From 0e1f5ff246a0833bc63e994f7dce4cd4f1779716 Mon Sep 17 00:00:00 2001
From: Kistaro Windrider <kistaro@gmail.com>
Date: Mon, 3 Apr 2023 00:17:01 -0700
Subject: [PATCH] Reversible policies

---
 koboldsim/aliases.go   |   1 +
 koboldsim/cardtypes.go | 147 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 148 insertions(+)
 create mode 100644 koboldsim/cardtypes.go

diff --git a/koboldsim/aliases.go b/koboldsim/aliases.go
index b71a085..1787343 100644
--- a/koboldsim/aliases.go
+++ b/koboldsim/aliases.go
@@ -8,3 +8,4 @@ import "git.chromaticdragon.app/kistaro/CardSimEngine/cardsim"
 type Player = cardsim.Player[*KoboldMine]
 type Card = cardsim.Card[*KoboldMine]
 type InfoPanel = cardsim.InfoPanel[*KoboldMine]
+type CardOption = cardsim.CardOption[*KoboldMine]
diff --git a/koboldsim/cardtypes.go b/koboldsim/cardtypes.go
new file mode 100644
index 0000000..0ea40ec
--- /dev/null
+++ b/koboldsim/cardtypes.go
@@ -0,0 +1,147 @@
+package koboldsim
+
+import (
+	"errors"
+
+	"git.chromaticdragon.app/kistaro/CardSimEngine/cardsim"
+)
+
+var (
+	ErrOptionNotEnabled = errors.New("option not enabled")
+	ErrPolicyNotEnacted = errors.New("cannot unenact policy that is not enacted")
+)
+
+type Policy interface {
+	cardsim.CardOption[*KoboldMine]
+	// Unenact reverses the previous enactment of this policy.
+	Unenact(p *Player) error
+
+	// LastEnacted informs this Policy which choice was last enacted; it will
+	// need to prepare to describe itself differently depending on whether
+	// this is itself or not. The policy must return the CardOption that should
+	// be used further, which is usually self.
+	//
+	// The Card that would present this Policy as an option must use this,
+	// and provide the active policy that this is a candidate to replace,
+	LastEnacted(CardOption) CardOption
+}
+
+// A SwitchingCard is an issue card that remembers which option was selected
+// previously, and undoes it before doing a different one. It is always valid
+// to draw.
+type SwitchingCard struct {
+	Name       cardsim.Message
+	Desc       cardsim.Message
+	IsUrgent   bool
+	After      func(*SwitchingCard, *Player, CardOption) error
+	Policies   []Policy
+	lastPolicy CardOption
+}
+
+// Title implements Card.
+func (s *SwitchingCard) Title(*Player) cardsim.Message {
+	return s.Name
+}
+
+// Urgent implements Card.
+func (s *SwitchingCard) Urgent(*Player) bool {
+	return s.IsUrgent
+}
+
+// Drawn implements Card.
+func (s *SwitchingCard) Drawn(*Player) bool {
+	return true
+}
+
+// EventText implements Card.
+func (s *SwitchingCard) EventText(*Player) (cardsim.Message, error) {
+	return s.Desc, nil
+}
+
+// Options implements Card.
+func (s *SwitchingCard) Options(p *Player) ([]CardOption, error) {
+	ret := make([]CardOption, len(s.Policies))
+	for i, p := range s.Policies {
+		ret[i] = p.LastEnacted(s.lastPolicy)
+	}
+	return ret, nil
+}
+
+// Then implements Card.
+func (s *SwitchingCard) Then(p *Player, o CardOption) error {
+	s.lastPolicy = o
+	if s.After != nil {
+		return s.After(s, p, o)
+	}
+	return nil
+}
+
+// BasicPolicy is a straightfoward implementation of Policy.
+type BasicPolicy struct {
+	UnenactedDesc  cardsim.Message
+	EnactedDesc    cardsim.Message
+	NothingChanged cardsim.Message
+	Do             func(*Player) (cardsim.Message, error)
+	Undo           func(*Player) error
+	CanDo          func(*Player) bool
+
+	currentlyEnacted bool
+}
+
+// YesWeCan returns true. It's the default value for BasicPolicy.CanDo / BasicPolicy.CanUndo.
+func YesWeCan(*Player) bool {
+	return true
+}
+
+// lastEnacted notifies b about the last-enacted policy in its group. It updates
+// b.currentlyEnacted accordingly and returns itself as a generic CardOption.
+//
+// It also installs placeholders if CanDo or CanUndo is unspecified.
+func (b *BasicPolicy) LastEnacted(c CardOption) CardOption {
+	b.currentlyEnacted = false
+	if o, ok := c.(*BasicPolicy); ok && o == b {
+		b.currentlyEnacted = true
+	}
+	if b.CanDo == nil {
+		b.CanDo = YesWeCan
+	}
+	return b
+}
+
+// OptionText implements CardOption.
+func (b *BasicPolicy) OptionText(*Player) (cardsim.Message, error) {
+	if b.currentlyEnacted {
+		return b.EnactedDesc, nil
+	}
+	return b.UnenactedDesc, nil
+}
+
+// Enact implements CardOption.
+func (b *BasicPolicy) Enact(p *Player) (cardsim.Message, error) {
+	if b.currentlyEnacted {
+		return b.NothingChanged, nil
+	}
+	if !b.CanDo(p) {
+		return nil, ErrOptionNotEnabled
+	}
+	return b.Do(p)
+}
+
+// Unenact implements Policy.
+func (b *BasicPolicy) Unenact(p *Player) error {
+	if !b.currentlyEnacted {
+		return ErrPolicyNotEnacted
+	}
+	return b.Undo(p)
+}
+
+// Enabled implements CardOption.
+func (b *BasicPolicy) Enabled(p *Player) bool {
+	if b.currentlyEnacted {
+		return true
+	}
+	if b.CanDo == nil {
+		b.CanDo = YesWeCan
+	}
+	return b.CanDo(p)
+}