Don't add an extra line when offering a "quit" prompt.

* "Uncooperative cards" is now a warning.
* Cards and actions get "Then" invoked before the card processor considers erroring out.
* Terminal UI: Errors and warnings from actions are displayed during the response; they're not only added to the temporary messages now.

README.md

@@ -42,7 +42,7 @@ A bucket of game state.
 
 ### Stat
 
-An arbitrary variable (or function, if it's calculated) tagged with some stuff to make it easier to display to the player.
+An arbitrary variable (or function, if it's calculated) tagged with some stuff to make it easier to display to the player. Stats can be extracted automatically (see "Stat Extraction" below).
 
 ### StatsCollection
 
@@ -57,3 +57,26 @@ There are some special errors that Rules can use to "communicate with" the rule
 ### Messages
 
 For now, strings but inconvenient. Intended to provide forwards compatibility when we eventually include some way to format text, where all the stuff written for "it's just a string" would break if not for having this extra type in the way to wrap it where we can stay compatible with "it's just a string" mode.
+
+## Stat Extraction
+The function `ExtractStats` creates a stats list automatically by searching through a struct's fields and methods. The following things are recognized as stats:
+
+* any method with a name like `StatFoo` or `HiddenStatFoo` (the latter are marked as invisible stats, which show up only in debug mode with the implementation in BasicStatsPane)
+* any exported field with a type that is already a `Stat`; the `Stored[T]` and `Hidden[T]` generic types are containers for this
+* any exported field tagged with `cardsim:"stat"`
+    * or `cardsim:"hidden"` for hidden stats. `"hiddenstat"` also works.
+    * you can use `"round2"` to round to two decimal places -- you can use any integer here, not just 2. works with both `float` types.
+    * `"hiddenround3"` (or any other number) creates a hidden rounded stat.
+    * To change the display name of a stat, use a separate tag phrase in addition to the stat tag, `cardsim_name:"name"`.
+        * For example: `cardsim:"stat" cardsim_name:"Stat Display Name"` creates a visible stat that shows up as "Stat Display Name".
+        * `cardsim:"hiddenround1" cardsim_name:"Hidden Rounded Stat"` creates an invisible stat that shows up, rounded to one decimal place, as "Hidden Rounded Stat".
+
+Stat extraction can implement most or all of your type's `Stats` method for you:
+
+```
+func (e *ExampleType) Stats() []cardsim.Stat {
+    return cardsim.ExtractStats(e)
+}
+```
+
+ExtractStats puts methods first (lexicographically), then fields (in the order they appear). You can use `cardsim.SortStats` to instead put visible stats before hidden stats, alphabetized (case-insensitive).

cardsim/card.go

@@ -101,6 +101,63 @@ func (b *BasicCard[C]) Drawn(_ *Player[C]) bool {
 	return true
 }
 
+// RefundAction returns a func that can be used as an AfterOption, which returns
+// the player's action point.
+func RefundAction[C StatsCollection]() func(c Card[C], p *Player[C], option CardOption[C]) error {
+	return func(c Card[C], p *Player[C], option CardOption[C]) error {
+		p.ActionsRemaining++
+		return nil
+	}
+}
+
+// A PanelCard is a Card that takes its title and text from an InfoPanel,
+// while options, urgency, and the post-option callback are specified
+// (like a BasicCard). It never does anything in particular when drawn.
+//
+// Omitting all options yields an inactionable card, which can be displayed
+// but not played. This can be useful for adding an info panel as a debug action.
+type PanelCard[C StatsCollection] struct {
+	Panel       InfoPanel[C]
+	IsUrgent    bool
+	CardOptions []CardOption[C]
+	// AfterOption is given the card itself as its first argument.
+	AfterOption func(c Card[C], p *Player[C], option CardOption[C]) error
+}
+
+// Title implements Card.
+func (c *PanelCard[C]) Title(p *Player[C]) Message {
+	return c.Panel.Title(p)
+}
+
+// Urgent implements Card.
+func (c *PanelCard[C]) Urgent(_ *Player[C]) bool {
+	return c.IsUrgent
+}
+
+// EventText implements Card.
+func (c *PanelCard[C]) EventText(p *Player[C]) (Message, error) {
+	msgs, err := c.Panel.Info(p)
+	return MultiMessage(msgs), err
+}
+
+// Options implements Card.
+func (c *PanelCard[C]) Options(_ *Player[C]) ([]CardOption[C], error) {
+	return c.CardOptions, nil
+}
+
+// Then implements Card.
+func (c *PanelCard[C]) Then(p *Player[C], option CardOption[C]) error {
+	if c.AfterOption == nil {
+		return nil
+	}
+	return c.AfterOption(c, p, option)
+}
+
+// Drawn implements Card.
+func (c *PanelCard[C]) Drawn(_ *Player[C]) bool {
+	return true
+}
+
 // A BasicOption is a CardOption with fixed text, effects, and output.
 // It's always enabled.
 type BasicOption[C StatsCollection] struct {
@@ -151,3 +208,17 @@ func (o *optionFunc[C]) Enact(p *Player[C]) (Message, error) {
 func (o *optionFunc[C]) Enabled(p *Player[C]) bool {
 	return true
 }
+
+// OnlyDiscardFree returns a []CardOption[C] providing a single option, which
+// returns the action point. It does not shuffle the card back into the deck
+// or draw a replacement (consider the AfterFunc for that if needed). This
+// can be used for cards that are displayable but not actionable, but show up
+// as cards rather than permanent or debug actions for some reason.
+func OnlyDiscardFree[C StatsCollection](msg Message) []CardOption[C] {
+	return []CardOption[C]{
+		OptionFunc(msg, func(p *Player[C]) (Message, error) {
+			p.ActionsRemaining++
+			return MsgStr("Okay."), nil
+		}),
+	}
+}

