# Architecture Document
Generated: Tuesday, September 16, 2025

## System Overview
The Angular Clarity Boilerplate is a frontend-only, single-page application (SPA) template. It is designed to serve as a foundational starting point for developing enterprise-grade web applications. The system provides a pre-configured, modular, and scalable architecture using the Angular framework and is visually styled with the VMware Clarity Design System. Its primary purpose is to accelerate development by providing a structured and feature-rich starting point.

## Architecture Pattern
The boilerplate is built upon a **Component-Based Architecture**, which is fundamental to the Angular framework. The UI is composed of a tree of reusable and encapsulated components.

The overall architectural pattern follows best practices for scalable Angular applications, emphasizing a **Modular Design**. The application is segregated into a `CoreModule`, a `SharedModule`, and is designed for the addition of multiple `FeatureModules`. This structure promotes separation of concerns, reusability, and maintainability.

## Component Design (Frontend)

- **AppModule:** The root module of the application, responsible for bootstrapping the `AppComponent` and importing essential modules like the `CoreModule` and `AppRoutingModule`.

- **AppComponent:** The main application shell component. It contains the primary layout, including the Clarity header, sidebar navigation, and the main content area where routed components are displayed via `<router-outlet>`.

- **CoreModule:** This module is designed to be imported only once by the `AppModule`. It contains singleton services, route guards, and other one-time setup logic (e.g., HTTP interceptors). This pattern prevents services from being provided multiple times across the application.

- **SharedModule:** This module contains commonly used components, directives, and pipes that can be reused across different feature modules. It is imported by feature modules whenever they need access to these shared elements. It primarily exports common Angular modules (like `CommonModule`, `FormsModule`) and Clarity UI modules.

- **Feature Modules (Conceptual):** The architecture is designed for developers to create new feature modules (e.g., `DashboardModule`, `AdminModule`). These modules encapsulate all the components, services, and routing related to a specific business domain. They are typically **lazy-loaded** to improve initial application load performance.

## Data Architecture

### Primary Database
- Not applicable. As a frontend-only boilerplate, this project does not include a database. It is designed to connect to any backend with a data persistence layer.

### Data Model (Client-Side)
- Data models will be defined using **TypeScript interfaces or classes** within feature modules. These models will represent the structure of data objects retrieved from or sent to the backend API.
- **Example `User` model:**
  ```typescript
  export interface User {
    id: number;
    name: string;
    email: string;
    role: 'admin' | 'user';
  }

  Of course. Here is the architecture_document.md for the Angular Clarity boilerplate project, presented in a single code block for easy copying.

Markdown

# Architecture Document
Generated: Tuesday, September 16, 2025

## System Overview
The Angular Clarity Boilerplate is a frontend-only, single-page application (SPA) template. It is designed to serve as a foundational starting point for developing enterprise-grade web applications. The system provides a pre-configured, modular, and scalable architecture using the Angular framework and is visually styled with the VMware Clarity Design System. Its primary purpose is to accelerate development by providing a structured and feature-rich starting point.

## Architecture Pattern
The boilerplate is built upon a **Component-Based Architecture**, which is fundamental to the Angular framework. The UI is composed of a tree of reusable and encapsulated components.

The overall architectural pattern follows best practices for scalable Angular applications, emphasizing a **Modular Design**. The application is segregated into a `CoreModule`, a `SharedModule`, and is designed for the addition of multiple `FeatureModules`. This structure promotes separation of concerns, reusability, and maintainability.

## Component Design (Frontend)

- **AppModule:** The root module of the application, responsible for bootstrapping the `AppComponent` and importing essential modules like the `CoreModule` and `AppRoutingModule`.

- **AppComponent:** The main application shell component. It contains the primary layout, including the Clarity header, sidebar navigation, and the main content area where routed components are displayed via `<router-outlet>`.

- **CoreModule:** This module is designed to be imported only once by the `AppModule`. It contains singleton services, route guards, and other one-time setup logic (e.g., HTTP interceptors). This pattern prevents services from being provided multiple times across the application.

- **SharedModule:** This module contains commonly used components, directives, and pipes that can be reused across different feature modules. It is imported by feature modules whenever they need access to these shared elements. It primarily exports common Angular modules (like `CommonModule`, `FormsModule`) and Clarity UI modules.

- **Feature Modules (Conceptual):** The architecture is designed for developers to create new feature modules (e.g., `DashboardModule`, `AdminModule`). These modules encapsulate all the components, services, and routing related to a specific business domain. They are typically **lazy-loaded** to improve initial application load performance.

## Data Architecture

### Primary Database
- Not applicable. As a frontend-only boilerplate, this project does not include a database. It is designed to connect to any backend with a data persistence layer.

### Data Model (Client-Side)
- Data models will be defined using **TypeScript interfaces or classes** within feature modules. These models will represent the structure of data objects retrieved from or sent to the backend API.
- **Example `User` model:**
  ```typescript
  export interface User {
    id: number;
    name: string;
    email: string;
    role: 'admin' | 'user';
  }
Data Flow
API Call: A component's method calls a function in its corresponding service (e.g., userService.getUsers()).

