path: root/go/game/targets.go

package game

import (
	"errors"
	"fmt"
	"slices"
	"strconv"
	"strings"

	"muhq.space/muhqs-game/go/log"
	"muhq.space/muhqs-game/go/utils"
)

type (
	TargetConstraintFunc func(any) error

	TargetDesc struct {
		target, req string
	}

	TargetRequirement struct {
		min, max int
	}

	Target struct {
		s           *LocalState
		desc        string
		requirement TargetRequirement
		constraint  TargetConstraintFunc
		sel         []any
	}

	Targets struct {
		idx int
		ts  []*Target
	}
)

var INVALID_TARGET_DESC = TargetDesc{}

func (t *Target) String() string {
	if len(t.sel) == 0 {
		return "undecided target"
	}

	if len(t.sel) == 1 {
		return fmt.Sprintf("%v", t.sel[0])
	}

	s := "["
	for _, sel := range t.sel {
		s += fmt.Sprintf("%v ", sel)
	}
	return s[:len(s)-1] + "]"
}

func (t *Targets) String() string {
	if len(t.ts) == 0 {
		return "no targets"
	}

	if len(t.ts) == 1 {
		return t.ts[0].String()
	}

	s := "["
	for _, t := range t.ts {
		s += fmt.Sprintf("%v ", t)
	}
	return s[:len(s)-1] + "]"
}

func newTargetWithSel(s *LocalState, desc TargetDesc, action Action, sel []any) *Target {
	t := &Target{
		s:           s,
		desc:        desc.target,
		constraint:  targetConstraint(desc.target, s, action),
		requirement: desc.requirement(),
		sel:         sel,
	}

	return t
}

func newTarget(s *LocalState, desc TargetDesc, action Action) *Target {
	return newTargetWithSel(s, desc, action, []any{})
}

func newUnitAiTarget(s *LocalState, desc TargetDesc, ai *UnitAI) *Target {
	// Dummy action allowing the parsing code to determine the controller of the AI
	dummyAction := NewPassPriority(ai.u.controller)
	return newTargetWithSel(s, desc, dummyAction, []any{})
}

func newConstraintTarget(s *LocalState, desc TargetDesc, constraint TargetConstraintFunc, action Action,
) *Target {
	return &Target{
		s:           s,
		desc:        desc.target,
		constraint:  constraint,
		requirement: desc.requirement(),
	}
}

func newTargets(targets ...*Target) *Targets {
	return &Targets{0, targets}
}

func newTargetDesc(desc string) TargetDesc {
	return TargetDesc{desc, "1"}
}

func newPileDropTargets(s *LocalState, a *PileDropAction) *Targets {
	pile := a.pile

	targets := newTargets()
	targets.ts = make([]*Target, 0, len(pile))

	desc := newTargetDesc("adjacent tile")
	for i, p := range pile {
		constraints := parseTileTargetConstraint(desc.target, s, a)
		// The selected tile must be available for the individual dropped card
		constraints = append(constraints, availableTileConstraint(a, p.Card()))
		// The selected tile must be not be previously selected in this action
		constraints = append(constraints, noPreviousSelectionConstraint(targets, i))

		targets.ts = append(targets.ts, newConstraintTarget(s, desc, conjunction(constraints...), a))
	}

	return targets
}

func newArtifactMoveTargets(s *LocalState, a *ArtifactMoveAction) *Targets {
	targets := newTargets()
	targets.ts = make([]*Target, 0, 2)

	u := a.Source().(*Unit)
	desc := newTargetDesc("available tile")
	constraints := []TargetConstraintFunc{tileTargetConstraint}
	constraints = append(constraints, availableTileConstraint(a, u.Card()))
	constraints = append(constraints, moveConstraint(s, a, u))
	moveTarget := newConstraintTarget(s, desc, conjunction(constraints...), a)
	targets.ts = append(targets.ts, moveTarget)