cardsim/debugging.go

@@ -0,0 +1,103 @@
+package cardsim
+
+// Named debug verbosity levels. Using the raw constants is fine too. This
+// is roughly consistent with "standard" meanings for these debug levels.
+const (
+	HideWarnings   = -1
+	NotDebugging   = 0
+	DebugWarning   = 1
+	DebugInfo      = 2
+	DebugDetail    = 3
+	DebugFine      = 4
+	DebugSuperfine = 5
+)
+
+// ActionCounterDebugCard constructs a BasicCard intended for use only as a
+// Debug Action that tinkers with the player's action counter.
+func ActionCounterDebugCard[C StatsCollection]() Card[C] {
+	return &BasicCard[C]{
+		CardTitle: MsgStr("Adjust Action Counter"),
+		CardText:  MsgStr("Change the number of actions you have available this turn."),
+		CardOptions: []CardOption[C]{
+			&BasicOption[C]{
+				Text: MsgStr("Get an extra action."),
+				Effect: func(p *Player[C]) error {
+					p.ActionsRemaining += 2 // counteract the one this costs
+					return nil
+				},
+				Output: MsgStr("Gotten."),
+			},
+			&BasicOption[C]{
+				Text: MsgStr("Waste an action."),
+				Effect: func(p *Player[C]) error {
+					return nil
+				},
+				Output: MsgStr("Wasted."),
+			},
+			&BasicOption[C]{
+				Text: MsgStr("Get a thousand actions."),
+				Effect: func(p *Player[C]) error {
+					p.ActionsRemaining = 1000
+					return nil
+				},
+				Output: MsgStr("ActionsRemaining set to 1000."),
+			},
+			&BasicOption[C]{
+				Text: MsgStr("Go to exactly 1 action remaining."),
+				Effect: func(p *Player[C]) error {
+					p.ActionsRemaining = 1
+					return nil
+				},
+				Output: MsgStr("ActionsRemaining set to 1."),
+			},
+			&BasicOption[C]{
+				Text: MsgStr("End the turn. (Set actions to 0.)"),
+				Effect: func(p *Player[C]) error {
+					p.ActionsRemaining = 0
+					return nil
+				},
+				Output: MsgStr("ActionsRemaining zeroed out."),
+			},
+		},
+	}
+}
+
+// DebugModeCard constructs a BasicCard to change the player's debug level.
+// It is intended for use only as a Debug Action.
+func DebugModeCard[C StatsCollection]() Card[C] {
+	return &BasicCard[C]{
+		CardTitle: MsgStr("Change Debug Level"),
+		CardText:  MsgStr("Adjust verbosity of output, or exit debug mode entirely (not recommended)."),
+		CardOptions: []CardOption[C]{
+			debugLevelOption[C]{1, "Enable debug mode. Show warnings."},
+			debugLevelOption[C]{2, "Enable debug mode. Show info messages."},
+			debugLevelOption[C]{3, "Enable debug mode. Show detailed messages."},
+			debugLevelOption[C]{4, "Enable debug mode. Show individual details of operations."},
+			debugLevelOption[C]{5, "Enable debug mode. Show every event in excruciating detail."},
+			debugLevelOption[C]{0, "NOT RECOMMENDED. Disable debugging (show warnings). IT CAN'T BE TURNED BACK ON."},
+			debugLevelOption[C]{-1, "NOT RECOMMENDED. Disable debugging (hide warnings). IT CAN'T BE TURNED BACK ON."},
+		},
+		AfterOption: RefundAction[C](),
+	}
+}
+
+type debugLevelOption[C StatsCollection] struct {
+	level       int
+	description string
+}
+
+// OptionText implements CardOption[C].
+func (d debugLevelOption[C]) OptionText(*Player[C]) (Message, error) {
+	return Msgf("Set debug level %d: %s", d.level, d.description), nil
+}
+
+// Enact implements CardOption[C].
+func (d debugLevelOption[C]) Enact(p *Player[C]) (Message, error) {
+	p.DebugLevel = d.level
+	return Msgf("Debug level is now %d.", d.level), nil
+}
+
+// Enabled implements CardOption[C].
+func (d debugLevelOption[C]) Enabled(p *Player[C]) bool {
+	return true
+}

