add method to peek the current shell

game/game.go

@@ -102,6 +102,15 @@ func (g *Game) PopShell() bool {
 	return *g.Prev
 }
 
+// Peek returns the current turn's shell if it is revealed for the player with
+// the given ID, or nil otherwise.
+func (g *Game) Peek(id player.ID) *bool {
+	if id != g.CurrentPlayer().ID || !g.Reveal {
+		return nil
+	}
+	return &g.Shells[0]
+}
+
 // Empty returns whether the shotgun is empty.
 func (g *Game) Empty() bool {
 	return len(g.Shells) == 0