package system

import (
	"io"
	"net"
	"net/http"
)

var (
	ResolveIp = net.IP{}
	PublicIp  = net.IP{}
)

const (
	KLocalHost = "127.0.0.1"
	url        = "https://myexternalip.com/raw"
)

func init() {
	ResolveIp, _ = GetResolveIP()
	PublicIp, _ = GetPublicIP()
}

func GetPublicIP() (net.IP, error) {
	return GetPublicIPWithUrl(url)
}

func GetPublicIPWithUrl(url string) (net.IP, error) {
	resp, err := http.Get(url)
	if err != nil {
		return net.IP{}, err
	}
	defer resp.Body.Close()
	ip, err := io.ReadAll(resp.Body)
	if err != nil {
		return net.IP{}, err
	}
	return net.ParseIP(string(ip)), nil
}

func PublicIPValid() bool {
	return len(PublicIp) > 0
}

// SelfExternalIP 自己外部IP，可能是局域网IP，公网IP
// lan 局域网优先
func SelfExternalIP(lan bool) string {
	if lan && IsLanIP(ResolveIp) {
		return ResolveIp.String()
	}
	if IsPublicIP(PublicIp) {
		return PublicIp.String()
	}
	return ResolveIp.String()
}

// IPIsSelf 是否是自己
func IPIsSelf(ip string) string {
	if PublicIp.String() == ip {
		return KLocalHost
	}
	if ResolveIp.String() == ip {
		return KLocalHost
	}
	return ip
}

// IsLanIP 是否局域网 192.168.x.x
func IsLanIP(IP net.IP) bool {
	return GetIPType(IP) == IptPriC
}

func IsPublicIP(IP net.IP) bool {
	return GetIPType(IP) == IptPub
}

func GetResolveIP() (net.IP, error) {

	adds, err := net.InterfaceAddrs()
	if err != nil {
		return net.IP{}, err
	}
	return parseAddress(adds), nil
}

func GetResolveIPV2() (net.IP, error) {
	faces, err := net.Interfaces()
	if err != nil {
		return nil, err
	}
	for _, face := range faces {
		if face.Flags&net.FlagUp == 0 {
			continue
		}
		if face.Flags&net.FlagLoopback != 0 {
			continue
		}
		adds, er := face.Addrs()
		if er != nil {
			return nil, er
		}
		return parseAddress(adds), nil
	}
	return nil, err
}

func parseAddress(adds []net.Addr) net.IP {
	for _, addr := range adds {
		ip := parseResolveIP(addr)
		if len(ip) > 0 {
			return ip
		}
	}
	return net.IP{}
}

func parseResolveIP(addr net.Addr) net.IP {
	var ip net.IP
	switch v := addr.(type) {
	case *net.IPNet:
		ip = v.IP
	case *net.IPAddr:
		ip = v.IP
	}
	if ip == nil || ip.IsLoopback() {
		return nil
	}
	ip = ip.To4()
	if ip == nil {
		return nil // not an ipv4 address
	}
	return ip
}

type IPType int8

const (
	IptUnk  = IPType(0)
	IptPub  = IPType(1)
	IptPriA = IPType(2)
	IptPriB = IPType(3)
	IptPriC = IPType(4)
)

func GetIPType(IP net.IP) IPType {
	if IP.IsLoopback() || IP.IsLinkLocalMulticast() || IP.IsLinkLocalUnicast() {
		return IptPub
	}
	if ip4 := IP.To4(); ip4 != nil {
		switch true {
		case ip4[0] == 10:
			return IptPriA
		case ip4[0] == 172 && ip4[1] >= 16 && ip4[1] <= 31:
			return IptPriB
		case ip4[0] == 192 && ip4[1] == 168:
			return IptPriC
		default:
			return IptPub
		}
	}
	return IptUnk
}

/**
 * 私有IP
A 类 10.0.0.0/8：10.0.0.0～10.255.255.255
B 类 172.16.0.0/12：172.16.0.0～172.31.255.255
C 192.168.0.0/16：192.168.0.0～192.168.255.255
*/