<?php
/************************
 ** Author: FabianPastor
 ** Description: Simple route file for mirroring telegram desktop update system
 ** 
 ** You can test it in local by using the PHP integrated Webserver:
 **   $ php -S localhost:8080 index.php
 ** Also if you want to use it on Apache2 make sure you have mod_rewrite enabled.
 ** This would be the content for the .htaccess 
       DirectorySlash Off
       Options FollowSymLinks Indexes
       DirectoryIndex index.php

       RewriteEngine on

       RewriteCond %{REQUEST_FILENAME}  -d
       RewriteRule  ^.*$  -  [L]

       RewriteCond %{REQUEST_FILENAME}  -f
       RewriteRule  ^.*$  -  [L]

       RewriteRule ^.*$    index.php [L]
 ** Note: I assume you have a basic knowledge of apache and know how to enable the use of
 ** .htaccess, enable mod_rewrite and so on. Don't ask me how to do things.
 ************************/
$options = json_decode(file_get_contents("options.json"));
// if(json_last_error()!==JSON_ERROR_NONE){ echo "Json Error: ".json_last_error_msg().PHP_EOL; exit();}

// If we recive a query for testing if there is a new update
if( preg_match("/\/([^\/]+)\/tupdates\/current\??(.*)/", $_SERVER["REQUEST_URI"], $matches) ){
  // Initializating variables and get the default values if no valid args are given
  $os = $matches[1];
  parse_str($matches[2], $args);
  
  $current_version=false; $alpha=false; $beta=false; $current=true; $official=false;
  
  if( isset($args['version'  ]) ) $current_version = $args['version'];
  if( isset($args['alpha'    ]) ) $alpha           = true;
  if( isset($args['beta'     ]) ) $beta            = true;
  if( isset($args['official' ]) ) $official        = true;
  
  if($beta||$alpha) $current=false;
  $branch = ($current?'stable':($alpha?'alpha':'beta'));
  
  $version     = (isset($options->$os->$branch->version)?$options->$os->$branch->version:"");
  $last_update = (isset($options->$os->$branch->date   )?$options->$os->$branch->date:0);
       
  if( !is_numeric($current_version) ) $current_version = (($version)?$version:1);
  
  switch($os){
    case 'win':   $osdir='tsetup/'; $osfile = 'tupdate';   break;  // $osdir='tsetup/tupdate'; break;
    case 'linux': $osdir='tlinux/'; $osfile = 'tlinuxupd'; break;  // $osdir='tlinux/tlinuxupd'; break;
    case 'mac':   $osdir='tmac/';   $osfile = 'tmacupd';   break;  // $osdir='tmac/tmacupd'; break;
    default:
    // Maybe it's a good idea to default some of the above??? idk...
      echo "Error: no valid OS given.";
      exit();
    break;
  }
  
  // Testing if we have new updates on tdesktop.com
  if($version=="" || ($last_update+15*60)<time()   ){
    $options->$os->$branch->date = time(); save($options);
    
    $query = ['version' => $current_version, $branch  => 1];
    $query = http_build_query($query,'','&',PHP_QUERY_RFC3986);
    $url = "http://tdesktop.com/$os/tupdates/current?$query";
    
    if( $str = file_get_contents($url) ){
      
      if( preg_match("/([0-9]+) : (.*)/", $str, $matches) ) $version = $matches[1];
      else {echo $str; exit;}
      
      // Seems we have a new version?
      $options->$os->$branch->response = $str; save($options);
      
      if( !file_exists($os) ) mkdir($os);
      
      if( !file_exists("$os/$osfile$version") ){
        // Yeah, it seems we have a new version to download.
        if($beta) {echo $str; exit();} // I can't download private beta T-T
        if( isset($matches[2]) ){
          if( !file_exists("$os/locked") ){
            // Yeey no other instance is downloading to the dir.
            // Making sure no one will download anyting while i am downloading 
            file_put_contents("$os/locked", "Delete this file if needed");
            if( $file_content = file_get_contents($matches[2]) ){
              // Downloading a new version, this may take some time...
              file_put_contents("$os/$osfile$version", $file_content);
              $options->$os->$branch->version = $version; save($options);
              unlink("$os/locked");
            }else{
              // Cant download from tdesktop.com, we forward them to the official link
              unlink("$os/locked");
              echo $str; 
              exit();
            }
          }else{
            // Downloading to the server. Getting the last version until finished
            $version = $options->$os->$branch->version;
          }
        }
      }else{
        $options->$os->$branch->version = $version; save($options);
      }
    }
    
  }
  
  if( $official ) {
    // Sending the last response known from the official servers
    echo $options->$os->$branch->response; 
    exit();
  }
  if( !file_exists("$os/$osfile$version") ){
    // Error: File not found in our server, redirecting to the official server
    echo "$version : http://updates.tdesktop.com/$osdir/$osfile$version";
    exit();
  }
  
  // Sending them to our server, we have this version!!
  echo "$version : http://{$_SERVER["HTTP_HOST"]}/$os/$osfile$version";
  exit();
} 

// If someone asks for a file diferent than the above
if( 
  $path = realpath(".".$_SERVER["REQUEST_URI"]) && // If its a valid path and
  strpos($path, __DIR__) !== false &&              // It's contained on the root path and
  is_file($path) &&                                //  Is a file and
  strpos(basename($path), ".") == false            // filename doesen't contain a "."
) return false;                                    // Return the given file

// If all the above fails... redirect to the telegram.org webpage
header("Location: https://desktop.telegram.org/");
exit();

// Just to make things shorter
function save($options){
  file_put_contents("options.json", json_encode($options,JSON_PRETTY_PRINT));
}