package listener

import (
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"regexp"
	"strconv"
	"strings"
	"tcp-proxy/pkg/common"
	"tcp-proxy/pkg/config"
	"tcp-proxy/pkg/logger"
	"tcp-proxy/pkg/proxy"

	"github.com/google/uuid"
)

type Target struct {
	Addr   string
	Listen string
}

type Listener struct {
	Targets []Target
	ctx     context.Context
	cancel  context.CancelFunc
}

type conn struct {
	net.Conn
}

// New listener
func New(list []config.Listen) (listener *Listener, err error) {
	if len(list) == 0 {
		return nil, errors.New("no listen data")
	}
	check := make(map[int]interface{})
	listener = &Listener{}
	listener.ctx, listener.cancel = context.WithCancel(context.Background())
	listener.Targets = make([]Target, 0)

	for k, v := range list {
		hosts, err := parseHost(v.TargetHost)
		if err != nil || len(hosts) == 0 {
			return nil, fmt.Errorf("host rule error: index: %d, %v", k, err)
		}
		startBindPort := v.ListenPort
		for _, it := range hosts {
			if _, ok := check[startBindPort]; ok {
				return nil, errors.New("bind port is used")
			}
			target := Target{}
			target.Addr = fmt.Sprintf("%s:%d", it, v.TargetPort)
			target.Listen = fmt.Sprintf(":%d", startBindPort)
			listener.Targets = append(listener.Targets, target)
			check[startBindPort] = nil
			startBindPort++
		}

	}

	check = nil

	return
}

func parseHost(s string) (ss []string, err error) {
	ip := net.ParseIP(s)
	if ip != nil {
		ss = append(ss, ip.String())
		return ss, nil
	}

	if match, err := regexp.MatchString(`^(?:(25[0-5]|2[0-4][0-9]|1?[0-9]{2}|[0-9])\.){3}(?:(2[0-5][0-9]|1?[0-9]{2}|[0-9]))\-(?:(25[0-9]|2[0-4][0-9]|1?[0-9]{2}|[0-9]))$`, s); match && err == nil {
		iprange := strings.Split(s, "-")
		start, err := strconv.Atoi(strings.Split(iprange[0], ".")[3])
		if err != nil {
			return nil, err
		}
		end, err := strconv.Atoi(iprange[1])
		if err != nil {
			return nil, err
		}

		if start > end {
			return nil, errors.New("start > end")
		}

		count := end - start + 1
		ss = make([]string, 0, count)
		regex := regexp.MustCompile(`\.[0-9]{1,3}$`)
		for i := 0; i < count; i++ {
			nip := regex.ReplaceAllString(iprange[0], fmt.Sprintf(".%d", start+i))
			ss = append(ss, nip)
		}
		return ss, nil
	}

	err = common.CheckDomain(s)
	if err != nil {
		return nil, err
	}
	ss = append(ss, s)

	return
}

func listen(ctx context.Context, bindPort, addr string) error {
	laddr, err := net.ResolveTCPAddr("tcp", bindPort)
	if err != nil {
		return err
	}

	listener, err := net.ListenTCP("tcp", laddr)
	if err != nil {
		return err
	}
	defer listener.Close()

	connChan := make(chan *net.TCPConn)

	go accept(ctx, listener, connChan)
	go handleConn(ctx, connChan, bindPort, addr)

	for {
		select {
		case <-ctx.Done():
			return nil
		}
	}

}

func accept(ctx context.Context, listener *net.TCPListener, connChan chan *net.TCPConn) {
	for {
		conn, err := listener.AcceptTCP()
		if err != nil {
			log.Println("accept error : ", err)
		} else {
			connChan <- conn
		}
		select {
		case <-ctx.Done():
			return
		default:
		}
	}
}
func handleConn(ctx context.Context, connChan chan *net.TCPConn, bindPort, addr string) {
	conf := config.Get()
	for {
		select {
		case <-ctx.Done():
			return
		case conn := <-connChan:
			laddr, err := net.ResolveTCPAddr("tcp", bindPort)
			if err != nil {
				log.Println("resolve local bind fail : ", err)
				conn.Close()
				break
			}

			raddr, err := net.ResolveTCPAddr("tcp", addr)
			if err != nil {
				log.Println("resolve remote addr fail : ", err)
				conn.Close()
				break
			}
			err = common.CheckRemoteTCP(raddr.IP.String(), raddr.Port, 2)
			if err != nil {
				log.Println("check remote tcp fail : ", err)
				conn.Close()
				break
			}

			connid := uuid.New().String()
			p := proxy.New(conn, laddr, raddr)
			p.Nagles = false
			p.OutputHex = true
			p.Log = logger.ColorLogger{
				VeryVerbose: conf.Verbose >= 2,
				Verbose:     conf.Verbose >= 1,
				Prefix:      fmt.Sprintf("Connection: %s ", connid),
				Color:       true,
			}
			go func() {
				defer conn.Close()
				err := p.Start(ctx)
				if err != nil || err != io.EOF {
					log.Println("conn err :: ", err)
				}
			}()
		}
	}
}

func (l *Listener) Listen() (err error) {
	for _, it := range l.Targets {
		go listen(l.ctx, it.Listen, it.Addr)
	}

	<-l.ctx.Done()
	return
}