package server

import (
	"context"
	"fmt"
	"log/slog"
	"net"
	"net/http"
	"os"
	"sync"
	"time"

	"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
	"google.golang.org/grpc/reflection"

	"go-grpc-gateway-template/internal/config"
	"go-grpc-gateway-template/internal/health"
	helloworldpb "go-grpc-gateway-template/proto/helloworld"
)

// Server wraps gRPC and HTTP servers with configuration
type Server struct {
	config      *config.Config
	logger      *slog.Logger
	grpcServer  *grpc.Server
	httpServer  *http.Server
	healthHandler *health.Handler
}

// New creates a new server instance
func New(cfg *config.Config) *Server {
	// Setup logger
	var handler slog.Handler
	if cfg.Log.Format == "json" {
		handler = slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
			Level: parseLogLevel(cfg.Log.Level),
		})
	} else {
		handler = slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
			Level: parseLogLevel(cfg.Log.Level),
		})
	}
	logger := slog.New(handler)

	// Create health handler
	healthHandler := health.NewHandler("1.0.0")

	return &Server{
		config:        cfg,
		logger:        logger,
		healthHandler: healthHandler,
	}
}

// Start starts both gRPC and HTTP servers
func (s *Server) Start(ctx context.Context) error {
	var wg sync.WaitGroup
	errChan := make(chan error, 2)

	// Start gRPC server
	wg.Add(1)
	go func() {
		defer wg.Done()
		if err := s.startGRPCServer(ctx); err != nil {
			errChan <- fmt.Errorf("gRPC server error: %w", err)
		}
	}()

	// Start HTTP server
	wg.Add(1)
	go func() {
		defer wg.Done()
		if err := s.startHTTPServer(ctx); err != nil && err != http.ErrServerClosed {
			errChan <- fmt.Errorf("HTTP server error: %w", err)
		}
	}()

	// Wait for servers to start
	go func() {
		wg.Wait()
		close(errChan)
	}()

	// Return first error if any
	return <-errChan
}

func (s *Server) startGRPCServer(ctx context.Context) error {
	lis, err := net.Listen("tcp", ":"+s.config.Server.GRPCPort)
	if err != nil {
		return fmt.Errorf("failed to listen on port %s: %w", s.config.Server.GRPCPort, err)
	}

	s.grpcServer = grpc.NewServer()
	
	// Register services
	greeter := &GreeterService{}
	helloworldpb.RegisterGreeterServer(s.grpcServer, greeter)
	
	// Enable reflection for development
	reflection.Register(s.grpcServer)

	s.logger.Info("Starting gRPC server", "port", s.config.Server.GRPCPort)
	
	return s.grpcServer.Serve(lis)
}

func (s *Server) startHTTPServer(ctx context.Context) error {
	// Create gRPC client connection
	conn, err := grpc.DialContext(
		ctx,
		"localhost:"+s.config.Server.GRPCPort,
		grpc.WithBlock(),
		grpc.WithTransportCredentials(insecure.NewCredentials()),
	)
	if err != nil {
		return fmt.Errorf("failed to dial gRPC server: %w", err)
	}

	// Create gateway mux
	gwMux := runtime.NewServeMux()
	
	// Register gRPC gateway handlers
	err = helloworldpb.RegisterGreeterHandler(ctx, gwMux, conn)
	if err != nil {
		return fmt.Errorf("failed to register gateway: %w", err)
	}

	// Create HTTP mux with health endpoint
	mux := http.NewServeMux()
	mux.Handle("/", gwMux)
	mux.Handle("/health", s.healthHandler)

	s.httpServer = &http.Server{
		Addr:         ":" + s.config.Server.HTTPPort,
		Handler:      mux,
		ReadTimeout:  30 * time.Second,
		WriteTimeout: 30 * time.Second,
		IdleTimeout:  120 * time.Second,
	}

	s.logger.Info("Starting HTTP server", "port", s.config.Server.HTTPPort)
	
	return s.httpServer.ListenAndServe()
}

// Shutdown gracefully shuts down the servers
func (s *Server) Shutdown(ctx context.Context) error {
	s.logger.Info("Shutting down servers...")

	var wg sync.WaitGroup
	
	// Shutdown HTTP server
	if s.httpServer != nil {
		wg.Add(1)
		go func() {
			defer wg.Done()
			if err := s.httpServer.Shutdown(ctx); err != nil {
				s.logger.Error("HTTP server shutdown error", "error", err)
			}
		}()
	}

	// Shutdown gRPC server
	if s.grpcServer != nil {
		wg.Add(1)
		go func() {
			defer wg.Done()
			s.grpcServer.GracefulStop()
		}()
	}

	wg.Wait()
	s.logger.Info("Servers stopped")
	return nil
}

// GreeterService implements the helloworld.Greeter service
type GreeterService struct {
	helloworldpb.UnimplementedGreeterServer
}

// SayHello implements the SayHello RPC method
func (g *GreeterService) SayHello(ctx context.Context, req *helloworldpb.HelloRequest) (*helloworldpb.HelloReply, error) {
	return &helloworldpb.HelloReply{
		Message: "Hello " + req.GetName(),
	}, nil
}

func parseLogLevel(level string) slog.Level {
	switch level {
	case "debug":
		return slog.LevelDebug
	case "info":
		return slog.LevelInfo
	case "warn":
		return slog.LevelWarn
	case "error":
		return slog.LevelError
	default:
		return slog.LevelInfo
	}
}