	constraints = []TargetConstraintFunc{tileTargetConstraint}
	constraints = append(constraints, availableTileConstraint(a, a.Artifact.Card()))
	constraints = append(constraints, func(t any) error {
		c := rangeTargetConstraint(moveTarget.sel[0], 1)
		return c(t)
	})
	constraints = append(constraints, noPreviousSelectionConstraint(targets, 1))
	targets.ts = append(targets.ts, newConstraintTarget(s, desc, conjunction(constraints...), a))

	return targets
}

func (d *TargetDesc) requirement() TargetRequirement {
	switch d.req {
	case "?":
		return TargetRequirement{0, 1}
	case "+":
		return TargetRequirement{1, -1}
	case "*":
		return TargetRequirement{0, -1}
	default:
		if strings.Contains(d.req, "-") {
			tokens := strings.SplitN(d.req, "-", 2)
			min, err := strconv.Atoi(tokens[0])
			if err != nil {
				log.Panicf("failed to parse target requirement %s: %v", d.req, err)
			}
			max, err := strconv.Atoi(tokens[1])
			if err != nil {
				log.Panicf("failed to parse target requirement %s: %v", d.req, err)
			}
			return TargetRequirement{min, max}
		}

		x, err := strconv.Atoi(d.req)
		if err != nil {
			log.Panicf("failed to parse target requirement %s: %v", d.req, err)
		}
		return TargetRequirement{x, x}
	}
}

var ErrTargetAlreadySelected = errors.New("already selected")

// AddSelection adds an object as selection to the target.
// If the provided object does not satisfy the target contraint err != nil is returned.
// Selecting the same object multiple times results in an error.
func (t *Target) AddSelection(sel any) (err error) {
	if slices.Contains(t.sel, sel) {
		return ErrTargetAlreadySelected
	}

	if err = t.constraint(sel); err == nil {
		t.sel = append(t.sel, sel)
	}
	return
}

func (t *Target) RequireSelection() bool { return len(t.sel) < t.requirement.min }
func (t *Target) HasSelection() bool     { return len(t.sel) > 0 }
func (t *Target) AllowSelection() bool {
	return (t.requirement.max == -1 || len(t.sel) < t.requirement.max) && len(t.Options()) > 0
}
func (t *Target) ClearSelection()   { t.sel = []any{} }
func (t *Target) NoSelection() bool { return len(t.sel) == 0 }
func (t *Target) Selection() []any  { return t.sel }

func (t *Target) Options() (options []any) {
	candidates := t.candidates()

	for _, candidate := range candidates {

		err := t.constraint(candidate)
		// TODO: Fix this if a single target allows multiple selections of the same object.
		if err == nil && slices.Contains(t.sel, candidate) {
			err = ErrTargetAlreadySelected
		}
		if err == nil {
			options = append(options, candidate)
		} else {
			log.Debug("no valid option", "candidate", candidate, "error", err)
		}
	}
	return options
}

// HasOptions reports if there is at least one possible target.
func (t *Target) HasOptions() bool {
	for _, candidate := range t.candidates() {
		if err := t.constraint(candidate); err == nil {
			return true
		}
	}
	return false
}

func (t *Target) CheckSelection(s *LocalState) error {
	if t.RequireSelection() {
		return errors.New("number of selected targets and required ones does not match")
	}

	if t.requirement.max != -1 && len(t.sel) > t.requirement.max {
		return fmt.Errorf("to many selection %d (%d allowed)", len(t.sel), t.requirement.max)
	}

	for _, sel := range t.sel {
		if err := t.constraint(sel); err != nil {
			return fmt.Errorf("selected target %s does not fit its desciption %s: %s",
				sel, t.desc, err)
		}
	}

	return nil
}

// AddSelection adds an object as selection to the current target.
func (t *Targets) AddSelection(sel any) error { return t.ts[t.idx].AddSelection(sel) }

func (t *Targets) HasSelections() bool {
	for _, t := range t.ts {
		if !t.HasSelection() {
			return false
		}
	}
	return true
}

func (t *Targets) ClearSelections() {
	for _, t := range t.ts {
		t.ClearSelection()
	}
}

func (t *Targets) NoSelections() bool {
	for _, t := range t.ts {
		if !t.NoSelection() {
			return false
		}
	}
	return true
}

