package main

// export GOEXPERIMENT=rangefunc
import "iter"

func Step(start, stop, step int) iter.Seq[int] {
	if step < 0 {
		return func(yield func(int) bool) {
			for i := start; i <= start && i > stop; i += step {
				next := yield(i)
				if !next {
					return
				}
			}
		}
	}

	if step > 0 {
		return func(yield func(int) bool) {
			for i := start; i >= start && i < stop; i += step {
				next := yield(i)
				if !next {
					println("stopped!")
					return
				}
			}
		}
	}

	return func(yield func(int) bool) { yield(start) }
}

func Fib() iter.Seq[uint] {
	return func(yield func(uint) bool) {
		previous, value := uint(1), uint(1)
		next := yield(value)
		for next {
			next = yield(value)
			value, previous = value+previous, value
			if value < previous {
				return
			}
		}
	}
}

func Fizzbuzzed[T int | uint](from iter.Seq[T]) iter.Seq2[T, string] {
	pull, stop := iter.Pull(from)
	return func(yield func(T, string) bool) {
		defer stop()
		for {
			var fizzbuzz string
			p, ok := pull()
			if !ok {
				return
			}
			if p%3 == 0 {
				fizzbuzz = "fizz"
			}
			if p%5 == 0 {
				fizzbuzz += "buzz"
			}
			if !yield(p, fizzbuzz) {
				return
			}
		}
	}
}

// func main() {
// 	for i, v := range Fizzbuzzed(Fib()) {
// 		println(i, v)
// 	}
// }

func countScan(n int) (func() bool, func() int) {
	pos := -1
	return func() bool {
			pos++
			return pos < n
		}, func() int {
			return pos
		}
}