package main

type Predicate[type T] func(t T) bool

type prevStream[type T] struct {
	req  chan struct{}
	data chan T
}

func (ps prevStream[T]) prevData() (T, bool) {
	ps.req <- struct{}{}
	d, ok := <-ps.data
	return d, ok
}

func (ps prevStream[T]) closePrev() {
	close(ps.req)
}

type genericStream[type T] struct {
	prevStream[T]
	nextReq  chan struct{}
	nextData chan T
}

func (gs *genericStream[T]) filter(predicate Predicate[T]) {
	for range gs.nextReq {
		data, ok := <-gs.prevStream.prevData()
		if !ok {
			close(gs.nextData)
			gs.prevStream.closePrev()
			return
		}

		for !predicate(data) {
			data, ok = <-gs. prevStream.prevData()
			if !ok {
				close(gs.nextData)
				gs.prevStream.closePrev()
				return
			}
		}
		gs.nextData <- data
	}
}

func main() {
}