Introduce InfoPanel.

InfoPanels are information displays that do not cost actions. One of them (the Prompt) is shown at the main menu; others can be made available as options in the menu, ether on an ongoing basis or for the current/next turn only.

cardsim/infopanel.go

@@ -0,0 +1,13 @@
+package cardsim
+
+// An InfoPanel displays some set of stats to the player. It does
+// not consume an action. It must not advance the state of the game
+// in any way.
+type InfoPanel[C StatsCollection] interface {
+	// Title returns the title of this InfoPanel, which is also used as the
+	// label presented to the player to access this panel.
+	Title(p *Player[C]) (Message, error)
+
+	// Info returns the contents of this InfoPanel.
+	Info(p *Player[C]) ([]Message, error)
+}

cardsim/player.go

@@ -4,16 +4,19 @@ import "math/rand"
 
 // Player stores all gameplay state for one player.
 type Player[C StatsCollection] struct {
-	Stats            C
-	Name             string
-	Deck             *Deck[C]
-	Hand             []Card[C]
-	HandLimit        int
-	ActionsPerTurn   int
-	ActionsRemaining int
-	PermanentActions []Card[C]
-	Rules            *RuleCollection[C]
-	Rand             rand.Rand
-	Turn             int
-	PendingMessages  []Message
+	Stats             C
+	Name              string
+	Deck              *Deck[C]
+	Hand              []Card[C]
+	HandLimit         int
+	ActionsPerTurn    int
+	ActionsRemaining  int
+	PermanentActions  []Card[C]
+	InfoPanels        []InfoPanel[C]
+	Prompt            InfoPanel[C]
+	Rules             *RuleCollection[C]
+	Rand              rand.Rand
+	Turn              int
+	TemporaryMessages []Message
+	TemporaryPanels   []InfoPanel[C]
 }