rgoue/game/object.go

package game

// ObjectKind is the category of an item. In C this was the o_type byte,
// which doubled as the character drawn on the map; the port separates the
// category (ObjectKind) from its display character (Glyph).
type ObjectKind int

// Item categories.
const (
	KindNone ObjectKind = iota
	KindPotion
	KindScroll
	KindFood
	KindWeapon
	KindArmor
	KindRing
	KindWand // a "stick": wand or staff
	KindAmulet
	KindGold
)

// Prompt-filter pseudo-kinds for item selection (rogue.h CALLABLE and
// R_OR_S): they never appear on an Object, only as getItem filters.
const (
	KindCallable    ObjectKind = -1
	KindRingOrStick ObjectKind = -2
)

// Category words shared by ObjectKind.String, the discovery list, and the
// ident table. (The bare identifiers Potion, Scroll, Ring, Gold are the
// glyph byte constants.)
const (
	potionName = "potion"
	scrollName = "scroll"
	ringName   = "ring"
	goldName   = "gold"
)

// Glyph returns the map/display character for this kind of object.
func (k ObjectKind) Glyph() byte {
	//nolint:exhaustive // C-faithful: only the cases C handled (approved 2026-07-07)
	switch k {
	case KindPotion:
		return Potion
	case KindScroll:
		return Scroll
	case KindFood:
		return Food
	case KindWeapon:
		return Weapon
	case KindArmor:
		return Armor
	case KindRing:
		return Ring
	case KindWand:
		return Stick
	case KindAmulet:
		return Amulet
	case KindGold:
		return Gold
	}

	return ' '
}

// String names the category the way the C type_name() did.
func (k ObjectKind) String() string {
	//nolint:exhaustive // C-faithful: only the cases C handled (approved 2026-07-07)
	switch k {
	case KindPotion:
		return potionName
	case KindScroll:
		return scrollName
	case KindFood:
		return "food"
	case KindWeapon:
		return "weapon"
	case KindArmor:
		return "suit of armor"
	case KindRing:
		return ringName
	default:
		return k.stringRest()
	}
}

// objectKindForGlyph is the reverse of Glyph: what category of item does a
// map character denote. Returns KindNone for non-item characters.
func objectKindForGlyph(ch byte) ObjectKind {
	switch ch {
	case Potion:
		return KindPotion
	case Scroll:
		return KindScroll
	case Food:
		return KindFood
	case Weapon:
		return KindWeapon
	case Armor:
		return KindArmor
	case Ring:
		return KindRing
	case Stick:
		return KindWand
	case Amulet:
		return KindAmulet
	case Gold:
		return KindGold
	}

	return KindNone
}

// MergesInPack reports whether picking up another of this kind merges into
// an existing pack entry's count (rogue.h ISMULT).
func (k ObjectKind) MergesInPack() bool {
	return k == KindPotion || k == KindScroll || k == KindFood
}

// stringRest names the remaining kinds, including the ring-or-stick
// prompt pseudo-kind (the tail of the C type_name switch).
func (k ObjectKind) stringRest() string {
	//nolint:exhaustive // C-faithful: only the cases C handled (approved 2026-07-07)
	switch k {
	case KindWand:
		return "wand or staff"
	case KindAmulet:
		return "amulet"
	case KindGold:
		return goldName
	case KindRingOrStick:
		return "ring, wand or staff"
	}

	return "bizarre thing"
}

// Object is the _o arm of the C THING union: anything that can lie on the
// floor or ride in a pack.
type Object struct {
	Kind       ObjectKind // what kind of object it is (o_type)
	Pos        Coord      // where it lives on the screen
	Text       string     // what it says if you read it
	Launch     WeaponKind // what you need to launch it (noWeapon if none)
	PackCh     byte       // what character it is in the pack
	Damage     DiceSpec   // damage if used like sword
	HurlDmg    DiceSpec   // damage if thrown
	Count      int        // count for plural objects
	Which      int        // which object of a type it is (index for the Kind's table)
	HPlus      int        // plusses to hit
	DPlus      int        // plusses to damage
	ArmorClass int        // armor protection (armor only)
	Charges    int        // charges remaining (wands and staffs only)
	GoldValue  int        // worth (gold piles only)
	Bonus      int        // magic bonus (rings only: protection, add strength, ...)
	Flags      ObjFlags
	Group      int    // group number for this object
	Label      string // label for object
}

