#!/usr/bin/perl
#
# Packetizer Web Services Proxy (pwsp)
# (Version 2.0)
#
# Copyright (C) 2009
# Packetizer, Inc.
#
# This script will accept requests from clients and then forward them
# to services.packetizer.com.  This is necessary since web browsers
# enforce a "same origin" policy which prevent them from loading
# pages from one domain and then accessing a different domain.
#
# As a very light-weight proxy, this code is intended to mimic the behavior
# as one would see it if accessing services.packetizer.com directly,
# though there is one important difference: one must specify the
# service desired via a URI parameter.  For example, to access the
# "time" service, one might access a URL like this:
#   http://www.packetizer.com/cgi-bin/pwsp?service=time&f=text
#
# Of course, the sample URL above would be different for your
# own web site.  Place this script in your cgi-bin directory
# and you should be all set.
#
# This CGI script was written for Apache, so some changes might be required
# to work with other web servers.
#

use CGI;
use URI::Escape;
use IO::Socket;

# Specify what to do when an alarm signal is received
$SIG{ALRM} = sub { die "socket timeout\n"; };

# URI template for Packetizer Web Services
$services_server = "services.packetizer.com";
$services_port   = 80;
$location = "/{service}/";

$query = new CGI;

#
# Look through the various parameters and extract the service parameter,
# preserving all of the other parameters
#
$init_param = 1;
$query_string = "";
foreach $param ($query->param)
{
    if ($param eq "service")
    {
        $service = $query->param($param);
    }
    else
    {
        if ($init_param)
        {
            $init_param = 0;
        }
        else
        {
            $query_string .= "&";
        }
        $query_string .= uri_escape($param);
        $query_string .= "=";
        $query_string .= uri_escape($query->param($param));
    }
}

#
# If a service was specified, then let's try to invoke the service
#
if (length($service) > 0)
{
    $location =~ s/{service}/$service/;

    if (length($query_string) > 0)
    {
        $location .= "?" . $query_string;
    }

    $retries = 3;
    while($retries > 0)
    {
        $remote = IO::Socket::INET->new( Proto    => "tcp",
                                         PeerAddr => "$services_server",
                                         PeerPort => "$services_port");
        last if ($remote);
        $retries--;
        sleep(4);
    }

    unless ($remote) { die "could no connect to remote server"; }

    print $remote "GET $location HTTP/1.1\r\n";

    # Produce the headers that of significance to Packetizer Web Services
    if (length($ENV{'HTTP_ACCEPT'}))
    {
        print $remote "Accept: " . $ENV{'HTTP_ACCEPT'} . "\r\n";
    }
    if (length($ENV{'HTTP_USER_AGENT'}))
    {
        print $remote "User-Agent:" . $ENV{'HTTP_USER_AGENT'} . "\r\n";
    }
    if (length($ENV{'HTTP_ACCEPT_LANGUAGE'}))
    {
        print $remote "Accept-Language:" . $ENV{'HTTP_ACCEPT_LANGUAGE'} . "\r\n";
    }
    if (length($ENV{'HTTP_ACCEPT_ENCODING'}))
    {
        print $remote "Accept-Encoding:" . $ENV{'HTTP_ACCEPT_ENCODING'} . "\r\n";
    }
    print $remote "Host: $services_server\r\n";
    print $remote "Connection: close\r\n";
    print $remote "\r\n";

    # Let's not wait too long for a reply, treating lengthy delays as a
    # 500 Internal Server error
    alarm(8);

    $discard = <$remote>;

    while(<$remote>)
    {
        print;
    }

    close($remote);

    # Turn off the alarm
    alarm(0);
}
else
{
    print "Status: 404\r\n";
    print "Content-Type: text/plain; charset=utf-8\r\n";
    print "\r\n";

    print "No service was specified.\n";
}