package main

import (
	"flag"
	"fmt"
	"log"
	"math"
	"math/rand"
	"sync"
	"time"
)

func main() {
	numPlayers := flag.Int("n", 2, "Number of players")
	sides := flag.Int("sides", 6, "How many sides the die should have")
	flag.Parse()

	if *numPlayers < 2 {
		log.Fatalf("we need at least 2 players")
	}

	if *sides < 2 {
		log.Fatalf("die needs at least two sides")
	}

	fmt.Println("Welcome to the game")
	fmt.Printf("There are %d players, each with a %d-sided die\n", *numPlayers, *sides)

	game(*numPlayers, *sides)
}

type Player struct {
	id    int
	score int
}

// The player with the lowest score wins.
func game(numPlayers, faces int) {
	// Get the game's winning number by throwing the die once.
	winningNumber := throwDie(faces)
	fmt.Printf("Winning number is %d\n", winningNumber)

	// The finishedPlayers channel communicates the number of turns a
	// player took to hit the winning number.
	finishedPlayers := make(chan Player)

	var wg sync.WaitGroup
	for i := range numPlayers {
		id := i + 1

		// Spawn a player.
		wg.Go(func() {
			var score int

			// Start rolling the dice!
			for {
				score++
				outcome := throwDie(faces)

				if outcome == winningNumber {
					fmt.Printf("Player %d threw a %d: the winning number! Their score is %d\n", id, winningNumber, score)
					finishedPlayers <- Player{id: id, score: score}
					return
				}

				fmt.Printf("Player %d threw a %d\n", id, outcome)
				time.Sleep(1 * time.Second)
			}
		})
	}

	go func() {
		wg.Wait()
		close(finishedPlayers)
	}()

	minPlayer := Player{score: math.MaxInt}

	for player := range finishedPlayers {
		if player.score < minPlayer.score {
			minPlayer = player
		}
	}

	fmt.Printf("Player %d won with a score of %d\n", minPlayer.id, minPlayer.score)
	fmt.Println("Thanks for playing!")
}

func throwDie(faces int) int {
	return rand.Intn(faces) + 1
}