package nets

import (
	"errors"
	"fmt"
	"math"
	"math/big"
	"net"
	"strconv"
	"strings"
)

// GetHostIpv4 获取本地内网IP
func GetHostIpv4() (string, error) {
	privates, err := getAllIPV4(func(ip net.IP) bool {
		return ip.IsPrivate()
	})
	if err != nil {
		return "", err
	}
	if len(privates) == 0 {
		return "", errors.New("no private ip")
	}
	return privates[0], nil
}

func getAllIPV4(filter func(net.IP) bool) (ips []string, err error) {
	// 获取所有网卡
	addrs, err := net.InterfaceAddrs()
	if err != nil {
		return
	}

	for _, addr := range addrs {
		// 这个网络地址是IP地址: ipv4, ipv6
		ipNet, isIpNet := addr.(*net.IPNet)
		if isIpNet && !ipNet.IP.IsLoopback() {
			// 跳过IPV6
			if ipNet.IP.To4() != nil {
				if filter(ipNet.IP) {
					ips = append(ips, ipNet.IP.String())
				}
			}
		}
	}
	return
}

func Address2i64(addr string) (int64, error) {
	idx := strings.Index(addr, ":")
	if idx < 0 {
		return 0, fmt.Errorf("invalid addr %s", addr)
	}
	ip, port := addr[0:idx], addr[idx+1:]
	portI, err := strconv.Atoi(port)
	if err != nil {
		return 0, err
	}
	ipI, err := Ip2i64(ip)
	if err != nil {
		return 0, err
	}
	return (int64(portI) << 32) | ipI, nil
}

func I642Address(addr int64) string {
	port := addr >> 32
	ip := addr & math.MaxUint32
	return fmt.Sprintf("%s:%d", I642Ip(ip), port)
}

func Ip2i64(ip string) (int64, error) {
	ip4 := net.ParseIP(ip).To4()
	if ip4 == nil {
		return 0, fmt.Errorf("invalid ip %s", ip)
	}
	ret := big.NewInt(0)
	ret.SetBytes(ip4)
	return ret.Int64(), nil
}

func I642Ip(ip int64) string {
	return fmt.Sprintf("%d.%d.%d.%d",
		byte(ip>>24), byte(ip>>16), byte(ip>>8), byte(ip))
}