Experiment with replacing weakrefs in AI blackboard with deleting signals, ideally making it easier to work with and harder to cause hard deletes (#74791)

## About The Pull Request

Replaces weakref usage in AI blackboards with deleting signals

All blackboard var setting must go through setters rather than directly

## Why It's Good For The Game

This both makes it a ton easier to develop AI for, and also makes it
harder for hard deletes to sneak in, as has been seen with recent 515
prs showing hard deletes in AI blackboards

(To quantify "making it easier to develop AI", I found multiple bugs in
existing AI code due to the usage of weakrefs.)

I'm looking for `@Jacquerel` `@tralezab` 's opinions on the matter, also
maybe `@LemonInTheDark` if they're interested

## Changelog

🆑 Melbert
refactor: Mob ai refactored once again
/🆑

code/datums/ai/generic/find_and_set.dm

@@ -10,7 +10,7 @@
 	. = ..()
 	var/find_this_thing = search_tactic(controller, locate_path, search_range)
 	if(find_this_thing)
-		controller.blackboard[set_key] = WEAKREF(find_this_thing)
+		controller.set_blackboard_key(set_key, find_this_thing)
 		finish_action(controller, TRUE)
 	else
 		finish_action(controller, FALSE)

code/datums/ai/generic/generic_behaviors.dm

@@ -31,20 +31,25 @@
 
 /datum/ai_behavior/break_spine/setup(datum/ai_controller/controller, target_key)
 	. = ..()
-	set_movement_target(controller, controller.blackboard[target_key])
+	var/atom/target = controller.blackboard[target_key]
+	if(QDELETED(target))
+		return FALSE
+	set_movement_target(controller, target)
 
 /datum/ai_behavior/break_spine/perform(seconds_per_tick, datum/ai_controller/controller, target_key)
 	var/mob/living/batman = controller.blackboard[target_key]
 	var/mob/living/big_guy = controller.pawn //he was molded by the darkness
 
-	if(batman.stat)
-		finish_action(controller, TRUE, target_key)
-
-	if(get_dist(batman, big_guy) >= give_up_distance)
+	if(QDELETED(batman) || get_dist(batman, big_guy) >= give_up_distance)
 		finish_action(controller, FALSE, target_key)
+		return
+
+	if(batman.stat != CONSCIOUS)
+		finish_action(controller, TRUE, target_key)
+		return
 
 	big_guy.start_pulling(batman)
-	big_guy.setDir(get_dir(big_guy, batman))
+	big_guy.face_atom(batman)
 
 	batman.visible_message(span_warning("[batman] gets a slightly too tight hug from [big_guy]!"), span_userdanger("You feel your body break as [big_guy] embraces you!"))
 
@@ -61,7 +66,9 @@
 
 /datum/ai_behavior/break_spine/finish_action(datum/ai_controller/controller, succeeded, target_key)
 	if(succeeded)
-		controller.blackboard -= target_key
+		var/mob/living/bane = controller.pawn
+		bane.stop_pulling()
+		controller.clear_blackboard_key(target_key)
 	return ..()
 
 /// Use in hand the currently held item
@@ -86,9 +93,8 @@
 
 /datum/ai_behavior/use_on_object/setup(datum/ai_controller/controller, target_key)
 	. = ..()
-	var/datum/weakref/target_ref = controller.blackboard[target_key]
-	var/target = target_ref?.resolve()
-	if(!target)
+	var/atom/target = controller.blackboard[target_key]
+	if(QDELETED(target))
 		return FALSE
 	set_movement_target(controller, target)
 
@@ -96,10 +102,8 @@
 	. = ..()
 	var/mob/living/pawn = controller.pawn
 	var/obj/item/held_item = pawn.get_item_by_slot(pawn.get_active_hand())
-	var/datum/weakref/target_ref = controller.blackboard[target_key]
-	var/atom/target = target_ref?.resolve()
-
-	if(!target || !pawn.CanReach(target))
+	var/atom/target = controller.blackboard[target_key]
+	if(QDELETED(target) || !pawn.CanReach(target))
 		finish_action(controller, FALSE)
 		return
 
