#!/usr/bin/perl -w
# updateHosts.pl  Andrew Kesterson  andrew@aklabs.net
# update the system hosts file with Mike's ad blocking file
# patch it up to include the newest entries
# this obviously needs to run as root if you're working on /etc/hosts

# I'm still learning perl. Don't harsh me too much.

use strict;
use LWP::Simple;
use Socket;
use Getopt::Std;
use Time::localtime;

my $URL = "http://everythingisnt.com/hosts";
my $hostfile = "/etc/hosts";
my $buffer;
my %args;
my $updating = 0;
my $usage = <<EOT;

updateHosts.pl : update your hosts file from Mike's ad blocking 
file at http://everythingisnt.com/hosts. New hosts are added,
nothing is removed.
   -h : this help
   -v : be verbose (default is to stay silent until an error occurs)
   -u : specify alternate hosts URL. Must be a UNIX /etc/hosts file
         (defaults to Mike's ad blocking file)
   -f : specify alternate filename to patch (defaults to /etc/hosts) 

EOT

getopts("hvu:f:", \%args);

if ( $args{h} ) {
   print $usage;
   exit;
}
if ( $args{u} ) {
   $URL = $args{u};
}
if ( $args{f} ) {
   $hostfile = $args{f};
}

unless (defined ( $buffer = get $URL ) ) {
   die "Couldn't grab updated host file from $URL\n";
}

my @newHosts = split /\n/, $buffer;
open(hostsFile, ">>$hostfile") or die "Couldn't open $hostfile for writing.";

if (defined $args{v} ) {
   print "Beginning update; due to calls to gethostbyname, the program might appear to hang while waiting to resolve.\n";
}

HOSTS: foreach my $host ( @newHosts ) {
   $host =~ m/(127.0.0.1\s\w.*)/;
   if ( defined $1 ) {
      $host = $1;
      $host =~ s/127.0.0.1\s//;
      $host =~ s/\s.*//;
   }
   else {
      # this should've returned us a hostname...
      next;
   }

   my @addresses = gethostbyname($host);
   # just checking to see if it already exists in etc-hosts as 127.0.0.1
   @addresses = map { inet_ntoa($_) } @addresses[ 4 ... $#addresses];
   foreach my $addr ( @addresses ) {
      if ( $args{v} ) {
         print "checking 127.0.0.1 against address for $host : $addr\n";
      }
      if ( $addr eq "127.0.0.1" ) {
         # skip this one.
         next HOSTS;
      }
      else {
         if ( $args{v} ) {
            print "adding $host\n";
         }
         if ( !$updating ) {
            # add a comment with the date if this is the first entry
            my $time = localtime;
            print hostsFile "\n# Updates from ", $time->year+1900 ,
                  "-", $time->mon+1, "-", $time->mday, "\n";
            $updating = 1;
         }
         print hostsFile "127.0.0.1\t", $host, "\n";
      }
   }
}

close hostsFile;