#!/usr/bin/env python

import re
import urllib3
import sys
import argparse
import math
import textwrap


def generate_ovpn(metric):
    results = fetch_ip_data()
    rfile = open('routes.txt', 'w')
    for ip, mask, _ in results:
        route_item = "route %s %s net_gateway %d\n" % (ip, mask, metric)
        rfile.write(route_item)
    rfile.close()
    print("Usage: Append the content of the newly created routes.txt to your openvpn config file,"
          " and also add 'max-routes %d', which takes a line, to the head of the file." % (len(results) + 20))


def generate_linux(metric):
    results = fetch_ip_data()
    upscript_header = textwrap.dedent("""\
    #!/bin/bash
    export PATH="/bin:/sbin:/usr/sbin:/usr/bin"
    
    OLDGW=`ip route show | grep '^default' | sed -e 's/default via \\([^ ]*\\).*/\\1/'`
    
    if [ $OLDGW == '' ]; then
        exit 0
    fi
    
    if [ ! -e /tmp/vpn_oldgw ]; then
        echo $OLDGW > /tmp/vpn_oldgw
    fi
    
    """)

    downscript_header = textwrap.dedent("""\
    #!/bin/bash
    export PATH="/bin:/sbin:/usr/sbin:/usr/bin"
    
    OLDGW=`cat /tmp/vpn_oldgw`
    
    """)

    upfile = open('ip-pre-up', 'w')
    downfile = open('ip-down', 'w')

    upfile.write(upscript_header)
    upfile.write('\n')
    downfile.write(downscript_header)
    downfile.write('\n')

    for ip, mask, _ in results:
        upfile.write('route add -net %s netmask %s gw $OLDGW\n' % (ip, mask))
        downfile.write('route del -net %s netmask %s\n' % (ip, mask))

    downfile.write('rm /tmp/vpn_oldgw\n')

    print("For pptp only, please copy the file ip-pre-up to the folder/etc/ppp,"
          "and copy the file ip-down to the folder /etc/ppp/ip-down.d.")


def generate_mac(metric):
    results = fetch_ip_data()

    upscript_header = textwrap.dedent("""\
    #!/bin/sh
    export PATH="/bin:/sbin:/usr/sbin:/usr/bin"
    
    OLDGW=`netstat -nr | grep '^default' | grep -v 'ppp' | sed 's/default *\\([0-9\.]*\\) .*/\\1/' | awk '{if($1){print $1}}'`

    if [ ! -e /tmp/pptp_oldgw ]; then
        echo "${OLDGW}" > /tmp/pptp_oldgw
    fi
    
    dscacheutil -flushcache

    route add 10.0.0.0/8 "${OLDGW}"
    route add 172.16.0.0/12 "${OLDGW}"
    route add 192.168.0.0/16 "${OLDGW}"
    """)

    downscript_header = textwrap.dedent("""\
    #!/bin/sh
    export PATH="/bin:/sbin:/usr/sbin:/usr/bin"
    
    if [ ! -e /tmp/pptp_oldgw ]; then
            exit 0
    fi
    
    OLDGW=`cat /tmp/pptp_oldgw`

    route delete 10.0.0.0/8 "${OLDGW}"
    route delete 172.16.0.0/12 "${OLDGW}"
    route delete 192.168.0.0/16 "${OLDGW}"
    """)

    upfile = open('ip-up', 'w')
    downfile = open('ip-down', 'w')

    upfile.write(upscript_header)
    upfile.write('\n')
    downfile.write(downscript_header)
    downfile.write('\n')

    for ip, _, mask in results:
        upfile.write('route add %s/%s "${OLDGW}"\n' % (ip, mask))
        downfile.write('route delete %s/%s ${OLDGW}\n' % (ip, mask))

    downfile.write('\n\nrm /tmp/pptp_oldgw\n')
    upfile.close()
    downfile.close()

    print("For pptp on mac only, please copy ip-up and ip-down to the /etc/ppp folder,"
          "don't forget to make them executable with the chmod command.")


def generate_win(metric):
    results = fetch_ip_data()

    upscript_header = textwrap.dedent("""@echo off
    for /F "tokens=3" %%* in ('route print ^| findstr "\\<0.0.0.0\\>"') do set "gw=%%*"
    