// Options returns the options of the current target.
func (t *Targets) Options() (options []any) { return t.ts[t.idx].Options() }

// HasOptions reports if each target has at least one possible target option.
func (ts *Targets) HasOptions() bool {
	for _, t := range ts.ts {
		if !t.HasOptions() {
			return false
		}
	}
	return true
}

func (t *Targets) Cur() *Target       { return t.ts[t.idx] }
func (t *Targets) Next()              { t.idx++ }
func (t *Targets) Targets() []*Target { return t.ts }

func (t *Targets) CheckTargets(s *LocalState) error {
	log.Debug("Check all sub targets", "targets", t.ts)
	for _, target := range t.ts {
		if err := target.CheckSelection(s); err != nil {
			return err
		}
	}

	return nil
}

// RequireSelection reports if any of the targets require a selection.
func (targets *Targets) RequireSelection() bool {
	for _, t := range targets.ts {
		if t.RequireSelection() {
			return true
		}
	}

	return false
}

// AllowSelection reports if any of the targets allow a selection.
func (targets *Targets) AllowSelection() bool {
	for _, t := range targets.ts {
		if t.AllowSelection() {
			return true
		}
	}

	return false
}

func conjunction(constraints ...TargetConstraintFunc) TargetConstraintFunc {
	return func(t any) error {
		for _, constraint := range constraints {
			if err := constraint(t); err != nil {
				return err
			}
		}

		return nil
	}
}

func disjunction(constraints ...TargetConstraintFunc) TargetConstraintFunc {
	return func(t any) error {
		var err error
		for _, constraint := range constraints {
			if err = constraint(t); err == nil {
				return nil
			}
		}

		return err
	}
}

func noPreviousSelectionConstraint(targets *Targets, idx int) TargetConstraintFunc {
	return func(t any) error {
		for i := 0; i < idx && i < targets.idx; i++ {
			target := targets.ts[i]
			if slices.Contains(target.sel, t) {
				return fmt.Errorf("Selection %v already selected for target %d", t, i)
			}
		}
		return nil
	}
}

func targetConstraint(desc string, s *LocalState, action Action) TargetConstraintFunc {
	if !strings.Contains(desc, " or ") {
		return singleTargetConstraint(desc, s, action)
	}

	descs := strings.Split(desc, " or ")
	constraints := make([]TargetConstraintFunc, 0, len(descs))
	for _, desc := range descs {
		constraints = append(constraints, singleTargetConstraint(desc, s, action))
	}

	return disjunction(constraints...)
}

func singleTargetConstraint(desc string, s *LocalState, action Action) TargetConstraintFunc {
	constraints := []TargetConstraintFunc{}
	if strings.Contains(desc, "permanent") {
		constraints = append(constraints, parsePermanentTargetConstraint(desc, s, action)...)
	} else if strings.Contains(desc, "unit") {
		constraints = append(constraints, parseUnitTargetConstraint(desc, s, action)...)
	} else if strings.Contains(desc, "artifact") {
		constraints = append(constraints, parseArtifactTargetConstraint(desc, s, action)...)
	} else if strings.Contains(desc, "tile") {
		constraints = append(constraints, parseTileTargetConstraint(desc, s, action)...)
	} else if strings.Contains(desc, "card") {
		constraints = append(constraints, parseCardTargetConstraint(desc, s, action)...)
		// } else if strings.Contains(desc, "action") {
		// constraints = append(constraints, parseActionTargetConstraint(desc, s, action)...)
	} else if strings.Contains(desc, "spell") {
		constraints = append(constraints, parseSpellTargetConstraint(desc, s, action)...)
	}

	return conjunction(constraints...)
}

func enemyPermanentTargetConstraint(action Action) TargetConstraintFunc {
	var sourceController *Player
	switch source := action.Source().(type) {
	case *Player:
		sourceController = source
	case Permanent:
		sourceController = source.Controller()
	default:
		log.Panicf("Unhandled source type %T in enemyPermanentTargetConstraint", source)
	}