cardsim/deck.go

@@ -279,3 +279,145 @@ func (d *Deck[C]) Strip(shouldRemove func(idx int, c Card[C]) bool) int {
 	d.cards = Strip(d.cards, shouldRemove)
 	return origLen - d.Len()
 }
+
+// DeckDebugger is a Card[C], intended for use only as a debug action, that
+// lists the top 10 cards of the deck (without checking if they are drawable)
+// and allows various sorts of deck manipulation for free. It can't be drawn.
+type DeckDebugger[C StatsCollection] struct{}
+
+// Title implements Card[C].
+func (DeckDebugger[C]) Title(p *Player[C]) Message {
+	return MsgStr("Debug Mode Deck Controls")
+}
+
+// Urgent implements Card[C] as used in permanent actions. It's always valid
+// to use the deck debugger. Debug actions do not check urgency flags, but this
+// marks itself as urgent-compatible just in case.
+func (DeckDebugger[C]) Urgent(p *Player[C]) bool {
+	return true
+}
+
+// Drawn implements Card[C]. It can't be drawn.
+func (DeckDebugger[C]) Drawn(p *Player[C]) bool {
+	return false
+}
+
+// EventText implements Card[C]. It lists the top ten cards of the deck and
+// a few deck-related and hand-related stats.
+func (DeckDebugger[C]) EventText(p *Player[C]) (Message, error) {
+	var msgs []Message
+
+	msgs = append(msgs, Msgf("The Deck contains %d cards.", p.Deck.Len()))
+	if p.Deck.Len() > 0 {
+		portion := p.Deck.cards
+		msgs = append(msgs, nil)
+		topness := "All"
+		if p.Deck.Len() > 10 {
+			portion = p.Deck.cards[:10]
+			topness = "Top 10"
+		}
+		msgs = append(msgs, Msgf("%s cards in the Deck:", topness))
+		for i, c := range portion {
+			urgency := " "
+			if c.Urgent(p) {
+				urgency = "!"
+			}
+			msgs = append(msgs, Msgf(" %s %2d) %v", urgency, i+1, c.Title(p)))
+		}
+	}
+	msgs = append(msgs, nil)
+	msgs = append(msgs, Msgf("At the start of each turn, the Player draws to %d cards. The player has %d cards in hand.", p.HandLimit, len(p.Hand)))
+	return MultiMessage(msgs), nil
+}
+
+// Options implements Card[C]. It offers many possible actions.
+func (DeckDebugger[C]) Options(p *Player[C]) ([]CardOption[C], error) {
+	ret := []CardOption[C]{
+		&BasicOption[C]{
+			Text: MsgStr("Draw a card."),
+			Effect: func(p *Player[C]) error {
+				return p.Draw()
+			},
+			Output: MsgStr("Done."),
+		},
+		&BasicOption[C]{
+			Text: MsgStr("Shuffle the deck."),
+			Effect: func(p *Player[C]) error {
+				return p.Deck.Shuffle()
+			},
+			Output: MsgStr("Done."),
+		},
+		&BasicOption[C]{
+			Text: MsgStr("Shuffle top half."),
+			Effect: func(p *Player[C]) error {
+				return p.Deck.ShuffleTop(0.5)
+			},
+			Output: MsgStr("Done."),
+		},
+		&BasicOption[C]{
+			Text: MsgStr("Shuffle bottom half."),
+			Effect: func(p *Player[C]) error {
+				return p.Deck.ShuffleBottom(0.5)
+			},
+			Output: MsgStr("Done."),
+		},
+	}
+	for _, n := range []int{1, 3, 5, 10} {
+		if p.Deck.Len() <= n {
+			break
+		}
+
+		// We don't want the functions we're creating to all share the same "n"
+		// field -- we want to create distinct functions that move distinct
+		// numbers of cards. For more information on what's going on here, see
+		// https://eli.thegreenplace.net/2019/go-internals-capturing-loop-variables-in-closures/
+		//
+		// For the curious, the Go developers don't like the gotcha that
+		// this "shadow variable with itself" workaround patches over either.
+		// Here's the guy who implemented apologizing for it and discussing
+		// changing it: https://github.com/golang/go/discussions/56010
+		//
+		// "Loop variables being per-loop instead of per-iteration is the only
+		//  design decision I know of in Go that makes programs incorrect more
+		//  often than it makes them correct." -- Russ Cox (rsc)
+		n := n
+		invN := p.Deck.Len() - n
+		ret = append(ret,
+			&BasicOption[C]{
+				Text: Msgf("Move the top %d card(s) to the bottom of the deck, in order.", n),
+				Effect: func(p *Player[C]) error {
+					p.Deck.cards = append(p.Deck.cards, p.Deck.cards[:n]...)
+					p.Deck.cards = p.Deck.cards[n:]
+					return nil
+				},
+				Output: MsgStr("Done."),
+			},
+			&BasicOption[C]{
+				Text: Msgf("Move the bottom %d card(s) to the top of the deck, in order.", n),
+				Effect: func(p *Player[C]) error {
+					p.Deck.cards = append(p.Deck.cards, p.Deck.cards[:invN]...)
+					p.Deck.cards = p.Deck.cards[invN:]
+					return nil
+				},
+				Output: MsgStr("Done."),
+			},
+		)
+
+		if n > 1 {
+			ret = append(ret, &BasicOption[C]{
+				Text: Msgf("Shuffle the top %d card(s) of the deck.", n),
+				Effect: func(p *Player[C]) error {
+					return p.Deck.ShufflePart(0, n)
+				},
+				Output: MsgStr("Done."),
+			})
+		}
+	}
+	return ret, nil
+}
+
+// Then implements Card[C]. It refunds the action point.
+func (DeckDebugger[C]) Then(p *Player[C], o CardOption[C]) error {
+	p.ActionsRemaining++
+	return nil
+}

cardsim/messages.go

@@ -12,6 +12,12 @@ type Message interface {
 	fmt.Stringer
 }
 
+// Titled desccribes any type that returns a Message as a title, given a Player
+// (which it may ignore).
+type Titled[C StatsCollection] interface {
+	Title(*Player[C]) Message
+}
+
 type stringMessage string
 
 func (s stringMessage) String() string {
@@ -29,6 +35,19 @@ func Msgf(f string, args ...any) Message {
 	return stringMessage(fmt.Sprintf(f, args...))
 }
 
+// ErrorMessage returns a Message representing an Error.
+// This is preferred over Msgf for errors, since future versions of the library
+// may perform special message formatting for errors.
+func ErrorMessage(e error) Message {
+	if e == nil {
+		return nil
+	}
+	if IsSeriousError(e) {
+		return MultiMessage{MsgStr("SERIOUS ERROR:"), Msgf("%v", e)}
+	}
+	return MultiMessage{MsgStr("Warning:"), Msgf("%v", e)}
+}
+
 // A SpecialMessage is a specific, uniquely identifiable message.
 type SpecialMessage struct {
 	msg Message

cardsim/player.go

@@ -8,13 +8,14 @@ import (
 )
 
 var (
-	ErrUncooperativeCards = errors.New("a milion cards refused to join the hand")
+	ErrInvalidCard   = errors.New("invalid card specified")
-	ErrInvalidCard        = errors.New("invalid card specified")
+	ErrInvalidChoice = errors.New("invalid choice specified")
-	ErrInvalidChoice      = errors.New("invalid choice specified")
+	ErrNotUrgent     = errors.New("action not urgent when urgent card is available")
-	ErrNotUrgent          = errors.New("action not urgent when urgent card is available")
+	ErrNoActions     = errors.New("no actions remaining")
-	ErrNoActions          = errors.New("no actions remaining")
+	ErrNotDebugging  = errors.New("this is a debug-only feature and you're not in debug mode")
 
-	WarningStalemate = errors.New("no actions can be taken")
+	WarningStalemate         = &Warning{errors.New("no actions can be taken")}
+	WarningUncoperativeCards = &Warning{errors.New("a milion cards refused to join the hand")}
 )
 
 // Player stores all gameplay state for one player at a specific point in time.
@@ -104,6 +105,10 @@ type Player[C StatsCollection] struct {
 	// card is in the hand.
 	PermanentActions []Card[C]
 
+	// DebugActions are PermanentActions only available when the player is in
+	// debug mode. InitPlayer adds some standard debugging actions by default.
+	DebugActions []Card[C]
+
 	// InfoPanels lists informational views available to the player. The Prompt
 	// is the InfoPanel shown before the main action menu.
 	InfoPanels []InfoPanel[C]
@@ -170,6 +175,12 @@ func InitPlayer[C StatsCollection](stats C) *Player[C] {
 		HandLimit:      1,
 		ActionsPerTurn: 1,
 		Rules:          NewRuleCollection[C](),
+		DebugActions: []Card[C]{
+			&DeckDebugger[C]{},
+			&PanelCard[C]{Panel: RuleDumper[C]{}},
+			ActionCounterDebugCard[C](),
+			DebugModeCard[C](),
+		},
 	}
 }
 
