<?php
// $Id: announce_core.php,v 1.7.2.2 2009/06/27 16:46:59 overall Exp $

/**
 * @file
 * The announce portion of the tracker module.
 *
 * Accepts the input from the users torrent client
 * and acts accordingly.
 */

// Require the bt functions
require_once('bt_common.inc');

//set_error_handler('announce_error_handler');

// Include bootstrap.inc and run the bootstrap
require_once('includes/bootstrap.inc');
drupal_bootstrap(DRUPAL_BOOTSTRAP_DATABASE);

// Include "module.inc" because it's used by "user" module. We use it also.
require_once('includes/module.inc');

// Refresh module list (because "user" module use "module_list")
module_list(TRUE);

// for "user_load" function
drupal_load('module', 'user');

// Include settings functions
require_once('module_settings.inc');

// Include "bt_tracker" module settings
module_load_include('inc', 'bt_tracker', 'bt_tracker.settings');

// Initializes $conf so we can use variable_get & setting_get
$conf = variable_init(isset($conf) ? $conf : array());

$_tracker_name = setting_get('bt_tracker', 'name');
$_tracker_version = '6.x-9.x-dev';
$_tracker_scope = setting_get('bt_tracker', 'scope');
$_maximum_simultaneous_downloads = setting_get('bt_tracker', 'maximum_simultaneous_downloads');
$_minimum_ratio = setting_get('bt_tracker', 'minimum_ratio');

// Do not continue parsing if the module is not enabled and let the client know that the tracker is offline.
if (setting_get('bt_tracker', 'enabled') != 1) {
  bt_error('Tracker is Offline');
}

// Init empty respone
$response = array();

// This will contain the values of the request for easier access later.
$request = array();

$_required_keys = array('info_hash', 'peer_id', 'port', 'uploaded', 'downloaded', 'left');
$_optional_keys = array('ip', 'numwant', 'num want', 'num_want', 'no_peer_id', 'key', 'trackerid', 'event', 'compact');

// Add passkey to the list of required keys when the scope is set to private.
if ($_tracker_scope == 2) {
  $_required_keys[] = 'passkey';
}
else {
  $_optional_keys[] = 'passkey';
}

//$params = $_GET;
// Temporary workaround for http://drupal.org/node/508606 (this is the problem of some clients)
parse_str(str_replace('?', '&', $_SERVER['QUERY_STRING']), $params);

// Check for missing keys in the querystring
foreach( $_required_keys as $key )
  if( !array_key_exists($key, $params) )
    bt_error('Missing Key: '. $key);
  else
    $request[$key] = strip_magic($params[$key]);

// Check for optional keys in the querystring
foreach( $_optional_keys as $key )
  if( array_key_exists($key, $params) )
    $request[$key] = strip_magic($params[$key]);

// For $request structure see http://wiki.theory.org/BitTorrentSpecification#Tracker_Request_Parameters

// passkey
if( isset($request['passkey']) )
{
  if( $_tracker_scope == 0 )
  {
    $response['warning message'] = 'Passkey is not needed: '.$request['passkey'];

    unset($request['passkey']);
  }
  else if( strlen($request['passkey']) != 40 ) //TODO: add passkey existance validation
    bt_error('Invalid passkey: '. $request['passkey']);
}
else if( $_tracker_scope == 2 )
  bt_error('Passkey is needed!');

// info_hash
if (strlen($request['info_hash']) != 20) {
  bt_error('Invalid info_hash ('. strlen($request['info_hash']) .' - '. urlencode($request['info_hash']) .')');
}
$request['info_hash'] = bin2hex($request['info_hash']);

// no_peer_id
if (!array_key_exists('no_peer_id', $request)) {
  $request['no_peer_id'] = 0;
}

// peer_id
if ((strlen($request['peer_id']) != 20)) {
  bt_error('Invalid peer_id ('. strlen($request['peer_id']) .' - '. urlencode($request['peer_id']) .')');
}
$request['peer_id'] = bin2hex($request['peer_id']);

// key
if( isset($request['key']) )
  $request['key'] = bin2hex($request['key']);

