mar/lib/client.js

MAR - Message & Reply, is a RPC library based on message exchange.

var net = require('net')
  , EventEmitter = require('events').EventEmitter;

var Client = module.exports = function() {
  this._reset();
};

Client.prototype.__proto__ = EventEmitter.prototype;

Client.prototype.connect = function(address) {
  var that = this;

  this._socket = new net.Socket();

  this._socket.setEncoding('utf8');
  this._socket.setNoDelay(true);

  this._socket.on('data', function(data) {
    var tokens = that._tokenizer(data);
    for (var i = 0, len = tokens.length; i < len; i++) {
      that._process(tokens[i]);
    }
  });
  this._socket.on('connect', function() {
    that.emit('connect');
  });
  this._socket.on('error', function(e) {
    that.emit('error', e);
  });
  this._socket.on('close', function() {
    that._reset();
    that.emit('close');
  });
  this._socket.connect(address);
};

Client.prototype.close = function() {
  this._socket.end();
};

Client.prototype.message = function(subject, data, fn) {
  var msg = {
    subject: subject,
    data: data
  }

  if (fn) {
    msg.id = this._uniqueId();
    msg.reply = true;
    this._callbacks[msg.id] = fn;
  }

  this._socket.write(JSON.stringify(msg) + '\0');
};

Client.prototype._process = function(msg) {
  var that = this;

  try {
    msg = JSON.parse(msg);
    if (!this._callbacks[msg.id]) return;

    var err = msg.err || undefined;
    var data = msg.data || undefined;

    var fn = this._callbacks[msg.id];
    delete this._callbacks[msg.id];
    fn(err, data);
  } catch (e) {
    this.emit('error', e);
  }
};

Client.prototype._reset = function() {
  for (var key in this._callbacks) {
    var fn = this._callbacks[key];
    fn(new Error('connection lost'));
  }
  this._buffer = '';
  this._nextId = 0;
  this._callbacks = {};
  this._socket = null;
};

Client.prototype._uniqueId = function() {
  return this._nextId++;
};

Client.prototype._tokenizer = function(data) {
  this._buffer += data;

  var result = this._buffer.split('\0');
  if (result.length == 1) return [];

  var last = result.pop();
  if (last === '') {
    this._buffer = '';
    return result;
  } else {
    this._buffer = last;
    return result;
  }
};