fsm.js

/**
 * A state. It's just data.
 */
function State(name) {
	this.name = name || Math.ceil(Math.random()*1000000);
	this.transitions = {};
	this.actions = {
		onEnter: [],
		onExit: []
	};
}
State.prototype.addTransition = function(eventName, targetState) {
	this.transitions[eventName] = targetState;
	return this;
};
State.prototype.onEnter = function(fn) {
	this.actions.onEnter.push(fn);
	return this;
};
State.prototype.onExit = function(fn) {
	this.actions.onExit.push(fn);
	return this;
};


/**
 * State machine. It changes states, and it runs the enter and exit actions in the states.
 *
 * param.startState {State} The starting state. Default: new State('State 1')
 * param.states {[State]} An array of states
 *
 */
function FSM(params) {
	this.parent = params.parent || null;
	this.state = params.startState || new State('State 1');
	this.states = params.states || [this.state];

	// TODO: DRY this up
	// Run starting states entry actions
	for (var j = this.state.actions.onEnter.length - 1; j >= 0; j--) {
		if(typeof this.state.actions.onEnter[j] === 'function') this.state.actions.onEnter[j](this.parent);
	};
}
FSM.prototype.triggerEvent = function(eventName) {
	// Check if current state will exit on this event

	var nextState = this.state.transitions[eventName];

	// No transition? Then warn and gettouttahere!
	if(!nextState) {
		console.warn('State ', this.state.name, 'has no transition for event', eventName);
		return this;
	}


	// Transition exists... find the state and go to it!
	for (var i = this.states.length - 1; i >= 0; i--) {
		if(this.states[i].name == nextState) {
			
			// perform the exit actions of current state
			for (var j = this.state.actions.onExit.length - 1; j >= 0; j--) {
				if(typeof this.state.actions.onExit[j] === 'function') this.state.actions.onExit[j](this.parent);
			};

			// Switch to next state
			this.state = this.states[i];

			// perform the entry actions of current state
			for (var j = this.state.actions.onEnter.length - 1; j >= 0; j--) {
				if(typeof this.state.actions.onEnter[j] === 'function') this.state.actions.onEnter[j](this.parent);
			};

			return;
		}
	};

	// Couldn't find the state...
	console.error('State', this.state.name, 'could not transition to state', nextState, ': It does not exist');
	return this;
};
FSM.prototype.createState = function(name) {
	var state = new State(name);
	this.states.push(state);
	return state;
};
FSM.prototype.deleteState = function(stateName) {
	if(typeof this.states[stateName] === 'Object') delete this.states[stateName];
};