a specific conversation (paginated).
    *   `POST /api/conversations/one-to-one`: Create a 1:1 conversation.
    *   `POST /api/conversations/group`: Create a group conversation.
    *   `POST /api/messages`: Send a message (HTTP fallback if WebSocket not connected).
*   **WebSocket API (Backend):**
    *   `wss://api.yourdomain.com/ws/chat`: WebSocket endpoint for real-time communication.
    *   **Events (Client to Server):**
        *   `send_message`: { `conversationId`, `content`, `type`, `attachmentUrl` }
        *   `user_typing`: { `conversationId` }
        *   `read_message`: { `messageId`, `conversationId` }
    *   **Events (Server to Client):**
        *   `new_message`: { `messageId`, `conversationId`, `senderId`, `content`, `type`, `attachmentUrl`, `sentAt` }
        *   `user_status_update`: { `userId`, `status` }
        *   `typing_indicator`: { `userId`, `conversationId` }
        *   `conversation_update`: { `conversationId`, `type`... } (e.g., new member in group)



---

## REQUIREMENTS UPDATE - 2025-10-10 04:18:09


## Update: Requirements Document Alignment Note (2025-10-10T[timestamp])
The detailed Functional (FR), Non-Functional (NFR), Data, and Interface Requirements outlined in this document are in strong alignment with the strategic direction, core features, and architectural considerations specified in the `io8codermaster_breakdown.md` and `io8codermaster_plan.md` for the Messaging App project. Particular emphasis on `NFR-001` (Message Latency), `NFR-002` (Concurrent Users), `NFR-003` (Authentication), `NFR-004` (Authorization), `NFR-005` (Data Encryption), and `NFR-006` (Horizontal Scaling) directly addresses the core concerns of performance, security, and scalability highlighted in the codermaster documents. The phased approach for `FR-010` through `FR-018` (Group Messaging, Notifications, Media Sharing) also reflects the planned incremental feature expansion.


---

## REQUIREMENTS UPDATE - 2025-10-10 04:19:20

```markdown
# Requirements Document
Generated: 2025-10-10T04:04:00.075502

## Functional Requirements

### FR-001: User Registration
-   **Description:** The system shall allow new users to register an account with a unique email and password.
-   **Acceptance Criteria:**
    -   User can submit registration form.
    -   System validates unique email format and strong password policy.
    -   Upon successful registration, a new user record is created in the database.
    -   User is either automatically logged in or redirected to the login page.
-   **Priority:** High (Milestone 1: Core Messaging MVP, as per `.io8codermaster_breakdown.md`)

### FR-002: User Login
-   **Description:** The system shall allow registered users to log in securely using their email and password.
-   **Acceptance Criteria:**
    -   User can submit login credentials.
    -   System authenticates credentials against stored user data.
    -   Upon successful authentication, a secure session token (e.g., JWT) is issued.
    -   User is redirected to the main application dashboard/chat interface.
    -   System provides clear feedback for invalid credentials.
-   **Priority:** High (Milestone 1: Core Messaging MVP)

### FR-003: User Profile Management
-   **Description:** The system shall allow authenticated users to view and update their profile information.
-   **Acceptance Criteria:**
    -   User can access a dedicated profile page.
    -   User can update fields such as username, email (with re-verification), and potentially a profile picture.
    -   Changes are validated and persisted in the database.
    -   Profile updates are reflected across the application (e.g., in chat lists).
-   **Priority:** Medium (Milestone 1: Core Messaging MVP)

### FR-004: Display User List
-   **Description:** The system shall display a list of other registered users with whom the authenticated user can chat.
-   **Acceptance Criteria:**
    -   The user list is available in a dedicated sidebar or section of the UI, leveraging Angular Clarity components.
    -   Each entry displays the user's name and online/offline status (presence).
    -   Clicking a user's name opens a one-to-one chat window with that user.
-   **Priority:** High (Milestone 1: Core Messaging MVP)

### FR-005: Send One-to-One Text Message
-   **Description:** The system shall enable an authenticated user to send real-time text messages to another selected user.
