'use strict';

var dnsjs = require('dns-suite');
var crypto = require('crypto');
var dgram = require('dgram');

function request(queryAb, opts) {
  var handlers = {};
  var server = dgram.createSocket({
    type: 'udp4'
  , reuseAddr: true
  });

  handlers.onError = function (err) {
    if (opts.onError) { opts.onError(err); }
    server.close();
  };
  handlers.onMessage = function (bin) {
    if (!opts.mdns) {
      server.close();
    }

    if (opts.onMessage) { opts.onMessage(bin); }
  };
  handlers.onListening = function () {
    /*jshint validthis:true*/
    var server = this;
    var nameservers;
    var index;
    server.nameserver = opts.nameserver;

    if (!server.nameserver) {
      nameservers = require('dns').getServers();
      index = crypto.randomBytes(2).readUInt16BE(0) % nameservers.length;
      server.nameserver = nameservers[index];
    }

    if (opts.mdns || '224.0.0.251' === opts.nameserver) {
      server.setBroadcast(true);
      server.addMembership(opts.nameserver);
    }

    if (opts.onListening) { opts.onListening.apply(server); }

    server.send(Buffer.from(queryAb), opts.port, server.nameserver, function () {
      if (opts.onSent) { opts.onSent({ port: opts.port, nameserver: server.nameserver }); }
    });
  };

  server.on('error', handlers.onError);
  server.on('message', handlers.onMessage);
  server.on('listening', handlers.onListening);

  // 0 dns request
  // 53 dns server
  // 5353 mdns
  if (opts.mdns) {
    server.bind(opts.port /*5353*/);
    setTimeout(function () {
      server.close();
    }, opts.timeout || (5 * 1000));
  }
  else {
    server.bind(0);
  }
}

function requestJson(query, opts) {
  var queryAb = dnsjs.DNSPacket.write(query);
  var options = {
    onError: opts.onError
  , onMessage: function (nb) {
      var packet = dnsjs.DNSPacket.parse(nb.buffer.slice(nb.byteOffset, nb.byteOffset + nb.byteLength));

      opts.onMessage(packet);
    }
  , onListening: opts.onListening
  , onSent: opts.onSent
  , mdns: opts.mdns
  , nameserver: opts.nameserver
  , port: opts.port
  , timeout: opts.timeout
  };

  return request(queryAb, options);
}

module.exports.request = request;
module.exports.requestJson = requestJson;