@@ -261,9 +272,9 @@ func (p *Player[C]) StartNextTurn() error {
 }
 
 // Draw draws a card into the hand, informing the card that it has been drawn.
-// If more than a million cards refuse to enter the hand, this crashes with
+// If more than a million cards refuse to enter the hand, this gives up and
-// ErrUncooperativeCards. If the deck does not have enough cards, this
+// returns WarningUncooperativeCards. If the deck does not have enough cards,
-// returns WarningTooFewCards.
+// this returns WarningTooFewCards.
 func (p *Player[C]) Draw() error {
 	for attempts := 0; attempts < 1000000; attempts++ {
 		if p.Deck.Len() == 0 {
@@ -275,13 +286,13 @@ func (p *Player[C]) Draw() error {
 			return nil
 		}
 	}
-	return ErrUncooperativeCards
+	return WarningUncoperativeCards
 }
 
 // FillHand draws up to the hand limit, informing cards that they have been
-// drawn. If more than a million cards refuse to enter the hand, this crashes
+// drawn. If more than a million cards refuse to enter the hand, this gives up
-// with ErrUncooperativeCards. If the deck does not have enough cards, this
+// and returns WarningUncooperativeCards. If the deck does not have enough
-// returns WarningTooFewCards.
+// cards, this returns WarningTooFewCards.
 func (p *Player[C]) FillHand() error {
 	var lastErr error
 	for p.Deck.Len() > 0 && len(p.Hand) < p.HandLimit {
@@ -308,6 +319,38 @@ func (p *Player[C]) HasUrgentCards() bool {
 	return false
 }
 
+// EnactableType is an enumeration representing a category of enactable thing.
+// Debug actions, permanent actions, and cards behave equivalently in many ways,
+// so EnactableType allows parts of the program to work with any of these and
+// represent which one they apply to.
+type EnactableType int
+
+const (
+	// InvalidEnactable is an uninitialized EnactableType value with no meaning.
+	// Using it is generally an error. If you initialize EnactableType fields
+	// with this value when your program has not yet calculated what type of
+	// enactable will be used, CardSimEngine will be able to detect bugs where
+	// such a calcualation, inadvertently, does not come to any conclusion.
+	// Unlike NothingEnactable, there are no circumstances where this has a
+	// specific valid meaning.
+	InvalidEnactable = EnactableType(iota)
+
+	// NothingEnactable specifically represents not enacting anything. In some
+	// contexts, it's an error to use it; in others, it is a sentinel value
+	// for "do not enact anything". Unlike InvalidEnactable, this has a specific
+	// valid meaning, it's just that the meaning is specifically "nothing".
+	NothingEnactable
+
+	// CardEnactable refers to a card in the hand.
+	CardEnactable
+
+	// PermanentActionEnactable refers to an item in the permanent actions list.
+	PermanentActionEnactable
+
+	// DebugActionEnactable refers to an item in the debug actions list.
+	DebugActionEnactable
+)
+
 // EnactCardUnchecked executes a card choice, removes it from the hand, and
 // decrements the ActionsRemaining. It does not check for conflicting Urgent
 // cards or already being out of actions. If no such card or card choice
@@ -343,17 +386,14 @@ func (p *Player[C]) EnactCardUnchecked(cardIdx, choiceIdx int) (Message, error)
 
 	ret, err := options[choiceIdx].Enact(p)
 	errs.Add(err)
-	if IsSeriousError(err) {
-		p.State = GameCrashed
-		return ret, errs.Emit()
-	}
-
 	err = card.Then(p, options[choiceIdx])
 	errs.Add(err)
+
+	err = errs.Emit()
 	if IsSeriousError(err) {
 		p.State = GameCrashed
 	}
-	return ret, errs.Emit()
+	return ret, err
 }
 
 // EnactCard executes a card choice, removes it from the hand, and decrements
@@ -381,10 +421,31 @@ func (p *Player[C]) EnactCard(cardIdx, choiceIdx int) (Message, error) {
 // result of enacting the permanent action. If enacting the card causes a
 // serious error, the State becomes GameCrashed.
 func (p *Player[C]) EnactPermanentActionUnchecked(actionIdx, choiceIdx int) (Message, error) {
-	if actionIdx < 0 || actionIdx >= len(p.PermanentActions) {
+	return p.enactActionUnchecked(p.PermanentActions, actionIdx, choiceIdx)
-		return nil, fmt.Errorf("%w: no action #%d when %d permanent actions exist", ErrInvalidCard, actionIdx, len(p.PermanentActions))
+}
+
+// EnactDebugActionUnchecked executes a debug action and decrements the
+// ActionsRemaining, even though most debug actions will want to refund that
+// action point. (Consistency with other actions is important.) It does not
+// check for Urgent cards or for already being out of actions. If no such action
+// or card option exists, or the option is not enabled, this returns nil and
+// ErrInvalidCard or ErrInvalidChoice without changing anything. If the player
+// is not in debug mode (DebugLevel >= 1), this returns ErrNotDebugging.
+// Otherwise, this returns the result of enacting the debug action. If enacting
+// the action causes a serious error, the State becomes GameCrashed.
+func (p *Player[C]) EnactDebugActionUnchecked(actionIdx, choiceIdx int) (Message, error) {
+	if p.DebugLevel < 1 {
+		return nil, ErrNotDebugging
 	}
-	card := p.PermanentActions[actionIdx]
+	return p.enactActionUnchecked(p.DebugActions, actionIdx, choiceIdx)
+}
+
+// enactActionUnchecked implements EnactPermanentActionUnchecked and EnactDebugActionUnchecked.
+func (p *Player[C]) enactActionUnchecked(actionSource []Card[C], actionIdx, choiceIdx int) (Message, error) {
+	if actionIdx < 0 || actionIdx >= len(actionSource) {
+		return nil, fmt.Errorf("%w: no action #%d when %d actions exist", ErrInvalidCard, actionIdx, len(actionSource))
+	}
+	card := actionSource[actionIdx]
 	var errs ErrorCollector
 	options, err := card.Options(p)
 	if IsSeriousError(err) {
@@ -393,12 +454,12 @@ func (p *Player[C]) EnactPermanentActionUnchecked(actionIdx, choiceIdx int) (Mes
 	}
 	errs.Add(err)
 	if choiceIdx < 0 || choiceIdx > len(options) {
-		errs.Add(fmt.Errorf("%w: no option #%d on permanent action #%d with %d options", ErrInvalidChoice, choiceIdx, actionIdx, len(options)))
+		errs.Add(fmt.Errorf("%w: no option #%d on action #%d with %d options", ErrInvalidChoice, choiceIdx, actionIdx, len(options)))
 		return nil, errs.Emit()
 	}
 	chosen := options[choiceIdx]
 	if !chosen.Enabled(p) {
-		errs.Add(fmt.Errorf("%w: option #%d on permanent action #%d is not enabled", ErrInvalidChoice, choiceIdx, actionIdx))
+		errs.Add(fmt.Errorf("%w: option #%d on action #%d is not enabled", ErrInvalidChoice, choiceIdx, actionIdx))
 		return nil, errs.Emit()
 	}
 
