dance-lessons-coach/AGENTS.md

# DanceLessonsCoach - AI Agent Documentation

This file documents the AI agents, tools, and development workflow for the DanceLessonsCoach project.

## 🎯 Project Overview

**DanceLessonsCoach** is a Go-based web service with CLI capabilities, featuring:
- RESTful JSON API with Chi router
- High-performance Zerolog logging
- Interface-based architecture
- Context-aware services
- Comprehensive testing

## 📋 Development Timeline

### Phase 1: Foundation (Completed ✅)
- Go 1.26.1 environment setup
- Project structure with `cmd/` and `pkg/` directories
- Core Greet service implementation
- CLI interface
- Unit tests

### Phase 2: Web API (Completed ✅)
- Chi router integration
- Versioned API endpoints (`/api/v1`)
- Health endpoint (`/api/health`)
- JSON responses with proper headers

### Phase 3: Logging & Architecture (Completed ✅)
- Zerolog integration with Trace level
- Context-aware logging
- Interface-based design patterns
- Dependency injection

### Phase 4: Documentation & Testing (Completed ✅)
- Comprehensive AGENTS.md
- README.md with usage instructions
- Server management guide
- API endpoint documentation

### Phase 5: Configuration Management (Completed ✅)
- Viper integration for configuration
- Environment variable support with DLC_ prefix
- Customizable server host/port
- Configurable shutdown timeout
- Configuration validation and logging
- Example configuration file

## 🛠️ Tools & Technologies

| Component | Technology | Version |
|-----------|------------|---------|
| Language | Go | 1.26.1 |
| Router | Chi | v5.2.5 |
| Logging | Zerolog | v1.35.0 |
| Configuration | Viper | v1.21.0 |
| Testing | Standard Library | - |
| Dependency Management | Go Modules | - |

## 🗺️ Project Structure

```
DanceLessonsCoach/
├── cmd/
│   ├── greet/          # CLI application
│   │   └── main.go
│   └── server/         # Web server
│       └── main.go
├── pkg/
│   ├── config/         # Configuration management
│   │   └── config.go    # Viper-based config
│   ├── greet/          # Core domain logic
│   │   ├── api_v1.go    # API handlers
│   │   ├── greet.go     # Service implementation
│   │   └── greet_test.go # Unit tests
│   └── server/         # HTTP server
│       └── server.go
├── go.mod              # Dependencies
├── go.sum              # Dependency checksums
├── config.example.yaml # Configuration template
├── README.md           # User documentation
├── AGENTS.md           # This file
└── .gitignore          # Ignore patterns
```

## 🚀 Server Management

### Using the Server Control Script

A convenient shell script is provided for managing the server lifecycle:

```bash
# Navigate to project directory
cd /Users/gabrielradureau/Work/Vibe/DanceLessonsCoach

# Start the server
./scripts/start-server.sh start

# Check server status
./scripts/start-server.sh status

# Test API endpoints
./scripts/start-server.sh test

# View server logs
./scripts/start-server.sh logs

# Stop the server
./scripts/start-server.sh stop
```

**Server Control Script Commands:**
- `start` - Start the server in background with proper logging
- `stop` - Stop the server gracefully
- `restart` - Restart the server
- `status` - Check if server is running
- `logs` - Show recent server logs
- `test` - Test all API endpoints

### Manual Server Management

If you prefer manual control:

```bash
# Navigate to project directory
cd /Users/gabrielradureau/Work/Vibe/DanceLessonsCoach

# Run server in background
go run cmd/server/main.go &
```

**Expected output:**
```
Server running on :8080
[INF] Starting HTTP server on :8080
[TRC] Registering greet routes
[TRC] Greet routes registered
```

**Features:**
- Context-aware server initialization
- Graceful shutdown handling
- Signal-based termination (SIGINT, SIGTERM)
- 30-second shutdown timeout
- Proper resource cleanup

### Configuration Management

The server supports flexible configuration through environment variables with the `DLC_` prefix:

