// Copyright 2025 The frp Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"flag"
	"fmt"
	"net"
	"os"
	"os/signal"
	"syscall"

	v1 "github.com/fatedier/frp/pkg/config/v1"
	"github.com/fatedier/frp/pkg/vnet"
)

func main() {
	// Parse command-line flags
	listenAddr := flag.String("listen", ":8000", "Server listen address (ip:port)")
	serverTUNAddr := flag.String("tun", "10.20.0.1/24", "Server TUN device address")
	flag.Parse()

	// Listen for incoming connections
	listener, err := net.Listen("tcp", *listenAddr)
	if err != nil {
		fmt.Printf("Failed to listen on %s: %v\n", *listenAddr, err)
		return
	}
	defer listener.Close()

	fmt.Printf("Server listening on %s\n", *listenAddr)
	fmt.Printf("Server TUN address: %s\n", *serverTUNAddr)

	// Set up vnet controller on the server
	serverCfg := v1.VirtualNetConfig{
		Address: *serverTUNAddr, // Server TUN device address
	}
	serverController := vnet.NewController(serverCfg)
	if err := serverController.Init(); err != nil {
		fmt.Printf("Server init error: %v\n", err)
		return
	}

	// Start the controller
	go func() {
		if err := serverController.Run(); err != nil {
			fmt.Printf("Server run error: %v\n", err)
		}
	}()

	// Handle shutdown gracefully
	c := make(chan os.Signal, 1)
	signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)

	go func() {
		<-c
		fmt.Println("\nShutting down server...")
		os.Exit(0)
	}()

	fmt.Println("Waiting for client connection...")
	// Accept and handle connections
	for {
		conn, err := listener.Accept()
		if err != nil {
			fmt.Printf("Error accepting connection: %v\n", err)
			continue
		}

		fmt.Printf("New client connected from %s\n", conn.RemoteAddr())

		// Wrap the connection
		rwc := &readWriteCloserConn{conn}

		// Register the connection
		if err := serverController.RegisterServerConn("client", rwc); err != nil {
			fmt.Printf("Register server connection error: %v\n", err)
			conn.Close()
			continue
		}

		fmt.Println("VPN tunnel established with client")
		fmt.Printf("Server TUN: %s\n", *serverTUNAddr)
	}
}

// readWriteCloserConn wraps net.Conn as io.ReadWriteCloser
type readWriteCloserConn struct {
	net.Conn
}

func (rwc *readWriteCloserConn) Read(p []byte) (n int, err error) {
	return rwc.Conn.Read(p)
}

func (rwc *readWriteCloserConn) Write(p []byte) (n int, err error) {
	return rwc.Conn.Write(p)
}

func (rwc *readWriteCloserConn) Close() error {
	return rwc.Conn.Close()
}