state-based event handler helper

state.js

// State machine, for event handlers and other mischief
define([], function() { "use strict";
///////////////////////
var stateM = {
    create: function(target, config) {
		var instance = Object.create(stateM.proto);
		instance.statesHash = {};
		instance.statesStack = [];
		instance.begunStates = {};
		instance.listeners = [];
		instance.target = target;
		instance.config = config;
		return instance;
	},
	proto: {}
};

// Calls the state handler for given phase/state
// Handler is bound to stateM.target.
stateM.proto.callState = function(phase, args) {
	var retval, d;
	var state = args[0];
	// return if appropriate handler doesn't exist
	if (
		!state ||
		!this.config[state] ||
		!this.config[state][phase] ||
		typeof this.config[state][phase] !== 'function'
	) {
		return;
	}
	args = [].slice.call(args, 1);
	if (this.debug) {
		d = phase + " handler";
		if (args[0] && args[0].type) d += ":" + args[0].type;
		this.debugPhase(state, d);
	}
	return this.config[state][phase].apply(this.target, args);
};
// Returns a callback function bound to a state change
stateM.proto.bindFunc = function(phase, args) {
	if (!this[phase] || typeof this[phase] !== 'function') return;
	args = [].slice.call(args);
	args.unshift(this);
	return this[phase].bind.apply(this[phase], args);
};

stateM.proto.enter = function(state) {
	// return if state was already entered
	if (this.statesHash[state]) return;
	this.debugPhase(state, 'enter');
	this.statesHash[state] = true;
	this.currentState = state;
	this.statesStack.push(state);
	if (!this.begunStates[state]) {
		// run begin handler
		this.begunStates[state] = true;
		this.callState('begin', arguments);
	}
	return this.callState('enter', arguments);
};
stateM.proto.enterH = function(state) {
	return this.bindFunc('enter', arguments);
};

stateM.proto.leave = function(state) {
	var retval;
	// return if state is not entered
	if (!this.statesHash[state]) return;
	this.debugPhase(state, 'leave');
	this.currentState = this.statesStack.pop();
	this.statesHash[state] = false;
	return this.callState('leave', arguments);
};
stateM.proto.leaveH = function(state) {
	return this.bindFunc('leave', arguments);
};

stateM.proto.change = function(state) {
	this.debugPhase(state, 'change');
	this.leaveAll(arguments);
	return this.enter.apply(this, arguments);
};
stateM.proto.changeH = function(state) {
	return this.bindFunc('change', arguments);
};
stateM.proto.leaveAll = function() {
	var state, args = [].slice.call(arguments);
	while (state = this.statesStack.pop()) {
		args[0] = state;
		this.leave.apply(this, args);
	}
};
stateM.proto.debugPhase = function(state, phase) {
	if (!this.debug) return;
	console.log('[' + this.statesStack.join(' ') + '] ' + state + '/' + phase);
};

///////////////////////
return stateM; });