package telnet

import (
	"fmt"
	"net"
	"strings"
	"time"
)

var listener *net.TCPListener
var clientNum int

// Server - Init TCP Server
func Run(addrStr string) {
	addr := fmt.Sprintf("[%s]:4100", addrStr)
	tcpAddr, err := net.ResolveTCPAddr("tcp", addr)
	if err != nil {
		fmt.Println("[Telnet] net.ResolveTCPAddr fail:", addr)
		return
	}
	listener, err := net.ListenTCP("tcp", tcpAddr)
	if err != nil {
		fmt.Println("[Telnet] failed to listen:", err)
		return
	}
	fmt.Println("[Telnet] Listen on", addr)

	go func() {
		for {
			conn, err := listener.Accept()
			if err != nil {
				fmt.Println(err.Error())
				continue
			} else if clientNum >= 9 {
				fmt.Println("too many telnet request connection")
				conn.Close()
				continue
			}

			clientNum++
			fmt.Println("[Telnet] A new Connection", clientNum)
			fmt.Println("[Telnet] TCP Accept from:", conn.RemoteAddr().String())

			go start(conn)
		}
	}()
}

// Start - Start TCP read channel
func start(conn net.Conn) {
	defer closeConnection(conn)

	conn.Write([]byte(help_menu))
	conn.Write([]byte(prompt))
	for {
		buffer := make([]byte, 128)
		conn.SetReadDeadline(time.Now().Add(time.Minute*10))
		_, err := conn.Read(buffer)
		if err != nil {
			fmt.Println("[Telnet] Error", err)
			break
		}
		buf := string(buffer)
		pos := strings.Index(buf, "\n")
		if pos < 0 || pos > 127 {
			break
		}
		cmd := buf[:pos]

		sep := strings.Fields(cmd)
		if len(sep) <= 0 {
			conn.Write([]byte(prompt))
			continue
		}
		if sep[0] == "help" {
			conn.Write([]byte(help_menu))
			conn.Write([]byte(prompt))
			continue
		}
		if sep[0] == "q" || sep[0] == "quit" {
			break
		}

		rsp := HandleTelnetRequest(sep)
		conn.Write([]byte(rsp))
		conn.Write([]byte(prompt))
	}
}

func closeConnection(conn net.Conn) {
	conn.Close()
	clientNum--
	fmt.Printf("[Telnet] Now, %d connections is alive.\n", clientNum)
}

func Stop() {
	if listener != nil {
		listener.Close()
	}
}