aws-sdk/lib/state_machine.js

function AcceptorStateMachine(states, state) {
  this.currentState = state || null;
  this.states = states || {};
}

AcceptorStateMachine.prototype.runTo = function runTo(finalState, done, bindObject, inputError) {
  if (typeof finalState === 'function') {
    inputError = bindObject; bindObject = done;
    done = finalState; finalState = null;
  }

  var self = this;
  var state = self.states[self.currentState];
  state.fn.call(bindObject || self, inputError, function(err) {
    if (err) {
      if (state.fail) self.currentState = state.fail;
      else return done ? done.call(bindObject, err) : null;
    } else {
      if (state.accept) self.currentState = state.accept;
      else return done ? done.call(bindObject) : null;
    }
    if (self.currentState === finalState) {
      return done ? done.call(bindObject, err) : null;
    }

    self.runTo(finalState, done, bindObject, err);
  });
};

AcceptorStateMachine.prototype.addState = function addState(name, acceptState, failState, fn) {
  if (typeof acceptState === 'function') {
    fn = acceptState; acceptState = null; failState = null;
  } else if (typeof failState === 'function') {
    fn = failState; failState = null;
  }

  if (!this.currentState) this.currentState = name;
  this.states[name] = { accept: acceptState, fail: failState, fn: fn };
  return this;
};

/**
 * @api private
 */
module.exports = AcceptorStateMachine;