package forward

import (
	"context"
	"encoding/binary"
	"fmt"
	"io"
	"log"
	"net"
	"strconv"
	"sync"
	"time"

	"csz.net/goForward/conf"
	"csz.net/goForward/sql"
)

type ConnectionStats struct {
	conf.ConnectionStats
	TotalBytesOld  uint64     `gorm:"-"`
	TotalBytesLock sync.Mutex `gorm:"-"`
	TCPConnections []net.Conn `gorm:"-"` // 用于存储 TCP 连接
	TcpTime        int        `gorm:"-"` // TCP无传输时间
}

// 保存多个连接信息
type LargeConnectionStats struct {
	Connections []*ConnectionStats `json:"connections"`
}

// 复用缓冲区
var bufPool = sync.Pool{
	New: func() interface{} {
		return make([]byte, 4096)
	},
}

// 开启转发，负责分发具体转发
func Run(stats *ConnectionStats) {
	defer releaseResources(stats) // 在函数返回时释放资源
	var ctx, cancel = context.WithCancel(context.Background())
	var innerWg sync.WaitGroup
	defer cancel()
	innerWg.Add(1)
	go func() {
		stats.printStats(ctx)
		innerWg.Done()
	}()
	fmt.Printf("【%s】监听端口 %s 转发至 %s:%s\n", stats.Protocol, stats.LocalPort, stats.RemoteAddr, stats.RemotePort)
	if stats.Protocol == "udp" {
		// UDP转发
		localAddr, err := net.ResolveUDPAddr("udp", ":"+stats.LocalPort)
		if err != nil {
			log.Fatalln("解析本地地址时发生错误:", err)
		}
		remoteAddr, err := net.ResolveUDPAddr("udp", stats.RemoteAddr+":"+stats.RemotePort)
		if err != nil {
			log.Fatalln("解析远程地址时发生错误:", err)
		}
		conn, err := net.ListenUDP("udp", localAddr)
		if err != nil {
			log.Fatalln("监听时发生错误:", err)
		}
		defer conn.Close()
		go func() {
			for {
				select {
				case stopPort := <-conf.Ch:
					if stopPort == stats.LocalPort+stats.Protocol {
						fmt.Printf("【%s】停止监听端口 %s\n", stats.Protocol, stats.LocalPort)
						conn.Close()
						cancel()
						return
					} else {
						conf.Ch <- stopPort
						time.Sleep(3 * time.Second)
					}
				default:
					time.Sleep(1 * time.Second)
				}
			}
		}()
		innerWg.Add(1)
		go func() {
			stats.handleUDPConnection(conn, remoteAddr, ctx)
			innerWg.Done()
		}()
	} else {
		// TCP转发
		listener, err := net.Listen("tcp", ":"+stats.LocalPort)
		if err != nil {
			log.Fatalln("监听时发生错误:", err)
		}
		defer listener.Close()
		go func() {
			for {
				select {
				case stopPort := <-conf.Ch:
					fmt.Println("通道信息:" + stopPort)
					fmt.Println("当前端口:" + stats.LocalPort)
					if stopPort == stats.LocalPort+stats.Protocol {
						fmt.Printf("【%s】停止监听端口 %s\n", stats.Protocol, stats.LocalPort)
						listener.Close()
						cancel()
						// 遍历并关闭所有 TCP 连接
						for _, conn := range stats.TCPConnections {
							conn.Close()
						}
						return
					} else {
						conf.Ch <- stopPort
						time.Sleep(3 * time.Second)
					}
				default:
					time.Sleep(1 * time.Second)
				}
			}
		}()
		for {
			clientConn, err := listener.Accept()
			if err != nil {
				log.Println("【"+stats.LocalPort+"】接受连接时发生错误:", err)
				cancel()
				break
			}
			innerWg.Add(1)
			go func() {
				stats.handleTCPConnection(clientConn, ctx, cancel)
				innerWg.Done()
			}()
		}
	}
	innerWg.Wait()
}

// TCP转发
func (cs *ConnectionStats) handleTCPConnection(clientConn net.Conn, ctx context.Context, cancel context.CancelFunc) {
	defer clientConn.Close()
	remoteConn, err := net.Dial("tcp", cs.RemoteAddr+":"+cs.RemotePort)
	if err != nil {
		log.Println("【"+cs.LocalPort+"】连接远程地址时发生错误:", err)
		return
	}
	defer remoteConn.Close()
	cs.TCPConnections = append(cs.TCPConnections, clientConn, remoteConn) // 添加连接到列表
	var copyWG sync.WaitGroup
	copyWG.Add(2)
	go func() {
		defer copyWG.Done()
		if err := cs.copyBytes(clientConn, remoteConn); err != nil {
			log.Println("复制字节时发生错误:", err)
			cancel() // Assuming `cancel` is the cancel function from the context
		}
	}()
	go func() {
		defer copyWG.Done()
		if err := cs.copyBytes(remoteConn, clientConn); err != nil {
			log.Println("复制字节时发生错误:", err)
			cancel() // Assuming `cancel` is the cancel function from the context
		}
	}()
	for {
		select {
		case <-ctx.Done():
			// 如果上级 context 被取消，停止接收新连接
			return
		default:
			copyWG.Wait()
			return
		}
	}
}

