package main

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

func isPrivateIP(ip net.Addr) bool {
	// Check if the IP is private
	// https://en.wikipedia.org/wiki/Private_network

	// IPv4
	if ip4 := ip.(*net.TCPAddr).IP.To4(); ip4 != nil {
		if ip4[0] == 10 {
			return true
		}
		if ip4[0] == 172 && ip4[1] >= 16 && ip4[1] <= 31 {
			return true
		}
		if ip4[0] == 192 && ip4[1] == 168 {
			return true
		}
		return false
	} else {
		// IPv6
		ip6 := ip.(*net.TCPAddr).IP.To16()
		if ip6[0] == 0xfd && ip6[1] == 0x00 {
			return true
		}
		return false
	}
}

func downloadFile(url, p string) error {
	// download
	out, err := os.Create(p)
	if err != nil {
		return err
	}

	defer out.Close()
	req, err := goHttp.NewRequest("GET", url, nil)
	if err != nil {
		return err
	}

	resp, err := goHttp.DefaultClient.Do(req)
	if err != nil {
		return err
	}

	defer resp.Body.Close()
	_, err = io.Copy(out, resp.Body)
	if err != nil {
		return err
	}

	return nil
}