Typescript event hook and hookable boxed value classes

woohah.ts

/// This interface defines an event listener
interface Listener<Event> {
	(event: Event): void
}

/// This interface represents a hookable type
interface Hookable<Event> {
	/// Attach a handler to this hookable
	(handler: Listener<Event>): void
}

/// This interface represents an event hook
interface Hook<Event> extends Hookable<Event> {
	/// Send an event to all listeners
	(event: Event): void
	
	or<Other>(another: Hook<Other>) : Hookable<Event|Other>
}

/// This interface represents a hookable boxed value
interface Box<T> extends Hook<T> {
	/// Retrieve the value
	() : T
}

function chain() {
	// TODO
}

/// Create an event hook for a specific type of message
function hook<Event>(): Hook<Event> {
    var _handlers: Array<Function> = []
	var _busy = false

    function invoke() {
		if (arguments[0] instanceof Function) {
			_handlers.push(arguments[0])
		} else if (!_busy) {
			_busy = true
			for (var i = 0; i < _handlers.length; i++) {
				_handlers[i].apply(this, arguments)
			}
			_busy = false
		}
    }
	
	invoke["or"] = chain
	
    return <Hook<Event>> <any> invoke
}

/// Create a hookable boxed value (optionally with an initial value)
function box<T>(value?: T): Box<T> {
	var _value: T = value
    var _handlers: Array<Function> = []
	var _busy = false

    function invoke() {
		if (arguments.length === 0) {
			return _value
		} else if (arguments[0] instanceof Function) {
			_handlers.push(arguments[0])
		} else if (!_busy) {
			_value = arguments[0]
			_busy = true
			for (var i = 0; i < _handlers.length; i++) {
				_handlers[i].apply(this, arguments)
			}
			_busy = false
		}
    }

    return <Box<T>> invoke
}

// EXAMPLE:

class User
{
	first_name = box("Rasmus")
	last_name = box("Schultz")
}

var u = new User()

//u.first_name(name => console.log("Logged in: " + name))

u.first_name.or(u.last_name)((value) => console.log(value))

u.first_name("Rasmus")
u.last_name("Schultz")