	return func(t any) (err error) {
		p, _ := t.(Permanent)
		if !p.Controller().IsEnemy(sourceController) {
			err = fmt.Errorf("Controller %v of target %v is not an enemy of %v",
				p.Controller(), t, sourceController)
		}
		return
	}
}

func controlledPermanentTargetConstraint(action Action) TargetConstraintFunc {
	var sourceController *Player
	switch source := action.Source().(type) {
	case *Player:
		sourceController = source
	case Permanent:
		sourceController = source.Controller()
	default:
		log.Panicf("Unhandled source type %T in enemyPermanentTargetConstraint", source)
	}

	return func(t any) (err error) {
		p, _ := t.(Permanent)
		if p.Controller() != sourceController {
			err = fmt.Errorf("Controller %v of target %v is %v",
				p.Controller(), t, sourceController)
		}
		return
	}
}

var (
	ErrTargetNotAttackable  = errors.New("not attackable")
	ErrTargetOutOfRange     = errors.New("not in range")
	ErrTargetRangeProtected = errors.New("range protected")
)

func attackableTargetConstraint(action Action) TargetConstraintFunc {
	return func(t any) error {
		p, _ := t.(Permanent)
		if !p.Attackable() {
			return ErrTargetNotAttackable
		}

		if attackAction, ok := action.(*AttackAction); ok {
			attacker := attackAction.Source().(*Unit)
			ok, _ := attacker.AttackableTile(p.Tile())
			if !ok {
				return ErrTargetOutOfRange
			}
			d := DistanceBetweenPermanents(attacker, p)
			if d > 1 && p.RangeProtected() {
				return ErrTargetRangeProtected
			}
		}
		return nil
	}
}

func posFromTileOrPermanent(tileOrPermanent any) Position {
	switch obj := tileOrPermanent.(type) {
	case Position:
		return obj
	case *Tile:
		return obj.Position
	case Permanent:
		return TileOrContainingPermTile(obj).Position
	default:
		log.Panicf("Unhandled source type %T in posFromTileOrPermanent", tileOrPermanent)
		return INVALID_POSITION()
	}
}

func rangeTargetConstraint(source any, r int) TargetConstraintFunc {
	return func(t any) (err error) {
		sourcePos := posFromTileOrPermanent(source)
		targetPos := posFromTileOrPermanent(t)
		if !IsPositionInRange(sourcePos, targetPos, r) {
			err = fmt.Errorf("Position %v of target %v not in range %d of source's position %v",
				targetPos, t, r, sourcePos)
		}
		return
	}
}

func typeTargetConstraint[T any](typeDesc string) TargetConstraintFunc {
	return func(t any) (err error) {
		_, ok := t.(T)
		if !ok {
			err = fmt.Errorf("unexpected target type %T not %s", t, typeDesc)
		}
		return
	}
}

func permanentCardTypeConstraint(f func(CardType) bool) TargetConstraintFunc {
	return func(t any) (err error) {
		p, ok := t.(Permanent)
		if !ok {
			err = fmt.Errorf("unexpected target type %T not Permanent", t)
			return
		}

		c := p.Card()
		if !f(c.Type) {
			err = fmt.Errorf("unexpected target card type %v", c.Type)
			return
		}

		return
	}
}

func cardTypeConstraint(cardType CardType) TargetConstraintFunc {
	return func(t any) (err error) {
		c, ok := t.(*Card)
		if !ok {
			err = fmt.Errorf("unexpected target type %T not *Card", t)
			return
		}

		if c.Type != cardType {
			err = fmt.Errorf("unexpected card type: %v not %v", c.Type, cardType)
			return
		}

