#!/usr/bin/php5
<?php
  /*
    nmea_to_tcp - A simple TCP forwarder for NMEA 0183 or NMEA 0183 HS (AIS) data streams
    Copyright (C) 2010, Keversoft B.V., Houten, The Netherlands

    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, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */

  $PORT = 2000; # TCP server socket number
  $DEVICE = $argv[1];
  $BAUD_RATE = 38400;
  $CACHE_SIZE = 200;
  $CACHE_FILTER = array('!AIVDM,');

  error_reporting(E_ALL);
  $debug = true;
  $cache = array();
  $clients = array();
  $cacheIndex = 0;

  $c = stream_context_create(array('dio' =>
                              array('data_rate' => $BAUD_RATE,
                                    'data_bits' => 8,
                                    'stop_bits' => 1,
                                    'parity' => 0,
                                    'flow_control' => 0,
                                    'is_canonical' => 0,
                                    'timeout_secs' => 1,
                                    'timeout_usecs' => 1000)));

  $stream = fopen("dio.serial://" . $DEVICE, 'r+', false, $c);
  if (!$stream)
  {
    die("Unable to open NMEA port $DEVICE\n");
  }

  if (($server = socket_create(AF_INET, SOCK_STREAM, SOL_TCP)) < 0)
  {
    die("Failed to create socket: " . socket_strerror($server) . "\n");
  }
  if (($ret = socket_bind($server, '0.0.0.0', $PORT)) < 0)
  {
    die("Failed to bind socket: " . socket_strerror($ret) . "\n");
  }
  if (($ret = socket_listen($server)) < 0)
  {
    die("Failed to listen to socket: " . socket_strerror($ret) . "\n");
  }
  socket_set_nonblock($server);

  while (!feof($stream))
  {
    $read = rtrim(fgets($stream, 4000));
    if ($debug) echo "READ: $read\n";

    acceptNewClients();
    sendMessageToClients($read . "\r\n");
  }
  pclose($stream);
  return;

  function acceptNewClients()
  {
    global $clients, $cache, $server, $debug;

    while (($newClient = @socket_accept($server)) !== false)
    {
      if ($newClient < 0)
      {
        echo "Error on accept: " . socket_strerror($newClient) . "\n";
      }
      else
      {
        $clients[] = $newClient;

        if ($debug)
        {
          if (socket_getpeername($newClient, $address))
          {
            echo "New client ".$address."\n";
          }
          else
          {
            echo "New client ".$newClient."\n";
          }
        }

        sendCache($newClient);
      }
    }
  }

  function sendCache($client)
  {
    global $cache, $clients, $debug;

    $i = 0;

    foreach ($cache as $msg)
    {
      if (!updateClient($client, $msg))
      {
        socket_close($client);
        unset($clients[$key]);
        return;
      }
      $i++;
    }
    if ($debug) echo "Sent cached ".$i." messages.\n";
  }

  function sendMessageToClients($msg)
  {
    global $clients, $cache, $cacheIndex, $CACHE_SIZE, $CACHE_FILTER;

    foreach ($clients as $key => $client)
    {
      if (!updateClient($client, $msg))
      {
        socket_close($client);
        unset($clients[$key]);
      }
    }

    foreach ($CACHE_FILTER as $filter)
    {
      if (strpos($msg, $filter) !== false)
      {
        $cacheIndex += 1;
        $cache[$cacheIndex] = $msg;
        if ($cacheIndex > $CACHE_SIZE)
        {
          unset($cache[$cacheIndex - $CACHE_SIZE]);
        }
        break;
      }
    }
  }

  function updateClient($client, $msg)
  {
    global $debug;

    if ($debug) echo "writing ".strlen($msg)." bytes to client $client\n";
    for ($written = 0; $written < strlen($msg); $written += $fwrite)
    {
      $fwrite = socket_write($client, substr($msg, $written));
      if ($fwrite === false)
      {
        return false;
      }
      if ($debug) echo "written $fwrite to client $client\n";
    }
    return $written;
  }

?>