// newObject is list.c new_item() for objects: a zeroed Object with the
// same non-zero defaults the C code relies on.
func newObject() *Object {
	return &Object{Launch: noWeapon}
}

// whichLimit reports how many entries a kind's per-kind tables hold, so
// Which is a legal index exactly while 0 <= Which < whichLimit(Kind).
// Kinds whose Which is not a table index at all — food (0 ration, 1 the
// fruit), the amulet, gold, and the KindNone an unrecognized glyph maps
// to — report 0, meaning any value is acceptable, which is what C did
// with them too.
//
// Weapons count one past NumWeaponTypes on purpose: Items.Weapons is
// sized NumWeaponTypes+1 for the WeaponFlame dragon-breath entry, and
// fireBolt really does set Which = WeaponFlame on a live Object. That
// entry has no init_dam[] row, so initWeapon and createObj bound
// themselves by NumWeaponTypes instead.
func whichLimit(kind ObjectKind) int {
	//nolint:exhaustive // the remaining kinds do not index a per-kind table
	switch kind {
	case KindPotion:
		return int(NumPotionTypes)
	case KindScroll:
		return int(NumScrollTypes)
	case KindRing:
		return int(NumRingTypes)
	case KindWand:
		return int(NumWandTypes)
	case KindArmor:
		return int(NumArmorTypes)
	case KindWeapon:
		return int(NumWeaponTypes) + 1
	}

	return 0
}

// PotionKind returns Which as a potion kind; valid only for KindPotion.
func (o *Object) PotionKind() PotionKind { return PotionKind(o.Which) }

// ScrollKind returns Which as a scroll kind; valid only for KindScroll.
func (o *Object) ScrollKind() ScrollKind { return ScrollKind(o.Which) }

// RingKind returns Which as a ring kind; valid only for KindRing.
func (o *Object) RingKind() RingKind { return RingKind(o.Which) }

// WandKind returns Which as a wand kind; valid only for KindWand.
func (o *Object) WandKind() WandKind { return WandKind(o.Which) }

// WeaponKind returns Which as a weapon kind; valid only for KindWeapon.
func (o *Object) WeaponKind() WeaponKind { return WeaponKind(o.Which) }

// ArmorKind returns Which as an armor kind; valid only for KindArmor.
func (o *Object) ArmorKind() ArmorKind { return ArmorKind(o.Which) }

// hasValidWhich reports whether Which is a legal index into this
// object's per-kind tables. Objects the game builds itself always
// satisfy it; the wizard-create command and a restored save file are the
// only two ways a malformed one can appear, and both reject it (see
// createObj and validateSnapshotObjects).
//
// The Which >= 0 arm is unreachable from the keyboard: createObj derives
// Which with byte arithmetic (int(ch-'a') + 10), which wraps to a large
// positive value rather than going negative. It is kept as
// defense-in-depth for the non-keyboard source — a decoded save file,
// where Which is an int off the wire and can hold anything — and is
// exercised there by TestRestoreRejectsOutOfRangeWhich.
func (o *Object) hasValidWhich() bool {
	limit := whichLimit(o.Kind)

	return limit == 0 || (o.Which >= 0 && o.Which < limit)
}

// wizardCanCreate reports whether Which names something the wizard-create
// command can actually build. It is hasValidWhich narrowed for weapons:
// WeaponFlame owns a name-table slot but no init_dam[] row, so asking for
// it would leave initWeapon nothing to copy.
func (o *Object) wizardCanCreate() bool {
	if o.Kind == KindWeapon {
		return o.Which >= 0 && o.Which < int(NumWeaponTypes)
	}

	return o.hasValidWhich()
}

// attachObj is list.c attach(): push item onto the front of a list.
func attachObj(list *[]*Object, item *Object) {
	*list = append([]*Object{item}, *list...)
}

// detachObj is list.c detach(): remove item (by identity) from a list.
func detachObj(list *[]*Object, item *Object) {
	for i, o := range *list {
		if o == item {
			*list = append((*list)[:i], (*list)[i+1:]...)

			return
		}
	}
}