Service Layer: The service uses Angular's HttpClient to make an HTTP request to the backend API.

Data Retrieval: The service receives the HTTP response and typically returns an Observable of the data, typed with the appropriate TypeScript interface.

Component Update: The component subscribes to the Observable. Once the data is received, it updates its local state, triggering Angular's change detection to re-render the template and display the new data.

API Design (Backend Communication)
This boilerplate is backend-agnostic. It is designed to communicate with any backend that exposes a RESTful or GraphQL API.

Communication Protocol
HTTP/HTTPS: Communication is handled via standard HTTP requests using Angular's HttpClient service.

Example Service Implementation
An example of a service making API calls:
// in user.service.ts
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
import { User } from '../models/user.model';
import { environment } from '../../environments/environment';

@Injectable({
  providedIn: 'root'
})
export class UserService {
  private apiUrl = `${environment.apiBaseUrl}/users`;

  constructor(private http: HttpClient) { }

  getUsers(): Observable<User[]> {
    return this.http.get<User[]>(this.apiUrl);
  }

  getUserById(id: number): Observable<User> {
    return this.http.get<User>(`${this.apiUrl}/${id}`);
  }
}

Error Handling
HTTP interceptors can be provided in the CoreModule to handle API errors globally (e.g., logging errors, redirecting on 401 Unauthorized responses).

Security Architecture
Authentication: Authentication logic (e.g., handling JWTs, interacting with OAuth providers) should be encapsulated within an AuthService provided in the CoreModule.

Authorization (Route Guards): The architecture uses Angular's Route Guards to protect routes. An AuthGuard can be implemented to prevent unauthorized users from accessing certain parts of the application.

Client-Side Security: The boilerplate does not inherently protect against all client-side vulnerabilities. Developers should follow best practices for preventing XSS and CSRF attacks.

Scalability Considerations
Lazy Loading: The architecture strongly encourages the use of lazy-loaded feature modules. This ensures that the initial application bundle size remains small, leading to faster load times. As new features are added, they do not impact the initial load performance.

Modular Design: The strict separation of concerns into Core, Shared, and Feature modules makes the codebase easier to manage, test, and scale as the application grows in complexity.

State Management: For applications with complex state, a state management library like NgRx or Akita can be easily integrated into this architecture without requiring significant refactoring.

---

## ARCHITECTURE UPDATE - 2025-10-06 07:15:21


## Reliability Considerations
Generated: 2025-10-06 07:16:00
To ensure the reliability of the Working Notes Application, the following considerations are paramount:
-   **Error Handling:** Implement robust global error handling on both frontend (Angular's `ErrorHandler` and HTTP Interceptors) and backend (centralized exception handling in Flask). Provide meaningful error messages to the user while logging detailed errors server-side to facilitate debugging.
-   **Data Backup and Recovery:** The chosen database (PostgreSQL) should be configured with regular automated backups. In cloud environments (e.g., AWS RDS), this is typically a managed service. A recovery strategy should be in place to restore data in case of data loss or corruption.
-   **Monitoring and Logging:** Implement comprehensive application monitoring (e.g., Prometheus/Grafana for metrics, ELK stack for logs) to track application health, performance metrics, and error rates. Structured logging will be used across frontend and backend to facilitate debugging and incident response.
-   **Graceful Degradation:** Design the frontend to handle backend unavailability gracefully, perhaps by showing a clear "service unavailable" message rather than a complete application crash.

