// Package server provides the HTTP server for the Felt tournament engine.
// It configures chi router with middleware, defines route groups, and serves
// the SvelteKit SPA via go:embed.
package server

import (
	"context"
	"database/sql"
	"encoding/json"
	"log"
	"net/http"
	"time"

	"github.com/go-chi/chi/v5"
	chimw "github.com/go-chi/chi/v5/middleware"

	"github.com/felt-app/felt/frontend"
	"github.com/felt-app/felt/internal/auth"
	"github.com/felt-app/felt/internal/clock"
	"github.com/felt-app/felt/internal/server/middleware"
	"github.com/felt-app/felt/internal/server/routes"
	"github.com/felt-app/felt/internal/server/ws"
	natsserver "github.com/nats-io/nats-server/v2/server"
)

// Config holds server configuration.
type Config struct {
	Addr       string
	SigningKey []byte
	DevMode    bool
}

// Server wraps the HTTP server with all dependencies.
type Server struct {
	httpServer    *http.Server
	hub           *ws.Hub
	db            *sql.DB
	nats          *natsserver.Server
	authService   *auth.AuthService
	clockRegistry *clock.Registry
}

// New creates a new HTTP server with all routes and middleware configured.
func New(cfg Config, db *sql.DB, nats *natsserver.Server, hub *ws.Hub, authService *auth.AuthService, clockRegistry *clock.Registry) *Server {
	r := chi.NewRouter()

	// Global middleware
	r.Use(chimw.RequestID)
	r.Use(chimw.RealIP)
	r.Use(chimw.Logger)
	r.Use(chimw.Recoverer)

	// Request body size limit: 1MB default
	r.Use(middleware.MaxBytesReader(1 << 20)) // 1MB

	// CORS: permissive for development
	r.Use(corsMiddleware(cfg.DevMode))

	s := &Server{
		hub:           hub,
		db:            db,
		nats:          nats,
		authService:   authService,
		clockRegistry: clockRegistry,
	}

	// Auth handler
	authHandler := routes.NewAuthHandler(authService)

	// Clock handler
	clockHandler := routes.NewClockHandler(clockRegistry, db)

	// API routes
	r.Route("/api/v1", func(r chi.Router) {
		// Public endpoints (no auth required)
		r.Get("/health", s.handleHealth)

		// Auth endpoints (login is public, others require auth)
		r.Post("/auth/login", authHandler.HandleLogin)

		// Protected endpoints
		r.Group(func(r chi.Router) {
			r.Use(middleware.JWTAuth(cfg.SigningKey))

			// Auth endpoints that require authentication
			r.Get("/auth/me", authHandler.HandleMe)
			r.Post("/auth/logout", authHandler.HandleLogout)

			// Template building blocks and tournament templates
			templateRoutes := routes.NewTemplateRoutes(db)
			templateRoutes.Register(r)

			// Clock routes
			clockHandler.RegisterRoutes(r)

			// Stub endpoints -- return 200 for now
			r.Get("/tournaments", stubHandler("tournaments"))
			r.Get("/players", stubHandler("players"))
		})
	})

	// WebSocket endpoint
	r.Get("/ws", hub.HandleConnect)

	// SvelteKit SPA fallback (must be last)
	r.Handle("/*", frontend.Handler())

	s.httpServer = &http.Server{
		Addr:              cfg.Addr,
		Handler:           r,
		ReadHeaderTimeout: 10 * time.Second,
		ReadTimeout:       30 * time.Second,
		WriteTimeout:      60 * time.Second,
		IdleTimeout:       120 * time.Second,
		MaxHeaderBytes:    1 << 20, // 1MB
	}

	return s
}

// Handler returns the HTTP handler for use in tests.
func (s *Server) Handler() http.Handler {
	return s.httpServer.Handler
}

// ListenAndServe starts the HTTP server.
func (s *Server) ListenAndServe() error {
	log.Printf("server: listening on %s", s.httpServer.Addr)
	return s.httpServer.ListenAndServe()
}

// Shutdown gracefully shuts down the HTTP server.
func (s *Server) Shutdown(ctx context.Context) error {
	log.Printf("server: shutting down")
	return s.httpServer.Shutdown(ctx)
}

// handleHealth returns the health status of all subsystems.
func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	status := map[string]interface{}{
		"status": "ok",
		"subsystems": map[string]interface{}{
			"database": s.checkDatabase(),
			"nats":     s.checkNATS(),
			"websocket": map[string]interface{}{
				"status":  "ok",
				"clients": s.hub.ClientCount(),
			},
		},
		"timestamp": time.Now().UTC().Format(time.RFC3339),
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(status)
}

// checkDatabase verifies the database is operational.
func (s *Server) checkDatabase() map[string]interface{} {
	var result int
	err := s.db.QueryRow("SELECT 1").Scan(&result)
	if err != nil {
		return map[string]interface{}{
			"status": "error",
			"error":  err.Error(),
		}
	}
	return map[string]interface{}{
		"status": "ok",
	}
}

// checkNATS verifies the NATS server is operational.
func (s *Server) checkNATS() map[string]interface{} {
	if s.nats == nil {
		return map[string]interface{}{
			"status": "error",
			"error":  "not initialized",
		}
	}

	varz, err := s.nats.Varz(nil)
	if err != nil {
		return map[string]interface{}{
			"status": "error",
			"error":  err.Error(),
		}
	}

	return map[string]interface{}{
		"status":      "ok",
		"connections": varz.Connections,
		"jetstream":   s.nats.JetStreamEnabled(),
	}
}

// stubHandler returns a handler that responds with 200 and a JSON stub.
func stubHandler(name string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(map[string]interface{}{
			"status":  "stub",
			"name":    name,
			"message": "Not yet implemented",
		})
	}
}

// corsMiddleware returns CORS middleware. In dev mode, it's permissive.
func corsMiddleware(devMode bool) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			if devMode {
				w.Header().Set("Access-Control-Allow-Origin", "*")
			} else {
				// In production, only allow same-origin
				origin := r.Header.Get("Origin")
				if origin != "" {
					w.Header().Set("Access-Control-Allow-Origin", origin)
				}
			}
			w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS, PATCH")
			w.Header().Set("Access-Control-Allow-Headers", "Accept, Authorization, Content-Type, X-Request-ID")
			w.Header().Set("Access-Control-Allow-Credentials", "true")
			w.Header().Set("Access-Control-Max-Age", "300")

			if r.Method == "OPTIONS" {
				w.WriteHeader(http.StatusOK)
				return
			}

			next.ServeHTTP(w, r)
		})
	}
}