<?php
/* proxy.php -- provide a proxy for remote webservices
 * Part of the Defsem Widgets plugin for WordPress.
 *
 * Copyright 2008  Dean Scarff  <dos@scarff.id.au>
 *
 * 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, version 2.
 */

// The 'service' GET parameter selects which remote webservice to use.
// This script then retrieves the document from the remote server,
// optionally performs some transformations, and then forwards it on
// in its response.
// 
// This script is not a proxy in the RFC2616 (HTTP) sense.  However,
// it does try to do the right thing with headers so as to be
// transparent.

// HEADER PROCESSING //////////////////////////////////////////////////
if (!function_exists('getallheaders')):
// alternative implementation for non-Apache servers
function getallheaders() {
   $lines = explode("\n", $_SERVER['ALL_RAW']);
   $headers = array();
   preg_match_all('/^([^:]+):\s*((?:[^\n]+\n[ \t])*[^\n]+)\n/',
     $_SERVER['ALL_RAW'], $m, PREG_SET_ORDER);
   foreach ($m as $h) {
     $val = preg_replace('/\n\s+/g', ' ', $h[2]);
     $headers[$h[1]] = $val;
   }
   return $headers;
}

endif;

function filter_response_headers($ch, $content) {
  if (!preg_match('/^(?:Connection|Transfer-Encoding|Content-Encoding|Content-Length):/', $content)) {
    header($content);
  }
  return strlen($content);
}

// SERVICE RULES //////////////////////////////////////////////////////
function lastfm_jsonise($response) {
  if ($_GET['callback'])
    header('Content-Type: text/javascript; charset=utf-8');
  else
    header('Content-Type: text/x-json; charset=utf-8');

  if ($_GET['callback'])
    echo $_GET['callback'] . '(';

  if (0 < preg_match_all('/^\d+,(.+)$/m', $response, $m)) {

    if ($count = $_GET['count'])
      $m[1] = array_slice($m[1], 0, $count);

    foreach ($m[1] as &$trackname) {
      $trackname = "'" . addslashes($trackname) . "'";
    }
    echo '[' . implode(',', $m[1]) . ']';
  } else {
    echo '["Silence"]';
  }
  if ($_GET['callback'])
    echo ');';
}

function service_url() {
  $args = array();
  if ($_GET['count'])
    $args['count'] = (int)$_GET['count'];
  if ($_GET['callback'])
    $args['callback'] = $_GET['callback'];

  switch ($_GET['service']) {
    case 'lastfm':
      return 'http://ws.audioscrobbler.com/1.0/user/' . $_GET['user'] .
       '/recenttracks.txt';
    case 'delicious':
      return 'http://feeds.delicious.com/v2/json/' . $_GET['user'] . '?' .
       http_build_query($args);
    case 'delicious_tag':
      return 'http://feeds.delicious.com/v2/json/network/' . $_GET['user'] .
       "/" . $_GET['tag'] . '?' .
       http_build_query($args);
    case 'twitter':
      return 'http://twitter.com/statuses/user_timeline/' . $_GET['user'] .
       '.json?' .
       http_build_query($args);
    default:
      exit(0);
  }
}

function filter_response_body($ch, $body) {
  $len = strlen($body);
  switch ($_GET['service']) {
    case 'lastfm':
      lastfm_jsonise($body);
      break;
    case 'delicious':
      echo $body;
      break;
    case 'twitter':
      echo $body;
      break;
    default:
      echo $body;
      break;
  }
  return $len;
}

// MAIN ///////////////////////////////////////////////////////////////

$ch = curl_init();
$req = getallheaders();

// HTTP/1.1 wouldn't want us propagating these...
unset($req['Host']);
unset($req['Connection']);
unset($req['Accept-Encoding']);
if ($req['Referer']) {
  @curl_setopt($ch, CURLOPT_REFERER, $req['Referer']);
  unset($req['Referer']);
}
if ($req['User-Agent']) {
  @curl_setopt($ch, CURLOPT_USERAGENT, $request_headers['User-Agent']);
  unset($req['User-Agent']);
}
if ($req['If-Modified-Since']) {
  $time = strtotime($req['If-Modified-Since']);
  @curl_setopt($ch, CURLOPT_TIMEVALUE, $time);
  @curl_setopt($ch, CURLOPT_TIMECONDITION, CURL_TIMECOND_IFMODSINCE);
}

$url = service_url();
@curl_setopt($ch, CURLOPT_URL, $url);
@curl_setopt($ch, CURLOPT_HTTPHEADER, $req);
@curl_setopt($ch, CURLOPT_HEADER, 0);
@curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
@curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 8);
@curl_setopt($ch, CURLOPT_BUFFERSIZE, 2048); // should be enough for a header
@curl_setopt($ch, CURLOPT_HEADERFUNCTION, 'filter_response_headers');
$body = @curl_exec($ch);
if ($body)
  filter_response_body($ch, $body);
curl_close($ch);
?>