## Application Performance
Generated: 2025-10-06 07:16:00
Beyond initial boilerplate performance, the application's perceived speed and responsiveness for end-users will be critical, aligning with NFR-001 (Performance):
-   **Frontend Optimization:**
    -   **Lazy Loading:** As mentioned, feature modules (Auth, Notes) will be lazy-loaded to minimize initial bundle size and improve load times.
    -   **Change Detection:** Optimize Angular change detection strategy (e.g., `OnPush`) in performance-critical components to reduce rendering cycles.
    -   **Resource Optimization:** Ensure all static assets (e.g., images) are optimized for web delivery to minimize download sizes.
-   **Backend Optimization:**
    -   **Efficient Database Queries:** Use the ORM (SQLAlchemy) effectively to minimize N+1 query problems and ensure appropriate indexing on frequently queried columns (e.g., `Users.id`, `Notes.user_id`, `Notes.created_at`).
    -   **API Response Time:** Continuously monitor and optimize API endpoint response times, especially for frequently accessed operations like note retrieval and saving.
    -   **Caching (Future):** As a future scalability measure, introduce a caching layer (e.g., Redis) for frequently accessed, user-specific data to reduce database load and improve response times.

## User Experience (UX) Considerations
Generated: 2025-10-06 07:16:00
Building on the foundation of the Clarity Design System, the application's usability and overall user experience will be enhanced by:
-   **Intuitive Navigation:** Provide clear, consistent, and easy-to-understand navigation via the Clarity sidebar and header components, enabling users to effortlessly find and manage their notes.
-   **Responsive Design:** Ensure the application is fully responsive across various screen sizes (desktop, tablet, mobile) by leveraging Clarity's responsive grid system and media queries, providing an optimal user experience on any device.
-   **Feedback Mechanisms:** Implement immediate and clear visual feedback for user actions, such as loading indicators for ongoing API calls, concise success/error messages for CRUD operations, and real-time form validation feedback.
-   **Accessibility:** Adhere to web accessibility best practices, utilizing Clarity's built-in accessibility features to ensure the application is usable by a diverse range of users, including those with disabilities.

## Architecture Review and Confirmation
Generated: 2025-10-06 07:16:00
The comprehensive architecture defined for the "Working Notes Application" successfully addresses the user prompt and fully aligns with all functional (FR-006 to FR-012) and non-functional requirements (NFR-001 to NFR-005) as detailed in the `analysis_document.md` and `requirements_document.md`. The chosen Client-Server architecture, featuring an Angular SPA frontend (leveraging the Clarity boilerplate) and a Flask RESTful API backend, backed by a PostgreSQL database, provides a robust, secure, and scalable foundation. The detailed component design, data architecture, API specifications, and robust security measures are well-defined for the Minimum Viable Product (MVP). The inclusion of specific considerations for reliability, application performance, and user experience further solidifies the design, ensuring a high-quality and maintainable application that is well-prepared for future enhancements and growth.


---

## ARCHITECTURE UPDATE - 2025-10-06 07:38:05


# Architecture Document
Generated: 2025-10-06T07:45:00Z

## System Overview
The Notes Application extends an existing Angular Clarity frontend boilerplate with a new, dedicated RESTful API backend and a PostgreSQL database. The system is designed as a secure, personal information management tool enabling users to create, view, edit, and delete their private notes. It incorporates robust user authentication and strict authorization to ensure data ownership and privacy. The architecture facilitates a clear separation of concerns between the client-side UI, server-side business logic, and data persistence layers, aiming for high maintainability and scalability.

## Architecture Pattern
**Rich Client - API Gateway - Backend Services - Database**

This project adopts a layered architecture pattern, specifically a rich client (Angular) interacting with a backend API (functioning as an API Gateway for initial MVP) that handles business logic and data persistence. This approach leverages the strengths of a modern frontend framework for an intuitive user experience and a powerful, scalable backend for secure data management.

