#ifdef MULTIINSTANCE
SUBSYSTEM_DEF(instancing)
	name = "Instancing"
	runlevels = RUNLEVEL_INIT | RUNLEVEL_LOBBY | RUNLEVEL_SETUP | RUNLEVEL_GAME | RUNLEVEL_POSTGAME
	wait = 30 SECONDS
	flags = SS_KEEP_TIMING
	cpu_display = SS_CPUDISPLAY_LOW
	// This SS has the default init value since it needs to happen after the DB & redis

	/// Associative list of registered commands. K = command name | V = command datum
	var/list/datum/server_command/registered_commands = list()

/datum/controller/subsystem/instancing/Initialize()
	// Make sure no one broke things. This check will trip up CI
	if(init_order >= SSredis.init_order)
		CRASH("SSinstancing was set to init before SSredis. Who broke it?")

	// Dont even bother if we arent connected to redis or the DB
	if(!SSdbcore.IsConnected() || !SSredis.connected || !GLOB.configuration.system.enable_multi_instance_support)
		flags |= SS_NO_FIRE
		return

	// Setup our commands
	for(var/sct in subtypesof(/datum/server_command))
		var/datum/server_command/SC = new sct()
		if(isnull(SC.command_name))
			stack_trace("[SC.type] has no comamnd name set!")
			continue

		if(SC.command_name in registered_commands)
			stack_trace("A command with the name '[SC.command_name]' already exists!")

		registered_commands[SC.command_name] = SC

	var/amount_registered = length(registered_commands)
	log_startup_progress("Registered [amount_registered] server command[amount_registered == 1 ? "" : "s"].")

	// Announce startup to peers
	var/datum/server_command/new_round_announce/NRA = registered_commands["new_round_announce"]
	NRA.custom_dispatch(GLOB.configuration.general.server_name, SSmapping.map_datum.fluff_name, SSmapping.map_datum.technical_name)

/datum/controller/subsystem/instancing/fire(resumed)
	update_heartbeat()
	update_playercache()

/datum/controller/subsystem/instancing/proc/execute_command(source, command, list/arguments)
	// We aint enabled. Dont bother.
	if(!GLOB.configuration.system.enable_multi_instance_support)
		return

	var/datum/server_command/SC = registered_commands[command]
	if(!SC)
		CRASH("Attempted to execute command with ID '[command]' from [source], but that command didnt exist!")

	if((source == GLOB.configuration.system.instance_id) && SC.ignoreself)
		return // Dont self respond

	SC.execute(source, arguments)

/**
  * Playercache updater
  *
  * Updates the player cache in the DB. Different from heartbeat so we can force invoke it on player operations
  */
/datum/controller/subsystem/instancing/proc/update_playercache(optional_ckey)
	// We aint enabled. Dont bother.
	if(!GLOB.configuration.system.enable_multi_instance_support)
		return

	// You may be wondering, why the fuck is an "optional ckey" variable here
	// Well, this is invoked in client/New(), and needs to read from GLOB.clients
	// However, this proc sleeps, and if you sleep during client/New() once the client is in GLOB.clients, stuff breaks bad
	// (See my comment rambling in client/New())
	// By passing the ckey through, we can sleep in this proc and still get the data
	if(!SSdbcore.IsConnected())
		return
	// First iterate clients to get ckeys
	var/list/ckeys = list()
	for(var/client/C in GLOB.clients) // No code review. I am not doing the `as anything` bullshit, because we *do* need the type checks here to avoid null clients which do happen sometimes
		ckeys += C.ckey
	// Add our optional
	if(optional_ckey)
		ckeys += optional_ckey
	// Note: We dont have to sort the list here. The only time this is read for is a search,
	// and order doesnt matter for that.
	var/ckey_json = json_encode(ckeys)

	// Yes I care about performance savings this much here to mass execute this shit
	var/datum/db_query/dbq = SSdbcore.NewQuery("UPDATE instance_data_cache SET key_value=:json WHERE key_name='playerlist' AND server_id=:sid", list(
		"json" = ckey_json,
		"sid" = GLOB.configuration.system.instance_id
	))
	dbq.warn_execute(FALSE)
	qdel(dbq)

	var/datum/db_query/dbq2 = SSdbcore.NewQuery("UPDATE instance_data_cache SET key_value=:count WHERE key_name='playercount' AND server_id=:sid", list(
		"count" = length(ckeys),
		"sid" = GLOB.configuration.system.instance_id
	))
	dbq2.warn_execute(FALSE)
	qdel(dbq2)