**Available Configuration Options:**

| Option | Environment Variable | Default Value | Description |
|--------|---------------------|---------------|-------------|
| Host | `DLC_SERVER_HOST` | `0.0.0.0` | Server bind address |
| Port | `DLC_SERVER_PORT` | `8080` | Server listening port |
| Shutdown Timeout | `DLC_SHUTDOWN_TIMEOUT` | `30s` | Graceful shutdown timeout |
| JSON Logging | `DLC_LOGGING_JSON` | `false` | Enable JSON format logging |

**Usage Examples:**

```bash
# Custom port
export DLC_SERVER_PORT=9090
go run cmd/server/main.go &

# Custom host and port
export DLC_SERVER_HOST="127.0.0.1"
export DLC_SERVER_PORT=8081
go run cmd/server/main.go &

# Custom shutdown timeout
export DLC_SHUTDOWN_TIMEOUT=45s
go run cmd/server/main.go &

# Enable JSON logging
export DLC_LOGGING_JSON=true
go run cmd/server/main.go &
```

**Configuration File Support:**

A `config.example.yaml` file is provided as a template. By default, the application looks for `config.yaml` in the current working directory.

To specify a custom config file path, set the `DLC_CONFIG_FILE` environment variable:

```bash
DLC_CONFIG_FILE="/path/to/config.yaml" go run ./cmd/server
```

Example `config.yaml`:

```yaml
server:
  host: "0.0.0.0"
  port: 8080

shutdown:
  timeout: 30s

logging:
  json: false
```

**Configuration Loading:**
- **File-based configuration** takes highest precedence
- **Environment variables** override defaults but are overridden by config file
- **Default values** are used when no other configuration is provided
- All configuration is validated on startup
- Invalid configurations cause server startup failure
- Configuration values and source are logged at startup

**Verification:**
```bash
# Test with custom configuration
DLC_SERVER_PORT=9090 DLC_SERVER_HOST="127.0.0.1" go run cmd/server/main.go

# Verify it's running on the custom port
curl http://127.0.0.1:9090/api/health
# Expected: {"status":"healthy"}
```

### Checking Server Status

```bash
# Check health endpoint
curl -s http://localhost:8080/api/health

# Check readiness endpoint
curl -s http://localhost:8080/api/ready
```

**Expected responses:**
- Health: `{"status":"healthy"}`
- Readiness (normal): `{"ready":true}`
- Readiness (during shutdown): `{"ready":false}` with HTTP 503

**Endpoint Differences:**
- **Health endpoint** (`/api/health`): Indicates if the application is running and functional
- **Readiness endpoint** (`/api/ready`): Indicates if the application is ready to accept traffic

**Use Cases:**
- **Health**: Used by load balancers to check if the app is alive
- **Readiness**: Used by Kubernetes/service meshes to determine if the app can accept new requests

**During Graceful Shutdown:**
- Health endpoint continues to return `{"status":"healthy"}`
- Readiness endpoint returns `{"ready":false}` with HTTP 503 Service Unavailable
- This allows existing requests to complete while preventing new requests

### Stopping the Server

To stop the server gracefully:
```bash
# Send SIGTERM for graceful shutdown
kill -TERM $(lsof -ti :8080)

# Or send SIGINT (Ctrl+C equivalent)
pkill -INT -f "go run"
```

**Graceful shutdown process:**
1. Server receives termination signal
2. Logs shutdown message
3. Stops accepting new connections
4. Waits up to 30 seconds for active requests to complete
5. Closes all connections cleanly
6. Exits with proper cleanup

For force stop (if graceful shutdown hangs):
```bash
kill -9 $(lsof -ti :8080)
```

**Verification:**
```bash
curl -s http://localhost:8080/api/health
# Should return connection refused
```

## 🌐 API Endpoints

### Base URL
```
http://localhost:8080
```

### Health Check
```http
GET /api/health
```

**Response:**
```json
{"status":"healthy"}
```

### Readiness Check
```http
GET /api/ready
```

**Responses:**
- Normal operation: `{"ready":true}` (HTTP 200)
- During shutdown: `{"ready":false}` (HTTP 503 Service Unavailable)

**Purpose:** Indicates whether the server is ready to accept new requests. Returns false during graceful shutdown to allow existing requests to complete while preventing new ones.