		return
	}
}

var (
	permanentTargetConstraint  TargetConstraintFunc = typeTargetConstraint[Permanent]("Permanent")
	unitTargetConstraint       TargetConstraintFunc = typeTargetConstraint[*Unit]("*Unit")
	tileTargetConstraint       TargetConstraintFunc = typeTargetConstraint[*Tile]("*Tile")
	artifactTargetConstraint   TargetConstraintFunc = permanentCardTypeConstraint(CardType.IsArtifact)
	cardTargetConstraint       TargetConstraintFunc = typeTargetConstraint[*Card]("*Card")
	playActionTargetConstraint TargetConstraintFunc = typeTargetConstraint[*PlayAction]("*PlayAction")
	spellTargetConstraint      TargetConstraintFunc = cardTypeConstraint(CardTypes.Spell)
)

var ErrTargetHasShroud = errors.New("target has shroud")

func shroudedTargetContraint(t any) (err error) {
	p := t.(Permanent)
	if p.HasEffect("shroud") {
		err = ErrTargetHasShroud
	}
	return
}

func parsePermanentTargetConstraint(desc string, s *LocalState, action Action) []TargetConstraintFunc {
	constraints := []TargetConstraintFunc{permanentTargetConstraint, shroudedTargetContraint}

	if strings.Contains(desc, "enemy permanent") {
		constraints = append(constraints, enemyPermanentTargetConstraint(action))
	}

	if strings.Contains(desc, "attackable ") {
		constraints = append(constraints, attackableTargetConstraint(action))
	}

	if strings.Contains(desc, " in range ") {
		tokens := strings.SplitN(desc, " in range ", 2)
		r, err := strconv.Atoi(tokens[1])
		if err != nil {
			log.Panicf("Invalid range %s in target constraint %s", tokens[1], desc)
		}
		constraints = append(constraints, rangeTargetConstraint(action.Source(), r))
	}

	return constraints
}

func parseUnitTargetConstraint(desc string, _ *LocalState, action Action) []TargetConstraintFunc {
	constraints := []TargetConstraintFunc{unitTargetConstraint, shroudedTargetContraint}

	if strings.Contains(desc, "enemy unit") {
		constraints = append(constraints, enemyPermanentTargetConstraint(action))
	}

	if strings.Contains(desc, "you control") || strings.Contains(desc, "allied unit") {
		constraints = append(constraints, controlledPermanentTargetConstraint(action))
	}

	if strings.Contains(desc, " in range ") {
		tokens := strings.SplitN(desc, " in range ", 2)
		r, err := strconv.Atoi(tokens[1])
		if err != nil {
			log.Panicf("Invalid range %s in target constraint %s", tokens[1], desc)
		}
		constraints = append(constraints, rangeTargetConstraint(action.Source(), r))
	}

	return constraints
}

func parseArtifactTargetConstraint(constraint string, s *LocalState, action Action) []TargetConstraintFunc {
	constraints := []TargetConstraintFunc{artifactTargetConstraint}
	return constraints
}

func _relaxedTileTarget(t any) *Tile {
	switch t := t.(type) {
	case *Tile:
		return t
	case *Unit:
		return t.Tile()
	default:
		log.Panicf("Not handled target type %T", t)
	}

	return nil
}

func relaxedTileTarget(action Action, t any) *Tile {
	switch action.(type) {
	// Some actions allow to also move to Tile occupied by a crewable permanent
	case *MoveAction:
		return _relaxedTileTarget(t)
	case *ArtifactMoveAction:
		return _relaxedTileTarget(t)
	case *ArtifactSwitchAction:
		return _relaxedTileTarget(t)
	// Strict case
	default:
		return t.(*Tile)
	}
}

func availableTileConstraint(action Action, card *Card) TargetConstraintFunc {
	return func(t any) (err error) {
		tile := relaxedTileTarget(action, t)

		if card == nil {
			log.Panicf("Not implemented availability tile constraint for %T", action)
		}

		if tile.IsAvailableForCard(card) {
			return nil
		}
		log.Debug("tile not available", "tile", tile, "card", card)
		return fmt.Errorf("tile %v is not available for %s", tile, card.Name)
	}
}

func moveConstraint(_ *LocalState, action Action, u *Unit) TargetConstraintFunc {
	return func(t any) (err error) {
		// Some actions allow also unit targets as though they were tiles
		tile := relaxedTileTarget(action, t)
		if slices.Contains(u.MoveRangeTiles(), tile) {
			return nil
		}
		return fmt.Errorf("tile %v is not in %v's movement range", tile, u)
	}
}