@@ -406,17 +467,13 @@ func (p *Player[C]) EnactPermanentActionUnchecked(actionIdx, choiceIdx int) (Mes
 
 	ret, err := chosen.Enact(p)
 	errs.Add(err)
-	if IsSeriousError(err) {
-		p.State = GameCrashed
-		return ret, errs.Emit()
-	}
-
 	err = card.Then(p, chosen)
 	errs.Add(err)
-	if IsSeriousError(err) {
+	retErr := errs.Emit()
+	if IsSeriousError(retErr) {
 		p.State = GameCrashed
 	}
-	return ret, errs.Emit()
+	return ret, retErr
 }
 
 // EnactPermanentAction executes a permanently-available card and decrements
@@ -448,15 +505,11 @@ func (p *Player[C]) ReportError(e error) {
 	if e == nil || p.DebugLevel < -1 {
 		return
 	}
-	if p.DebugLevel < 0 && !IsSeriousError(e) {
+	minLvl := NotDebugging
-		return
-	}
-	p.ChapterBreak()
-	severity := "[Warning]"
 	if IsSeriousError(e) {
-		severity = "[ERROR]"
+		minLvl = HideWarnings
 	}
-	p.TemporaryMessages = append(p.TemporaryMessages, Msgf("%s: %v", severity, e))
+	p.Debug(minLvl, ErrorMessage(e))
 }
 
 // CanAct returns whether the player has actions theoretically available.
@@ -470,6 +523,7 @@ func (p *Player[C]) Debug(minLevel int, msg Message) {
 	if p.DebugLevel < minLevel || msg == nil {
 		return
 	}
+	p.ChapterBreak()
 	p.TemporaryMessages = append(p.TemporaryMessages, msg)
 }
 

cardsim/rules.go

@@ -4,6 +4,8 @@ import (
 	"errors"
 	"fmt"
 	"sort"
+
+	"github.com/kr/pretty"
 )
 
 // A Rule implements an operation run on every game turn.
@@ -402,3 +404,14 @@ func (r *RuleCollection[C]) applyDelayedUpdates() {
 		r.RemoveID(id)
 	}
 }
+
+// RuleDumper is an InfoPanel[C] that dumps all rules in P.
+type RuleDumper[C StatsCollection] struct{}
+
+func (RuleDumper[C]) Title(p *Player[C]) Message {
+	return MsgStr("Rule Dumper")
+}
+
+func (RuleDumper[C]) Info(p *Player[C]) ([]Message, error) {
+	return []Message{Msgf("%# v", pretty.Formatter(p.Rules))}, nil
+}

cardsim/sliceutil.go

@@ -145,3 +145,21 @@ func Strip[T any](slice []T, removeWhen func(idx int, t T) bool) []T {
 	}
 	return slice[:to]
 }
+
+// EnsureCapacity checks if `cap(slice)` is at least req. If so, it returns
+// slice unchanged. Otherwise, it copies `slice` to a new slice that is at least
+// capacity `req` (but may be larger) and returns the copy.
+//
+// It is reasonably efficient to use EnsureCapacity consecutively without
+// regard for the final overall capacity that a specific slice will need to be.
+func EnsureCapacity[T any](slice []T, req int) []T {
+	if cap(slice) >= req {
+		return slice
+	}
+	if req < 2*cap(slice) {
+		req = 2 * cap(slice)
+	}
+	ret := make([]T, len(slice), req)
+	copy(ret, slice)
+	return ret
+}

cardsim/terminalui.go

@@ -17,7 +17,7 @@ func RunSimpleTerminalUI[C StatsCollection](p *Player[C]) error {
 
 	for {
 		for p.CanAct() {
-			isCard, cardIdx, choiceIdx, err := pickNextAction(p)
+			actionType, cardIdx, choiceIdx, err := pickNextAction(p)
 			p.ReportError(err)
 			if IsSeriousError(err) {
 				if p.DebugLevel < 1 {
@@ -26,10 +26,18 @@ func RunSimpleTerminalUI[C StatsCollection](p *Player[C]) error {
 				continue
 			}
 			var msg Message
-			if isCard {
+			switch actionType {
+			case CardEnactable:
 				msg, err = p.EnactCard(cardIdx, choiceIdx)
-			} else {
+			case DebugActionEnactable:
+				msg, err = p.EnactDebugActionUnchecked(cardIdx, choiceIdx)
+			case PermanentActionEnactable:
 				msg, err = p.EnactPermanentAction(cardIdx, choiceIdx)
+			case NothingEnactable:
+				continue
+			default:
+				msg = nil
+				err = fmt.Errorf("invalid enaction type in action loop: %d", actionType)
 			}
 			p.ReportError(err)
 			if IsSeriousError(err) {
@@ -38,6 +46,10 @@ func RunSimpleTerminalUI[C StatsCollection](p *Player[C]) error {
 				}
 				continue
 			}
+			if err != nil {
+				display(ErrorMessage(err))
+				display(MsgStr(""))
+			}
 			display(msg)
 			wait()
 		}
@@ -77,7 +89,7 @@ func wait() {
 	fmt.Scanln()
 }
 