### Greet Service
```http
GET /api/v1/greet/
GET /api/v1/greet/{name}
```

**Examples:**
```bash
# Default greeting
curl http://localhost:8080/api/v1/greet/
# Response: {"message":"Hello world!"}

# Personalized greeting
curl http://localhost:8080/api/v1/greet/John
# Response: {"message":"Hello John!"}

# Another example
curl http://localhost:8080/api/v1/greet/Alice
# Response: {"message":"Hello Alice!"}
```

## 🔧 Development Workflow

### 1. Check Server Status
```bash
curl -s http://localhost:8080/api/health
```

### 2. Start Development Server
```bash
cd /Users/gabrielradureau/Work/Vibe/DanceLessonsCoach
go run cmd/server/main.go &
```

### 3. Test API Endpoints
```bash
# Test all endpoints as shown above
curl http://localhost:8080/api/v1/greet/YourName
```

### 4. Run Tests
```bash
# Run all tests
go test ./...

# Run specific package
go test ./pkg/greet/
```

### 5. Make Changes
- Edit source files in `pkg/` or `cmd/`
- Follow existing patterns and interfaces
- Add tests for new functionality

### 6. Stop and Restart
```bash
pkill -f "go"
go run cmd/server/main.go &
```

## 🧪 Testing

### Unit Tests
```bash
# Run all tests
go test ./...

# Run with verbose output
go test -v ./...

# Run specific test
go test ./pkg/greet/ -run TestService_Greet
```

### CLI Testing
```bash
# Default greeting
go run ./cmd/greet
# Output: Hello world!

# Personalized greeting
go run ./cmd/greet John
# Output: Hello John!
```

### API Testing
```bash
# Health check
curl http://localhost:8080/api/health

# Greet endpoints
curl http://localhost:8080/api/v1/greet/John
curl http://localhost:8080/api/v1/greet/
```

## 📝 Architecture Decisions

### Interface-Based Design
```go
type Greeter interface {
    Greet(ctx context.Context, name string) string
}
```

**Benefits:**
- Easy mocking for tests
- Dependency injection
- Multiple implementations
- Clear contracts

### Context-Aware Services
```go
func (s *Service) Greet(ctx context.Context, name string) string {
    log.Trace().Ctx(ctx).Str("name", name).Msg("Greet function called")
    // ...
}
```

**Benefits:**
- Request tracing
- Cancellation support
- Deadline propagation
- Metadata passing

### Server Context Management
```go
// Root context with cancellation
ctx, cancel := context.WithCancel(context.Background())
defer cancel()

// Server context with graceful shutdown
serverCtx, serverStop := context.WithCancel(ctx)

// HTTP server with context-aware shutdown
srv := &http.Server{
	Addr:    ":8080",
	Handler: server.Router(),
}

// Graceful shutdown with timeout
shutdownCtx, shutdownCancel := context.WithTimeout(
	context.Background(), 
	30*time.Second
)
defer shutdownCancel()

if err := srv.Shutdown(shutdownCtx); err != nil {
	log.Error().Err(err).Msg("Server shutdown failed")
}
```

**Benefits:**
- Graceful shutdown handling
- Signal-based termination (SIGINT, SIGTERM)
- 30-second timeout for active connections
- Proper resource cleanup
- Context propagation throughout server lifecycle

### Zerolog Logging
```go
zerolog.SetGlobalLevel(zerolog.TraceLevel)
log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr})
```

**Benefits:**
- High performance
- Structured logging
- Trace level detail
- Color output

### Versioned API
```go
router.Route("/api/v1", func(r chi.Router) {
    // v1 endpoints
})
```

**Benefits:**
- Backward compatibility
- Clear versioning
- Easy migration
- Parallel versions

## 🔍 Troubleshooting

### Port Already in Use
```bash
# Find and kill process using port 8080
kill -TERM $(lsof -ti :8080)
```

### Server Not Responding
```bash
# Check if running
curl -s http://localhost:8080/api/health

# Restart server
pkill -f "go"
go run cmd/server/main.go &
```

### Dependency Issues
```bash
# Clean and rebuild
go mod tidy
go build ./...
```

### Tests Failing
```bash
# Run with verbose output
go test -v ./...

# Check specific test
go test ./pkg/greet/ -run TestName
```

