#!/bin/sh
iprx='^([0-9]+\.){3}[0-9]+$'
valid() { echo "$1" | egrep -q "$iprx"; }
vote() { sort | uniq -c | sort -nr | head -1 | sed 's/^ *[0-9]\+ \+//'; }
get_dep()
{
  dep=$1
  [ "$(dpkg-query -s "$dep"|sed -ne 's/^Status: //p')" = "install ok installed" ] || sudo apt-get install "$dep" >&2
}

# urls from http://www.linuxquestions.org/questions/linux-networking-3/how-can-i-get-my-external-ip-address-from-behind-a-nat-333878/
websites='http://showip.codebrainz.ca/ http://www.whatismyip.com/automation/n09230945.asp http://www.showmyip.com/simple/ http://cfaj.freeshell.org/ipaddr.cgi https://secure.informaction.com/ipecho/ http://icanhazip.com/'
websites()
{
  get_dep curl
  timeout=2
  for ws in $websites; do
    ip=$(curl -s -m $timeout "$ws"|head -1)
    valid "$ip" && echo $ip || echo "failed to get ip from $ws" >&2
  done
}
stunserver_org()
{
  get_dep stun
  stun -v stunserver.org 1 2>&1|sed -ne 's/^MappedAddress *= *//p'|head -n1|cut -d: -f1;
}
dyndns_org()
{
  get_dep curl
  curl -m 5 -s http://checkip.dyndns.org/|sed -ne 's/.*Current IP Address: *\(\([0-9]\+\.\)\{3\}[0-9]\+\).*/\1/p';
}

ip()
{
  for cmd in websites stunserver_org dyndns_org; do
    $cmd
  done | egrep "$iprx" | vote
}
ip=$(ip)
valid "$ip" && { echo $ip; exit; }

echo 'could not find ip' >&2;
exit 1;