## AvatarSlotRegistry - Static registry of slot definitions.
##
## Each slot maps to one or more bones and defines what can be equipped there.
## This is the single source of truth for slot IDs, categories, mount bones,
## exclusivity, and body-part vs attachment classification.
##
## See docs/architecture/avatar.md §3.2 for the full slot specification.
class_name AvatarSlotRegistry extends RefCounted


# ---------------------------------------------------------------------------
# Slot definitions (mirrors §3.2 of the avatar spec)
# ---------------------------------------------------------------------------

## All known slot IDs, in canonical order.
const SLOT_IDS: PackedStringArray = [
	"head",
	"hair",
	"face",
	"torso",
	"chest",
	"back",
	"left_arm",
	"right_arm",
	"left_hand",
	"right_hand",
	"legs",
	"pants",
	"left_foot",
	"right_foot",
	"accessory",
]

## Body-part slots (exclusive, replace base mesh).
const BODY_PART_SLOTS: PackedStringArray = [
	"head", "torso", "legs", "left_arm", "right_arm",
]

## Attachment slots (layered on top of base mesh).
const ATTACHMENT_SLOTS: PackedStringArray = [
	"hair", "face", "chest", "back",
	"left_hand", "right_hand", "pants",
	"left_foot", "right_foot", "accessory",
]

## Slots that are multi-slot (multiple accessories can coexist).
const MULTI_SLOT_IDS: PackedStringArray = ["accessory"]


## Metadata for a single slot.
class SlotDefinition:
	## The slot ID string (e.g. "head", "hair").
	var slot_key: String
	## "body_part" or "attachment".
	var category: String
	## Primary mount bone name(s).
	var mount_bones: PackedStringArray
	## Whether at most one item can occupy this slot.
	var exclusive: bool
	## Whether this slot replaces a base mesh.
	var is_body_part: bool

	func _init(p_slot_key: String, p_category: String, p_mount_bones: PackedStringArray,
			p_exclusive: bool, p_is_body_part: bool) -> void:
		slot_key = p_slot_key
		category = p_category
		mount_bones = p_mount_bones
		exclusive = p_exclusive
		is_body_part = p_is_body_part


# Slot metadata lookup tables (indexed by SLOT_IDS position). Static: every
# caller uses AvatarSlotRegistry.method(...) directly on the class, never on
# an instance, so this data has to be built once at class-load time via
# _static_init() rather than an instance _init() that's never invoked.
# Each entry: { category, mount_bones, exclusive, is_body_part }
static var _slot_data: Dictionary = {}
static var _slot_definitions: Array[SlotDefinition] = []


static func _static_init() -> void:
	_build_registry()


static func _build_registry() -> void:
	_slot_data = {
		"head": {
			"category": "body_part",
			"mount_bones": ["Head"],
			"exclusive": true,
			"is_body_part": true,
		},
		"hair": {
			"category": "attachment",
			"mount_bones": ["HeadTop"],
			"exclusive": true,
			"is_body_part": false,
		},
		"face": {
			"category": "attachment",
			"mount_bones": ["Jaw"],
			"exclusive": true,
			"is_body_part": false,
		},
		"torso": {
			"category": "body_part",
			"mount_bones": ["Chest"],
			"exclusive": true,
			"is_body_part": true,
		},
		"chest": {
			"category": "attachment",
			"mount_bones": ["Chest"],
			"exclusive": true,
			"is_body_part": false,
		},
		"back": {
			"category": "attachment",
			"mount_bones": ["Chest"],
			"exclusive": true,
			"is_body_part": false,
		},
		"left_arm": {
			"category": "body_part",
			"mount_bones": ["LeftUpperArm"],
			"exclusive": true,
			"is_body_part": true,
		},
		"right_arm": {
			"category": "body_part",
			"mount_bones": ["RightUpperArm"],
			"exclusive": true,
			"is_body_part": true,
		},
		"left_hand": {
			"category": "attachment",
			"mount_bones": ["LeftHand"],
			"exclusive": true,
			"is_body_part": false,
		},
		"right_hand": {
			"category": "attachment",
			"mount_bones": ["RightHand"],
			"exclusive": true,
			"is_body_part": false,
		},
		"legs": {
			"category": "body_part",
			"mount_bones": ["Hips"],
			"exclusive": true,
			"is_body_part": true,
		},
		"pants": {
			"category": "attachment",
			"mount_bones": ["Hips"],
			"exclusive": true,
			"is_body_part": false,
		},
		"left_foot": {
			"category": "attachment",
			"mount_bones": ["LeftFoot"],
			"exclusive": true,
			"is_body_part": false,
		},
		"right_foot": {
			"category": "attachment",
			"mount_bones": ["RightFoot"],
			"exclusive": true,
			"is_body_part": false,
		},
		"accessory": {
			"category": "attachment",
			"mount_bones": ["Root"],
			"exclusive": false,
			"is_body_part": false,
		},
	}

