package patterns

type Observer interface {
	Update()
}

type Subject interface {
	Register(o Observer)
	Unregister(o Observer)
	Notify()
}

type subject struct {
	observers map[Observer]bool
}

func NewSubject() Subject {
	return &subject{
		observers: make(map[Observer]bool),
	}
}

func (s *subject) Register(o Observer) {
	s.observers[o] = true
}

func (s *subject) Unregister(o Observer) {
	delete(s.observers, o)
}

func (s *subject) Notify() {
	for o := range s.observers {
		o.Update()
	}
}