package fwd

import (
	"bufio"
	"context"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net"
	"proxy-server/gateway/app"
	"proxy-server/gateway/core"
	"proxy-server/gateway/debug"
	"proxy-server/gateway/env"
	"proxy-server/gateway/fwd/metrics"
	"proxy-server/utils"
	"strconv"
	"time"
)

func ListenData(ctx context.Context) error {
	dataPort := env.AppDataPort

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

	// 异步等待连接
	var connCh = make(chan net.Conn)
	go func() {
		for {
			conn, err := ls.Accept()
			if errors.Is(err, net.ErrClosed) {
				slog.Debug("数据通道监听关闭")
				return
			}
			if err != nil {
				slog.Error("接受数据通道连接失败", "err", err)
				return
			}
			select {
			case connCh <- conn:
			case <-ctx.Done():
				utils.Close(conn)
				return
			}
		}
	}()

	// 处理连接
	for {
		select {
		case <-ctx.Done():
			return nil
		case conn := <-connCh:
			app.DataConnWg.Add(1)
			go func() {
				defer app.DataConnWg.Done()
				defer func() {
					utils.Close(conn)
					slog.Debug("关闭数据通道连接")
				}()
				err := processDataConn(ctx, conn)
				if err != nil {
					slog.Error("处理数据通道连接失败", "err", err)
				}
			}()
		}
	}
}

func processDataConn(ctx context.Context, client net.Conn) error {
	var reader = bufio.NewReader(client)

	// 接收连接结果
	var buf = make([]byte, 17)
	_, err := io.ReadFull(reader, buf)
	if err != nil {
		return fmt.Errorf("从节点获取连接结果失败: %w", err)
	}

	tag := hex.EncodeToString(buf[0:16])
	status := buf[16]

	// 加载用户连接
	user, ok := app.UserConnMap.LoadAndDelete(tag)
	if !ok {
		return fmt.Errorf("用户连接已关闭，tag：%s", tag)
	}
	defer func() {
		utils.Close(user)
		slog.Debug("关闭用户连接")
	}()

	// 检查状态
	if status != 1 {
		return errors.New("目标地址建立连接失败")
	}

	data := time.Now()

	// 复制用户流量进行访问目标分析
	userCopyFrom, userCopyTo := io.Pipe()
	defer utils.Close(userCopyTo)

	teeUser := io.TeeReader(user, userCopyTo)
	go func() {
		err := analysisAndLog(user, userCopyFrom)
		if err != nil {
			slog.Error("数据解析失败", "err", err)
		}
	}()

	// 复制节点数据到用户
	var waitEdge = make(chan error)
	go func() {
		_, err := io.Copy(user, reader)
		switch {
		case errors.Is(err, net.ErrClosed):
			slog.Debug("节点连接意外关闭")
		case err != nil:
			slog.Error("读取节点数据失败", "err", err)
		default:
			slog.Debug("节点数据读取完成")
		}
		waitEdge <- err
	}()

	// 复制用户数据到节点
	var waitUser = make(chan error)
	go func() {
		_, err := io.Copy(client, teeUser)
		switch {
		case errors.Is(err, net.ErrClosed):
			slog.Debug("用户连接意外关闭")
		case err != nil:
			slog.Error("读取用户数据失败", "err", err)
		default:
			slog.Debug("用户数据读取完成")
		}
		waitUser <- err
	}()

	// 等待数据转发完成，关闭数据通道的时机：
	select {
	case <-ctx.Done():
		slog.Debug("服务关闭")
	case <-waitEdge:
	case <-waitUser:
		storeConnMatrics(user, data)
	}

	return nil
}

func storeConnMatrics(user *core.Conn, data time.Time) {
	proxy := time.Now()

	start, startOk := metrics.TimerStart.Load(user.Conn)
	auth, authOk := metrics.TimerAuth.Load(user.Conn)

	var authDuration time.Duration
	if startOk && authOk {
		authDuration = auth.(time.Time).Sub(start.(time.Time))
	}

	var dataDuration time.Duration
	if authOk {
		dataDuration = data.Sub(auth.(time.Time))
	}

	proxyDuration := proxy.Sub(data)

	var totalDuration time.Duration
	if startOk {
		totalDuration = proxy.Sub(start.(time.Time))
	}

	debug.ConsumingCh <- debug.Consuming{
		Auth:  authDuration,
		Data:  dataDuration,
		Proxy: proxyDuration,
		Total: totalDuration,
	}
}