pWiki/lib/types/event.js

/**********************************************************************
* 
*
*
* XXX need ability to extend event to implement proxy events...
* 		...i.e. .on(..) / ... get called on one object but the handler
* 		bound on a different object via a proxy event method...
* XXX is types/events the right place for this???
* XXX should we have .pre/.post events???
* XXX should we propogate event handling to parent/overloaded events???
*
**********************************************/  /* c8 ignore next 2 */
((typeof define)[0]=='u'?function(f){module.exports=f(require)}:define)
(function(require){ var module={} // make module AMD/node compatible...
/*********************************************************************/

var object = require('ig-object')



/*********************************************************************/
// Event method wrappers...

var EventCommand = 
module.EventCommand = 
object.Constructor('EventCommand', {
	name: null,
	__init__: function(name, data={}){
		Object.assign(this, data, {name}) },
})


module.TRIGGER = module.EventCommand('TRIGGER')



// Create an "eventful" method...
//
// The resulting method can be either called directly or via .trigger(..).
// Handlrs can be bound to it via .on(..) and unbound via .off(..) and 
// calling it will trigger the handlers either after the user func(..)
// return or when the user calles the passed handler(..) function.
//
// 	Eventful(name[, options])
// 		-> method
//
// 	Eventful(name, func[, options])
// 		-> method
//
//
//	Trigger the event...
//	method(...args)
//		-> ..
//
//
// 	func(handle, ...args)
// 		-> ..
//
//
//	trigger event handlers...
//	handle()
//	handle(true)
//		-> true
//		-> false
//
//	trigger event handlers and overload handler arguments...
//	handle(true, ...)
//		-> true
//		-> false
//
//	prevent event handlers from triggering...
//	handle(false)
//		-> undefined
//
//
//
// Special case: EventCommand...
//
//	EventCommand instance can be passed as the first argument of method, 
//	in this case the event function will get it but the event handlers 
//	will not...
//	This is done to be able to externally pass commands to event methods
//	that get handled in a special way by the function but not passed to 
//	the event handlers...
//
// 		method(<event-command>, ...args)
// 			-> ..
//
// 		func(handle, <event-command>, ...args)
// 			-> ..
//
//
//
// NOTE: calling handle(false) will exiplicitly disable calling the 
// 		handlers for that call...
var Eventful =
module.Eventful =
object.Constructor('Eventful', {

	handlerLocation: 'context',

	name: null,
	func: null,

	toString: function(){
		return this.func ?
			`${this.constructor.name} `
				+(this.func.toString()
					.replace(/^(function[^(]*\()[^,)]*, ?/, '$1')) 
			: `${this.constructor.name} function ${this.name}(){}` },

	__event_handlers__: null,
	bind: function(context, handler){
		var handlers = 
			// local...
			this.handlerLocation == 'method' ?
				(this.__event_handlers__ = this.__event_handlers__ || [])
			// context (default)...
			//: (context.__event_handlers__ == null ?
			: !context.hasOwnProperty('__event_handlers__') ?
				Object.defineProperty(context, '__event_handlers__', {
						value: {[this.name]: (handlers = [])},
						enumerable: false,
						configurable: true,
						writable: true,
					}) 
					&& handlers
			: (context.__event_handlers__[this.name] = 
				context.__event_handlers__[this.name] || [])
		// add handler...
		handlers.push(handler)
		return this },
	unbind: function(context, handler){
		var handlers = 
			this.handlerLocation == 'method' ?
				method.__event_handlers__
			//: (context.__event_handlers__ || {})[this.name]) || []
			: context.hasOwnProperty('__event_handlers__') ?
				(context.__event_handlers__ || {})[this.name] || []
			: []
		handlers.splice(0, handlers.length,
			...handlers.filter(function(h){
				return h !== handler
					&& h.__event_original_handler !== handler }))
		return this },

	__call__: function(context, ...args){
		var that = this
		var handlers = 
			this.handlerLocation == 'method' ?
				(this.__event_handlers__ || [])
			: []
		// context (default)...
		// NOTE: these are allways called...
		handlers = handlers
			//.concat((context.__event_handlers__ || {})[this.name] || [])
			.concat(context.hasOwnProperty('__event_handlers__') ?
				(context.__event_handlers__ || {})[this.name] || []
				: [])

		// NOTE: this will stop event handling if one of the handlers 
		// 		explicitly returns false...
		// NOTE: if the user does not call handle() it will be called 
		// 		after the event action is done but before it returns...
		// NOTE: to explicitly disable calling the handlers func must 
		// 		call handle(false)
		var did_handle = false
		var handle = function(run=true, ...alt_args){
			did_handle = true
			var a = (run === true 
					&& arguments.length > 1) ?
				alt_args
				: args
			a = a[0] instanceof EventCommand ?
				a.slice(1)
				: a
			return run ?
				handlers
					.reduce(function(res, handler){ 
						return res === true 
							&& handler.call(context, that.name, ...a) !== false }, true) 
				: undefined } 

		// call...
		var res = this.func ?
			this.func.call(context, handle, ...args)
			: undefined

		// call the handlers if the user either didn't call handle()
		// or explicitly called handle(false)...
		!did_handle
			&& handle()
		return res },

