crowns/card.go

package main

import (
	"fmt"
	"math/rand"
)

type Suit int

func (s Suit) String() string {
	switch s {
	case 0:
		return "♠"
	case 1:
		return "♥"
	case 2:
		return "♦"
	case 3:
		return "♣"
	case 4:
		return "★"
	default:
		panic("bad suit")
	}
}

type Card int

func (c Card) Joker() bool {
	return (c == 0)
}

func (c Card) Masked() bool {
	return (c == -1)
}

func (c Card) Suit() Suit {
	if c.Joker() || c.Masked() {
		panic("Suit on invalid")
	}

	return Suit(int(c) % 5)
}

func (c Card) Face() int {
	if c.Joker() || c.Masked() {
		panic("Face on invalid")
	}

	return int(c) / 5
}

func (c Card) String() string {
	if c.Joker() {
		return "Jok" // 🂿 U+1F0BF
	}

	if c.Masked() {
		return "INV" // Invalid
	}

	switch c.Face() {
	case 11:
		return fmt.Sprintf(" J%s", c.Suit().String())

	case 12:
		return fmt.Sprintf(" Q%s", c.Suit().String())

	case 13:
		return fmt.Sprintf(" K%s", c.Suit().String())

	default:
		return fmt.Sprintf("%2d%s", c.Face(), c.Suit().String())
	}

}

func NewMasked() Card {
	return Card(-1)
}

func NewJoker() Card {
	return Card(0)
}

func NewCardFrom(face int, suit Suit) Card {
	return Card(face*5 + int(suit))
}

func Shuffle(c []Card, entropy *rand.Rand) {
	entropy.Shuffle(len(c), func(i, j int) {
		c[i], c[j] = c[j], c[i]
	})
}

const DeckSize = 58 * 2

func Deck() []Card {
	// The full game deck is two 58-card decks
	// Each 58-card deck has 3 jokers plus {3..10 J Q K} in 5 suits.
	ret := make([]Card, 0, DeckSize)
	for i := 0; i < 6; i++ {
		ret = append(ret, NewJoker()) // Joker
	}

	for s := 0; s < 5; s++ {
		for f := 3; f < 14; f++ {
			ret = append(ret, NewCardFrom(f, Suit(s)), NewCardFrom(f, Suit(s)))
		}
	}

	return ret
}