FuncPolicy: function pointer policy

For when you don't want to go to the trouble of writing a type, but do need actual functions.

koboldsim/cardtypes.go

@@ -285,7 +285,7 @@ func (v *VerbosePolicy) Enact(p *Player) (cardsim.Message, error) {
 		msg, err = v.Variants[v.lastIdx].Enact(p)
 	}
 	if errors.Is(err, ErrUnimplemented) {
-		msg, err = v.Default.Enact()
+		msg, err = v.Default.Enact(p)
 	}
 	return msg, err
 }
@@ -339,6 +339,61 @@ func (v *VerbosePolicy) Enabled(p *Player) (result bool) {
 	return
 }
 
+// FuncPolicy implements Policy by calling specified functions. If they're
+// missing, it returns ErrUnimplemented. It handles Is itself. It also tracks
+// LastEnacted data (last index, which policy, is policy self) itself.
+type FuncPolicy struct {
+	OptionTextFunc func(*Player) (cardsim.Message, error)
+	EnactFunc      func(*Player) (cardsim.Message, error)
+	EnabledFunc    func(*Player) bool
+	UnenactFunc    func(*Player) error
+
+	// These three fields are assigned by LastEnacted and typically should not
+	// be set in the initializer.
+	LastEnactedIdx    int
+	LastEnactedPolicy Policy
+	WasEnactedLast    bool
+}
+
+func (f *FuncPolicy) OptionText(p *Player) (cardsim.Message, error) {
+	if f.OptionTextFunc == nil {
+		return nil, ErrUnimplemented
+	}
+	return f.OptionTextFunc(p)
+}
+
+func (f *FuncPolicy) Enact(p *Player) (cardsim.Message, error) {
+	if f.EnactFunc == nil {
+		return nil, ErrUnimplemented
+	}
+	return f.EnactFunc(p)
+}
+
+func (f *FuncPolicy) Enabled(p *Player) bool {
+	if f.EnabledFunc == nil {
+		panic(ErrUnimplemented)
+	}
+	return f.EnabledFunc(p)
+}
+
+func (f *FuncPolicy) Unenact(p *Player) error {
+	if f.UnenactFunc == nil {
+		return ErrUnimplemented
+	}
+	return f.UnenactFunc(p)
+}
+
+func (f *FuncPolicy) LastEnacted(i int, p Policy) {
+	f.LastEnactedIdx = i
+	f.LastEnactedPolicy = p
+	f.WasEnactedLast = f.Is(p)
+}
+
+func (f *FuncPolicy) Is(p Policy) bool {
+	fp, ok := p.(*FuncPolicy)
+	return ok && (f == fp)
+}
+
 // ShuffleIntoBottomHalf is a common "what to do with the card after?" behavior.
 func ShuffleIntoBottomHalf(c Card, p *Player, _ CardOption) error {
 	p.Deck.InsertRandomBottom(0.5, c)