package main

import (
	"flag"
	"fmt"
	"sync"
	"time"
)

type Ball struct{ hits int }

func main() {
	numSecs := flag.Int("s", 1, "Number of seconds game should last")
	flag.Parse()

	game(*numSecs)
}

func game(numSecs int) {
	var wg sync.WaitGroup
	p0 := make(chan Ball)

	p1 := player(1, &wg, p0)
	p2 := player(2, &wg, p1)
	t := time.Tick(time.Duration(numSecs) * time.Second)

	p0 <- Ball{}

loop:
	for b := range p2 {
		select {
		case p0 <- b:
		case <-t:
			break loop
		}
	}

	// This sets off a chain reaction that closes the other
	// p-channels (p1, p2, etc.)
	close(p0)

	wg.Wait()

	// If any of these prints out, we know we did something wrong.
	for range p0 {
		fmt.Println("P0")
	}

	for range p1 {
		fmt.Println("P1")
	}

	for range p2 {
		fmt.Println("P2")
	}

	fmt.Println("Done for real!")
}

func player(id int, wg *sync.WaitGroup, input <-chan Ball) <-chan Ball {
	out := make(chan Ball)

	wg.Go(func() {
		defer func() {
			close(out)
			fmt.Printf("(%d) finished\n", id)
		}()

		fmt.Printf("(%d) started\n", id)

		for b := range input {
			b.hits++
			fmt.Printf("(%d) %d\n", id, b.hits)
			time.Sleep(100 * time.Millisecond)

			out <- b
		}
	})

	return out
}