package emitter

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

type Emitter[E comparable] interface {
	On(E, func()) Listener[E]
	Off(Listener[E])
	Emit(E)
}

type BaseEmitter[E comparable] struct {
	listeners map[E]set.Set[Listener[E]]
}

func (e *BaseEmitter[E]) On(kind E, fn func()) Listener[E] {
	if e.listeners[kind] == nil {
		e.listeners[kind] = set.New[Listener[E]]()
	}

	listener := &BaseListener[E]{kind, fn}
	e.listeners[kind].Add(listener)
	return listener
}

func (e *BaseEmitter[E]) Off(listener Listener[E]) {
	kind := listener.Kind()
	if e.listeners[kind] != nil {
		e.listeners[kind].Remove(listener)
	}
}

func (e *BaseEmitter[E]) Emit(event E) {
	if e.listeners[event] == nil {
		e.listeners[event] = set.New[Listener[E]]()
	}

	for listener := range e.listeners[event].Items() {
		listener.Run()
	}
}

func New[E comparable]() *BaseEmitter[E] {
	return &BaseEmitter[E]{
		listeners: map[E]set.Set[Listener[E]]{},
	}
}