block-daemon.js

var EventEmitter = require('events').EventEmitter;
var util = require('util');

var BlockDaemon = function() {
  this._blockFilter = null;
  this.started = false;
  EventEmitter.call(this);
};
util.inherits(BlockDaemon, EventEmitter);

BlockDaemon.prototype.start = function() {
  if (!this.web3) {
    throw new Error('Must call `setWeb3` before starting for the first time');
  }
  if (!this.web3.isConnected()) {
    throw new Error('Web3 is not connected');
  }

  this._blockFilter = this.web3.eth.filter('latest', this.emit.bind(this, 'block'));
  this.started = true;
};

BlockDaemon.prototype.stop = function() {
  if (this._blockFilter) {
    this._blockFilter.stopWatching();
    this.started = false;
  }
};

BlockDaemon.prototype.setWeb3 = function(web3) {
  var started = this.started;
  this.stop();
  this.web3 = web3;
  if (started) {
    this.start();
  }
};