@@ -118,15 +122,13 @@
 
 /datum/ai_behavior/give/setup(datum/ai_controller/controller, target_key)
 	. = ..()
-	var/datum/weakref/target_ref = controller.blackboard[target_key]
-	set_movement_target(controller, target_ref?.resolve())
+	set_movement_target(controller, controller.blackboard[target_key])
 
 /datum/ai_behavior/give/perform(seconds_per_tick, datum/ai_controller/controller, target_key)
 	. = ..()
 	var/mob/living/pawn = controller.pawn
 	var/obj/item/held_item = pawn.get_active_held_item()
-	var/datum/weakref/target_ref = controller.blackboard[target_key]
-	var/atom/target = target_ref?.resolve()
+	var/atom/target = controller.blackboard[target_key]
 
 	if(!held_item) //if held_item is null, we pretend that action was succesful
 		finish_action(controller, TRUE)
@@ -185,14 +187,14 @@
 
 /datum/ai_behavior/consume/setup(datum/ai_controller/controller, target_key)
 	. = ..()
-	var/datum/weakref/target_ref = controller.blackboard[target_key]
-	set_movement_target(controller, target_ref?.resolve())
+	set_movement_target(controller, controller.blackboard[target_key])
 
 /datum/ai_behavior/consume/perform(seconds_per_tick, datum/ai_controller/controller, target_key, hunger_timer_key)
 	. = ..()
 	var/mob/living/living_pawn = controller.pawn
-	var/datum/weakref/target_ref = controller.blackboard[target_key]
-	var/obj/item/target = target_ref.resolve()
+	var/obj/item/target = controller.blackboard[target_key]
+	if(QDELETED(target))
+		return
 
 	if(!(target in living_pawn.held_items))
 		if(!living_pawn.get_empty_held_indexes() || !living_pawn.put_in_hands(target))
@@ -207,7 +209,7 @@
 /datum/ai_behavior/consume/finish_action(datum/ai_controller/controller, succeeded, target_key, hunger_timer_key)
 	. = ..()
 	if(succeeded)
-		controller.blackboard[hunger_timer_key] = world.time + rand(12 SECONDS, 60 SECONDS)
+		controller.set_blackboard_key(hunger_timer_key, world.time + rand(12 SECONDS, 60 SECONDS))
 
 /**
  * Drops items in hands, very important for future behaviors that require the pawn to grab stuff
@@ -234,9 +236,8 @@
 	if(!istype(living_pawn) || !isturf(living_pawn.loc))
 		return
 
-	var/datum/weakref/attack_ref = controller.blackboard[BB_ATTACK_TARGET]
-	var/atom/movable/attack_target = attack_ref?.resolve()
-	if(!attack_target || !can_see(living_pawn, attack_target, length=controller.blackboard[BB_VISION_RANGE]))
+	var/atom/movable/attack_target = controller.blackboard[BB_ATTACK_TARGET]
+	if(!attack_target || !can_see(living_pawn, attack_target, length = controller.blackboard[BB_VISION_RANGE]))
 		finish_action(controller, FALSE)
 		return
 
@@ -250,7 +251,7 @@
 
 /datum/ai_behavior/attack/finish_action(datum/ai_controller/controller, succeeded)
 	. = ..()
-	controller.blackboard[BB_ATTACK_TARGET] = null
+	controller.clear_blackboard_key(BB_ATTACK_TARGET)
 
 /// A proc representing when the mob is pushed to actually attack the target. Again, subtypes can be used to represent different attacks from different animals, or it can be some other generic behavior
 /datum/ai_behavior/attack/proc/attack(datum/ai_controller/controller, mob/living/living_target)
@@ -270,8 +271,7 @@
 	if(!istype(living_pawn) || !isturf(living_pawn.loc))
 		return
 
