package main

import (
	"fmt"
	"time"
)

type AsyncIterator[T any] struct {
	ch chan T
}

func (it *AsyncIterator[T]) Next() (T, bool) {
	v, ok := <-it.ch
	return v, ok
}

func CountToFive() *AsyncIterator[int] {
	it := &AsyncIterator[int]{
		ch: make(chan int),
	}

	go func() {
		defer close(it.ch)

		for i := 1; i <= 5; i++ {
			time.Sleep(time.Second)
			it.ch <- i
		}
	}()
	return it
}

// ModernCountToFive is an implementation of the Range-over-Func pattern of iterator.
// This was introduced in a golang 1.23+
func ModernCountToFive(yield func(int) bool) {
	for i := 1; i <= 5; i++ {
		time.Sleep(time.Second)
		if !yield(i) {
			return
		}
	}
}

func main() {
	iter := CountToFive()

	fmt.Println("Traditional (Eino style) iterator.")
	for {
		value, ok := iter.Next()

		if !ok {
			break
		}
		fmt.Println(value)
	}

	fmt.Println("Modern Range-over-Func iterator.")
	for i := range ModernCountToFive {
		fmt.Println(i)
	}
}