/**
 * Backend API: Layered architecture for scalability and maintainability.
 * 
 * ## Architecture Layers
 * 
 * ### Controllers (routes/)
 * - Handle HTTP requests and responses
 * - Validate input and format output
 * - Call services for business logic
 * 
 * ### Services (services/)
 * - Implement business logic
 * - Coordinate between controllers and repositories
 * - Handle validation and transformation
 * 
 * ### Repositories (repositories/)
 * - Data access layer
 * - Interact with databases or external APIs
 * - Return domain models
 * 
 * ### Models (models/)
 * - Data structures and types
 * - Validation schemas
 * 
 * ### Middleware (middleware/)
 * - Request validation
 * - Authentication/authorization
 * - Rate limiting
 * - Error handling
 * 
 * ## Adding New Endpoints
 * 
 * 1. Define the model in `models/`
 * 2. Implement repository logic in `repositories/`
 * 3. Implement service logic in `services/`
 * 4. Create controller in `routes/`
 * 5. Register route in `index.ts`
 */

import express from 'express'
import cors from 'cors'

// ---------------------------------------------------------------------------
// Configuration
// ---------------------------------------------------------------------------

const PORT = Number(process.env.PORT) || 8080
const CORS_ORIGIN = process.env.CORS_ORIGIN || 'http://localhost:3000'

// ---------------------------------------------------------------------------
// Express App Setup
// ---------------------------------------------------------------------------

const app = express()

app.use(cors({ origin: CORS_ORIGIN }))
app.use(express.json())

// ---------------------------------------------------------------------------
// Agent Routes
// ---------------------------------------------------------------------------

import { handleAgentRequest, handleAgentStreamRequest } from './routes/agentRoutes.js'

/** POST /api/agent - Run AI agent */
app.post('/api/agent', handleAgentRequest)

/** POST /api/agent/stream - Stream AI agent response */
app.post('/api/agent/stream', handleAgentStreamRequest)

// ---------------------------------------------------------------------------
// Health Check Endpoint
// ---------------------------------------------------------------------------

/** GET /health - Health check for Docker / orchestration */
app.get('/health', (req, res) => {
  res.status(200).json({ ok: true, timestamp: Date.now() })
})

// ---------------------------------------------------------------------------
// Error Handling Middleware
// ---------------------------------------------------------------------------

/** Global error handler for consistent error responses */
app.use((err: Error, req: express.Request, res: express.Response, next: express.NextFunction) => {
  console.error('Error:', err)
  res.status(500).json({ error: err.message ?? 'Internal server error' })
})

// ---------------------------------------------------------------------------
// Start Server
// ---------------------------------------------------------------------------

app.listen(PORT, '0.0.0.0', () => {
  console.log(`Backend listening on port ${PORT} (CORS: ${CORS_ORIGIN})`)
})

// ---------------------------------------------------------------------------
// Export for testing
// ---------------------------------------------------------------------------

export default app