Add Copilot instructions and AGENTS.md guide for repository

.github/copilot-instructions.md

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+# Copilot Instructions for ChatApp Backend
+
+## Project Overview
+
+ChatApp is a real-time messaging platform backend built with Java 21 and Spring Boot. It enables registered users to receive and respond to messages from anonymous users using WebSocket technology for real-time communication.
+
+## Tech Stack
+
+- **Language**: Java 21
+- **Framework**: Spring Boot 3.5.0
+- **Build Tool**: Maven
+- **Database**: PostgreSQL with Flyway migrations
+- **Real-time**: Spring WebSocket
+- **Security**: Spring Security with JWT and OAuth 2.0 (Google)
+- **ORM**: Spring Data JPA
+- **Utilities**: Lombok, Jackson
+- **Monitoring**: Spring Boot Actuator with Prometheus metrics
+- **Caching**: Redis (Spring Data Redis)
+
+## Build and Test Commands
+
+### Build
+```bash
+mvn clean install
+```
+
+### Run Application
+```bash
+mvn spring-boot:run
+```
+
+### Run Tests
+```bash
+mvn test
+```
+
+### Generate Coverage Report
+```bash
+mvn verify
+```
+
+The application runs on `http://localhost:8080` by default.
+
+## Project Structure
+
+```
+src/main/java/com/fredmaina/chatapp/
+├── ChatappApplication.java       # Main application entry point with @EnableCaching
+├── Auth/                          # Authentication and authorization module
+│   ├── controllers/              # REST controllers for auth endpoints
+│   ├── Dtos/                     # Data Transfer Objects (note capitalization)
+│   ├── Models/                   # Entity models
+│   ├── Repositories/             # JPA repositories
+│   ├── services/                 # Business logic (JWT, Auth)
+│   ├── configs/                  # Security configurations
+│   └── exceptions/               # Exception handling
+└── core/                         # Core chat functionality
+    ├── Controllers/              # Chat REST controllers
+    ├── DTOs/                     # Data Transfer Objects
+    ├── models/                   # Chat entity models
+    ├── Repositories/             # Chat repositories
+    ├── Services/                 # Chat and messaging services
+    └── config/                   # WebSocket and other configs
+```
+
+## Coding Conventions
+
+### General Practices
+- Use **Lombok** annotations to reduce boilerplate (`@Slf4j`, `@Data`, `@Builder`, etc.)
+- Follow Spring Boot best practices and conventions
+- Use constructor injection with `@Autowired` (or prefer constructor injection without @Autowired)
+- Use `@Valid` annotation for request body validation
+- Log important operations using SLF4J (`@Slf4j`)
+
+### Naming Conventions
+- **Controllers**: Suffix with `Controller` (e.g., `AuthController`, `ChatController`)
+- **Services**: Suffix with `Service` (e.g., `AuthService`, `ChatService`)
+- **DTOs**: Place in `Dtos/` or `DTOs/` directories (note mixed case in existing code)
+- **Repositories**: Suffix with `Repository` and extend Spring Data JPA interfaces
+- **Models/Entities**: Use JPA annotations (`@Entity`, `@Table`, etc.)
+
+### Package Structure
+- **Auth module**: Uses lowercase `controllers`, `services`, but capitalized `Dtos`, `Models`, `Repositories`
+- **Core module**: Uses capitalized `Controllers`, `Services`, `DTOs`, etc.
+- Maintain consistency within each module when adding new files
+
+### REST API Conventions
+- Base paths: `/api/auth` for authentication, `/api` for chat operations
+- Return `ResponseEntity<T>` with appropriate HTTP status codes
+- Use standard HTTP status codes:
+  - 200 OK for successful GET
+  - 201 Created for successful POST (registration)
+  - 401 Unauthorized for authentication failures
+  - 409 Conflict for duplicate resources
+- Use `@RequestBody` for request payloads
+- Use `@PathVariable` and `@RequestParam` for URL parameters
+
+### Security
+- **JWT Authentication**: Use for API authentication
+- **Google OAuth 2.0**: Supported for social login
+- **WebSocket Security**: Token-based for authenticated users, session-based for anonymous
+- Always validate and sanitize user input
+- Use Spring Security for endpoint protection
+- Store sensitive configuration in environment variables
+
+## Database
+
+### Flyway Migrations
+- Located in: `src/main/resources/db/migration/`
+- Naming: `V{number}__{description}.sql` (e.g., `V1__create_users_table.sql`)
+- Always create migrations for schema changes
+- Never modify existing migration files
+
+### Configuration
+Use environment variables for database connection:
+- `SPRING_DATASOURCE_URL`
+- `SPRING_DATASOURCE_USERNAME`
+- `SPRING_DATASOURCE_PASSWORD`
+
+## WebSocket
+
+- **Endpoint**: `/ws/chat`
+- **Authenticated users**: Connect with JWT token as query parameter (`?token=<JWT>`)
+- **Anonymous users**: Connect with `anonSessionId` in cookie
+- Message types: `ANON_TO_USER`, `USER_TO_ANON`, `MARK_AS_READ`
+
+## Testing
+
+- Tests located in: `src/test/java/com/fredmaina/chatapp/`
+- Use JUnit and Spring Boot Test annotations
+- Mock dependencies appropriately
+- Follow existing test patterns in `AuthServiceTest.java`
+- Code coverage tracked with JaCoCo
+
+## Environment Configuration
+
+Configuration is in `src/main/resources/application.properties`. Use environment variables:
+
+**Required**:
+- `JWT_SECRET` - Secret key for JWT signing
+- `GOOGLE_CLIENT_ID` - Google OAuth client ID
+- `GOOGLE_SECRET_ID` - Google OAuth client secret
+- `GOOGLE_REDIRECT_URI` - OAuth redirect URI
+
+**Optional**:
+- `security.allowed-origins` - CORS allowed origins
+- `security.allowed-methods` - CORS allowed methods
+- `security.allowed-headers` - CORS allowed headers
+
+## Common Patterns
+
+### Controller Pattern
+```java
+@Slf4j
+@Controller
+@RequestMapping("/api/...")
+public class ExampleController {
+    @Autowired
+    private ExampleService service;
+
+    @PostMapping("/endpoint")
+    public ResponseEntity<ResponseDto> method(@Valid @RequestBody RequestDto request) {
+        // Implementation
+    }
+}
+```
+
+### Service Pattern
+- Business logic goes in services
+- Services interact with repositories
+- Use transactions where appropriate (`@Transactional`)
+
+### Exception Handling
+- Global exception handling is implemented
+- Use custom exceptions when appropriate
+- Return meaningful error messages in responses
+
+## Additional Notes
+
+- The application uses caching (Redis) - consider cache invalidation when modifying data
+- Actuator endpoints available for monitoring
+- Prometheus metrics exposed for observability
+- Spring DevTools enabled for development
+- Follow the contribution guidelines in `CONTRIBUTING.md`

