Fix Weed Nodes in Walls (#3765)

# About the pull request

This PR makes it so weed nodes cannot be placed in a turf with density
set true (such as when you build a resin wall on top of yourself) or a
dense structure (such as a window frame). Nodes still can be placed
under doors while they are open. Marked it as balance but feel free to
change it to fix if you think it isn't balance.

If theres a situation where a weed node should be able to be placed in a
turf with density let me know and I can make the check exclusively for
resin walls. I can't think of any though.

# Explain why it's good for the game

Fixes #3745
Fixes #3770 

# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>


![image](https://github.com/cmss13-devs/cmss13/assets/76988376/89b16684-1f35-40f6-81f0-44855f28e732)

</details>

# Changelog
:cl: Drathek
balance: Weed nodes can no longer be placed in walls or window frames
(or any turf or structure with density)
refactor: Refactored the plant weeds ability code
/:cl:

code/modules/mob/living/carbon/xenomorph/abilities/general_powers.dm

@@ -4,70 +4,79 @@
 
 // Plant weeds
 /datum/action/xeno_action/onclick/plant_weeds/use_ability(atom/A)
-	var/mob/living/carbon/xenomorph/X = owner
+	var/mob/living/carbon/xenomorph/xeno = owner
 	if(!action_cooldown_check())
 		return
-	if(!X.check_state())
+	if(!xeno.check_state())
 		return
-	if(X.burrow)
+	if(xeno.burrow)
 		return
 
-	var/turf/T = X.loc
+	var/turf/turf = xeno.loc
 
-	if(!istype(T))
-		to_chat(X, SPAN_WARNING("You can't do that here."))
+	if(!istype(turf))
+		to_chat(xeno, SPAN_WARNING("You can't do that here."))
 		return
 
-	var/is_weedable = T.is_weedable()
+	if(turf.density)
+		to_chat(xeno, SPAN_WARNING("You can't do that here."))
+		return
+
+	var/is_weedable = turf.is_weedable()
 	if(!is_weedable)
-		to_chat(X, SPAN_WARNING("Bad place for a garden!"))
+		to_chat(xeno, SPAN_WARNING("Bad place for a garden!"))
 		return
 	if(!plant_on_semiweedable && is_weedable < FULLY_WEEDABLE)
-		to_chat(X, SPAN_WARNING("Bad place for a garden!"))
+		to_chat(xeno, SPAN_WARNING("Bad place for a garden!"))
 		return
 
-	var/obj/effect/alien/weeds/node/N = locate() in T
-	if(N && N.weed_strength >= X.weed_level)
-		to_chat(X, SPAN_WARNING("There's a pod here already!"))
+	var/obj/effect/alien/weeds/node/node = locate() in turf
+	if(node && node.weed_strength >= xeno.weed_level)
+		to_chat(xeno, SPAN_WARNING("There's a pod here already!"))
 		return
 
-	var/obj/effect/alien/resin/trap/resin_trap = locate() in T
+	var/obj/effect/alien/resin/trap/resin_trap = locate() in turf
 	if(resin_trap)
-		to_chat(X, SPAN_WARNING("You can't weed on top of a trap!"))
+		to_chat(xeno, SPAN_WARNING("You can't weed on top of a trap!"))
 		return
 
-	var/list/to_convert
-	if(N)
-		to_convert = N.children.Copy()
-
-	var/obj/effect/alien/weeds/W = locate(/obj/effect/alien/weeds) in T
-	if (W && W.weed_strength >= WEED_LEVEL_HIVE)
-		to_chat(X, SPAN_WARNING("These weeds are too strong to plant a node on!"))
+	var/obj/effect/alien/weeds/weed = node || locate() in turf
+	if(weed && weed.weed_strength >= WEED_LEVEL_HIVE)
+		to_chat(xeno, SPAN_WARNING("These weeds are too strong to plant a node on!"))
 		return
 
-	var/area/AR = get_area(T)
-	if(isnull(AR) || !(AR.is_resin_allowed))
-		if(AR.flags_area & AREA_UNWEEDABLE)
-			to_chat(X, SPAN_XENOWARNING("This area is unsuited to host the hive!"))
+	for(var/obj/structure/struct in turf)
+		if(struct.density && !(struct.flags_atom & ON_BORDER)) // Not sure exactly if we need to test against ON_BORDER though
+			to_chat(xeno, SPAN_WARNING("You can't do that here."))
 			return
-		to_chat(X, SPAN_XENOWARNING("It's too early to spread the hive this far."))
+
+	var/area/area = get_area(turf)
+	if(isnull(area) || !(area.is_resin_allowed))
+		if(area.flags_area & AREA_UNWEEDABLE)
+			to_chat(xeno, SPAN_XENOWARNING("This area is unsuited to host the hive!"))
+			return
+		to_chat(xeno, SPAN_XENOWARNING("It's too early to spread the hive this far."))
 		return
 
-	if (!check_and_use_plasma_owner())
+	if(!check_and_use_plasma_owner())
 		return
 
-	X.visible_message(SPAN_XENONOTICE("\The [X] regurgitates a pulsating node and plants it on the ground!"), \
+	var/list/to_convert
+	if(node)
+		to_convert = node.children.Copy()
+
+	xeno.visible_message(SPAN_XENONOTICE("\The [xeno] regurgitates a pulsating node and plants it on the ground!"), \
 	SPAN_XENONOTICE("You regurgitate a pulsating node and plant it on the ground!"), null, 5)
-	var/obj/effect/alien/weeds/node/new_node = new node_type(X.loc, src, X)
+	var/obj/effect/alien/weeds/node/new_node = new node_type(xeno.loc, src, xeno)
 
 	if(to_convert)
-		for(var/weed in to_convert)
-			var/turf/target_turf = get_turf(weed)
+		for(var/cur_weed in to_convert)
+			var/turf/target_turf = get_turf(cur_weed)
 			if(target_turf && !target_turf.density)
 				new /obj/effect/alien/weeds(target_turf, new_node)
-			qdel(weed)
+			qdel(cur_weed)
 
-	playsound(X.loc, "alien_resin_build", 25)
+	playsound(xeno.loc, "alien_resin_build", 25)
 	apply_cooldown()
 	return ..()