class_name AssetCacheManager
extends RefCounted
## Manages client-side disk caching of downloaded 3D model assets and collections.
## Caches assets locally under user://asset_cache/ to prevent duplicate network fetches.

const CACHE_DIR: String = "user://asset_cache"

static var _instance = null


static func get_instance():
	if _instance == null:
		var script := load("res://scripts/studio/asset_cache_manager.gd")
		_instance = script.new()
	return _instance


func _init() -> void:
	_ensure_cache_dir()


func _ensure_cache_dir() -> void:
	if not DirAccess.dir_exists_absolute(CACHE_DIR):
		DirAccess.make_dir_recursive_absolute(CACHE_DIR)


func get_cache_path(asset_key: String) -> String:
	var clean_key := asset_key.replace("/", "_").replace("\\", "_").replace(":", "_")
	if not clean_key.ends_with(".glb") and not clean_key.ends_with(".gltf"):
		clean_key += ".glb"
	return "%s/%s" % [CACHE_DIR, clean_key]


func has_cached(asset_key: String) -> bool:
	var p := get_cache_path(asset_key)
	return FileAccess.file_exists(p)


func get_cached_path_if_exists(asset_key: String) -> String:
	var p := get_cache_path(asset_key)
	if FileAccess.file_exists(p):
		return p
	return ""


func store_asset(asset_key: String, data: PackedByteArray) -> String:
	_ensure_cache_dir()
	var path := get_cache_path(asset_key)
	var fa := FileAccess.open(path, FileAccess.WRITE)
	if fa != null:
		fa.store_buffer(data)
		fa.close()
		return path
	return ""


func read_asset(asset_key: String) -> PackedByteArray:
	var path := get_cache_path(asset_key)
	if not FileAccess.file_exists(path):
		return PackedByteArray()
	var fa := FileAccess.open(path, FileAccess.READ)
	if fa != null:
		var buf := fa.get_buffer(fa.get_length())
		fa.close()
		return buf
	return PackedByteArray()


func load_model(asset_key: String) -> Node:
	var path := get_cached_path_if_exists(asset_key)
	if path == "":
		return null

	if path.ends_with(".glb") or path.ends_with(".gltf"):
		var gltf := GLTFDocument.new()
		var state := GLTFState.new()
		var err := gltf.append_from_file(path, state)
		if err == OK:
			return gltf.generate_scene(state)
	elif ResourceLoader.exists(path):
		var res := load(path)
		if res is PackedScene:
			return (res as PackedScene).instantiate()

	return null


func get_cached_items() -> Array[String]:
	_ensure_cache_dir()
	var items: Array[String] = []
	var dir := DirAccess.open(CACHE_DIR)
	if dir != null:
		dir.list_dir_begin()
		var file_name := dir.get_next()
		while file_name != "":
			if not dir.current_is_dir() and not file_name.begins_with("."):
				items.append(file_name)
			file_name = dir.get_next()
		dir.list_dir_end()
	return items


func clear_cache() -> int:
	_ensure_cache_dir()
	var count := 0
	var dir := DirAccess.open(CACHE_DIR)
	if dir != null:
		dir.list_dir_begin()
		var file_name := dir.get_next()
		while file_name != "":
			if not dir.current_is_dir():
				DirAccess.remove_absolute("%s/%s" % [CACHE_DIR, file_name])
				count += 1
			file_name = dir.get_next()
		dir.list_dir_end()
	return count