## 📚 Code Examples

### Adding New API Endpoint
```go
// 1. Add to interface
func (h *apiV1GreetHandler) RegisterRoutes(router chi.Router) {
    router.Get("/", h.handleGreetQuery)
    router.Get("/{name}", h.handleGreetPath)
    router.Post("/custom", h.handleCustomGreet) // New endpoint
}

// 2. Implement handler
func (h *apiV1GreetHandler) handleCustomGreet(w http.ResponseWriter, r *http.Request) {
    // Parse request
    // Call service
    // Return JSON response
}
```

### Adding Logging
```go
// Trace level logging
log.Trace().Ctx(ctx).Str("key", "value").Msg("message")

// Info level
log.Info().Msg("Important event")

// Error level
log.Error().Err(err).Msg("Error occurred")
```

### Using Context
```go
// Pass context through calls
func handler(w http.ResponseWriter, r *http.Request) {
    result := service.Greet(r.Context(), "John")
    // ...
}

// Create context with values
ctx := context.WithValue(r.Context(), "key", "value")

// Create context with timeout
ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
defer cancel()
```

## 🎓 Best Practices

### Code Organization
- Keep handlers thin, move logic to services
- Use interfaces for dependencies
- Separate route registration from handlers
- Group related functionality

### Error Handling
- Return proper HTTP status codes
- Log errors with context
- Don't expose internal errors to clients
- Use structured error responses

### Performance
- Use Zerolog's Trace level sparingly in production
- Avoid allocations in hot paths
- Use context timeouts for external calls
- Batch database operations

### Testing
- Test interfaces, not implementations
- Use table-driven tests
- Test error cases
- Mock dependencies

## 📈 Future Enhancements

### Potential Features
- [ ] Configuration management
- [ ] Database integration
- [ ] Authentication/Authorization
- [ ] Rate limiting
- [ ] Metrics and monitoring
- [ ] Docker containerization
- [ ] CI/CD pipeline

### Architectural Improvements
- [ ] Request validation middleware
- [ ] OpenAPI/Swagger documentation
- [ ] Graceful shutdown
- [ ] Configuration hot reload
- [ ] Circuit breakers

## 📝 Changelog

### 2026-04-03 - Current Version
- ✅ Zerolog integration with Trace level
- ✅ Context-aware Greet service
- ✅ Fixed route structure `/api/v1/greet/*`
- ✅ Comprehensive server management guide
- ✅ Verified all API endpoints working
- ✅ Updated documentation

### 2026-04-02 - Web API Implementation
- ✅ Chi router integration
- ✅ Versioned API endpoints
- ✅ JSON responses
- ✅ Health endpoint
- ✅ Interface-based design

### 2026-04-01 - Foundation
- ✅ Go 1.26.1 setup
- ✅ Project structure
- ✅ Core Greet service
- ✅ CLI interface
- ✅ Unit tests

## 🤖 AI Agent Information

**Agent:** Mistral Vibe CLI Agent
**Version:** devstral-2
**Role:** Development Assistant
**Capabilities:**
- Code generation and refactoring
- Test creation
- Documentation
- Architecture guidance
- Best practices enforcement

## 📋 Quick Reference

### Common Commands
```bash
# Start server
go run cmd/server/main.go &

# Test API
curl http://localhost:8080/api/v1/greet/John

# Run tests
go test ./...

# Stop server
pkill -f "go"

# CLI usage
go run ./cmd/greet John
```

### Project Structure
```
cmd/        # Entry points
pkg/        # Core logic
  greet/    # Domain services
  server/   # HTTP server
go.mod      # Dependencies
README.md   # User docs
AGENTS.md   # This file
```

### Key Interfaces
```go
type Greeter interface {
    Greet(ctx context.Context, name string) string
}

type ApiV1Greet interface {
    RegisterRoutes(router chi.Router)
}
```

## 📞 Support

For issues or questions:
1. Check this documentation
2. Review test cases
3. Examine existing implementations
4. Consult Go and Chi documentation
5. Ask the AI agent for guidance

This documentation provides a complete guide to developing, testing, and maintaining the DanceLessonsCoach project using the established patterns and best practices.