// ip
if (!empty($request['ip'])) {
  $request['ip'] = stripslashes($request['ip']);
}
else {
  $request['ip'] = $_SERVER['REMOTE_ADDR'];
}
$request['textual_ip'] = $request['ip'];
$request['ip'] = bt_ip_text2bin($request['textual_ip']);
if ($request['ip'] === FALSE) {
  bt_error('Wrong IP format ('.$request['textual_ip'].')');
}

// port
$request['port'] = (int)$request['port'];
if( !$request['port'] || ($request['port'] > 0xFFFF) )
  bt_error('Invalid port: '. $request['port']);

// uploaded
$request['uploaded'] = (int)$request['uploaded'];

// downloaded
$request['downloaded'] = (int)$request['downloaded'];

// left
$request['left'] = (int)$request['left'];

// event
if (array_key_exists('event', $request)) {
  switch (strtolower(stripslashes($request['event']))) {
    case 'started':
    case 'stopped':
    case 'completed':
    case '':
      break;
    default:
      $request['event'] = '';
  }

  $request['event'] = strtolower(stripslashes($request['event']));
}
else {
  $request['event'] = '';
}

// numwant
if (!array_key_exists('numwant', $request)) {
  foreach (array('num want', 'num_want') as $key) {
    if (array_key_exists($key, $request)) {
      $request['numwant'] = 0 + $request[$key];
      unset($request[$key]);
      break;
    }
  }
}
if (array_key_exists('numwant', $request)) {
  if ($request['numwant'] == 0) {
    $request['numwant'] = 30;
  }
}
else {
  $request['numwant'] = 30;
}

// trackerid
if (array_key_exists('trackerid', $request)) {
  $request['trackerid'] = strtolower(stripslashes($request['trackerid']));
}
else {
  $request['trackerid'] = $_tracker_name .'-'. $_tracker_version;
}

/* ************************************************************************ */
/* ******************** DONE EVALUATING GET PARAMETERS ******************** */
/* ************************************************************************ */

// Set default values
$uid = 0;

// Lookup the torrent
$torrent = db_fetch_object(db_query("SELECT fid FROM {bt_torrents} WHERE info_hash = '%s'", $request['info_hash']));
if(!empty($torrent)) {
  $request['fid'] = $torrent->fid; 
} else {
  bt_error('Torrent does not exist, please consider uploading it.');
}

// Save current announce time to use the same value in all queries and calculations
$request['current_announce'] = time();

// Start the generating the response.
if ($_tracker_scope == 2) {
  // Lookup the user and validate permission to use the tracker.
  $uid = db_result(db_query("SELECT uid FROM {bt_tracker_users} WHERE passkey = '%s'", $request['passkey']));

  if (empty($uid)) {
    bt_error('Passkey does not exist please re-download torrent.');
  }

  // Determine if the user has permission to use the tracker.
  $user = user_load(array('uid' => $uid));

  if (!user_access('download torrent', $user)) {
    bt_error('User does not have permission to user the tracker.');
  }

  // Check to make sure the user meets minimum requirements
  //TODO: also use IP, client_id, ...
  if ($_maximum_simultaneous_downloads != 0) {
    $connection_count = db_result(db_query("SELECT COUNT(uid) FROM {bt_tracker_connections} WHERE uid = %d", $uid));
    if ($connection_count > $_maximum_simultaneous_downloads) {
      bt_error('Too many simultaneous downloads, the limit is '. $_maximum_simultaneous_downloads);
    }
  }

  if ($_minimum_ratio) {
    $ratio = db_result(db_query("SELECT bytes_downloaded / bytes_uploaded FROM {bt_tracker_users} WHERE uid = %d"));

    if (!$ratio) {
      $ratio = 0;
    }
  }

  // Verify that the user has achieved the minimum ratio
  if ($_minimum_ratio && $ratio < $_minimum_ratio) {
    bt_error('Minimum ratio has not been met, you have '. $ratio .', and you need '. $_minimum_ratio);
  }