	__init__: function(name, func, options={}){
		options = func && typeof(func) != 'function' ?
			func
			: options
		Object.assign(this, options)
		Object.defineProperty(this, 'name', { value: name })
		func 
			&& typeof(func) == 'function'
			&& Object.defineProperty(this, 'func', { 
				value: func, 
				enumerable: false,
			}) },
})


// Extends Eventful(..) adding ability to bind events via the 
// resulting method directly by passing it a function...
//
//	Event(name[, options])
//		-> method
//
//	Event(name, func[, options])
//		-> method
//
//
//	Bind handler...
//	method(handler)
//		-> this
//
//	Unbind handler...
//	method(handler, false)
//		-> this
//
//	Trigger handlers...
//	method(...args)
//		-> this
//
//
//	func(handle, ...args)
//
//
// Special case:
//
//	Force trigger event...
//	method(TRIGGER, ...args)
//		-> this
//
// This will pass args to the event action regardless whether the first 
// arg is a function or not...
var Event =
module.Event =
object.Constructor('Event', Eventful, {
	toString: function(){
		return this.orig_func ?
			'Event '
				+this.orig_func.toString()
					.replace(/^(function[^(]*\()[^,)]*, ?/, '$1')
			: `Event function ${this.name}(){}`},
	__call__: function(context, ...args){
		// NOTE: when the first arg is an event command this will
		// 		fall through to calling the action...
		typeof(args[0]) == 'function' ?
			// add handler...
			this.bind(context, args[0])
			// call the action...
			: object.parentCall(Event.prototype.__call__, this, context, ...args)
			// XXX workaround for above line -- remove when fully tested...
			//: Eventful.prototype.__call__.call(this, context, ...args)
		return context }, 
})


// Like Event(..) but produces an event method that can only be triggered 
// via .trigger(name, ...), calling this is a no-op...
var PureEvent =
module.PureEvent =
object.Constructor('PureEvent', Event, {
	toString: function(){
		return `PureEvent ${this.name}(){}`},
	__init__: function(name, options={}){
		object.parentCall(PureEvent.prototype.__init__, this,
			name, 
			function(handle, trigger){ 
				trigger === module.TRIGGER 
					|| handle(false) }, options) },
})



//---------------------------------------------------------------------
// Mixins...

// XXX might be nice to add support to pre/post handlers...
// XXX still not sure about the builtin-local event control flow...
// XXX do we need to be able to force global handler???
var EventHandlerMixin = 
module.EventHandlerMixin = object.Mixin('EventHandlerMixin', {
	//__event_handlers__: null,

	on: function(evt, func){
		// event...
		if(evt in this 
				&& this[evt].bind){
			this[evt].bind(this, func)
		// non-event...
		} else {
			//this.__event_handlers__ == null
			!this.hasOwnProperty('__event_handlers__')
				&& Object.defineProperty(this, '__event_handlers__', {
					value: {},
					enumerable: false,
					configurable: true,
					writable: true,
				})
			;(this.__event_handlers__[evt] = 
					this.__event_handlers__[evt] || [])
				.push(func) }
		return this },
	one: function(evt, func){
		var handler
		this.on(evt, 
			handler = Object.assign(
				function(handle, ...args){
					this.off(evt, handler)
					return func.call(this, handle, ...args) }.bind(this),
				{__event_original_handler: func}))
		return this },
	// XXX do we need .off(evt, 'all')
	off: function(evt, func){
		// event...
		if(evt in this 
				&& this[evt].unbind){
			this[evt].unbind(this, func)
		// non-event...
		} else {
			var handlers = this.__event_handlers__
				&& (this.__event_handlers__[evt] || [])
			handlers
				&& handlers.splice(0, handlers.length,
					...handlers.filter(function(h){
						return h !== func 
							&& h.__event_original_handler !== func })) }
		return this },
	// XXX revise...
	trigger: function(evt, ...args){
		evt in this ?
			// XXX add a better check...
			this[evt](module.TRIGGER, ...args)
			//: this.__event_handlers__
			: this.hasOwnProperty('__event_handlers__')
				&& (this.__event_handlers__[evt] || [])
					.forEach(function(h){ h(evt, ...args) }) 
		return this },
})


// NOTE: this can't be added via Object.assign(..), use object.mixinFlat(..) 
// 		instead...
var EventDocMixin = 
module.EventDocMixin = object.Mixin('EventDocMixin', {
	get eventful(){
		return object.deepKeys(this)
			.filter(function(n){ 
				// avoid triggering props...
				return !object.values(this, n, true).next().value.get
					// XXX this is too strict...
					&& (this[n] || {}).constructor === Eventful}.bind(this)) },
	get events(){
		return object.deepKeys(this)
			.filter(function(n){ 
				// avoid triggering props...
				return !object.values(this, n, true).next().value.get
					// XXX this is too strict...
					&& (this[n] || {}).constructor === Event }.bind(this)) },
})


var EventMixin = 
module.EventMixin = 
object.Mixin('EventMixin', 
	EventHandlerMixin,
	EventDocMixin)




/**********************************************************************
* vim:set ts=4 sw=4 :                               */ return module })