# Copyright (C) 2007–2015  Alex Schroeder <alex@gnu.org>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

use strict;
use v5.10;

AddModuleDescription('multi-url-spam-block.pl', 'Multiple Link Ban Extension');

our ($BannedContent, @MyInitVariables, %AdminPages, %PlainTextPages, $FullUrlPattern, $LocalNamesPage);

*OldMultiUrlBannedContent = \&BannedContent;
*BannedContent = \&NewMultiUrlBannedContent;

our ($MultiUrlWhiteList, $MultiUrlLimit);

$MultiUrlLimit = 10;
$MultiUrlWhiteList = 'UrlWhitelist';

push(@MyInitVariables, sub {
       $MultiUrlWhiteList = FreeToNormal($MultiUrlWhiteList);
       $AdminPages{$MultiUrlWhiteList} = 1;
       $PlainTextPages{$MultiUrlWhiteList} = 1;
     });

sub NewMultiUrlBannedContent {
  my $str = shift;
  if (not $LocalNamesPage
      or GetParam('title', '') ne $LocalNamesPage) {
    my $rule = MultiUrlBannedContent($str);
    return $rule if $rule;
  }
  return OldMultiUrlBannedContent($str);
}

sub MultiUrlBannedContent {
  my $str = shift;
  my @urls = $str =~ /$FullUrlPattern/g;
  my %domains;
  my %whitelist;
  my $max = 0;
  my $label = '[a-z]([a-z0-9-]*[a-z0-9])?'; # RFC 1034
  foreach (split(/\n/, GetPageContent($MultiUrlWhiteList))) {
    next unless m/^\s*($label\.$label)/i;
    $whitelist{$1} = 1;
  }
  foreach my $url (@urls) {
    my @urlparts = split('/', $url, 4);
    my $domain = $urlparts[2];
    my @domainparts = split('\.', $domain);
    splice(@domainparts, 0, -2); # no subdomains
    $domain = join('.', @domainparts);
    next if $whitelist{$domain};
    $domains{$domain}++;
    $max = $domains{$domain} if $domains{$domain} > $max;
  }
  return Ts('You linked more than %s times to the same domain. It would seem that only a spammer would do this. Your edit is refused.', $MultiUrlLimit)
    if $max > $MultiUrlLimit;
}