var (
	ErrTargetWrongTileType    = errors.New("wrong tile type")
	ErrTargetNotConnectedTile = errors.New("not connected")
)

func parseTileTargetConstraint(desc string, s *LocalState, action Action) []TargetConstraintFunc {
	constraints := []TargetConstraintFunc{}

	if moveAction, ok := action.(*MoveAction); ok {
		u := moveAction.Source().(*Unit)
		constraints = append(constraints, moveConstraint(s, action, u))
	} else {
		constraints = append(constraints, tileTargetConstraint)
	}

	var player *Player
	switch a := action.(type) {
	case *PlayAction:
		player = a.Source().(*Player)
	}

	var card *Card
	switch a := action.(type) {
	case *PlayAction:
		card = a.Card
	case *MoveAction:
		card = a.Card
	case *StreetAction:
		card = a.Card
	case *FullAction:
		card = a.Card
	}

	if strings.Contains(desc, "spawn") {
		if player == nil {
			log.Panicf("Not implemented spawn tile constraint for %T", action)
		}

		constraints = append(constraints, func(t any) (err error) {
			tile := relaxedTileTarget(action, t)
			availableSpawnTiles := s.AvailableSpawnTiles(player, card)
			log.Debug("check possible spawn tile", "tile", tile, "spawns", availableSpawnTiles)
			if slices.Contains(availableSpawnTiles, tile) {
				log.Debug("is spawn tile", "tile", tile)
				return nil
			}
			return fmt.Errorf("tile %v is no spawn tile", tile)
		})
	}

	if strings.Contains(desc, "available") {
		constraints = append(constraints, availableTileConstraint(action, card))
	}

	if strings.Contains(desc, "water") {
		constraints = append(constraints, func(t any) (err error) {
			tile := t.(*Tile)
			if tile.Water {
				return nil
			}
			return fmt.Errorf("tile %v is not a water tile", tile)
		})
	}

	if strings.Contains(desc, "adjacent") {
		var origin any
		if pda, ok := action.(*PileDropAction); ok {
			origin = pda.tile
		} else {
			origin = action.Source()
		}
		constraints = append(constraints, rangeTargetConstraint(origin, 1))
	}

	if strings.Contains(desc, "free") {
		constraints = append(constraints, func(t any) (err error) {
			tile := t.(*Tile)
			if tile.IsFree() {
				return nil
			}
			return fmt.Errorf("tile %v is occupied by %v", tile, tile.Permanent)
		})
	}

	for name := range TileNames {
		if strings.Contains(desc, name) {
			// FIXME: skip spawn tile type constraint since it colides with available water spawns
			if name == "spawn" {
				continue
			}

			tileType := TileNames[name]
			if strings.Contains(desc, "connected") {
				// Find connected tiles
				u := action.Source().(*Unit)
				graph := s.Map().generateConnectedMovementRangeGraphFor(u, tileType)
				tiles := []*Tile{}
				for _, pos := range PositionsInRange(u.Tile().Position, u.Movement.Range, false) {
					tile := s.Map().TileAt(pos)
					if tile == nil || tile.Type != tileType {
						continue
					}

					_, err := findPathTo(graph, u, pos)
					if err != nil {
						continue
					}

					tiles = append(tiles, tile)
				}

				// Check if tile is connected
				constraints = append(constraints, func(t any) (err error) {
					tile := t.(*Tile)
					if !slices.Contains(tiles, tile) {
						err = ErrTargetNotConnectedTile
					}
					return
				})
			}

