package ui

type EventFn func(Context) bool

type EventStateFn func(Context, interface{})

func NewEvents() *Events {
	return &Events{events: map[uint]EventStateFn{}}
}

type Events struct {
	nextID uint
	events map[uint]EventStateFn
}

type EventHandler interface {
	AddHandler(EventFn) uint
	AddHandlerState(EventStateFn) uint
	RemoveHandler(uint)
}

func (e *Events) Notify(ctx Context, state interface{}) bool {
	if e.events == nil {
		return false
	}
	for _, handler := range e.events {
		handler(ctx, state)
	}
	return len(e.events) > 0
}

func (e *Events) AddHandler(handler EventFn) uint {
	return e.AddHandlerState(func(ctx Context, _ interface{}) { handler(ctx) })
}

func (e *Events) AddHandlerState(handler EventStateFn) uint {
	if e.events == nil {
		e.events = map[uint]EventStateFn{}
	}
	id := e.nextID
	e.nextID++
	e.events[id] = handler
	return id
}

func (e *Events) RemoveHandler(id uint) { delete(e.events, id) }