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/basic_mobs/basic_ai_behaviors/basic_attacking.dm

@@ -4,22 +4,22 @@
 
 /datum/ai_behavior/basic_melee_attack/setup(datum/ai_controller/controller, target_key, targetting_datum_key, hiding_location_key)
 	. = ..()
-	//Hiding location is priority
-	var/datum/weakref/weak_target = controller.blackboard[hiding_location_key] || controller.blackboard[target_key]
-	var/atom/target = weak_target?.resolve()
-	if(!target)
-		return FALSE
 	var/datum/targetting_datum/targetting_datum = controller.blackboard[targetting_datum_key]
-	if (!targetting_datum)
-		return
+	if(isnull(targetting_datum))
+		CRASH("No target datum was supplied in the blackboard for [controller.pawn]")
+
+	//Hiding location is priority
+	var/atom/target = controller.blackboard[hiding_location_key] || controller.blackboard[target_key]
+	if(QDELETED(target))
+		return FALSE
+
 	set_movement_target(controller, target)
 
 /datum/ai_behavior/basic_melee_attack/perform(seconds_per_tick, datum/ai_controller/controller, target_key, targetting_datum_key, hiding_location_key)
 	. = ..()
 	var/mob/living/basic/basic_mob = controller.pawn
 	//targetting datum will kill the action if not real anymore
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/atom/target = weak_target?.resolve()
+	var/atom/target = controller.blackboard[target_key]
 	var/datum/targetting_datum/targetting_datum = controller.blackboard[targetting_datum_key]
 
 	if(!targetting_datum.can_attack(basic_mob, target))
@@ -28,7 +28,7 @@
 
 	var/hiding_target = targetting_datum.find_hidden_mobs(basic_mob, target) //If this is valid, theyre hidden in something!
 
-	controller.blackboard[hiding_location_key] = hiding_target
+	controller.set_blackboard_key(hiding_location_key, hiding_target)
 
 	if(hiding_target) //Slap it!
 		basic_mob.melee_attack(hiding_target)
@@ -39,7 +39,7 @@
 /datum/ai_behavior/basic_melee_attack/finish_action(datum/ai_controller/controller, succeeded, target_key, targetting_datum_key, hiding_location_key)
 	. = ..()
 	if(!succeeded)
-		controller.blackboard -= target_key
+		controller.clear_blackboard_key(target_key)
 
 /datum/ai_behavior/basic_melee_attack/average_speed
 	action_cooldown = 1 SECONDS
@@ -55,9 +55,8 @@
 
 /datum/ai_behavior/basic_ranged_attack/setup(datum/ai_controller/controller, target_key, targetting_datum_key, hiding_location_key)
 	. = ..()
-	var/datum/weakref/weak_target = controller.blackboard[hiding_location_key] || controller.blackboard[target_key]
-	var/atom/target = weak_target?.resolve()
-	if(!target)
+	var/atom/target = controller.blackboard[hiding_location_key] || controller.blackboard[target_key]
+	if(QDELETED(target))
 		return FALSE
 	set_movement_target(controller, target)
 
@@ -65,8 +64,7 @@
 	. = ..()
 	var/mob/living/basic/basic_mob = controller.pawn
 	//targetting datum will kill the action if not real anymore
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/atom/target = weak_target?.resolve()
+	var/atom/target = controller.blackboard[target_key]
 	var/datum/targetting_datum/targetting_datum = controller.blackboard[targetting_datum_key]
 
 	if(!targetting_datum.can_attack(basic_mob, target))
@@ -80,7 +78,7 @@
 		finish_action(controller, FALSE, target_key)
 		return
 
-	controller.blackboard[hiding_location_key] = WEAKREF(hiding_target)
+	controller.set_blackboard_key(hiding_location_key, hiding_target)
 
 	if(shots>1)
 		var/atom/burst_target = final_target
@@ -94,4 +92,4 @@
 /datum/ai_behavior/basic_ranged_attack/finish_action(datum/ai_controller/controller, succeeded, target_key, targetting_datum_key, hiding_location_key)
 	. = ..()
 	if(!succeeded)
-		controller.blackboard -= target_key
+		controller.clear_blackboard_key(target_key)

code/datums/ai/basic_mobs/basic_ai_behaviors/pick_up_item.dm

@@ -7,18 +7,16 @@
 
 /datum/ai_behavior/pick_up_item/setup(datum/ai_controller/controller, target_key, storage_key)
 	. = ..()
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/obj/item/target = weak_target?.resolve()
+	var/obj/item/target = controller.blackboard[target_key]
 	return isitem(target) && isturf(target.loc) && !target.anchored
 
 /datum/ai_behavior/pick_up_item/perform(seconds_per_tick, datum/ai_controller/controller, target_key, storage_key)
 	. = ..()
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/obj/item/target = weak_target?.resolve()
-	if(!isturf(target?.loc)) // Someone picked it up or it got deleted
+	var/obj/item/target = controller.blackboard[target_key]
+	if(QDELETED(target) || !isturf(target.loc)) // Someone picked it up or it got deleted
 		finish_action(controller, FALSE, target_key)
 		return
-	if(!in_range(controller.pawn, target)) // It teleported
+	if(!controller.pawn.Adjacent(target)) // It teleported
 		finish_action(controller, FALSE, target_key)
 		return
 	pickup_item(controller, target, storage_key)
@@ -26,22 +24,21 @@
 
