From 629f433cccd048136870ae0cc48f17674013e281 Mon Sep 17 00:00:00 2001
From: SteelSlayer <alexgcopeland123@yahoo.com>
Date: Sun, 6 Sep 2020 10:08:40 -0500
Subject: [PATCH] SScleanup

---
 code/__DEFINES/subsystems.dm          |  4 +--
 code/controllers/subsystem/cleanup.dm | 40 +++++++++++++++++++++++++++
 paradise.dme                          |  1 +
 3 files changed, 43 insertions(+), 2 deletions(-)
 create mode 100644 code/controllers/subsystem/cleanup.dm

diff --git a/code/__DEFINES/subsystems.dm b/code/__DEFINES/subsystems.dm
index 153eca7f373..392f6e2e4dd 100644
--- a/code/__DEFINES/subsystems.dm
+++ b/code/__DEFINES/subsystems.dm
@@ -48,7 +48,7 @@
 #define INIT_ORDER_GARBAGE 19
 #define INIT_ORDER_DBCORE 18
 #define INIT_ORDER_BLACKBOX 17
-#define INIT_ORDER_SERVER_MAINT 16
+#define INIT_ORDER_CLEANUP 16
 #define INIT_ORDER_INPUT 15
 #define INIT_ORDER_RESEARCH 14
 #define INIT_ORDER_EVENTS 13
@@ -89,7 +89,7 @@
 #define FIRE_PRIORITY_NANOMOB       10
 #define FIRE_PRIORITY_NIGHTSHIFT	10
 #define FIRE_PRIORITY_IDLE_NPC		10
-#define FIRE_PRIORITY_SERVER_MAINT	10
+#define FIRE_PRIORITY_CLEANUP		10
 #define FIRE_PRIORITY_TICKETS		10
 #define FIRE_PRIORITY_RESEARCH		10
 #define FIRE_PRIORITY_GARBAGE		15
diff --git a/code/controllers/subsystem/cleanup.dm b/code/controllers/subsystem/cleanup.dm
new file mode 100644
index 00000000000..51ae9c02ef8
--- /dev/null
+++ b/code/controllers/subsystem/cleanup.dm
@@ -0,0 +1,40 @@
+/**
+ * # Cleanup Subsystem
+ *
+ * For now, all it does is periodically clean the supplied global lists of any null values they may contain.
+ *
+ * Why is this important?
+ *
+ * Sometimes, these lists can gain nulls due to errors.
+ * For example, when a dead player trasitions from the `dead_mob_list` to the `alive_mob_list`, a null value may get stuck in the dead mob list.
+ * This can cause issues when other code tries to do things with the values in the list, but are instead met with null values.
+ * These problems are incredibly hard to track down and fix, so this subsystem is a solution to that.
+ */
+SUBSYSTEM_DEF(cleanup)
+	name = "Null cleanup"
+	wait = 30 SECONDS
+	flags = SS_POST_FIRE_TIMING
+	priority = FIRE_PRIORITY_CLEANUP
+	init_order = INIT_ORDER_CLEANUP
+	runlevels = RUNLEVEL_LOBBY | RUNLEVELS_DEFAULT
+	offline_implications = "Certain global lists will no longer be cleared of nulls, which may result in runtimes. No immediate action is needed."
+	/// A list of global lists we want the subsystem to clean.
+	var/list/lists_to_clean
+
+/datum/controller/subsystem/cleanup/Initialize(start_timeofday)
+	. = ..()
+	// If you want this subsystem to clean out nulls from a specific list, add it here.
+	lists_to_clean = list(
+		GLOB.clients,
+		GLOB.player_list,
+		GLOB.mob_list,
+		GLOB.alive_mob_list,
+		GLOB.dead_mob_list,
+		GLOB.human_list,
+		GLOB.carbon_list
+	)
+
+/datum/controller/subsystem/cleanup/fire(resumed)
+	for(var/L in lists_to_clean)
+		var/list/_list = L
+		listclearnulls(_list)
diff --git a/paradise.dme b/paradise.dme
index 5e88b673231..1577b6b1144 100644
--- a/paradise.dme
+++ b/paradise.dme
@@ -216,6 +216,7 @@
 #include "code\controllers\subsystem\atoms.dm"
 #include "code\controllers\subsystem\changelog.dm"
 #include "code\controllers\subsystem\chat.dm"
+#include "code\controllers\subsystem\cleanup.dm"
 #include "code\controllers\subsystem\events.dm"
 #include "code\controllers\subsystem\fires.dm"
 #include "code\controllers\subsystem\garbage.dm"