	# Build SlotDefinition objects.
	for slot_id in SLOT_IDS:
		var data = _slot_data[slot_id]
		var def := SlotDefinition.new(
			slot_id,
			data["category"],
			PackedStringArray(data["mount_bones"]),
			data["exclusive"],
			data["is_body_part"],
		)
		_slot_definitions.append(def)


# ---------------------------------------------------------------------------
# Public API
# ---------------------------------------------------------------------------

## Returns the list of all known slot IDs.
static func get_slot_ids() -> PackedStringArray:
	return SLOT_IDS


## Returns true if *slot_id* is a known slot.
static func has_slot(slot_id: String) -> bool:
	return slot_id in SLOT_IDS


## Returns the SlotDefinition for a slot, or null if unknown.
static func get_slot(slot_id: String) -> SlotDefinition:
	if not has_slot(slot_id):
		return null
	for def in _slot_definitions:
		if def.slot_key == slot_id:
			return def
	return null


## Returns all SlotDefinition objects in canonical order.
static func get_slot_definitions() -> Array[SlotDefinition]:
	return _slot_definitions


## Returns the category for a slot ("body_part" or "attachment").
static func get_category(slot_id: String) -> String:
	if not has_slot(slot_id):
		push_error("AvatarSlotRegistry: unknown slot '%s'" % slot_id)
		return ""
	return _slot_data[slot_id]["category"]


## Returns the primary mount bone(s) for a slot.
static func get_mount_bones(slot_id: String) -> PackedStringArray:
	if not has_slot(slot_id):
		push_error("AvatarSlotRegistry: unknown slot '%s'" % slot_id)
		return PackedStringArray()
	return PackedStringArray(_slot_data[slot_id]["mount_bones"])


## Returns whether the slot is exclusive (at most one item).
static func is_exclusive(slot_id: String) -> bool:
	if not has_slot(slot_id):
		push_error("AvatarSlotRegistry: unknown slot '%s'" % slot_id)
		return true
	return _slot_data[slot_id]["exclusive"]


## Returns whether the slot is a body-part slot (replaces base mesh).
static func is_body_part_slot(slot_id: String) -> bool:
	if not has_slot(slot_id):
		push_error("AvatarSlotRegistry: unknown slot '%s'" % slot_id)
		return false
	return _slot_data[slot_id]["is_body_part"]


## Returns whether the slot is a multi-slot (e.g. accessory).
static func is_multi_slot(slot_id: String) -> bool:
	return slot_id in MULTI_SLOT_IDS


## Returns the list of body-part slot IDs.
static func get_body_part_slots() -> PackedStringArray:
	return BODY_PART_SLOTS


## Returns the list of attachment slot IDs.
static func get_attachment_slots() -> PackedStringArray:
	return ATTACHMENT_SLOTS


## Validates that an asset's declared slot matches the slot it is placed in.
static func validate_slot_assignment(asset_slot: String, slot_id: String) -> bool:
	return asset_slot == slot_id


## Returns the canonical order index for a slot (for serialization order).
static func get_slot_index(slot_id: String) -> int:
	return SLOT_IDS.find(slot_id)