use threads;
use Socket;
use strict;
use warnings;

my $banned_type = {
	"cab" => 1,
    "class" => 1,
	"dat" => 1,
	"exe" => 1,
	"gif" => 1,
    "ico" => 1,
    "js" => 1,
	"swf" => 1
};

my $banned_site = {
    "ad.doubleclick.net" => 1,
    "lz.mainentrypoint.com" => 1,
    "search-itnow.com" => 1,
    "www.ftstock.com" => 1,
    "www.newshub.com" => 1
};

use constant RES_400 => "HTTP/1.1 400 Bad Request\r\n\r\n";

my $proto = getprotobyname('tcp');
socket(BROWSER_LISTENER, PF_INET, SOCK_STREAM, $proto) || die "Failed to create socket: $!";
setsockopt(BROWSER_LISTENER, SOL_SOCKET, SO_REUSEADDR, pack("l", 1)) || die "Failed to setsockopt: $!";
bind(BROWSER_LISTENER, sockaddr_in(8080, INADDR_ANY)) || die "Failed to bind: $!";
listen(BROWSER_LISTENER, SOMAXCONN) || die "Failed to listen: $!";  
print "Internet filter started\n";
while (1) {
	my $browser;
	accept($browser, BROWSER_LISTENER);
	my $req;
	my $chunk;
	do {
	} until (!sysread($browser, $chunk, 10000) || ($req .= $chunk) =~ m/\r\n\r\n/);
	my $host = ($req =~ m/Host:\s*(.*?)\r/)[0];
	my ($method, $page) = ($req =~ m/^(.*?)\s+(.*?)\s/);
	print "Received request for [$method, $page]\n";
	if ($host && $page) {
		if (is_banned_site($host) || is_banned_type($page)) {
			#print "[$host, $page] is banned\n";
			print $browser RES_400;
			close($browser);
		} else {
			threads->create(\&process_one_req, $browser, $req, $method, $host)->detach();
		}
	} else {
		close($browser);
	}
}

sub process_one_req {
	my ($browser, $req, $method, $host) = @_;
    my $iaddr = inet_aton($host) || die "no host: $host";
	my $paddr = sockaddr_in(80, $iaddr);    
	$proto = getprotobyname('tcp');
    my $remote;
	socket($remote, PF_INET, SOCK_STREAM, $proto) || die "socket: $!";
    connect($remote, $paddr) || die "connect: $!";
	print $remote $req, "\r\n";
	my $chunk;
	while (sysread($remote, $chunk, 10000)) {
		print $browser $chunk; 
	}
	close($remote);
	undef($remote);
	close($browser);
	undef($browser);
	undef($req);
	undef($host);
}

sub is_banned_site {
    my $site = shift;
    return 1 if (exists($banned_site->{$site}));

    if ($site =~ m/offeroptimizer/) {
        return 1;
    }
    if ($site =~ m/revenue.net$/) {
        return 1;
    }
    if ($site =~ m/popupsponsor.com$/) {
        return 1;
    }
    if ($site =~ m/hitbox.com$/) {
        return 1;
    }
    return 0;
}

sub is_banned_type {
	return (exists($banned_type->{(split(/\./, shift))[-1]})) ? 1 : 0;
}