    """)

    upfile = open('vpnup.bat', 'w')
    downfile = open('vpndown.bat', 'w')

    upfile.write(upscript_header)
    upfile.write('\n')
    upfile.write('ipconfig /flushdns\n\n')

    downfile.write("@echo off")
    downfile.write('\n')

    for ip, mask, _ in results:
        upfile.write('route add %s mask %s %s metric %d\n' % (ip, mask, "%gw%", metric))
        downfile.write('route delete %s\n' % (ip))

    upfile.close()
    downfile.close()

    #    up_vbs_wrapper=open('vpnup.vbs','w')
    #    up_vbs_wrapper.write('Set objShell = CreateObject("Wscript.shell")\ncall objShell.Run("vpnup.bat",0,FALSE)')
    #    up_vbs_wrapper.close()
    #    down_vbs_wrapper=open('vpndown.vbs','w')
    #    down_vbs_wrapper.write('Set objShell = CreateObject("Wscript.shell")\ncall objShell.Run("vpndown.bat",0,FALSE)')
    #    down_vbs_wrapper.close()

    print("For pptp on windows only, run vpnup.bat before dialing to vpn,"
          "and run vpndown.bat after disconnected from the vpn.")


def generate_android(metric):
    results = fetch_ip_data()

    upscript_header = textwrap.dedent("""\
    #!/bin/sh
    alias nestat='/system/xbin/busybox netstat'
    alias grep='/system/xbin/busybox grep'
    alias awk='/system/xbin/busybox awk'
    alias route='/system/xbin/busybox route'
    
    OLDGW=`netstat -rn | grep ^0\.0\.0\.0 | awk '{print $2}'`
    
    """)

    downscript_header = textwrap.dedent("""\
    #!/bin/sh
    alias route='/system/xbin/busybox route'
    
    """)

    upfile = open('vpnup.sh', 'w')
    downfile = open('vpndown.sh', 'w')

    upfile.write(upscript_header)
    upfile.write('\n')
    downfile.write(downscript_header)
    downfile.write('\n')

    for ip, mask, _ in results:
        upfile.write('route add -net %s netmask %s gw $OLDGW\n' % (ip, mask))
        downfile.write('route del -net %s netmask %s\n' % (ip, mask))

    upfile.close()
    downfile.close()

    print("Old school way to call up/down script from openvpn client. "
          "use the regular openvpn 2.1 method to add routes if it's possible")


def fetch_ip_data():
    # fetch data from apnic
    print("Fetching data from apnic.net, it might take a few minutes, please wait...")
    url = r'https://ftp.apnic.net/apnic/stats/apnic/delegated-apnic-latest'
    data = urllib3.urlopen(url).read()

    cnregex = re.compile(r'apnic\|cn\|ipv4\|[0-9\.]+\|[0-9]+\|[0-9]+\|a.*', re.IGNORECASE)
    cndata = cnregex.findall(data)

    results = []

    for item in cndata:
        unit_items = item.split('|')
        starting_ip = unit_items[3]
        num_ip = int(unit_items[4])

        imask = 0xffffffff ^ (num_ip - 1)
        # convert to string
        imask = hex(imask)[2:]
        mask = [0] * 4
        mask[0] = imask[0:2]
        mask[1] = imask[2:4]
        mask[2] = imask[4:6]
        mask[3] = imask[6:8]

        # convert str to int
        mask = [int(i, 16) for i in mask]
        mask = "%d.%d.%d.%d" % tuple(mask)

        # mask in *nix format
        mask2 = 32 - int(math.log(num_ip, 2))

        results.append((starting_ip, mask, mask2))

    return results


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description="Generate routing rules for vpn.")
    parser.add_argument('-p', '--platform',
                        dest='platform',
                        default='openvpn',
                        nargs='?',
                        help="Target platforms, it can be openvpn, mac, linux,"
                             "win, android. openvpn by default.")
    parser.add_argument('-m', '--metric',
                        dest='metric',
                        default=5,
                        nargs='?',
                        type=int,
                        help="Metric setting for the route rules")

    args = parser.parse_args()

    if args.platform.lower() == 'openvpn':
        generate_ovpn(args.metric)
    elif args.platform.lower() == 'linux':
        generate_linux(args.metric)
    elif args.platform.lower() == 'mac' or args.platform.lower() == 'darwin':
        generate_mac(args.metric)
    elif args.platform.lower() == 'win':
        generate_win(args.metric)
    elif args.platform.lower() == 'android':
        generate_android(args.metric)
    else:
        print >> sys.stderr, "Platform %s is not supported." % args.platform
        exit(1)