AGENTS.md

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+# AGENTS.md
+
+A guide for AI coding agents working on this repository.
+
+## Setup commands
+- Install dependencies: `mvn clean install`
+- Start dev server: `mvn spring-boot:run`
+- Run tests: `mvn test`
+- Generate coverage report: `mvn verify`
+
+## Tech stack
+- Java 21
+- Spring Boot 3.5.0
+- PostgreSQL with Flyway migrations
+- Spring Security with JWT and OAuth 2.0
+- Spring WebSocket for real-time messaging
+- Redis for caching
+- Maven for build management
+
+## Code style
+- Use Lombok annotations (`@Slf4j`, `@Data`, `@Builder`) to reduce boilerplate
+- Follow Spring Boot best practices and conventions
+- Use constructor injection for dependencies
+- Use `@Valid` annotation for request body validation
+- Log important operations using SLF4J
+
+## Project structure
+- `src/main/java/com/fredmaina/chatapp/Auth/` - Authentication module (lowercase `controllers/`, `services/` but capitalized `Dtos/`, `Models/`, `Repositories/`)
+- `src/main/java/com/fredmaina/chatapp/core/` - Core chat functionality (capitalized `Controllers/`, `Services/`, `DTOs/`)
+- `src/main/resources/db/migration/` - Flyway database migrations
+- `src/test/java/` - Test files
+
+## Database migrations
+- Location: `src/main/resources/db/migration/`
+- Naming: `V{number}__{description}.sql` (e.g., `V1__create_users_table.sql`)
+- Never modify existing migration files
+- Always create new migrations for schema changes
+
+## API conventions
+- Auth endpoints: `/api/auth`
+- Chat endpoints: `/api`
+- Return `ResponseEntity<T>` with appropriate HTTP status codes
+- Use standard status codes: 200 OK, 201 Created, 401 Unauthorized, 409 Conflict
+
+## WebSocket
+- Endpoint: `/ws/chat`
+- Authenticated users: JWT token as query parameter (`?token=<JWT>`)
+- Anonymous users: Session ID in cookie
+- Message types: `ANON_TO_USER`, `USER_TO_ANON`, `MARK_AS_READ`
+
+## Security
+- JWT authentication for API endpoints
+- Google OAuth 2.0 for social login
+- Store sensitive config in environment variables (`JWT_SECRET`, `GOOGLE_CLIENT_ID`, etc.)
+- Always validate and sanitize user input
+
+## Testing
+- Tests in: `src/test/java/com/fredmaina/chatapp/`
+- Use JUnit 5 and Spring Boot Test annotations
+- Mock dependencies with Mockito
+- Follow existing patterns in `AuthServiceTest.java`