-	var/datum/weakref/follow_ref = controller.blackboard[BB_FOLLOW_TARGET]
-	var/atom/movable/follow_target = follow_ref?.resolve()
+	var/atom/movable/follow_target = controller.blackboard[BB_FOLLOW_TARGET]
 	if(!follow_target || get_dist(living_pawn, follow_target) > controller.blackboard[BB_VISION_RANGE])
 		finish_action(controller, FALSE)
 		return
@@ -285,7 +285,7 @@
 
 /datum/ai_behavior/follow/finish_action(datum/ai_controller/controller, succeeded)
 	. = ..()
-	controller.blackboard[BB_FOLLOW_TARGET] = null
+	controller.clear_blackboard_key(BB_FOLLOW_TARGET)
 
 
 
@@ -316,8 +316,7 @@
 /datum/ai_behavior/setup_instrument/perform(seconds_per_tick, datum/ai_controller/controller, song_instrument_key, song_lines_key)
 	. = ..()
 
-	var/datum/weakref/instrument_ref = controller.blackboard[song_instrument_key]
-	var/obj/item/instrument/song_instrument = instrument_ref.resolve()
+	var/obj/item/instrument/song_instrument = controller.blackboard[song_instrument_key]
 	var/datum/song/song = song_instrument.song
 	var/song_lines = controller.blackboard[song_lines_key]
 
@@ -333,8 +332,7 @@
 /datum/ai_behavior/play_instrument/perform(seconds_per_tick, datum/ai_controller/controller, song_instrument_key)
 	. = ..()
 
-	var/datum/weakref/instrument_ref = controller.blackboard[song_instrument_key]
-	var/obj/item/instrument/song_instrument = instrument_ref.resolve()
+	var/obj/item/instrument/song_instrument = controller.blackboard[song_instrument_key]
 	var/datum/song/song = song_instrument.song
 
 	song.start_playing(controller.pawn)
@@ -354,5 +352,5 @@
 		possible_targets += thing
 	if(!possible_targets.len)
 		finish_action(controller, FALSE)
-	controller.blackboard[target_key] = WEAKREF(pick(possible_targets))
+	controller.set_blackboard_key(target_key, pick(possible_targets))
 	finish_action(controller, TRUE)

code/datums/ai/generic/generic_subtrees.dm

@@ -8,8 +8,7 @@
  * * BB_SONG_LINES - not set by this subtree, is the song loaded into the song datum.
  */
 /datum/ai_planning_subtree/generic_play_instrument/SelectBehaviors(datum/ai_controller/controller, seconds_per_tick)
-	var/datum/weakref/player_ref = controller.blackboard[BB_SONG_INSTRUMENT]
-	var/obj/item/instrument/song_player = player_ref?.resolve()
+	var/obj/item/instrument/song_player = controller.blackboard[BB_SONG_INSTRUMENT]
 
 	if(!song_player)
 		controller.queue_behavior(/datum/ai_behavior/find_and_set/in_hands, BB_SONG_INSTRUMENT, /obj/item/instrument)
@@ -47,15 +46,16 @@
  * * BB_NEXT_HUNGRY - set by this subtree, is when the controller is next hungry
  */
 /datum/ai_planning_subtree/generic_hunger/SelectBehaviors(datum/ai_controller/controller, seconds_per_tick)
-	//inits the blackboard timer
-	if(!controller.blackboard[BB_NEXT_HUNGRY])
-		controller.blackboard[BB_NEXT_HUNGRY] = world.time + rand(0, 30 SECONDS)
+	var/next_eat = controller.blackboard[BB_NEXT_HUNGRY]
+	if(!next_eat)
+		//inits the blackboard timer
+		next_eat = world.time + rand(0, 30 SECONDS)
+		controller.set_blackboard_key(BB_NEXT_HUNGRY, next_eat)
 
-	if(world.time < controller.blackboard[BB_NEXT_HUNGRY])
+	if(world.time < next_eat)
 		return
 
-	var/datum/weakref/food_ref = controller.blackboard[BB_FOOD_TARGET]
-	if(!food_ref?.resolve())
+	if(!controller.blackboard[BB_FOOD_TARGET])
 		controller.queue_behavior(/datum/ai_behavior/find_and_set/edible, BB_FOOD_TARGET, /obj/item, 2)
 		return