-func displayMainMenu[C StatsCollection](p *Player[C]) (actionsOffset, handOffset, max int) {
+func displayMainMenu[C StatsCollection](p *Player[C]) (debugOffset, actionsOffset, handOffset, max int) {
 	cls()
 	needsDivider := displayMessageSection(p)
 	if needsDivider {
@@ -85,10 +97,14 @@ func displayMainMenu[C StatsCollection](p *Player[C]) (actionsOffset, handOffset
 	}
 	displayOnePanel(p, p.Prompt)
 	divider()
-	actionsOffset = displayStatsMenu(p)
+	debugOffset = displayStatsMenu(p)
-	if actionsOffset > 0 {
+	if debugOffset > 0 {
 		divider()
 	}
+	actionsOffset = displayDebugActionsMenu(p, debugOffset)
+	if actionsOffset > debugOffset {
+		fmt.Println()
+	}
 	handOffset = displayPermanentActionsMenu(p, actionsOffset)
 	if handOffset > actionsOffset {
 		fmt.Println()
@@ -97,9 +113,9 @@ func displayMainMenu[C StatsCollection](p *Player[C]) (actionsOffset, handOffset
 	return // uses named return values
 }
 
-func pickNextAction[C StatsCollection](p *Player[C]) (isCard bool, cardIdx int, choiceIdx int, err error) {
+func pickNextAction[C StatsCollection](p *Player[C]) (actionType EnactableType, cardIdx int, choiceIdx int, err error) {
 	for {
-		actionsOffset, handOffset, max := displayMainMenu(p)
+		debugOffset, actionsOffset, handOffset, max := displayMainMenu(p)
 
 		divider()
 		fmt.Printf("%d actions remaining.\n", p.ActionsRemaining)
@@ -117,9 +133,8 @@ func pickNextAction[C StatsCollection](p *Player[C]) (isCard bool, cardIdx int,
 		case "s", "stat", "stats", "i", "info", "p", "panel", "panels", "infopanel", "infopanels":
 			statsMode(p)
 		case "a", "act", "actions":
-			var committed bool
+			actionType, cardIdx, choiceIdx, err = actionsMode(p, true)
-			isCard, cardIdx, choiceIdx, committed, err = actionsMode(p, true)
+			if actionType != NothingEnactable {
-			if committed {
 				return
 			}
 		case "q", "quit", "exit":
@@ -132,21 +147,27 @@ func pickNextAction[C StatsCollection](p *Player[C]) (isCard bool, cardIdx int,
 			} else if i > max {
 				fmt.Println("That's not on this menu. If the menu is too big to read, choose a detail view.")
 				wait()
-			} else if i <= actionsOffset {
+			} else if i <= debugOffset {
 				cls()
 				displayOnePanel(p, p.InfoPanels[i-1])
 				wait()
+			} else if i <= actionsOffset {
+				i = i - debugOffset - 1
+				option, promptErr := promptCard(p, p.DebugActions[i], DebugActionEnactable)
+				if option >= 0 || IsSeriousError(promptErr) {
+					return DebugActionEnactable, i, option, promptErr
+				}
 			} else if i <= handOffset {
 				i = i - actionsOffset - 1
-				option, promptErr := promptCard(p, p.PermanentActions[i])
+				option, promptErr := promptCard(p, p.PermanentActions[i], PermanentActionEnactable)
 				if option >= 0 || IsSeriousError(promptErr) {
-					return false, i, option, promptErr
+					return PermanentActionEnactable, i, option, promptErr
 				}
 			} else {
 				i = i - handOffset - 1
-				option, promptErr := promptCard(p, p.Hand[i])
+				option, promptErr := promptCard(p, p.Hand[i], CardEnactable)
 				if option >= 0 || IsSeriousError(promptErr) {
-					return true, i, option, nil
+					return CardEnactable, i, option, nil
 				}
 			}
 		}
@@ -179,7 +200,7 @@ func lightDivider() {
 
 func confirmQuit() {
 	divider()
-	fmt.Println("Are you sure you want to quit? (Y/N) > ")
+	fmt.Printf("Are you sure you want to quit? (Y/N) > ")
 	s := getResponse()
 	if s == "y" || s == "yes" {
 		fmt.Println("Bye!")
@@ -222,9 +243,7 @@ func displayStatsMenu[C StatsCollection](p *Player[C]) int {
 	}
 	fmt.Println("Info Panels")
 	fmt.Println("-----------")
-	for i, s := range p.InfoPanels {
+	displayNumberedTitles(p, p.InfoPanels, 0)
-		fmt.Printf("[%2d]: %s\n", i+1, s.Title(p).String())
-	}
 	return len(p.InfoPanels)
 }
 
@@ -234,30 +253,42 @@ func displayPermanentActionsMenu[C StatsCollection](p *Player[C], offset int) in
 	}
 	fmt.Println("Always Available")
 	fmt.Println("----------------")
-	for i, s := range p.PermanentActions {
+	displayNumberedTitles(p, p.PermanentActions, offset)
-		fmt.Printf("[%2d]: %s\n", i+offset+1, s.Title(p))
-	}
 	return offset + len(p.PermanentActions)
 }
 
+func displayDebugActionsMenu[C StatsCollection](p *Player[C], offset int) int {
+	if p.DebugLevel < 1 || len(p.DebugActions) == 0 {
+		return offset
+	}
+	fmt.Println("Debug Mode")
+	fmt.Println("----------")
+	displayNumberedTitles(p, p.DebugActions, offset)
+	return offset + len(p.DebugActions)
+}
+
 func displayHandMenu[C StatsCollection](p *Player[C], offset int) int {
 	if len(p.Hand) == 0 {
 		return offset
 	}
 	fmt.Println("Hand")
 	fmt.Println("----")
-	for i, s := range p.Hand {
+	displayNumberedTitles(p, p.Hand, offset)
+	return offset + len(p.Hand)
+}
+
+func displayNumberedTitles[C StatsCollection, T Titled[C]](p *Player[C], cards []T, offset int) {
+	for i, s := range cards {
 		fmt.Printf("[%2d]: %s\n", i+offset+1, s.Title(p))
 	}
-	return offset + len(p.Hand)
 }
 
