package main

import (
	"flag"
	"fmt"
	"net"
	"os"
	"strconv"
	"strings"
)

/**
扫描地址
*/
var ipAddrs chan string = make(chan string)

//扫描结果
var result chan string = make(chan string)

//线程数
var thread chan int = make(chan int)
var nowThread int

//关闭程序
var clo chan bool = make(chan bool)

//保存结果
func writeResult() {
	fileName := "result.txt"
	fout,err := os.Create(fileName)
	if err != nil {
		//文件创建失败
		fmt.Println(fileName + " create error")
	}
	defer fout.Close()
	s,ok := <-result
	for ok {
		fout.WriteString(s + "\r\n")
		s,ok = <-result
	}
	//通知进程退出
	clo <- true
}

//根据线程参数启动扫描线程
func runScan() {
	t,ok := <-thread
	nowThread = t
	if ok {
		for i := 0; i < nowThread; i++ {
			go scan(strconv.Itoa(i))
		}
	}
	//等待线程终止
	for <-thread == 0 {
		nowThread--
		if nowThread == 0 {
			//全部线程已终止,关闭结果写入,退出程序
			close(result)
			break
		}
	}
}

/**
扫描线程
*/
func scan(threadId string) {
	s,ok := <-ipAddrs //循环从通道中拿地址
	for ok {
		fmt.Println("[thread-" + threadId + "] scan:" + s)
		_,err := net.Dial("tcp",s)
		if err == nil {
			//端口开放
			result <- s
		}
		s,ok = <-ipAddrs //循环从通道中拿地址
	}
	fmt.Println("[thread-" + threadId + "] end")
	thread <- 0
}

//获取下一个IP
func nextIp(ip string) string {
	ips := strings.Split(ip,".")
	var i int
	for i = len(ips) - 1; i >= 0; i-- {
		n,_ := strconv.Atoi(ips[i])
		if n >= 255 {
			//进位
			ips[i] = "1"
		} else {
			//+1
			n++
			ips[i] = strconv.Itoa(n)
			break
		}
	}

	if i == -1 {
		//全部IP段都进行了进位,说明此IP本身已超出范围
		return ""
	}

	ip = ""
	leng := len(ips)
	for i := 0; i < leng; i++ {
		if i == leng-1 {
			ip += ips[i]
		} else {
			ip += ips[i] + "."
		}
	}
	return ip
}

//生成IP地址列表
func processIp(startIp,endIp string) []string {
	var ips = make([]string,0)
	for ; startIp != endIp; startIp = nextIp(startIp) {
		if startIp != "" {
			ips = append(ips,startIp)
		}
	}
	ips = append(ips,startIp)
	return ips
}

//处理参数
func processFlag(arg []string) {
	//开始IP,结束IP
	var startIp,endIp string
	//端口
	var ports []int = make([]int,0)
	index := 0
	startIp = arg[index]
	si := net.ParseIP(startIp)
	if si == nil {
		//开始IP不合法
		fmt.Println("'startIp' Setting error")
		return
	}
	index++
	endIp = arg[index]
	ei := net.ParseIP(endIp)
	if ei == nil {
		//未指定结束IP,即只扫描一个IP
		endIp = startIp
	} else {
		index++
	}

	tmpPort := arg[index]
	if strings.Index(tmpPort,"-") != -1 {
		//连续端口
		tmpPorts := strings.Split(tmpPort,"-")
		var startPort,endPort int
		var err error
		startPort,err = strconv.Atoi(tmpPorts[0])
		if err != nil || startPort < 1 || startPort > 65535 {
			//开始端口不合法
			return
		}

		if len(tmpPorts) >= 2 {
			//指定结束端口
			endPort,err = strconv.Atoi(tmpPorts[1])
			if err != nil || endPort < 1 || endPort > 65535 || endPort < startPort {
				//结束端口不合法
				fmt.Println("'endPort' Setting error")
				return
			}
		} else {
			//未指定结束端口
			endPort = 65535
		}
		for i := 0; startPort+i <= endPort; i++ {
			ports = append(ports,startPort+i)
		}
	} else {
		//一个或多个端口
		ps := strings.Split(tmpPort,",")
		for i := 0; i < len(ps); i++ {
			p,err := strconv.Atoi(ps[i])
			if err != nil {
				//端口不合法
				fmt.Println("'port' Setting error")
				return
			}
			ports = append(ports,p)
		}
	}
	index++
	t,err := strconv.Atoi(arg[index])
	if err != nil {
		//线程不合法
		fmt.Println("'thread' Setting error")
		return
	}
	//最大线程2048
	if t < 1 {
		t = 1
	} else if t > 2048 {
		t = 2048
	}
	//传送启动线程数
	thread <- t
	//生成扫描地址列表
	ips := processIp(startIp,endIp)
	il := len(ips)
	for i := 0; i < il; i++ {
		pl := len(ports)
		for j := 0; j < pl; j++ {
			ipAddrs <- ips[i] + ":" + strconv.Itoa(ports[j])
		}
	}
	close(ipAddrs)
}

func main() {
	flag.Parse()
	if flag.NArg() != 3 && flag.NArg() != 4 {
		//参数不合法
		fmt.Println("Parameter error")
		return
	}
	//获取参数
	args := make([]string,4)
	for i := 0; i < flag.NArg(); i++ {
		args = append(args,flag.Arg(i))
	}
	//启动扫描线程
	go runScan()
	//启动结果写入线程
	go writeResult()
	//参数处理
	processFlag(args)
	//等待退出指令
	<-clo
	fmt.Println("Exit")
}