-   **Acceptance Criteria:**
    -   User can type messages into a dedicated input field within a chat window.
    -   Messages are sent by pressing Enter or clicking a send button.
    -   Sent messages are displayed immediately in the sender's chat window.
    -   Messages are routed to the recipient in real-time via WebSocket.
    -   Messages are persisted in the database.
-   **Priority:** High (Milestone 1: Core Messaging MVP)

### FR-006: Receive One-to-One Text Message
-   **Description:** The system shall enable an authenticated user to receive real-time text messages from another user.
-   **Acceptance Criteria:**
    -   Incoming messages from an active chat partner are displayed instantly in the chat window.
    -   Messages received while the user is offline are displayed upon their next login.
    -   Messages include sender's name and timestamp.
-   **Priority:** High (Milestone 1: Core Messaging MVP)

### FR-007: View One-to-One Chat History
-   **Description:** The system shall allow users to view the complete history of their one-to-one conversations with another user.
-   **Acceptance Criteria:**
    -   When a chat window is opened, previous messages with that user are loaded and displayed chronologically.
    -   The chat history should be scrollable, with older messages loading on demand (pagination/infinite scroll).
-   **Priority:** High (Milestone 1: Core Messaging MVP)

### FR-008: User Presence Indicator
-   **Description:** The system shall display the online/offline status of other users in the user list and chat windows.
-   **Acceptance Criteria:**
    -   A visual indicator (e.g., colored dot) next to a user's name signifies their online or offline status.
    -   Status updates occur in real-time as users connect or disconnect.
-   **Priority:** High (Milestone 1: Core Messaging MVP)

### FR-009: Group Chat Creation (Phase 2)
-   **Description:** The system shall allow users to create new group chat rooms and invite other users, as outlined in Milestone 2 of `.io8codermaster_breakdown.md`.
-   **Acceptance Criteria:**
    -   User can initiate creation of a new group chat.
    -   User can provide a group name and select members from their contact list.
    -   A new group chat entry appears in the user's chat list.
-   **Priority:** Medium (Milestone 2: Enhanced Communication & Features)

### FR-010: Send and Receive Group Messages (Phase 2)
-   **Description:** The system shall enable authenticated users to send and receive text messages within a group chat.
-   **Acceptance Criteria:**
    -   Messages sent in a group chat are delivered to all active members of that group in real-time.
    -   Messages are persisted and visible in the group's chat history for all members.
-   **Priority:** Medium (Milestone 2: Enhanced Communication & Features)

### FR-011: Real-time Notifications (Phase 2)
-   **Description:** The system shall provide real-time notifications for new messages and relevant events (e.g., user online/offline, group invite), as outlined in Milestone 2 of `.io8codermaster_breakdown.md`.
-   **Acceptance Criteria:**
    -   In-app notifications (e.g., badge counts, toast messages) are displayed for unread messages.
    -   Notifications are dismissed when the relevant chat is viewed.
-   **Priority:** Medium (Milestone 2: Enhanced Communication & Features)

### FR-012: Media Sharing (Phase 2)
-   **Description:** The system shall allow users to share images and potentially other file types within one-to-one and group chats, as outlined in Milestone 2 of `.io8codermaster_breakdown.md`.
-   **Acceptance Criteria:**
    -   User can select an image/file to attach to a message.
    -   Shared media is uploaded to a storage service and a link/preview is displayed in the chat.
    -   Recipients can view/download shared media.
-   **Priority:** Low (Milestone 2: Enhanced Communication & Features)

## Non-Functional Requirements

### NFR-001: Performance
-   **Description:** The application must provide low-latency message delivery and a responsive user interface, addressing the performance risk from `.io8codermaster_plan.md`.
-   **Acceptance Criteria:**
    -   Average message delivery time (sender to receiver) shall be less than 200ms for 95% of messages under normal load.
    -   Frontend UI responsiveness (e.g., navigation, chat window loading) shall be perceived as instantaneous (less than 500ms for 90% of interactions).
    -   The backend API shall respond to non-real-time requests (e.g., profile update) within 300ms for 90% of requests.