 // promptCard asks the player to take an action on a card. Returns the option
 // they chose, or -1 if there was a serious error or they cancelled selection.
-func promptCard[C StatsCollection](p *Player[C], card Card[C]) (optionIdx int, err error) {
+func promptCard[C StatsCollection](p *Player[C], card Card[C], cardType EnactableType) (optionIdx int, err error) {
 	// Iterate until the player makes a valid choice.
 	for {
-		opts, valid, err := displayCard(p, card, true)
+		opts, valid, err := displayCard(p, card, cardType, true)
 		if IsSeriousError(err) {
 			return -1, err
 		}
@@ -295,11 +326,11 @@ func promptCard[C StatsCollection](p *Player[C], card Card[C]) (optionIdx int, e
 	}
 }
 
-func displayCard[C StatsCollection](p *Player[C], card Card[C], canAct bool) ([]CardOption[C], bool, error) {
+func displayCard[C StatsCollection](p *Player[C], card Card[C], cardType EnactableType, canAct bool) ([]CardOption[C], bool, error) {
 	cls()
 	t := card.Title(p).String()
 	urgent := card.Urgent(p)
-	if urgent {
+	if urgent && cardType == CardEnactable {
 		t = "[URGENT!] " + t
 	}
 	fmt.Println(t)
@@ -315,7 +346,7 @@ func displayCard[C StatsCollection](p *Player[C], card Card[C], canAct bool) ([]
 	fmt.Println()
 	fmt.Println(SectionBreak.String())
 	fmt.Println()
-	if !urgent && p.HasUrgentCards() {
+	if !urgent && cardType != DebugActionEnactable && p.HasUrgentCards() {
 		fmt.Println("<You have more urgent matters to attend to! You cannot act on this right now.>")
 		fmt.Println()
 		canAct = false
@@ -385,12 +416,16 @@ func statsMode[C StatsCollection](p *Player[C]) error {
 	}
 }
 
-func actionsMode[C StatsCollection](p *Player[C], canAct bool) (isCard bool, cardIdx, choiceIdx int, committed bool, err error) {
+func actionsMode[C StatsCollection](p *Player[C], canAct bool) (actionType EnactableType, cardIdx, choiceIdx int, err error) {
 	var errs ErrorCollector
 	for {
 		cls()
-		pOff := displayPermanentActionsMenu(p, 0)
+		dOff := displayDebugActionsMenu(p, 0)
-		if pOff > 0 {
+		if dOff > 0 {
+			fmt.Println()
+		}
+		pOff := displayPermanentActionsMenu(p, dOff)
+		if pOff > dOff {
 			fmt.Println()
 		}
 		max := displayHandMenu(p, pOff)
@@ -400,7 +435,7 @@ func actionsMode[C StatsCollection](p *Player[C], canAct bool) (isCard bool, car
 			fmt.Println("That's a problem. The game is stuck.")
 			confirmQuit()
 			errs.Add(WarningStalemate)
-			return false, -1, -1, true, errs.Emit()
+			return NothingEnactable, -1, -1, errs.Emit()
 		}
 
 		fmt.Println()
@@ -412,7 +447,7 @@ func actionsMode[C StatsCollection](p *Player[C], canAct bool) (isCard bool, car
 		input := getResponse()
 		switch input {
 		case "b", "back":
-			return false, -1, -1, false, errs.Emit()
+			return NothingEnactable, -1, -1, errs.Emit()
 		case "q", "quit":
 			confirmQuit()
 		default:
@@ -423,35 +458,51 @@ func actionsMode[C StatsCollection](p *Player[C], canAct bool) (isCard bool, car
 			} else if v < 1 || v > max {
 				fmt.Println("That's not a card or action.")
 				wait()
-			} else if v <= pOff {
+			} else if v <= dOff {
 				v--
 				if canAct {
-					optIdx, err := promptCard(p, p.PermanentActions[v])
+					optIdx, err := promptCard(p, p.DebugActions[v], DebugActionEnactable)
 					errs.Add(err)
 					if optIdx >= 0 || IsSeriousError(err) {
-						return false, v, optIdx, true, errs.Emit()
+						return DebugActionEnactable, v, optIdx, errs.Emit()
 					}
 				} else {
-					_, _, err := displayCard(p, p.PermanentActions[v], false)
+					_, _, err := displayCard(p, p.DebugActions[v], DebugActionEnactable, false)
 					errs.Add(err)
 					if IsSeriousError(err) {
-						return false, -1, -1, true, errs.Emit()
+						return DebugActionEnactable, -1, -1, errs.Emit()
+					}
+					wait()
+				}
+			} else if v <= pOff {
+				v = v - dOff - 1
+				if canAct {
+					optIdx, err := promptCard(p, p.PermanentActions[v], PermanentActionEnactable)
+					errs.Add(err)
+					if optIdx >= 0 || IsSeriousError(err) {
+						return PermanentActionEnactable, v, optIdx, errs.Emit()
+					}
+				} else {
+					_, _, err := displayCard(p, p.PermanentActions[v], PermanentActionEnactable, false)
+					errs.Add(err)
+					if IsSeriousError(err) {
+						return PermanentActionEnactable, -1, -1, errs.Emit()
 					}
 					wait()
 				}
 			} else {
 				v = v - pOff - 1
 				if canAct {
-					optIdx, err := promptCard(p, p.Hand[v])
+					optIdx, err := promptCard(p, p.Hand[v], CardEnactable)
 					errs.Add(err)
 					if optIdx >= 0 || IsSeriousError(err) {
-						return true, v, optIdx, false, errs.Emit()
+						return CardEnactable, v, optIdx, errs.Emit()
 					}
 				} else {
-					_, _, err := displayCard(p, p.Hand[v], false)
+					_, _, err := displayCard(p, p.Hand[v], CardEnactable, false)
 					errs.Add(err)
 					if IsSeriousError(err) {
-						return false, -1, -1, false, errs.Emit()
+						return CardEnactable, -1, -1, errs.Emit()
 					}
 					wait()
 				}
@@ -464,7 +515,7 @@ func actionsMode[C StatsCollection](p *Player[C], canAct bool) (isCard bool, car
 func review[C StatsCollection](p *Player[C]) error {
 	var errs ErrorCollector
 	for {
-		actionsOffset, handOffset, max := displayMainMenu(p)
+		debugOffset, actionsOffset, handOffset, max := displayMainMenu(p)
 		divider()
 		fmt.Println("No actions remaining.")
 		fmt.Printf("(C)ontinue, review just (M)essages, (I)nfo Panels, (A)ctions, or an item (1-%d), or (Q)uit? > ", max)
@@ -485,7 +536,7 @@ func review[C StatsCollection](p *Player[C]) error {
 				return errs.Emit()
 			}
 		case "a", "act", "actions":
-			_, _, _, _, err := actionsMode(p, false)
+			_, _, _, err := actionsMode(p, false)
 			errs.Add(err)
 			if IsSeriousError(err) {
 				return errs.Emit()
@@ -498,31 +549,34 @@ func review[C StatsCollection](p *Player[C]) error {
 			i, err := strconv.Atoi(input)
 			if err != nil {
 				fmt.Println("Sorry, I don't understand.")
-				wait()
 			} else if i <= 0 || i > max {
 				fmt.Println("That's not on this menu. If the menu is too big to read, choose a detail view.")
-				wait()
+			} else if i <= debugOffset {
-			} else if i <= actionsOffset {
 				cls()
 				displayOnePanel(p, p.InfoPanels[i-1])
-				wait()
+			} else if i <= actionsOffset {
+				i = i - debugOffset - 1
+				_, _, err := displayCard(p, p.DebugActions[i], DebugActionEnactable, false)
+				errs.Add(err)
+				if IsSeriousError(err) {
+					return errs.Emit()
+				}
 			} else if i <= handOffset {
 				i = i - actionsOffset - 1
-				_, _, err := displayCard(p, p.PermanentActions[i], false)
+				_, _, err := displayCard(p, p.PermanentActions[i], PermanentActionEnactable, false)
 				errs.Add(err)
 				if IsSeriousError(err) {
 					return errs.Emit()
 				}
-				wait()
 			} else {
 				i = i - handOffset - 1
-				_, _, err := displayCard(p, p.Hand[i], false)
+				_, _, err := displayCard(p, p.Hand[i], CardEnactable, false)
 				errs.Add(err)
 				if IsSeriousError(err) {
 					return errs.Emit()
 				}
-				wait()
 			}
+			wait()
 		}
 	}
 }