  // Passkey is marked for reset
  $passkey_status = db_result(db_query("SELECT passkey_status FROM {bt_tracker_users} WHERE passkey = '%s'", $request['passkey']));
  if ($passkey_status == 1) {
      bt_error("Passkey is marked for reset, please re-download your torrents.");
  }
  else {
    // Check if there are two peers (distinct IP) downloading with the same passkey
    $distinct_ip_connection_count = db_result(db_query("SELECT COUNT(DISTINCT btc.ip) FROM {bt_tracker_connections} btc INNER JOIN {bt_tracker_users} btu on btu.uid = btc.uid WHERE btu.passkey = '%s'", $request['passkey']));
    if ( $distinct_ip_connection_count > 1) {
      db_query("UPDATE {bt_tracker_users} SET passkey_status = 1 WHERE uid = %d", $uid);
      bt_error("Passkey is already in use by another peer. The passkey has been marked to be reset, please re-download all of your active torrents.");
    }
  }
  
  // Update Last user successful BitTorrent tracker activity time
  db_query("UPDATE {bt_tracker_users} SET last_activity = %d WHERE uid = %d", $request['current_announce'], $uid);
}

// Retrieve the information for the users previous request
$tracker_connection = db_fetch_array(db_query("SELECT bytes_uploaded, bytes_downloaded, last_announce FROM {bt_tracker_connections} WHERE (peer_id = '%s' AND peer_key = '%s') AND fid = %d", $request['peer_id'], $request['key'], $request['fid']));
if (!$tracker_connection) {
  $tracker_connection['bytes_uploaded'] = 0;
  $tracker_connection['bytes_downloaded'] = 0;
}

// Update statistics if we are within a mized environment
if (($_tracker_scope == 1) && array_key_exists('passkey', $request)) {
  // Set the statistics for the appropriate user.
  db_query("UPDATE {bt_tracker_users} SET bytes_uploaded = bytes_uploaded + %d, bytes_downloaded = bytes_downloaded + %d WHERE passkey = %b", ($request['uploaded'] - $tracker_connection['bytes_uploaded']), ($request['downloaded'] - $tracker_connection['bytes_downloaded']), $request['passkey']);
}

// Calc current upload and download speeds
if (isset($tracker_connection['last_announce']) && ($time_delta = $request['current_announce'] - $tracker_connection['last_announce']) && ($time_delta > 0)) {
  $request['upload_speed'] = round(($request['uploaded'] - $tracker_connection['bytes_uploaded'])/$time_delta);
  $request['download_speed'] = round(($request['downloaded'] - $tracker_connection['bytes_downloaded'])/$time_delta);
} else {
  $request['upload_speed'] = 0;
  $request['download_speed'] = 0;
}

// Last seed
$torrent = db_fetch_object(db_query("SELECT total_size FROM {bt_torrents} WHERE fid = %d", $request['fid']));
//TODO: maybe wrong seeding condition (!)
if( /*$request['downloaded'] == $torrent->total_size*/ $request['left'] == 0 )
  db_query("UPDATE {bt_torrents} bt SET last_seed = %d WHERE fid = %d", $request['current_announce'], $request['fid']);

//Note: When a new tracker added to already started torrent in the client (uTorrent 1.8.2). Client doesn't send 'started' event for new tracker.
//Note: In some cases client can not send 'stopped' event (before next 'started' event), so we need to prevent a new start.
if (!$request['event'] || ($request['event'] == 'started')) {
  $connection_exists = db_result(db_query("SELECT COUNT(*) > 0 FROM {bt_tracker_connections} WHERE (peer_id = '%s' AND peer_key = '%s') AND fid = %d LIMIT 1", $request['peer_id'], $request['key'], $request['fid']));
  if( !$connection_exists ) {
    $request['event'] = 'started';
  }
  else {
    unset($request['event']);
  }
}

if ($request['event'] != 'stopped' && $request['event'] != 'started') {
  // Update the connection statistics in the connections table
  db_query("UPDATE {bt_tracker_connections} SET uid = %d, ip = '%s', port = %d, bytes_uploaded = %d, bytes_downloaded = %d, bytes_left = %d, upload_speed = %d, download_speed = %d, last_announce = %d WHERE (peer_id = '%s' AND peer_key = '%s') AND fid = %d", $uid, $request['ip'], $request['port'], $request['uploaded'], $request['downloaded'], $request['left'], $request['upload_speed'], $request['download_speed'], $request['current_announce'], $request['peer_id'], $request['key'], $request['fid']);

