feat(examples): a shifumi (rock, paper, scissors) smart contract

examples/gno.land/r/demo/games/shifumi/gno.mod

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+module gno.land/r/demo/games/shifumi

examples/gno.land/r/demo/games/shifumi/shifumi.gno

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+package shifumi
+
+import (
+	"errors"
+	"std"
+	"strconv"
+)
+
+const (
+	empty = iota
+	rock
+	paper
+	scissors
+	last
+)
+
+type game struct {
+	player1, player2 std.Address // shifumi is a 2 players game
+	move1, move2     int         // can be empty, rock, paper, or scissors
+}
+
+var games = []*game{}
+
+func (g *game) play(player std.Address, move int) error {
+	if !(move > empty && move < last) {
+		return errors.New("invalid move")
+	}
+	if player != g.player1 && player != g.player2 {
+		return errors.New("invalid player")
+	}
+	if player == g.player1 && g.move1 == empty {
+		g.move1 = move
+		return nil
+	}
+	if player == g.player2 && g.move2 == empty {
+		g.move2 = move
+		return nil
+	}
+	return errors.New("already played")
+}
+
+func (g *game) winner() int {
+	if g.move1 == empty || g.move2 == empty {
+		return -1
+	}
+	if g.move1 == g.move2 {
+		return 0
+	}
+	if g.move1 == rock && g.move2 == scissors ||
+		g.move1 == paper && g.move2 == rock ||
+		g.move1 == scissors && g.move2 == paper {
+		return 1
+	}
+	return 2
+}
+
+// NewGame creates a new game where player1 is the caller and player2 the argument.
+// A new game index is returned.
+func NewGame(player std.Address) int {
+	games = append(games, &game{player1: std.GetOrigCaller(), player2: player})
+	return len(games) - 1
+}
+
+// Play executes a move for the game at index idx, where move can be:
+// 1 (rock), 2 (paper), 3 (scissors).
+func Play(idx, move int) {
+	if err := games[idx].play(std.GetOrigCaller(), move); err != nil {
+		panic(err)
+	}
+}
+
+func Render(path string) string {
+	mov1 := []string{"", " 🤜  ", " 🫱  ", " 👉  "}
+	mov2 := []string{"", " 🤛  ", " 🫲  ", " 👈  "}
+	win := []string{"pending", "draw", "player1", "player2"}
+
+	output := `# 👊  ✋  ✌️  Shifumi
+Actions:
+* [NewGame](r/demo/games/shifumi?help&__func=NewGame) opponentAddress
+* [Play](r/demo/games/shifumi?help&__func=Play) gameIndex move (1=rock, 2=paper, 3=scissors)
+
+ game  | player1 |     | player2 |       | win 
+ --- | --- | --- | --- | --- | ---
+`
+	for i := len(games) - 1; i >= 0; i-- {
+		g := games[i]
+		output += strconv.Itoa(i) + " | " +
+			short(g.player1) + " | " + mov1[g.move1] + " | " +
+			short(g.player2) + " | " + mov2[g.move2] + " | " +
+			win[g.winner()+1] + "\n"
+	}
+	return output
+}
+
+func short(addr std.Address) string {
+	if len(addr) < 10 {
+		return string(addr)
+	}
+	return string(addr)[:10] + "..."
+}