// UDP转发
func (cs *ConnectionStats) handleUDPConnection(localConn *net.UDPConn, remoteAddr *net.UDPAddr, ctx context.Context) {
	for {
		select {
		case <-ctx.Done():
			return
		default:
			buf := bufPool.Get().([]byte)
			n, _, err := localConn.ReadFromUDP(buf)
			if err != nil {
				log.Println("【"+cs.LocalPort+"】从源读取时发生错误:", err)
				return
			}
			fmt.Printf("收到长度为 %d 的UDP数据包\n", n)
			cs.TotalBytesLock.Lock()
			cs.TotalBytes += uint64(n)
			cs.TotalBytesLock.Unlock()

			// 处理消息的边界和错误情况
			go func() {
				cs.forwardUDPMessage(localConn, remoteAddr, buf[:n])
				bufPool.Put(buf)
			}()
		}
	}
}

func (cs *ConnectionStats) forwardUDPMessage(localConn *net.UDPConn, remoteAddr *net.UDPAddr, message []byte) {
	// 在消息前面添加消息长度信息
	length := make([]byte, 2)
	binary.BigEndian.PutUint16(length, uint16(len(message)))
	// 组合消息长度和实际消息
	data := append(length, message...)
	_, err := localConn.WriteToUDP(data, remoteAddr)
	if err != nil {
		log.Println("【"+cs.LocalPort+"】写入目标时发生错误:", err)
	}

}

func (cs *ConnectionStats) copyBytes(dst, src net.Conn) error {
	buf := bufPool.Get().([]byte)
	defer bufPool.Put(buf)
	for {
		n, err := src.Read(buf)
		if n > 0 {
			cs.TotalBytesLock.Lock()
			cs.TotalBytes += uint64(n)
			cs.TotalBytesLock.Unlock()
			_, err := dst.Write(buf[:n])
			if err != nil {
				log.Println("【"+cs.LocalPort+"】写入目标时发生错误:", err)
				return err
			}
		}
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Println("【"+cs.LocalPort+"】从源读取时发生错误:", err)
			break
		}
	}
	// 关闭连接
	dst.Close()
	src.Close()
	return nil
}

// 定时打印和处理流量变化
func (cs *ConnectionStats) printStats(ctx context.Context) {
	ticker := time.NewTicker(10 * time.Second)
	defer ticker.Stop() // 在函数结束时停止定时器
	for {
		select {
		case <-ticker.C:
			cs.TotalBytesLock.Lock()
			if cs.TotalBytes > cs.TotalBytesOld {
				if cs.Protocol == "tcp" {
					cs.TcpTime = 0
				}
				var total string
				if cs.TotalBytes > 0 && float64(cs.TotalBytes)/(1024*1024) < 0.5 {
					total = strconv.FormatFloat(float64(cs.TotalBytes)/(1024), 'f', 2, 64) + "KB"
				} else {
					total = strconv.FormatFloat(float64(cs.TotalBytes)/(1024*1024), 'f', 2, 64) + "MB"
				}
				fmt.Printf("【%s】端口 %s 统计流量: %s\n", cs.Protocol, cs.LocalPort, total)
				//统计更换单位
				var gb uint64 = 1073741824
				if cs.TotalBytes >= gb {
					cs.TotalGigabyte = cs.TotalGigabyte + 1
					sql.UpdateForwardGb(cs.Id, cs.TotalGigabyte)
					cs.TotalBytes = cs.TotalBytes - gb
				}
				cs.TotalBytesOld = cs.TotalBytes
				sql.UpdateForwardBytes(cs.Id, cs.TotalBytes)
				fmt.Printf("【%s】端口 %s 当前连接数: %d\n", cs.Protocol, cs.LocalPort, len(cs.TCPConnections))
			} else {
				if cs.Protocol == "tcp" {
					// fmt.Printf("【%s】端口 %s 当前超时秒: %d\n", cs.Protocol, cs.LocalPort, cs.TcpTime)
					if cs.TcpTime >= conf.TcpTimeout {
						// fmt.Printf("【%s】端口 %s 超时关闭\n", cs.Protocol, cs.LocalPort)
						for i := len(cs.TCPConnections) - 1; i >= 0; i-- {
							conn := cs.TCPConnections[i]
							conn.Close()
							// 从连接列表中移除关闭的连接
							cs.TCPConnections = append(cs.TCPConnections[:i], cs.TCPConnections[i+1:]...)
						}
					} else {
						cs.TcpTime = cs.TcpTime + 5
					}
				}
			}
			cs.TotalBytesLock.Unlock()
		//当协程退出时执行
		case <-ctx.Done():
			return
		}
	}
}

// 关闭 TCP 连接并从切片中移除
func closeTCPConnections(stats *ConnectionStats) {
	stats.TotalBytesLock.Lock()
	defer stats.TotalBytesLock.Unlock()
	for i, conn := range stats.TCPConnections {
		conn.Close()
		stats.TCPConnections[i] = nil
	}
	stats.TCPConnections = nil // 清空切片
}

// 释放资源
func releaseResources(stats *ConnectionStats) {
	closeTCPConnections(stats)
}