package fwd

import (
	"bufio"
	"context"
	"encoding/binary"
	"io"
	"log/slog"
	"net"
	"proxy-server/pkg/utils"
	"proxy-server/server/fwd/core"
	"proxy-server/server/fwd/dispatcher"
	"proxy-server/server/pkg/env"
	"strconv"
	"strings"
	"sync"

	"github.com/pkg/errors"
)

type Config struct {
}

type Service struct {
	Config *Config
	ctx    context.Context
	cancel context.CancelFunc

	userConnMap sync.Map

	fwdLesWg   utils.CountWaitGroup
	ctrlConnWg utils.CountWaitGroup
	dataConnWg utils.CountWaitGroup
	userConnWg utils.CountWaitGroup
}

func New(config *Config) *Service {
	if config == nil {
		config = &Config{}
	}

	ctx, cancel := context.WithCancel(context.Background())
	return &Service{
		Config: config,
		ctx:    ctx,
		cancel: cancel,

		userConnMap: sync.Map{},

		fwdLesWg:   utils.CountWaitGroup{},
		ctrlConnWg: utils.CountWaitGroup{},
		dataConnWg: utils.CountWaitGroup{},
		userConnWg: utils.CountWaitGroup{},
	}
}

func (s *Service) Close() {
	s.cancel()
}

func (s *Service) Run() {
	slog.Info("启动 fwd 服务")

	errQuit := make(chan struct{})
	defer close(errQuit)

	wg := sync.WaitGroup{}

	// 控制通道监听
	wg.Add(1)
	go func() {
		defer wg.Done()
		err := s.startCtrlTun()
		if err != nil {
			slog.Error("fwd 控制通道监听发生错误", "err", err)
			errQuit <- struct{}{}
			return
		}
	}()

	// 数据通道监听
	wg.Add(1)
	go func() {
		defer wg.Done()
		err := s.startDataTun()
		if err != nil {
			slog.Error("fwd 数据通道监听发生错误", "err", err)
			errQuit <- struct{}{}
			return
		}
	}()

	// 等待退出
	select {
	case <-s.ctx.Done():
		slog.Info("fwd 服务主动退出")
	case <-errQuit:
		slog.Warn("fwd 服务异常退出")
		s.Close()
	}

	wg.Wait()
	s.dataConnWg.Wait()
	s.ctrlConnWg.Wait()
	s.fwdLesWg.Wait()
	s.userConnWg.Wait()

	// 清理资源
	s.userConnMap.Range(func(key, value any) bool {
		conn := value.(core.Conn)
		utils.Close(conn)
		return true
	})
	s.userConnMap.Clear()

	s.ctrlConnWg.Wait()
	slog.Debug("控制通道连接已关闭")
	s.dataConnWg.Wait()
	slog.Debug("数据通道连接已关闭")
	s.fwdLesWg.Wait()
	slog.Debug("转发服务已关闭")
	wg.Wait()
	slog.Info("fwd 服务已退出")
}

func (s *Service) startCtrlTun() error {
	ctrlPort := env.AppCtrlPort
	slog.Debug("监听控制通道", slog.Uint64("port", uint64(ctrlPort)))

	// 监听端口
	ls, err := net.Listen("tcp", ":"+strconv.Itoa(int(ctrlPort)))
	if err != nil {
		return errors.Wrap(err, "监听控制通道失败")
	}
	defer utils.Close(ls)

	// 处理连接
	connCh := utils.ChanConnAccept(s.ctx, ls)
	for {
		select {
		case <-s.ctx.Done():
			return nil
		case conn, ok := <-connCh:
			if !ok {
				return errors.New("获取连接失败")
			}
			s.ctrlConnWg.Add(1)
			go func() {
				defer s.ctrlConnWg.Done()
				err := s.processCtrlConn(conn)
				if err != nil {
					slog.Error("处理控制通道连接失败", "err", err)
					utils.Close(conn)
				}
			}()
		}
	}
}

func (s *Service) processCtrlConn(conn net.Conn) error {
	slog.Debug("客户端连入", "addr", conn.RemoteAddr().String())
	reader := bufio.NewReader(conn)

	// 获取转发端口
	portBuf, err := utils.ReadBuffer(reader, 2)
	if err != nil {
		return errors.Wrap(err, "获取转发端口失败")
	}
	port := binary.BigEndian.Uint16(portBuf)

	// 启动转发服务
	proxy, err := dispatcher.New(port)
	if err != nil {
		return errors.Wrap(err, "创建 socks 转发服务失败")
	}
	defer proxy.Close()

	s.fwdLesWg.Add(1)
	go func() {
		defer s.fwdLesWg.Done()
		err := proxy.Run()
		if err != nil {
			slog.Error("代理服务运行失败", "err", err)
			return
		}
	}()

