package httpreverse

import (
	"strconv"
	"strings"
)

func IPCIDR(ip string) (string, int, error) {
	if !strings.Contains(ip, "/") {
		return ip, 32, nil
	}
	tmp := strings.Split(ip, "/")
	cidr, err := strconv.Atoi(tmp[1])
	if err != nil {
		return "", 0, err
	}
	intIp, err := IP2Int(tmp[0])
	if err != nil {
		return "", 0, err
	}
	ip, err = Int2IP(int((uint32(intIp) >> (32 - cidr)) << (32 - cidr)))
	return ip, cidr, err
}

func IPEnd(ip string, cidr int) (string, error) {
	intIp, err := IP2Int(ip)
	if err != nil {
		return "", err
	}
	ip, err = Int2IP(int(uint32(intIp) | ((uint32(4294967295) << cidr) >> cidr)))
	return ip, err
}

func IPStart(ip string, cidr int) (string, error) {
	intIp, err := IP2Int(ip)
	if err != nil {
		return "", err
	}
	ip, err = Int2IP(int((uint32(intIp) >> (32 - cidr)) << (32 - cidr)))
	return ip, err
}

func IPInRange(cidrip, ip string) (bool, error) {
	w, c, err := IPCIDR(cidrip)
	if err != nil {
		return false, err
	}
	f, _, err := IPCIDR(ip + "/" + strconv.Itoa(c))
	if err != nil {
		return false, err
	}
	return w == f, nil
}

func IPinRange2(startIP string, cidr int, ip string) (bool, error) {
	f, _, err := IPCIDR(ip + "/" + strconv.Itoa(cidr))
	if err != nil {
		return false, err
	}
	return startIP == f, nil
}

func IP2Int(ipAddr string) (int, error) {
	var ipNum uint32 = 0
	ipFilter := strings.Split(ipAddr, ".")
	for i := 0; i < len(ipFilter); i++ {
		num, err := strconv.ParseUint(ipFilter[len(ipFilter)-1-i], 10, 32)
		ipNum |= (uint32(num) << (8 * uint32(i)))
		if err != nil {
			return 0, err
		}
	}
	return int(ipNum), nil
}

func Int2IP(intIP int) (string, error) {
	var result string
	var ip uint32
	ip = uint32(intIP)
	for i := 0; i < 4; i++ {
		result += strconv.FormatUint(uint64(uint8(ip>>uint8((3-i)*8))), 10) + "."
	}
	return result[0 : len(result)-1], nil
}