-   **Priority:** High

### NFR-002: Security
-   **Description:** The application must protect user data and communications from unauthorized access and ensure secure operations, addressing the critical security risks and constraints from `.io8codermaster_breakdown.md` and `.io8codermaster_plan.md`.
-   **Acceptance Criteria:**
    -   All communications between frontend and backend (REST and WebSockets) shall be encrypted using TLS/SSL.
    -   User passwords shall be securely hashed and salted before storage.
    -   Authentication tokens (e.g., JWT) shall be used, with appropriate expiration and refresh mechanisms.
    -   Backend APIs shall implement input validation to prevent common vulnerabilities (e.g., XSS, SQL injection).
    -   Access control mechanisms shall ensure users can only access their own data and authorized conversations.
    -   Adherence to OWASP Top 10 guidelines shall be implemented.
-   **Priority:** Critical

### NFR-003: Scalability
-   **Description:** The system must be designed to scale horizontally to accommodate a growing number of concurrent users and message volume, as highlighted as a key constraint and risk in `.io8codermaster_breakdown.md` and `.io8codermaster_plan.md`.
-   **Acceptance Criteria:**
    -   The system shall support at least 1,000 concurrent active users with message delivery performance maintained.
    -   The backend services and real-time layer shall be containerized and deployable in a clustered environment.
    -   Database architecture should support growth in user and message data (e.g., sharding or replication capabilities).
-   **Priority:** High

### NFR-004: Usability
-   **Description:** The application shall provide an intuitive, consistent, and easy-to-use interface, leveraging the Clarity Design System as per the base project (`.io8codermaster_breakdown.md`).
-   **Acceptance Criteria:**
    -   User interface shall adhere to the Clarity Design System guidelines for components, typography, and color palettes.
    -   Key actions (sending a message, selecting a user) shall be discoverable within 3 clicks.
    -   Error messages shall be clear, concise, and actionable.
    -   The application shall be fully responsive across common desktop and mobile browser sizes.
-   **Priority:** High

### NFR-005: Reliability
-   **Description:** The application shall maintain high availability and ensure message delivery.
-   **Acceptance Criteria:**
    -   The system shall have an uptime of 99.9% (excluding planned maintenance).
    -   Messages sent shall be guaranteed to be delivered (at least once) to the recipient, even if the recipient is temporarily offline.
    -   Robust error handling and logging mechanisms shall be in place for both frontend and backend.
-   **Priority:** High

### NFR-006: Maintainability
-   **Description:** The codebase and infrastructure shall be easy to understand, modify, and extend, facilitating future development and bug fixes.
-   **Acceptance Criteria:**
    -   Code shall be modular, following established design patterns and best practices for Angular (frontend) and chosen backend framework.
    -   Comprehensive inline code comments and external documentation (e.g., API documentation, architecture diagrams) shall be provided.
    -   Automated unit and integration tests shall cover at least 80% of the codebase.
    -   Dependencies shall be managed and updated regularly.
-   **Priority:** Medium

### NFR-007: Real-time Capability
-   **Description:** Core messaging functionalities must operate in real-time, providing immediate updates, as this is a core requirement of the messaging app (`.io8codermaster_breakdown.md`).
-   **Acceptance Criteria:**
    -   New messages appear on the recipient's screen without requiring a page refresh.
    -   User online/offline status updates are reflected within 5 seconds.
    -   Typing indicators (if implemented) update within 2 seconds.
-   **Priority:** Critical

## Data Requirements

#### 1. User Entity
-   **Purpose:** Stores user authentication and profile information, supporting FR-001, FR-002, FR-003.
-   **Fields:**
    -   `id` (UUID, Primary Key)
    -   `username` (String, Unique)
    -   `email` (String, Unique, Required)
    -   `password_hash` (String, Required)
    -   `profile_picture_url` (String, Optional)
    -   `status` (Enum: 'online', 'offline', 'away', Default: 'offline')
    -   `created_at` (Timestamp)
    -   `updated_at` (Timestamp)

#### 2. Message Entity
-   **Purpose:** Stores individual chat messages, supporting FR-005, FR-006, FR-007.
