package reactive

import "context"

type Observable[T any] interface {
	Observe(ctx context.Context) <-chan Notification[T]
}

type FnObservable[T any] func(ctx context.Context) <-chan Notification[T]

func (f FnObservable[T]) Observe(ctx context.Context) <-chan Notification[T] {
	return f(ctx)
}

func Cold[T any](f func(ctx context.Context) <-chan Notification[T]) Observable[T] {
	return FnObservable[T](f)
}

func LazyHot[T any](f func(chan<- Notification[T])) Observable[T] {
	var lazy chan Notification[T] = nil

	return FnObservable[T](func(ctx context.Context) <-chan Notification[T] {
		if lazy == nil {
			lazy = make(chan Notification[T])
			go func() {
				f(lazy)
			}()
		}
		return lazy
	})
}

func Hot[T any](c <-chan Notification[T]) Observable[T] {
	return FnObservable[T](func(ctx context.Context) <-chan Notification[T] { return c })
}

func FromChannel[T any](c <-chan T) Observable[T] {
	ch := make(chan Notification[T])
	go func() {
		for v := range c {
			ch <- MakeNext(v)
		}
	}()
	return Hot(ch)
}