package countdown

import (
	"fmt"
	"io"
	"time"
)

const (
	finalWord      = "Go!"
	countdownStart = 3
)

type Sleeper interface {
	Sleep()
}

type DefaultSleeper struct{}

func (d *DefaultSleeper) Sleep() {
	time.Sleep(1 * time.Second)
}

func Countdown(out io.Writer, sleeper Sleeper) {
	// XXX: The sequence is not tested
	for i := countdownStart; i > 0; i-- {
		fmt.Fprintf(out, "%d\n", i)
		// This is difficult to test!
		sleeper.Sleep()
	}
	fmt.Fprint(out, finalWord)
}