From aecb32c4b45b414114649bec947ce20dd9569a16 Mon Sep 17 00:00:00 2001
From: Lucy <lucy@absolucy.moe>
Date: Thu, 15 May 2025 12:17:16 -0400
Subject: [PATCH] Make stack merging much less of a potential lagfest (#91015)

---
 code/game/objects/items/stacks/stack.dm | 63 +++++++++++++++----------
 1 file changed, 39 insertions(+), 24 deletions(-)

diff --git a/code/game/objects/items/stacks/stack.dm b/code/game/objects/items/stacks/stack.dm
index 3cf2c637d7f..9a5862ca54a 100644
--- a/code/game/objects/items/stacks/stack.dm
+++ b/code/game/objects/items/stacks/stack.dm
@@ -83,6 +83,9 @@
 
 	. = ..()
 
+	if(merge)
+		. = INITIALIZE_HINT_LATELOAD
+
 	var/materials_mult = amount
 	if(LAZYLEN(mat_override))
 		materials_mult *= mat_amt
@@ -90,15 +93,6 @@
 	if(LAZYLEN(mats_per_unit))
 		initialize_materials(mats_per_unit, materials_mult)
 
-	if(merge)
-		for(var/obj/item/stack/item_stack in loc)
-			if(item_stack == src)
-				continue
-			if(can_merge(item_stack))
-				INVOKE_ASYNC(src, PROC_REF(merge_without_del), item_stack)
-				if(is_zero_amount(delete_if_zero = FALSE))
-					return INITIALIZE_HINT_QDEL
-
 	recipes = get_main_recipes().Copy()
 	if(material_type)
 		var/datum/material/what_are_we_made_of = GET_MATERIAL_REF(material_type) //First/main material
@@ -111,19 +105,51 @@
 
 	update_weight()
 	update_appearance()
-	var/static/list/loc_connections = list(
-		COMSIG_ATOM_ENTERED = PROC_REF(on_movable_entered_occupied_turf),
-	)
-	AddElement(/datum/element/connect_loc, loc_connections)
 
 	if(is_path_in_list(merge_type, GLOB.golem_stack_food_directory))
 		AddComponent(/datum/component/golem_food, golem_food_key = merge_type)
 
+/obj/item/stack/LateInitialize()
+	merge_with_loc()
+
+/obj/item/stack/Moved(atom/old_loc, movement_dir, forced, list/old_locs, momentum_change)
+	. = ..()
+	if((!throwing || throwing.target_turf == loc) && old_loc != loc && (flags_1 & INITIALIZED_1))
+		merge_with_loc()
+
 ///Called to lazily update the materials of the item whenever the used or if more is added
 /obj/item/stack/proc/update_custom_materials()
 	if(length(mats_per_unit))
 		set_custom_materials(mats_per_unit, amount)
 
+/obj/item/stack/proc/find_other_stack(list/already_found)
+	if(QDELETED(src) || isnull(loc))
+		return
+	for(var/obj/item/stack/item_stack in loc)
+		if(item_stack == src || QDELING(item_stack) || (item_stack.amount >= item_stack.max_amount))
+			continue
+		if(!(item_stack.flags_1 & INITIALIZED_1))
+			stack_trace("find_other_stack found uninitialized stack in loc? skipping for now")
+			continue
+		var/stack_ref = REF(item_stack)
+		if(already_found[stack_ref])
+			continue
+		if(can_merge(item_stack))
+			already_found[stack_ref] = TRUE
+			return item_stack
+
+/// Tries to merge the stack with everything on the same tile.
+/obj/item/stack/proc/merge_with_loc()
+	var/list/already_found = list() // change to alist whenever dreamchecker and such finally supports that
+	var/obj/item/other_stack = find_other_stack(already_found)
+	var/sanity = max_amount // just in case
+	while(other_stack && sanity > 0)
+		sanity--
+		if(merge(other_stack))
+			return FALSE
+		other_stack = find_other_stack(already_found)
+	return TRUE
+
 /obj/item/stack/apply_material_effects(list/materials)
 	. = ..()
 	if(amount)
@@ -662,17 +688,6 @@
 	. = merge_without_del(target_stack, limit)
 	is_zero_amount(delete_if_zero = TRUE)
 
-/// Signal handler for connect_loc element. Called when a movable enters the turf we're currently occupying. Merges if possible.
-/obj/item/stack/proc/on_movable_entered_occupied_turf(datum/source, atom/movable/arrived)
-	SIGNAL_HANDLER
-
-	// Edge case. This signal will also be sent when src has entered the turf. Don't want to merge with ourselves.
-	if(arrived == src)
-		return
-
-	if(!arrived.throwing && can_merge(arrived))
-		INVOKE_ASYNC(src, PROC_REF(merge), arrived)
-
 /obj/item/stack/hitby(atom/movable/hitting, skipcatch, hitpush, blocked, datum/thrownthing/throwingdatum)
 	if(can_merge(hitting, inhand = TRUE))
 		merge(hitting)