extends Node
class_name DownloadManager
## Handles downloading game files with progress tracking and checksum verification

signal download_started(file_name: String, total_size: int)
signal download_progress(downloaded: int, total: int, percentage: float)
signal download_completed(file_path: String)
signal download_failed(error: String)

var http_request: HTTPRequest
var download_path: String = ""
var expected_checksum_md5: String = ""
var expected_checksum_sha256: String = ""
var total_size: int = 0
var is_downloading: bool = false

func _ready() -> void:
	http_request = HTTPRequest.new()
	add_child(http_request)
	http_request.request_completed.connect(_on_download_completed)
	http_request.download_file = ""  # We'll set this per download
	
	# Ensure directories exist
	_ensure_directories()

func _ensure_directories() -> void:
	var dir := DirAccess.open("user://")
	if dir:
		if not dir.dir_exists("game"):
			dir.make_dir("game")
		if not dir.dir_exists("backup"):
			dir.make_dir("backup")
		if not dir.dir_exists("temp"):
			dir.make_dir("temp")

func _process(_delta: float) -> void:
	if is_downloading and http_request:
		var downloaded := http_request.get_downloaded_bytes()
		var body_size := http_request.get_body_size()
		
		if body_size > 0:
			var percentage := (float(downloaded) / float(body_size)) * 100.0
			emit_signal("download_progress", downloaded, body_size, percentage)

func download_file(url: String, file_name: String, size: int = 0, md5: String = "", sha256: String = "") -> void:
	if is_downloading:
		emit_signal("download_failed", "Download already in progress")
		return
	
	download_path = "user://temp/" + file_name
	expected_checksum_md5 = md5
	expected_checksum_sha256 = sha256
	total_size = size
	is_downloading = true
	
	# Set download file path
	http_request.download_file = download_path
	
	print("[DownloadManager] Starting download: ", url)
	print("[DownloadManager] Saving to: ", download_path)
	
	emit_signal("download_started", file_name, size)
	
	var error := http_request.request(url)
	if error != OK:
		is_downloading = false
		emit_signal("download_failed", "Failed to initiate download: " + str(error))

func _on_download_completed(result: int, response_code: int, _headers: PackedStringArray, _body: PackedByteArray) -> void:
	is_downloading = false
	
	if result != HTTPRequest.RESULT_SUCCESS:
		emit_signal("download_failed", "Download failed with result: " + str(result))
		return
	
	if response_code != 200:
		emit_signal("download_failed", "Server returned error: " + str(response_code))
		return
	
	# Verify checksum if provided
	if expected_checksum_md5 != "" or expected_checksum_sha256 != "":
		if not _verify_checksum():
			emit_signal("download_failed", "Checksum verification failed - file may be corrupted")
			# Delete corrupted file
			var dir := DirAccess.open("user://temp/")
			if dir:
				dir.remove(download_path.get_file())
			return
	
	print("[DownloadManager] Download completed: ", download_path)
	emit_signal("download_completed", download_path)

func _verify_checksum() -> bool:
	## Verify the downloaded file's checksum
	var file := FileAccess.open(download_path, FileAccess.READ)
	if not file:
		print("[DownloadManager] Could not open file for checksum verification")
		return false
	
	var content := file.get_buffer(file.get_length())
	file.close()
	
	# Verify MD5 if provided
	if expected_checksum_md5 != "":
		var ctx := HashingContext.new()
		ctx.start(HashingContext.HASH_MD5)
		ctx.update(content)
		var calculated_md5 := ctx.finish().hex_encode()
		
		if calculated_md5.to_lower() != expected_checksum_md5.to_lower():
			print("[DownloadManager] MD5 mismatch! Expected: ", expected_checksum_md5, " Got: ", calculated_md5)
			return false
		print("[DownloadManager] MD5 checksum verified")
	
	# Verify SHA256 if provided
	if expected_checksum_sha256 != "":
		var ctx := HashingContext.new()
		ctx.start(HashingContext.HASH_SHA256)
		ctx.update(content)
		var calculated_sha256 := ctx.finish().hex_encode()
		
		if calculated_sha256.to_lower() != expected_checksum_sha256.to_lower():
			print("[DownloadManager] SHA256 mismatch! Expected: ", expected_checksum_sha256, " Got: ", calculated_sha256)
			return false
		print("[DownloadManager] SHA256 checksum verified")
	
	return true

func cancel_download() -> void:
	if is_downloading:
		http_request.cancel_request()
		is_downloading = false
		print("[DownloadManager] Download cancelled")