/**
  * Heartbeat updater
  *
  * Updates the heartbeat in the DB. Used so other servers can see when this one was alive
  */
/datum/controller/subsystem/instancing/proc/update_heartbeat()
	// this could probably just go in fire() but clean code and profiler ease who cares
	var/datum/db_query/dbq = SSdbcore.NewQuery("UPDATE instance_data_cache SET key_value=NOW() WHERE key_name='heartbeat' AND server_id=:sid", list(
		"sid" = GLOB.configuration.system.instance_id
	))
	dbq.warn_execute()
	qdel(dbq)

/**
  * Seed data
  *
  * Seeds all our data into the DB for other servers to discover from.
  * This is called during world/New() instead of on initialize so it can be done *instantly*
  */
/datum/controller/subsystem/instancing/proc/seed_data()
	// We aint enabled. Dont bother.
	if(!GLOB.configuration.system.enable_multi_instance_support)
		return

	// We need to seed a lot of keys, so lets just use a key-value-pair-map to do this easily
	var/list/kvp_map = list()
	kvp_map["server_name"] = GLOB.configuration.general.server_name // Name of the server
	kvp_map["server_port"] = world.port // Server port (used for redirection and topics)
	kvp_map["topic_key"] = GLOB.configuration.system.topic_key // Server topic key (used for topics)
	kvp_map["internal_ip"] = GLOB.configuration.system.internal_ip // Server internal IP (used for topics)
	kvp_map["playercount"] = length(GLOB.clients) // Server client count (used for status info)
	kvp_map["playerlist"] = json_encode(list()) // Server client list. Used for dupe login checks. This gets filled in later
	kvp_map["heartbeat"] = SQLtime() // SQL timestamp for heartbeat purposes. Any server without a heartbeat in the last 60 seconds can be considered dead
	// Also note for above. You may say "But AA you dont need to JSON encode it, just use "\[]"."
	// Well to that I say, no. This is meant to be JSON regardless, and it should represent that. This proc is ran once during world/New()
	// An extra nanosecond of load will make zero difference.

	for(var/key in kvp_map)
		var/datum/db_query/dbq = SSdbcore.NewQuery("INSERT INTO instance_data_cache (server_id, key_name, key_value) VALUES (:sid, :kn, :kv) ON DUPLICATE KEY UPDATE key_value=:kv2", // Is this necessary? Who knows!
			list(
				"sid" = GLOB.configuration.system.instance_id,
				"kn" = key,
				"kv" = "[kvp_map[key]]", // String encoding IS necessary since these tables use strings, not ints
				"kv2" = "[kvp_map[key]]", // Dont know if I need the second but better to be safe
			)
		)
		dbq.warn_execute(FALSE) // Do NOT async execute here because world/New() shouldnt sleep. EVER. You get issues if you do.
		qdel(dbq)

/**
  * Player checker
  *
  * Check all connected peers to see if a player exists in the player cache
  * This is used to make sure players dont log into 2 servers at once
  * Arguments:
  * ckey - The ckey to check if they are logged into another server
  */
/datum/controller/subsystem/instancing/proc/check_player(ckey)
	// We aint enabled. Dont bother.
	if(!GLOB.configuration.system.enable_multi_instance_support)
		return

	// Please see above rant on L127
	var/datum/db_query/dbq1 = SSdbcore.NewQuery({"
		SELECT server_id, key_value FROM instance_data_cache WHERE server_id IN
		(SELECT server_id FROM instance_data_cache WHERE server_id != :sid AND
		key_name='heartbeat' AND last_updated BETWEEN NOW() - INTERVAL 60 SECOND AND NOW())
		AND key_name IN ("playerlist")"}, list(
		"sid" = GLOB.configuration.system.instance_id
	))
	if(!dbq1.warn_execute())
		qdel(dbq1)
		return

	while(dbq1.NextRow())
		var/list/other_server_cache = json_decode(dbq1.item[2])
		if(ckey in other_server_cache)
			var/target_server = dbq1.item[1] // Yes. This var is necessary.
			qdel(dbq1)
			return target_server

	qdel(dbq1)
	return null // If we are here, it means we didnt find our player on another server
#endif