smoketest/cards.go

@@ -85,7 +85,7 @@ func (i inverseDivision) OptionText(p *player) (cardsim.Message, error) {
 
 func (i inverseDivision) Enact(p *player) (cardsim.Message, error) {
 	if p.Stats.Number.Value == 0 {
-		return nil, errors.New("you can't divide by zero!")
+		return nil, errors.New("you can't divide by zero")
 	}
 	p.Stats.Number.Value = int(i) / p.Stats.Number.Value
 	return cardsim.MsgStr("Inverse divided."), nil
@@ -119,8 +119,8 @@ func initDeck(d *cardsim.Deck[*SmokeTestCollection]) {
 func installPermanentActions(pa *[]card) {
 	*pa = []card{
 		&cardsim.BasicCard[*SmokeTestCollection]{
-			CardTitle: cardsim.MsgStr("Reset to 0"),
+			CardTitle: cardsim.MsgStr("Reset Number"),
-			CardText:  cardsim.MsgStr("Resets Number to 0."),
+			CardText:  cardsim.MsgStr("Resets Number to a fixed value."),
 			CardOptions: []cardOption{
 				&cardsim.BasicOption[*SmokeTestCollection]{
 					Text: cardsim.MsgStr("Reset to 0."),
@@ -130,12 +130,6 @@ func installPermanentActions(pa *[]card) {
 					},
 					Output: cardsim.MsgStr("Done."),
 				},
-			},
-		},
-		&cardsim.BasicCard[*SmokeTestCollection]{
-			CardTitle: cardsim.MsgStr("Reset to 1000000"),
-			CardText:  cardsim.MsgStr("Resets Number to one million."),
-			CardOptions: []cardOption{
 				&cardsim.BasicOption[*SmokeTestCollection]{
 					Text: cardsim.MsgStr("Reset to 1,000,000"),
 					Effect: func(p *player) error {
@@ -146,18 +140,5 @@ func installPermanentActions(pa *[]card) {
 				},
 			},
 		},
-		&cardsim.BasicCard[*SmokeTestCollection]{
-			CardTitle: cardsim.MsgStr("Draw a card"),
-			CardText:  cardsim.MsgStr("Draw an extra card."),
-			CardOptions: []cardOption{
-				&cardsim.BasicOption[*SmokeTestCollection]{
-					Text: cardsim.MsgStr("Draw an extra card."),
-					Effect: func(p *player) error {
-						return p.Draw()
-					},
-					Output: cardsim.MsgStr("Drawn. Probably."),
-				},
-			},
-		},
 	}
 }

smoketest/main.go

@@ -5,8 +5,6 @@ import (
 	"fmt"
 
 	"git.chromaticdragon.app/kistaro/CardSimEngine/cardsim"
-
-	"github.com/kr/pretty"
 )
 
 func main() {
@@ -45,7 +43,6 @@ func main() {
 			Name:  cardsim.MsgStr("Stats"),
 			Intro: cardsim.MsgStr("Hi! These are the smoke test stats."),
 		},
-		ruledumper{},
 	}
 	p.Prompt = prompt{}
 	p.DebugLevel = 5
@@ -69,15 +66,6 @@ func (prompt) Info(p *cardsim.Player[*SmokeTestCollection]) ([]cardsim.Message,
 	return []cardsim.Message{
 		cardsim.MsgStr("Here, have some stuff."),
 		cardsim.Msgf("It's turn %d according to the player and turn %d according to me.", p.TurnNumber, p.Stats.Turns.Value),
+		cardsim.Msgf("The current Number is %d. It tastes like %s.", p.Stats.Number.Value, p.Stats.Flavor.Value),
 	}, nil
 }
-
-type ruledumper struct{}
-
-func (ruledumper) Title(p *player) cardsim.Message {
-	return cardsim.MsgStr("Rule Dumper")
-}
-
-func (ruledumper) Info(p *player) ([]cardsim.Message, error) {
-	return []cardsim.Message{cardsim.Msgf("%# v", pretty.Formatter(p.Rules))}, nil
-}