  if ($request['event'] == 'completed') {
    // Increment the downloaded field in torrents
    db_query("UPDATE {bt_torrents} bt SET downloaded = downloaded + 1 WHERE fid = %d", $request['fid']);
  }
}
else if ($request['event'] == 'started') {
  // Add the connection to the connections table
  db_query("INSERT INTO {bt_tracker_connections} (uid, peer_id, peer_key, ip, port, fid, bytes_uploaded, bytes_downloaded, bytes_left, upload_speed, download_speed, last_announce) VALUES (%d, '%s', '%s', '%s', %d, %d, %d, %d, %d, %d, %d, %d)", $uid, $request['peer_id'], $request['key'], $request['ip'], $request['port'], $request['fid'], $request['uploaded'], $request['downloaded'], $request['left'], $request['upload_speed'], $request['download_speed'], $request['current_announce']);
}
else if ($request['event'] == 'stopped') {
  // Remove the connection from the connections table
  db_query("DELETE FROM {bt_tracker_connections} WHERE (peer_id = '%s' AND peer_key = '%s') AND fid = %d", $request['peer_id'], $request['key'], $request['fid']);
}


// Build the response object

// Collect peers from other (remote) trackers
/*
$fid = $request['fid']; //db_result(db_query("SELECT fid FROM {bt_torrents} WHERE info_hash = '%s'", $request['info_hash']));
$file = field_file_load($fid);
$torrent_data = bdecode_file($file['filepath']);
$announce_tier_list = torrent_get_announce_tier_list($torrent_data);
$remote_request = $params;
unset($remote_request['passkey']);
$remote_request_query = http_build_query($remote_request, '', '&');
$remote_tracker_response_list = array();
//TODO: corrent this loop according to http://bittorrent.org/beps/bep_0012.html
foreach( $announce_tier_list as $announce_tier )
  foreach( $announce_tier as $announce_url )
  {
    if( strpos($announce_url, '?') === false )
      $announce_url .= '?';
    else
      $announce_url = rtrim($announce_url, '&').'&';

    $stream_context = stream_context_create(array('http' => array('user_agent' => $_SERVER['HTTP_USER_AGENT'])));
    $remote_response_encoded = @file_get_contents($announce_url.$remote_request_query, false, $stream_context);

    if( $remote_response_encoded !== false )
      $remote_tracker_response_list[] = strip_excess(bdecode($remote_response_encoded));
      //$remote_tracker_response_list[$announce_url] = strip_excess(bdecode($remote_response_encoded));
  }
*/

// Retrieve the list of current connections
$response['peers'] = array();
//$tracker_connection_list_result = db_query("SELECT peer_id, ip, port FROM {bt_tracker_connections} WHERE (fid = %d) AND (peer_id <> '%s') LIMIT %d", $request['fid'], $request['peer_id'], $request['numwant']);
$tracker_connection_list_result = db_query("SELECT peer_id, ip, port FROM {bt_tracker_connections} WHERE (fid = %d) LIMIT %d", $request['fid'], $request['numwant']); //666
while($tracker_connection = db_fetch_array($tracker_connection_list_result)) {
  $response_peer = array(
    'peer id' => pack('H*', $tracker_connection['peer_id']),
    'ip' => bt_ip_bin2text($tracker_connection['ip'], TRUE),
    'port' => $tracker_connection['port'],
  );
  $response['peers'][] = $response_peer;
}

$total_tracker_response_list = (isset($remote_tracker_response_list) ? $remote_tracker_response_list : array());
$total_tracker_response_list[] = $response;
//$total_tracker_response_list['-local-'] = $response;

$response = torrent_merge_tracker_response_list($total_tracker_response_list);

$response['interval'] = setting_get('bt_tracker', 'announce_interval');
$response['min interval'] = setting_get('bt_tracker', 'announce_min_interval');

// Pack "peers" (this is optional)
$response['peers'] = torrent_pack_peers($response['peers']);

// Return the response
bencode_response_raw(bencode($response));

//restore_error_handler();