// Simple design exercise: represent a deck of cards for blackjack.
package main

import (
	"math/rand"
	"fmt"
	"os"
)

type Card int8
type Suit int8
const (
	Spades Suit = iota
	Hearts
	Clubs
	Diamonds
)
type Rank int8	// 1 = ace, 2 = deuce, 10 = 10, 11 = jack, etc.

func (c Card) Suit() Suit {
	return Suit(c / 13)
}

func (c Card) Rank() Rank {
	return Rank(int8(c % 13) + 1)
}

func (r Rank) String() string {
	if r == 1 {
		return "A"
	} else if r < 11 {
		return fmt.Sprintf("%d", r)
	} else {
		return []string{"J", "Q", "K"}[r - 11]
	}
}

func (s Suit) String() string {
	return string(([]rune("♠♥♣♢"))[s])
}

func (c Card) String() string {
	return fmt.Sprintf("%v%v", c.Rank(), c.Suit())
}

type Hand []Card

func (hand Hand) BlackjackValue() int {
	total := 0
	aces := 0
	for _, c := range hand {
		rank := c.Rank()
		if rank > 9 {
			total += 10
		} else if rank > 1 {
			total += int(rank)
		} else {	      // ace
			aces++
			total += 1
		}
	}

	for total < 21 && aces > 0 {
		aces--
		total += 10
	}

	return total
}

func Shuffle() []Card {
	var cards [52]Card
	for j, c := range rand.Perm(len(cards)) {
		cards[j] = Card(c)
	}
	return cards[0:len(cards)]
}

func main() {
	rand.Seed(int64(os.Getpid()))
	deck := Shuffle()
	hand := Hand(deck[0:4])
	for _, card := range hand {
		fmt.Printf("%v ", card)
	}
	fmt.Printf("→ %v\n", hand.BlackjackValue())
}