package main

import (
	"context"
	"crypto/tls"
	"io"
	"log"
	"net"
)

type TCP struct {
	config *Config
}

func NewTCPServer(c *Config) TCP {
	return TCP{config: c}
}

func (tcp TCP) Listen() error {
	ln, err := net.Listen("tcp", tcp.config.Listen)
	if err != nil {
		return err
	}
	defer ln.Close()

	log.Println("accepting tcp on", tcp.config.Listen)
	for {
		conn, err := ln.Accept()
		if err != nil {
			return err
		}
		go func() {
			defer conn.Close()

			conn2, err := func() (net.Conn, error) {
				if tcp.config.TCPProxyTLS {
					return tls.Dial("tcp", tcp.config.TCPProxy, &tls.Config{})
				}
				return net.Dial("tcp", tcp.config.TCPProxy)
			}()
			if err != nil {
				log.Println(err)
				return
			}
			defer conn2.Close()

			ctx, can := context.WithCancel(context.Background())
			defer can()

			errc := make(chan error)
			go func() {
				_, err := io.Copy(conn, conn2)
				select {
				case errc <- err:
				case <-ctx.Done():
					close(errc)
				}
			}()
			go func() {
				_, err := io.Copy(conn2, conn)
				select {
				case errc <- err:
				case <-ctx.Done():
					close(errc)
				}
			}()
			<-errc
		}()
	}
}