## AvatarCatalog - Asset catalog management.
##
## Manages the mapping of asset IDs to their metadata and resource paths.
## Loads the catalog manifest from disk and provides lookup by ID and slot.
##
## The catalog is loaded from `res://assets/avatars/catalog.json` which follows
## the format specified in avatar.md §7.2.

class_name AvatarCatalog
extends RefCounted

# Preloaded rather than referenced by global class_name -- see avatar_loadout.gd.
const AvatarLoadout := preload("res://scripts/avatar/avatar_loadout.gd")


## Emitted when the catalog is loaded successfully.
signal catalog_loaded

## Emitted when the catalog fails to load.
signal catalog_load_failed(error_message: String)

## Catalog manifest structure:
## { "assets": { "id": { "type", "slot", "path", "version", ... } } }
var _catalog: Dictionary = {}
var _loaded: bool = false
var _catalog_path: String = "res://assets/avatars/catalog.json"


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

## Load the catalog from disk. Call this before any lookups.
func load_catalog(path: String = _catalog_path) -> Error:
	_catalog_path = path
	_catalog = {}

	var file = FileAccess.open(path, FileAccess.READ)
	if file == null:
		var err = FileAccess.get_open_error()
		catalog_load_failed.emit("Cannot open catalog: %s (error %d)" % [path, err])
		return err

	var json_text: String = file.get_as_text()
	file.close()

	var result: Variant = JSON.parse_string(json_text)
	if result == null or not result is Dictionary:
		catalog_load_failed.emit("Invalid JSON in catalog: %s" % path)
		return ERR_PARSE_ERROR

	var json: Dictionary = result as Dictionary

	if not json.has("assets"):
		catalog_load_failed.emit("Catalog missing 'assets' key")
		return ERR_INVALID_DATA

	_catalog = json["assets"]
	_loaded = true
	catalog_loaded.emit()
	return OK


## Check if the catalog has been loaded.
func is_loaded() -> bool:
	return _loaded


## Resolve an asset by its ID.
## Returns a Dictionary with keys: type, slot, path, version, etc.
## Returns null if the asset ID is not found.
func resolve(id: String) -> Dictionary:
	if not _loaded:
		return {}
	return _catalog.get(id, {})


## Check if an asset ID exists in the catalog.
func has_asset(id: String) -> bool:
	if not _loaded:
		return false
	return _catalog.has(id)


## Get all assets that belong to a given slot.
## Returns an array of asset ID strings.
func get_assets_by_slot(slot: String) -> Array[String]:
	if not _loaded:
		return []
	var result: Array[String] = []
	for id in _catalog:
		var asset: Dictionary = _catalog[id]
		if asset.get("slot") == slot:
			result.append(id)
	return result


## Get all asset IDs in the catalog.
func get_all_ids() -> Array[String]:
	if not _loaded:
		return []
	return _catalog.keys()


## Validate a loadout against the catalog.
## Returns a Dictionary with "valid" (bool) and "errors" (Array[String]).
func validate_loadout(loadout: AvatarLoadout) -> Dictionary:
	var errors: Array[String] = []

	# Check base_body
	if loadout.base_body.is_empty():
		errors.append("Loadout missing base_body")
	elif not has_asset(loadout.base_body):
		errors.append("Unknown base_body asset: %s" % loadout.base_body)
	else:
		var base: Dictionary = resolve(loadout.base_body)
		if base.get("type") != "base_body":
			errors.append("base_body asset '%s' is not type 'base_body'" % loadout.base_body)

	# Check each slot
	for slot_id in loadout.slots:
		var slot_value = loadout.slots[slot_id]

		if slot_value == null:
			continue

		if slot_id == "accessory":
			# Accessory is an array
			if not slot_value is Array:
				errors.append("Slot '%s' must be an array" % slot_id)
				continue
			for item_id in slot_value:
				if not has_asset(item_id):
					errors.append("Unknown accessory asset: %s" % item_id)
				else:
					var asset: Dictionary = resolve(item_id)
					if asset.get("slot") != slot_id:
						errors.append("Accessory '%s' slot '%s' does not match slot '%s'" % [
							item_id, asset.get("slot"), slot_id
						])
		else:
			# Exclusive slot - single value
			if not slot_value is String:
				errors.append("Slot '%s' must be a string or null" % slot_id)
				continue
			if not has_asset(slot_value):
				errors.append("Unknown asset in slot '%s': %s" % [slot_id, slot_value])
			else:
				var asset: Dictionary = resolve(slot_value)
				if asset.get("slot") != slot_id:
					errors.append("Asset '%s' slot '%s' does not match slot '%s'" % [
						slot_value, asset.get("slot"), slot_id
					])

	return {
		"valid": errors.is_empty(),
		"errors": errors
	}


## Compute a hash of the loadout for change detection.
## Returns a 32-bit hash value (GDScript has no fixed-width uint type — int
## is 64-bit signed, the value is just constrained to 32 bits of range).
static func compute_loadout_hash(loadout: AvatarLoadout) -> int:
	var hasher = HashingContext.new()
	hasher.start(HashingContext.HASH_SHA256)

	hasher.update(loadout.base_body.to_utf8_buffer())
	for slot_id in loadout.slots:
		var slot_value = loadout.slots[slot_id]
		hasher.update(slot_id.to_utf8_buffer())
		if slot_value is Array:
			for item in slot_value:
				hasher.update(item.to_utf8_buffer())
		elif slot_value is String:
			hasher.update(slot_value.to_utf8_buffer())

	var hash_bytes = hasher.finish()
	return hash_bytes[0] | (hash_bytes[1] << 8) | (hash_bytes[2] << 16) | (hash_bytes[3] << 24)


## Get the catalog path.
func get_catalog_path() -> String:
	return _catalog_path