'use strict';

module.exports.create = function (cli, dnsd) {
  function runTcp() {
    var tcpServer = require('net').createServer({ }, function (c) {
      c.on('error', function (err) {
        console.warn("TCP Connection Error:");
        console.warn(err);
      });
      c.on('data', function (nb) {
        //console.log('TCP data.length:', nb.length);
        //console.log(nb.toString('hex'));

        // DNS packets include a 2-byte length header
        var count = nb.length;
        var length = nb[0] << 8;
        length = length | nb[1];
        count -= 2;
        // TODO slice?
        nb._dnsByteOffset = nb.byteOffset + 2;

        if (length !== count) {
          console.error("Handling TCP packets > 512 bytes not implemented.");
          c.end();
          return;
        }

        // TODO pad two bytes for lengths
        dnsd.onMessage(nb, function (err, newAb, dbgmsg) {
          var lenbuf = Buffer.from([ newAb.length >> 8, newAb.length & 255 ]);
          // TODO XXX generate legit error packet
          if (err) { console.error("Error", err); c.end(); return; }
          console.log('TCP ' + dbgmsg);

          c.write(lenbuf);
          c.end(newAb);
        });
      });
      c.on('end', function () {
        console.log('TCP client disconnected from server');
      });
    });

    tcpServer.on('error', function (err) {
      if ('EADDRINUSE' === err.code) {
        console.error("Port '" + cli.port + "' is already in use.");
        tcpServer.close();
        process.exit(0);
      }
      if ('EACCES' === err.code) {
        console.error("Could not bind on port '" + cli.port + "': EACCESS (you probably need root permissions)");
        tcpServer.close();
        process.exit(0);
      }
      console.error("TCP Server Error:");
      console.error(err);
      tcpServer.close(function () {
        setTimeout(runTcp, 1000);
      });
    });

    tcpServer.listen(cli.port, function () {
      console.log('TCP Server bound');
    });

    return tcpServer;
  }

  return runTcp();
};