/**
  * # Persistent Data Subsystem
  *
  * Provides a centralised handler for persistent data reading and writing.
  * The subsystem does not do any actual spawning itself, as this focuses on objects and mobs
  * Should anything that is turf persistence related added in, that can be chucked into this SS
  * Its quite a simple subsystem. For now, anyways.
  *
  */
SUBSYSTEM_DEF(persistent_data)
	name = "Persistent Data"
	init_order = INIT_ORDER_PERSISTENCE // -95 | Loads after EVERYTHING else
	flags = SS_NO_FIRE
	/// List of atoms registered into the subsystem for persistent data storage. Can be anything at all
	var/list/registered_atoms = list()
	/// Set to true after a the end of the round to prevent griefing being saved
	var/data_saved = FALSE

/datum/controller/subsystem/persistent_data/Initialize()
	// Load all the data of registered atoms
	for(var/atom/A in registered_atoms)
		A.persistent_load()

/datum/controller/subsystem/persistent_data/Shutdown()
	save()

/datum/controller/subsystem/persistent_data/proc/save()
	// Stops data from being saved twice
	if(data_saved)
		return
	data_saved = TRUE

	// Save all the data of registered atoms
	for(var/atom/A in registered_atoms)
		A.persistent_save()


/**
  * Proc to register an atom with SSpersistent_data
  *
  * This will add any provided atom to the list of registered atoms, and add it to the Initialization queue
  * If the system has already initialized, it calls persistent_load() at that moment
  *
  * Arguments:
  * * A - Atom to register
  */
/datum/controller/subsystem/persistent_data/proc/register(atom/A)
	registered_atoms |= A
	if(initialized)
		A.persistent_load()

/**
  * Atom Persistent Loader
  *
  * Overridden on every atom which needs to load persistent data
  */
/atom/proc/persistent_load()
	stack_trace("peristent_load() called on an atom which does not have persistent data storage!")

/**
  * Atom Persistent Saver
  *
  * Overridden on every atom which needs to save persistent data
  */
/atom/proc/persistent_save()
	stack_trace("peristent_save() called on an atom which does not have persistent data storage!")