*   **Client Layer (Frontend):** The Angular application, built upon the Clarity Boilerplate, serves as the rich client. It handles all UI rendering, user interaction, client-side routing, and makes API calls to the backend.
*   **API Gateway Layer (Backend API):** For the MVP, the backend RESTful API service acts as a de-facto API Gateway. It exposes all necessary endpoints for user authentication and note management, serving as the single entry point for client requests. It encapsulates business logic and interacts with the database.
*   **Backend Services Layer (within API):** Logical separation of services within the backend (e.g., `UserService`, `NoteService`) to handle specific domains. This allows for clear organization and future refactoring into distinct microservices if the application complexity grows.
*   **Data Layer (Database):** PostgreSQL is used for persistent storage of user and note data.

**Justification:** This pattern is chosen for its clear separation of concerns, which enhances maintainability, testability, and allows for independent scaling of frontend and backend components. It provides a solid foundation that can evolve towards a more granular microservices architecture in future phases if needed, without requiring a complete rewrite of the core components. The existing Angular Clarity boilerplate naturally fits the rich client model.

## Component Design

### Frontend Components (Angular - Clarity Boilerplate Extension)
*   **AppModule:** Root module, responsible for bootstrapping the application and configuring global services and routes. Integrates `CoreModule`, `SharedModule`, and feature modules.
*   **CoreModule:** (Already exists) Provides singleton services (e.g., `AuthService`, `NoteService`, `HttpInterceptor` for error handling and JWT attachment), guards (e.g., `AuthGuard`), and ensures they are instantiated once. Responsible for application-wide functionalities like authentication token management.
*   **SharedModule:** (Already exists) Contains reusable UI components (e.g., custom form controls, loading indicators), directives, and pipes that are used across multiple feature modules. It will be extended to include any new generic components useful for the notes app.
*   **AuthModule:** A lazy-loaded feature module for all authentication-related components and routing.
    *   **LoginComponent:** Handles user login using email and password (FR-002).
    *   **RegisterComponent:** Handles new user registration (FR-001).
    *   **PasswordResetComponent:** Initiates password reset (FR-003).
    *   **AuthService:** Manages user authentication state, interacts with backend auth API, stores/retrieves JWT.
*   **NotesModule:** A lazy-loaded feature module for all note management functionality.
    *   **NoteListComponent:** Displays a paginated/sortable list of user's notes (FR-005).
    *   **NoteDetailComponent:** Displays the full content of a single note (FR-006).
    *   **NoteEditorComponent:** Provides an interface for creating and editing notes (FR-004, FR-007).
    *   **NoteService:** Manages CRUD operations for notes, interacts with backend notes API, enforces note ownership (FR-009).

### Backend Components (FastAPI)
*   **Main Application:** Entry point for the FastAPI application.
*   **Routers/Controllers:** Handle incoming HTTP requests, validate input, and delegate to service layers.
    *   **AuthRouter:** Endpoints for `/auth/register`, `/auth/login`, `/auth/password-reset`.
    *   **NotesRouter:** Endpoints for `/notes` (GET, POST), `/notes/{id}` (GET, PUT, DELETE).
*   **Services:** Contain the core business logic and interact with the repository layer.
    *   **UserService:** Manages user creation, authentication, password hashing, and user data retrieval.
    *   **NoteService:** Manages note CRUD operations, ensures note ownership for all actions.
*   **Repositories/Data Access Layer:** Abstract database interactions, mapping Python objects to database records.
    *   **UserRepository:** CRUD operations for `User` entity.
    *   **NoteRepository:** CRUD operations for `Note` entity.
*   **Models:** Pydantic models for request/response data validation and SQLAlchemy models for database schema definition.
*   **Security Utilities:** Functions for password hashing (bcrypt), JWT encoding/decoding, and dependency injection for authentication/authorization checks.

### Database Components (PostgreSQL)
*   **Users Table:** Stores user information (`id`, `email`, `password_hash`, `created_at`, `updated_at`).
*   **Notes Table:** Stores note information (`id`, `user_id`, `title`, `content`, `created_at`, `updated_at`).
*   **Indexes:** Optimized indexes on `user_id` in the `notes` table for efficient retrieval of user-specific notes, and on `email` in the `users` table for unique login identification.

