package emitter

import "git.maximhutz.com/max/lambda/pkg/set"

type Observer[T any] struct {
	fn      func(T)
	message string
	emitter *Emitter[T]
}

type Emitter[T any] struct {
	listeners map[string]*set.Set[*Observer[T]]
}

func Ignore[T any](fn func()) func(T) {
	return func(T) { fn() }
}

func (e *Emitter[T]) On(message string, fn func(T)) *Observer[T] {
	observer := &Observer[T]{
		fn:      fn,
		message: message,
		emitter: e,
	}

	if e.listeners == nil {
		e.listeners = map[string]*set.Set[*Observer[T]]{}
	}

	if e.listeners[message] == nil {
		e.listeners[message] = set.New[*Observer[T]]()
	}

	e.listeners[message].Add(observer)
	return observer
}

func (o *Observer[T]) Off() {
	if o.emitter.listeners[o.message] == nil {
		return
	}

	o.emitter.listeners[o.message].Remove(o)
}

func (e *Emitter[T]) Emit(message string, value T) {
	if e.listeners[message] == nil {
		return
	}

	for listener := range *e.listeners[message] {
		listener.fn(value)
	}
}