			// Tile type constraint
			constraints = append(constraints, func(t any) error {
				tile := t.(*Tile)
				if tile.Type == tileType {
					return nil
				}
				return ErrTargetWrongTileType
			})
		}
	}

	return constraints
}

func parseCardTargetConstraint(desc string, s *LocalState, action Action) []TargetConstraintFunc {
	constraints := []TargetConstraintFunc{cardTargetConstraint}

	player := action.Source().(*Player)
	origins := []*Player{player}
	originDesc := player.Name + "'s"

	if strings.Contains(desc, "opponent") {
		originDesc = "a opponent's"
		origins = []*Player{}
		for _, p := range s.Players() {
			if p.IsEnemy(player) {
				origins = append(origins, p)
			}
		}
	}

	if strings.Contains(desc, "hand") || strings.Contains(desc, "store") ||
		strings.Contains(desc, "discard pile") {

		if player == nil {
			log.Panicf("Not implemented PileOfCards constraint for %T", action)
		}

		var pocs []PileOfCards
		pocDesc := ""
		if strings.Contains(desc, "hand") {
			pocDesc = "hand"
		} else if strings.Contains(desc, "store") {
			pocDesc = "store"
		} else if strings.Contains(desc, "discard pile") {
			pocDesc = "discard pile"
		}

		// TODO: support player specific constraints

		for _, p := range origins {
			switch pocDesc {
			case "hand":
				pocs = append(pocs, p.Hand)
			case "store":
				if p.gameState.Map().HasStores() {
					for _, s := range p.AvailableStores() {
						pocs = append(pocs, s)
					}
				} else {
					pocs = append(pocs, p.Store)
				}
			case "discard pile":
				pocs = append(pocs, p.DiscardPile)
			}
		}

		constraints = append(constraints, func(t any) (err error) {
			c := t.(*Card)
			for _, poc := range pocs {
				if poc.Contains(c) {
					return nil
				}
			}
			return fmt.Errorf("card %s is not in %s %s", c.Name, originDesc, pocDesc)
		})
	}

	return constraints
}

func playedCardTypeConstraint(cardType CardType) TargetConstraintFunc {
	return func(t any) error {
		pa := t.(*PlayAction)
		if pa.Card.Type != cardType {
			return fmt.Errorf("played cardtype %s not %s", pa.Card.Type, cardType)
		}
		return nil
	}
}

func parseSpellTargetConstraint(desc string, s *LocalState, action Action) []TargetConstraintFunc {
	var constraints []TargetConstraintFunc

	// The target has to be a declared play action
	if strings.Contains(desc, "declared") {
		constraints = []TargetConstraintFunc{
			playActionTargetConstraint,
			playedCardTypeConstraint(CardTypes.Spell),
			func(t any) error {
				pa := t.(*PlayAction)
				if !utils.InterfaceSliceContains(utils.TypedSliceToInterfaceSlice(s.stack.Actions), pa) {
					return fmt.Errorf("action %s not declared", pa)
				}
				return nil
			},
		}
		// The target may be any spell card
	} else {
		constraints = []TargetConstraintFunc{
			cardTargetConstraint,
			spellTargetConstraint,
		}
	}

	return constraints
}

func (t *Target) candidates() []any {
	c := []any{}
	if strings.Contains(t.desc, "unit") ||
		strings.Contains(t.desc, "artifact") ||
		strings.Contains(t.desc, "permanent") {

		c = append(c, utils.TypedSliceToInterfaceSlice(t.s.Permanents())...)
	}

	if strings.Contains(t.desc, "tile") {
		c = append(c, utils.TypedSliceToInterfaceSlice(t.s.Map().AllTiles())...)
	}

	if strings.Contains(t.desc, "card") {
		cards := NewPileOfCards()
		switch t.desc {
		case "hand card":
			for _, p := range t.s.Players() {
				cards.AddPoc(p.Hand)
			}
		case "store card":
			if t.s.Map().HasStores() {
				for _, store := range t.s.Stores() {
					cards.AddPoc(store)
				}
			} else {
				for _, p := range t.s.Players() {
					cards.AddPoc(p.Store)
				}
			}
		default:
			log.Panicf("Unimplemented card options for %s", t.desc)
		}
		c = append(c, utils.TypedSliceToInterfaceSlice(cards.Cards())...)
	}

	if strings.Contains(t.desc, "declared") {
		c = append(c, utils.TypedSliceToInterfaceSlice(t.s.stack.Actions)...)
	}

	return c
}