'use strict';

function getRespBody(err, debug) {
  if (debug) {
    return err.toString();
  }

  if (err.code === 'ECONNREFUSED') {
    return 'The connection was refused. Most likely the service being connected to '
      + 'has stopped running or the configuration is wrong.';
  }

  return 'Bad Gateway: ' + err.code;
}

function sendBadGateway(conn, err, debug) {
  var body = getRespBody(err, debug);

  conn.write([
    'HTTP/1.1 502 Bad Gateway'
  , 'Date: ' + (new Date()).toUTCString()
  , 'Connection: close'
  , 'Content-Type: text/html'
  , 'Content-Length: ' + body.length
  , ''
  , body
  ].join('\r\n'));
  conn.end();
}

module.exports.getRespBody = getRespBody;
module.exports.sendBadGateway = sendBadGateway;

module.exports.create = function (deps, config) {
  function proxy(conn, newConnOpts, firstChunk, decrypt) {
    var connected = false;
    newConnOpts.allowHalfOpen = true;
    var newConn = deps.net.createConnection(newConnOpts, function () {
      connected = true;

      if (firstChunk) {
        newConn.write(firstChunk);
      }

      newConn.pipe(conn);
      conn.pipe(newConn);
    });

    // Listening for this largely to prevent uncaught exceptions.
    conn.on('error', function (err) {
      console.log('proxy client error', err);
    });
    newConn.on('error', function (err) {
      if (connected) {
        // Not sure how to report this to a user or a client. We can assume that some data
        // has already been exchanged, so we can't really be sure what we can send in addition
        // that wouldn't result in a parse error.
        console.log('proxy remote error', err);
      } else {
        console.log('proxy connection error', err);
        if (decrypt) {
          sendBadGateway(decrypt(conn), err, config.debug);
        } else {
          sendBadGateway(conn, err, config.debug);
        }
      }
    });

    // Make sure that once one side closes, no I/O activity will happen on the other side.
    conn.on('close', function () {
      newConn.destroy();
    });
    newConn.on('close', function () {
      conn.destroy();
    });
  }

  proxy.getRespBody = getRespBody;
  proxy.sendBadGateway = sendBadGateway;
  return proxy;
};