// Copyright 2017 gf Author(https://github.com/gogf/gf). All Rights Reserved.
//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://github.com/gogf/gf.
//

// Package gipv4 provides useful API for IPv4 address handling.
package gipv4

import (
    "encoding/binary"
    "net"
    "strconv"
    "strings"
    "regexp"
    "fmt"
    "github.com/gogf/gf/g/text/gregex"
)

// 判断所给地址是否是一个IPv4地址
func Validate(ip string) bool {
    return gregex.IsMatchString(`^((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)$`, ip)
}

// Get the IPv4 address corresponding to a given Internet host name.
func GetHostByName(hostname string) (string, error) {
    ips, err := net.LookupIP(hostname)
    if ips != nil {
        for _, v := range ips {
            if v.To4() != nil {
                return v.String(), nil
            }
        }
        return "", nil
    }
    return "", err
}

// Get a list of IPv4 addresses corresponding to a given Internet host name.
func GetHostsByName(hostname string) ([]string, error) {
    ips, err := net.LookupIP(hostname)
    if ips != nil {
        var ipStrs []string
        for _, v := range ips {
            if v.To4() != nil {
                ipStrs = append(ipStrs, v.String())
            }
        }
        return ipStrs, nil
    }
    return nil, err
}

// Get the Internet host name corresponding to a given IP address.
func GetNameByAddr(ipAddress string) (string, error) {
    names, err := net.LookupAddr(ipAddress)
    if names != nil {
        return strings.TrimRight(names[0], "."), nil
    }
    return "", err
}

// IP字符串转为整形.
func Ip2long(ipAddress string) uint32 {
    ip := net.ParseIP(ipAddress)
    if ip == nil {
        return 0
    }
    return binary.BigEndian.Uint32(ip.To4())
}

// ip整形转为字符串
func Long2ip(properAddress uint32) string {
    ipByte := make([]byte, 4)
    binary.BigEndian.PutUint32(ipByte, properAddress)
    return net.IP(ipByte).String()
}

// 获得ip的网段，例如：192.168.2.102 -> 192.168.2
func GetSegment(ip string) string {
    r        := `^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$`
    reg, err := regexp.Compile(r)
    if err != nil {
        return ""
    }
    ips := reg.FindStringSubmatch(ip)
    if ips == nil {
        return ""
    }
    return fmt.Sprintf("%s.%s.%s", ips[1], ips[2], ips[3])
}

// 解析地址，形如：192.168.1.1:80 -> 192.168.1.1, 80
func ParseAddress(addr string) (string, int) {
    r        := `^(.+):(\d+)$`
    reg, err := regexp.Compile(r)
    if err != nil {
        return "", 0
    }
    result := reg.FindStringSubmatch(addr)
    if result != nil {
        i, _ := strconv.Atoi(result[2])
        return result[1], i
    }
    return "", 0
}

// 获取本地局域网ip列表
func IntranetIP() (ips []string, err error) {
    ips        = make([]string, 0)
    ifaces, e := net.Interfaces()
    if e != nil {
        return ips, e
    }
    for _, iface := range ifaces {
        if iface.Flags&net.FlagUp == 0 {
            continue // interface down
        }

        if iface.Flags & net.FlagLoopback != 0 {
            continue // loopback interface
        }

        // ignore warden bridge
        if strings.HasPrefix(iface.Name, "w-") {
            continue
        }

        addrs, e := iface.Addrs()
        if e != nil {
            return ips, e
        }

        for _, addr := range addrs {
            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() {
                continue
            }

            ip = ip.To4()
            if ip == nil {
                continue // not an ipv4 address
            }

            ipStr := ip.String()
            if IsIntranet(ipStr) {
                ips = append(ips, ipStr)
            }
        }
    }
    return ips, nil
}

// 判断所给ip是否为局域网ip
// A类 10.0.0.0--10.255.255.255
// B类 172.16.0.0--172.31.255.255
// C类 192.168.0.0--192.168.255.255
func IsIntranet(ipStr string) bool {
    // ip协议保留的局域网ip
    if strings.HasPrefix(ipStr, "10.") || strings.HasPrefix(ipStr, "192.168.") {
        return true
    }
    if strings.HasPrefix(ipStr, "172.") {
        // 172.16.0.0 - 172.31.255.255
        arr := strings.Split(ipStr, ".")
        if len(arr) != 4 {
            return false
        }

        second, err := strconv.ParseInt(arr[1], 10, 64)
        if err != nil {
            return false
        }

        if second >= 16 && second <= 31 {
            return true
        }
    }

    return false
}