## Data Architecture

### Data Model (Entities and Relationships)
*   **User:**
    *   `id` (UUID, PK)
    *   `email` (String, Unique, Required)
    *   `password_hash` (String, Required - salted and hashed)
    *   `created_at` (Timestamp, Auto)
    *   `updated_at` (Timestamp, Auto)
*   **Note:**
    *   `id` (UUID, PK)
    *   `user_id` (UUID, FK to User.id, Required)
    *   `title` (String, Required, Max 255)
    *   `content` (Text, Optional - rich-text)
    *   `created_at` (Timestamp, Auto)
    *   `updated_at` (Timestamp, Auto)

**Relationship:** `User` 1 -- M `Note` (One user can have many notes; each note belongs to exactly one user).

### Data Flow
1.  **User Authentication:**
    *   User enters credentials on Frontend `LoginComponent`.
    *   `AuthService` sends `POST /auth/login` to Backend API.
    *   Backend `AuthRouter` validates credentials, hashes password, compares with `password_hash` in `Users` table via `UserService` and `UserRepository`.
    *   On success, Backend generates JWT and sends it back to Frontend.
    *   Frontend `AuthService` stores JWT securely (e.g., in `localStorage` or `HttpOnly` cookie for refresh tokens) and updates authentication state.

2.  **Note Management (e.g., Create Note):**
    *   Authenticated user interacts with `NoteEditorComponent` to create a new note.
    *   `NoteService` sends `POST /notes` to Backend API, including JWT in `Authorization` header.
    *   Backend `NotesRouter` intercepts request:
        *   Validates JWT and extracts `user_id` (AuthN/AuthZ).
        *   Validates input `title` and `content`.
        *   `NoteService` creates new note record, associating it with the extracted `user_id`, and saves to `Notes` table via `NoteRepository`.
    *   Backend returns new note details to Frontend.
    *   Frontend `NoteService` updates local state, `NoteListComponent` refreshes.

3.  **Secure Access Control (FR-009):**
    *   All API endpoints for note management (`/notes`, `/notes/{id}`) require a valid JWT.
    *   Backend middleware or dependencies ensure the `user_id` extracted from the JWT matches the `user_id` associated with the requested note for all GET, PUT, DELETE operations.

## API Design

**RESTful API Principles:** Adheres to RESTful principles for resource-oriented design, statelessness, and standard HTTP methods.

**Base URL:** `/api/v1` for versioning.

**Authentication:** JWT (JSON Web Tokens) passed in the `Authorization: Bearer <token>` header for all protected endpoints.

**Data Format:** All requests and responses will use `application/json`.

**Error Handling:** Standard HTTP status codes will be used to indicate success or failure, with JSON bodies providing more detailed error messages.
*   `200 OK`, `201 Created`, `204 No Content` for success.
*   `400 Bad Request` for invalid input.
*   `401 Unauthorized` for missing/invalid JWT.
*   `403 Forbidden` for insufficient permissions (e.g., accessing another user's note).
*   `404 Not Found` for non-existent resources.
*   `429 Too Many Requests` for rate limiting.
*   `500 Internal Server Error` for unexpected server issues.

### Key Endpoints (as per `requirements_document.md`)
*   **User Authentication:**
    *   `POST /auth/register`: Register new user, returns token and user info.
    *   `POST /auth/login`: Login user, returns token and user info.
    *   `POST /auth/password-reset`: Initiate password reset, returns message.
*   **Note Management (Protected):**
    *   `GET /notes`: Retrieve list of current user's notes (with sorting, pagination).
    *   `GET /notes/{id}`: Retrieve a specific note by ID (owned by user).
    *   `POST /notes`: Create a new note for the current user.
    *   `PUT /notes/{id}`: Update an existing note by ID (owned by user).
    *   `DELETE /notes/{id}`: Delete a note by ID (owned by user).

## Security Architecture

1.  **Authentication (FR-001, FR-002, NFR-002):**
    *   **JWT-based Authentication:** Backend issues short-lived JWTs upon successful login. Tokens are signed with a strong secret key. Frontend stores tokens securely (e.g., `localStorage` for access token, `HttpOnly` cookies for refresh token if implemented later) and attaches them to `Authorization` headers for API requests.
    *   **Password Hashing:** User passwords are never stored in plain text. `bcrypt` (or similar strong, adaptive hashing algorithm) is used to hash passwords with a unique salt before storage in PostgreSQL (NFR-002).
    *   **Rate Limiting:** Backend implements rate limiting on login and registration endpoints to mitigate brute-force attacks (NFR-002).