	// 监听客户端连接
	errCh := make(chan error)
	defer close(errCh)
	go func() {
		_, err := reader.ReadByte()
		errCh <- err
	}()

	// 处理连接
	for {
		select {
		case <-s.ctx.Done():
			return nil
		case err := <-errCh:
			switch {
			case strings.Contains(err.Error(), "An existing connection was forcibly closed by the remote host."):
				slog.Debug("客户端主动断开连接")
				return nil
			case err == nil:
				return errors.New("客户端握手失败")
			default:
				return errors.Wrap(err, "客户端意外断开连接")
			}
		case user := <-proxy.Conn:
			s.userConnWg.Add(1)
			go func() {
				defer s.userConnWg.Done()
				err := s.processUserConn(user, conn)
				if err != nil {
					slog.Error("处理用户连接失败", "err", err)
					utils.Close(user)
				}
			}()
		}
	}
}

func (s *Service) startDataTun() error {
	dataPort := env.AppDataPort
	slog.Debug("监听数据通道", slog.Uint64("port", uint64(dataPort)))

	// 监听端口
	ls, err := net.Listen("tcp", ":"+strconv.Itoa(int(dataPort)))
	if err != nil {
		return errors.Wrap(err, "监听数据通道失败")
	}
	defer utils.Close(ls)

	// 处理连接
	connCh := utils.ChanConnAccept(s.ctx, ls)
	for {
		select {
		case <-s.ctx.Done():
			return nil
		case conn, ok := <-connCh:
			if !ok {
				return errors.New("获取连接失败")
			}
			s.dataConnWg.Add(1)
			go func() {
				defer s.dataConnWg.Done()
				defer utils.Close(conn)
				err := s.processDataConn(conn)
				if err != nil {
					slog.Error("处理数据通道失败", "err", err)
				}
			}()
		}
	}
}

func (s *Service) processDataConn(client net.Conn) error {
	slog.Info("客户端准备接收数据 " + client.RemoteAddr().String())

	// 读取 tag
	var tag string
	select {
	case <-s.ctx.Done():
		return nil
	default:
		tagLen, err := utils.ReadByte(client)
		if err != nil {
			return errors.Wrap(err, "从客户端获取 tag 失败")
		}
		tagBuf, err := utils.ReadBuffer(client, int(tagLen))
		if err != nil {
			return errors.Wrap(err, "从客户端获取 tag 失败")
		}
		tag = string(tagBuf)
	}

	// 找到用户连接
	userAny, ok := s.userConnMap.Load(tag)
	if !ok {
		return errors.New("查找用户连接失败")
	}
	user := userAny.(*core.Conn)
	defer utils.Close(user)
	defer s.userConnMap.Delete(tag)

	// 发送目标地址
	select {
	case <-s.ctx.Done():
		return nil
	default:
		dest := user.Dest.String()
		destLen := len(dest)
		destBuf := make([]byte, 1+destLen)
		destBuf[0] = byte(destLen)
		copy(destBuf[1:], dest)
		_, err := client.Write(destBuf)
		if err != nil {
			return errors.Wrap(err, "向客户端发送目标地址失败")
		}
	}

	// 数据转发
	userPipeReader, userPipeWriter := io.Pipe()
	defer utils.Close(userPipeWriter)
	teeUser := io.TeeReader(user, userPipeWriter)
	go func() {
		err := analysisAndLog(user, userPipeReader)
		if err != nil {
			slog.Error("数据解析失败", "err", err)
		}
	}()

	wg := sync.WaitGroup{}
	wg.Add(2)
	go func() {
		defer wg.Done()
		_, err := io.Copy(client, teeUser)
		if err != nil {
			slog.Error("数据转发失败 user->client", "err", err)
		}
	}()
	go func() {
		defer wg.Done()
		_, err := io.Copy(user, client)
		if err != nil {
			if errors.Is(err, net.ErrClosed) {

			} else {
				// slog.Error("数据转发失败 client->user", "err", err, "errType", reflect.TypeOf(err))
			}
		}
	}()

	select {
	case <-s.ctx.Done():
	case <-utils.ChanWgWait(s.ctx, &wg):
	}

	return nil
}

func (s *Service) processUserConn(user *core.Conn, ctrl net.Conn) error {

	// 发送 tag
	tag := user.Tag
	tagLen := len(tag)
	tagBuf := make([]byte, 1+tagLen)
	tagBuf[0] = byte(tagLen)
	copy(tagBuf[1:], tag)

	_, err := ctrl.Write(tagBuf)
	if err != nil {
		return errors.Wrap(err, "向控制通道发送 tag 失败")
	}

	// 记录用户连接
	s.userConnMap.Store(user.Tag, user)

	return nil
}