<?php

define('BOT_TOKEN', 'Din-API-Nøgle');
define('API_URL', 'https://api.telegram.org/bot'.BOT_TOKEN.'/');

function apiRequestWebhook($method, $parameters) {
  if (!is_string($method)) {
    error_log("Method name must be a string\n");
    return false;
  }

  if (!$parameters) {
    $parameters = array();
  } else if (!is_array($parameters)) {
    error_log("Parameters must be an array\n");
    return false;
  }

  $parameters["method"] = $method;

  header("Content-Type: application/json");
  echo json_encode($parameters);
  return true;
}

function exec_curl_request($handle) {
  $response = curl_exec($handle);

  if ($response === false) {
    $errno = curl_errno($handle);
    $error = curl_error($handle);
    error_log("Curl returned error $errno: $error\n");
    curl_close($handle);
    return false;
  }

  $http_code = intval(curl_getinfo($handle, CURLINFO_HTTP_CODE));
  curl_close($handle);

  if ($http_code >= 500) {
    // do not want to DDOS server if something goes wrong
    sleep(10);
    return false;
  } else if ($http_code != 200) {
    $response = json_decode($response, true);
    error_log("Request has failed with error {$response['error_code']}: {$response['description']}\n");
    if ($http_code == 401) {
      throw new Exception('Invalid access token provided');
    }
    return false;
  } else {
    $response = json_decode($response, true);
    if (isset($response['description'])) {
      error_log("Request was successfull: {$response['description']}\n");
    }
    $response = $response['result'];
  }

  return $response;
}

function apiRequest($method, $parameters) {
  if (!is_string($method)) {
    error_log("Method name must be a string\n");
    return false;
  }

  if (!$parameters) {
    $parameters = array();
  } else if (!is_array($parameters)) {
    error_log("Parameters must be an array\n");
    return false;
  }

  foreach ($parameters as $key => &$val) {
    // encoding to JSON array parameters, for example reply_markup
    if (!is_numeric($val) && !is_string($val)) {
      $val = json_encode($val);
    }
  }
  $url = API_URL.$method.'?'.http_build_query($parameters);

  $handle = curl_init($url);
  curl_setopt($handle, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($handle, CURLOPT_CONNECTTIMEOUT, 5);
  curl_setopt($handle, CURLOPT_TIMEOUT, 60);

  return exec_curl_request($handle);
}

function apiRequestJson($method, $parameters) {
  if (!is_string($method)) {
    error_log("Method name must be a string\n");
    return false;
  }

  if (!$parameters) {
    $parameters = array();
  } else if (!is_array($parameters)) {
    error_log("Parameters must be an array\n");
    return false;
  }

  $parameters["method"] = $method;

  $handle = curl_init(API_URL);
  curl_setopt($handle, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($handle, CURLOPT_CONNECTTIMEOUT, 5);
  curl_setopt($handle, CURLOPT_TIMEOUT, 60);
  curl_setopt($handle, CURLOPT_POSTFIELDS, json_encode($parameters));
  curl_setopt($handle, CURLOPT_HTTPHEADER, array("Content-Type: application/json"));

  return exec_curl_request($handle);
}

function processMessage($message) {
  // process incoming message
  $message_id = $message['message_id'];
  $chat_id = $message['chat']['id'];
  if (isset($message['text'])) {
    // incoming text message
    $text = $message['text'];

    if (strpos($text, "/start") === 0) {
      apiRequest("sendMessage", array('chat_id' => $chat_id, "text" => 'Hi, dnsbot lets you do basic DNS lookups like get host name, get reverse DNS and a MX lookup.'));
    }
    else if (strpos($text, "/mx") === 0) {
      $domain = explode(" ", $text)[1]; //The command is written /mx example.com so extract example.com
      $hosts = array();
      getmxrr($domain, $hosts); //Get MX record command, returns a array with the domain names
      if($hosts != null)
      {
      error_log("command from telegram: \n"); //Log to /var/log/apache2/error.log
      error_log($hosts);
      foreach($hosts as $host) { //Loop throught the array
        $result = $result . $host . ' ' . gethostbyname($host) . chr(10); //add domain name and IP address to the string.
      }
    }
    else {
        $result = "unknown host or server error";
    }
      apiRequest("sendMessage", array('chat_id' => $chat_id, "text" => $result)); //Send the message back to the user
    }
    else if (strpos($text, "/getip") === 0) {
      $ip = explode(" ", $text)[1]; //get the domain
      error_log("command from telegram: \n");
      $result = gethostbyname($ip);
      if($result != null) //Check if there is a result otherwise print a error. Either the user put in garbage or the domain dont exist
      {
      error_log($result);
    }
    else {
        $result = "unknown host or server error";
    }
      apiRequest("sendMessage", array('chat_id' => $chat_id, "text" => $result));
    }
    else if (strpos($text, "/gethost") === 0) {
      $ip = explode(" ", $text)[1];
      error_log("command from telegram: \n");
      $result = gethostbyaddr($ip);;
      error_log($result);
      if($result != null)
      {
      error_log($result);
    }
    else {
        $result = "unknown host or server error";
    }
      apiRequest("sendMessage", array('chat_id' => $chat_id, "text" => $result));
    }
     else if (strpos($text, "/stop") === 0) {
      // stop now
    } else {
      apiRequestWebhook("sendMessage", array('chat_id' => $chat_id, "reply_to_message_id" => $message_id, "text" => 'Unknown command!')); //User send a command that we dont understand
    }
  } else {
    apiRequest("sendMessage", array('chat_id' => $chat_id, "text" => 'I understand only text messages')); //User send a file or something else...
  }
}

$content = file_get_contents("php://input");
$update = json_decode($content, true);
if (php_sapi_name() == 'cli') {
  // if run from console, set or delete webhook
  echo 'test';
  exit;
}

if (!$update) {
  // receive wrong update, must not happen
  exit;
}

if (isset($update["message"])) {
  processMessage($update["message"]);
}