2.  **Authorization (FR-009, NFR-002):**
    *   **Role-Based Access Control (RBAC):** Not strictly required for MVP, but the framework for user-specific ownership is in place. Each note is explicitly linked to a `user_id`.
    *   **Note Ownership Enforcement:** All CRUD operations on notes on the backend verify that the `user_id` extracted from the authenticated JWT matches the `user_id` of the note being accessed/modified/deleted. Attempts to access notes not owned by the user result in `403 Forbidden` (FR-009).

3.  **Data Protection (NFR-002):**
    *   **HTTPS/TLS:** All data in transit between the frontend and backend is encrypted using HTTPS/TLS to prevent eavesdropping and tampering.
    *   **Input Validation:** Comprehensive input validation on both frontend and backend (using Angular forms validation and FastAPI Pydantic models) to prevent common vulnerabilities like SQL Injection, XSS, and buffer overflows (NFR-002).
    *   **Environment Variables:** Sensitive configurations (e.g., database credentials, JWT secret) are managed via environment variables and are not hardcoded in the application (NFR-002).

## Scalability Considerations

1.  **Stateless Backend (NFR-004):** The FastAPI backend will be designed to be completely stateless. All session-related data is handled by JWTs, allowing any instance of the backend service to handle any request, facilitating easy horizontal scaling.
2.  **Containerization (NFR-004):** Docker will be used to containerize the frontend, backend, and database services. This provides isolated, consistent, and portable environments, making it straightforward to deploy multiple instances of the backend service behind a load balancer.
3.  **Database Optimization (NFR-004):**
    *   **Indexing:** Appropriate database indexes (e.g., on `user_id` in the `notes` table) will be created to speed up query performance for retrieving user-specific notes.
    *   **Connection Pooling:** Backend will use connection pooling to efficiently manage database connections, reducing overhead.
    *   **Query Optimization:** SQL queries will be optimized for performance, especially for fetching lists of notes and individual notes (NFR-001).
4.  **API Design for Scale:** Pagination and sorting parameters will be implemented for `GET /notes` endpoint to efficiently handle a large number of notes without overwhelming the client or server (NFR-004).
5.  **Frontend Performance (NFR-001):** Lazy loading of Angular feature modules (`AuthModule`, `NotesModule`) will be implemented to minimize initial bundle size and improve load times.



---

## ARCHITECTURE UPDATE - 2025-10-06 07:38:46


## Monitoring and Logging
Generated: 2025-10-06T07:45:00Z

To ensure the application's operational health, performance, and security, a robust monitoring and logging strategy will be implemented.

### Application Metrics
*   Collect real-time metrics for backend API response times, error rates, and resource utilization (CPU, memory, network I/O) to identify performance bottlenecks (NFR-001).
*   Monitor frontend performance metrics such as page load times, Lighthouse scores, and user interaction responsiveness.

### Structured Logging
*   Implement structured logging (e.g., JSON format) across both frontend (via a centralized logging service) and backend services.
*   Logs will capture essential request details (user ID, request path, status code), error messages, and critical application events, facilitating easier searching, filtering, and analysis.

### Alerting
*   Configure automated alerts based on predefined thresholds for key metrics (e.g., high error rates, prolonged high CPU usage, slow API responses) and critical log patterns.
*   Alerts will be integrated with communication channels to ensure proactive incident response.

## Future Enhancements / Roadmap (Post-MVP)
Generated: 2025-10-06T07:45:00Z

The current architecture provides a solid foundation for the MVP. Future phases, particularly Phase 3 as outlined in the `requirements_document.md`, will introduce additional features:

### Search (FR-010)
*   Integration of a full-text search solution to enable users to search their notes by keywords in titles or content. This will require dedicated backend indexing services and a robust search mechanism.

### Note Categorization/Tagging (FR-011)
*   Extension of the data model to include entities for `Categories` or `Tags` with a many-to-many relationship to `Notes`.
*   This will necessitate updates to API endpoints for creating, associating, and filtering notes by tags/categories, as well as new frontend UI components for tag management and display.