-   **Fields:**
    -   `id` (UUID, Primary Key)
    -   `sender_id` (UUID, Foreign Key to User.id, Required)
    -   `receiver_id` (UUID, Foreign Key to User.id, Optional, for 1:1 chats)
    -   `chat_room_id` (UUID, Foreign Key to ChatRoom.id, Optional, for group chats)
    -   `content` (Text, Required)
    -   `timestamp` (Timestamp, Required)
    -   `type` (Enum: 'text', 'image', 'file', Default: 'text')
    -   `read_status` (Boolean, Default: false)
    -   `media_url` (String, Optional, for 'image' or 'file' types)

#### 3. ChatRoom Entity (for Group Chats - Phase 2)
-   **Purpose:** Stores metadata for group chat rooms, supporting FR-009, FR-010.
-   **Fields:**
    -   `id` (UUID, Primary Key)
    -   `name` (String, Required)
    -   `description` (Text, Optional)
    -   `created_by` (UUID, Foreign Key to User.id, Required)
    -   `created_at` (Timestamp)
    -   `updated_at` (Timestamp)

#### 4. ChatRoomMember Entity (for Group Chats - Phase 2)
-   **Purpose:** Links users to chat rooms, supporting FR-009, FR-010.
-   **Fields:**
    -   `id` (UUID, Primary Key)
    -   `chat_room_id` (UUID, Foreign Key to ChatRoom.id, Required)
    -   `user_id` (UUID, Foreign Key to User.id, Required)
    -   `joined_at` (Timestamp)
    -   `role` (Enum: 'member', 'admin', Default: 'member')

## Interface Requirements

#### 1. User Interface (Frontend - Angular Clarity)
-   **Overall Layout:** Main layout with a header, a persistent left-hand sidebar for user/chat lists, and a primary content area for active chat windows, consistent with the existing Angular Clarity boilerplate, as specified in `.io8codermaster_breakdown.md`.
-   **Components (leveraging Clarity):**
    -   **Login/Registration Forms:** Clarity form components for user input and validation.
    -   **User List:** A scrollable list of users, displaying name, profile picture (if available), and real-time online status.
    -   **Chat Window:** Area displaying messages chronologically, including sender name, content, and timestamp. Should support scrolling for history.
    -   **Message Input:** A text area and send button for composing and sending messages.
    -   **Profile Page:** Forms for editing user details, displaying current profile information.
    -   **Notification Banners/Toasts:** For system-wide alerts or new message notifications (Phase 2).
-   **Navigation:** Intuitive navigation between the user list, active chats, and profile settings.
-   **Responsiveness:** The UI must adapt gracefully to various screen sizes, from desktop to mobile devices.

#### 2. API Requirements (Backend - RESTful & WebSocket)
-   **RESTful API (for Authentication & User/Profile Management):**
    -   `POST /api/auth/register`: User registration.
    -   `POST /api/auth/login`: User login, returns JWT.
    -   `GET /api/users`: Retrieve a list of all registered users (or contacts).
    -   `GET /api/users/{id}`: Retrieve a specific user's profile.
    -   `PUT /api/users/{id}`: Update authenticated user's profile.
    -   `GET /api/chats/history/{userId}`: Retrieve 1:1 chat history with a specific user.
    -   `GET /api/groups/{groupId}/history`: Retrieve group chat history (Phase 2).
-   **WebSocket API (for Real-time Messaging & Presence):**
    -   **Connection:** Establish a secure WebSocket connection after successful user authentication.
    -   **Message Sending:** `send_message` event with payload (sender_id, receiver_id/chat_room_id, content, type, etc.).
    -   **Message Receiving:** `receive_message` event with message payload.
    -   **Presence Updates:** `user_online`, `user_offline`, `user_typing` events.
    -   **Notifications:** `new_message_notification`, `group_invite_notification` events.
-   **Error Handling:** APIs shall return standardized error responses (HTTP status codes for REST, specific error codes/messages for WebSockets).

```
