class_name ServerProcess
## Manages the Rust simulation server as a subprocess (D-020).

var _pid: int = -1


## Start the server process. Returns the PID, or -1 on failure.
## Validates that server_path exists and is accessible before spawning.
func start(server_path: String, args: Array = []) -> int:
	if _pid > 0 and is_alive():
		push_warning("ServerProcess: server already running (pid %d)" % _pid)
		return _pid
	if not FileAccess.file_exists(server_path):
		push_error("ServerProcess: server binary not found at %s" % server_path)
		return -1
	_pid = OS.create_process(server_path, args)
	if _pid <= 0:
		push_error("ServerProcess: failed to start server at %s" % server_path)
	return _pid


## Check if the server process is still running.
## NOTE: OS.is_process_running() doesn't distinguish starting/healthy/zombie.
## TODO: Add health check (e.g. TCP readiness probe) when server supports it.
func is_alive() -> bool:
	if _pid <= 0:
		return false
	return OS.is_process_running(_pid)


## Stop the server process.
## TODO: Send graceful shutdown signal before SIGKILL when server supports it.
func stop() -> void:
	if _pid > 0 and is_alive():
		OS.kill(_pid)
	_pid = -1


## Get the server PID (-1 if not started).
func get_pid() -> int:
	return _pid


## Clean up on destruction — kill the server if still running.
func _notification(what: int) -> void:
	if what == NOTIFICATION_PREDELETE:
		stop()