 /datum/ai_behavior/pick_up_item/finish_action(datum/ai_controller/controller, success, target_key, storage_key)
 	. = ..()
-	controller.blackboard[target_key] = null
+	controller.clear_blackboard_key(target_key)
 
 /datum/ai_behavior/pick_up_item/proc/pickup_item(datum/ai_controller/controller, obj/item/target, storage_key)
 	var/atom/pawn = controller.pawn
 	drop_existing_item(controller, storage_key)
 	pawn.visible_message(span_notice("[pawn] picks up [target]."))
 	target.forceMove(pawn)
-	controller.blackboard[storage_key] = WEAKREF(target)
+	controller.set_blackboard_key(storage_key, target)
 	return TRUE
 
 /datum/ai_behavior/pick_up_item/proc/drop_existing_item(datum/ai_controller/controller, storage_key)
-	var/datum/weakref/carried_ref = controller.blackboard[storage_key]
-	var/obj/item/carried_item = carried_ref?.resolve()
+	var/obj/item/carried_item = controller.blackboard[storage_key]
 	if(!carried_item)
 		return
-	controller.blackboard[storage_key] = null
+	controller.clear_blackboard_key(storage_key)
 	var/atom/pawn = controller.pawn
 	if(carried_item.loc != pawn)
 		return

code/datums/ai/basic_mobs/basic_ai_behaviors/run_away_from_target.dm

@@ -7,9 +7,8 @@
 	var/run_distance = 9
 
 /datum/ai_behavior/run_away_from_target/setup(datum/ai_controller/controller, target_key, hiding_location_key)
-	var/datum/weakref/weak_target = controller.blackboard[hiding_location_key] || controller.blackboard[target_key]
-	var/atom/target = weak_target?.resolve()
-	if(!target)
+	var/atom/target = controller.blackboard[hiding_location_key] || controller.blackboard[target_key]
+	if(QDELETED(target))
 		return FALSE
 	if(!plot_path_away_from(controller, target))
 		return FALSE
@@ -17,9 +16,8 @@
 
 /datum/ai_behavior/run_away_from_target/perform(seconds_per_tick, datum/ai_controller/controller, target_key, hiding_location_key)
 	. = ..()
-	var/datum/weakref/weak_target = controller.blackboard[hiding_location_key] || controller.blackboard[target_key]
-	var/atom/target = weak_target?.resolve()
-	var/escaped =  !target || !can_see(controller.pawn, target, run_distance) // If we can't see it we got away
+	var/atom/target = controller.blackboard[hiding_location_key] || controller.blackboard[target_key]
+	var/escaped =  QDELETED(target) || !can_see(controller.pawn, target, run_distance) // If we can't see it we got away
 	if (escaped)
 		finish_action(controller, succeeded = TRUE, target_key = target_key, hiding_location_key = hiding_location_key)
 		return
@@ -43,4 +41,4 @@
 
 /datum/ai_behavior/run_away_from_target/finish_action(datum/ai_controller/controller, succeeded, target_key, hiding_location_key)
 	. = ..()
-	controller.blackboard[target_key] = null
+	controller.clear_blackboard_key(target_key)

code/datums/ai/basic_mobs/basic_ai_behaviors/step_towards_turf.dm

@@ -11,13 +11,12 @@
 	var/step_distance = 3
 
 /datum/ai_behavior/step_towards_turf/setup(datum/ai_controller/controller, turf_key)
-	var/datum/weakref/weak_turf = controller.blackboard[turf_key]
-	var/turf/target_turf = weak_turf?.resolve()
-	if (!target_turf || target_turf.is_blocked_turf(exclude_mobs = TRUE))
+	var/turf/target_turf = controller.blackboard[turf_key]
+	if (QDELETED(target_turf) || target_turf.is_blocked_turf(exclude_mobs = TRUE))
 		target_turf = find_destination_turf(args)
 		if (!target_turf)
 			return FALSE
-		controller.blackboard[turf_key] = WEAKREF(target_turf)
+		controller.set_blackboard_key(turf_key, target_turf)
 
 	if (target_turf.z != controller.pawn.z)
 		return FALSE

code/datums/ai/basic_mobs/basic_ai_behaviors/stop_and_stare.dm

@@ -4,16 +4,14 @@
 
 /datum/ai_behavior/stop_and_stare/setup(datum/ai_controller/controller, target_key)
 	. = ..()
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/atom/movable/target = weak_target?.resolve()
+	var/atom/movable/target = controller.blackboard[target_key]
 	return ismovable(target) && isturf(target.loc) && ismob(controller.pawn)
 
 /datum/ai_behavior/stop_and_stare/perform(seconds_per_tick, datum/ai_controller/controller, target_key)
 	// i don't really like doing this but we wanna make sure that the cooldown is pertinent to what we need for this specific controller before we invoke parent
 	action_cooldown = controller.blackboard[BB_STATIONARY_COOLDOWN]
 	. = ..()
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/atom/movable/target = weak_target?.resolve()
+	var/atom/movable/target = controller.blackboard[target_key]
 	if(!ismovable(target) || !isturf(target.loc)) // just to make sure that nothing funky happened between setup and perform
 		return
 

code/datums/ai/basic_mobs/basic_ai_behaviors/targeted_mob_ability.dm

@@ -5,12 +5,9 @@
 /datum/ai_behavior/targeted_mob_ability
 
 /datum/ai_behavior/targeted_mob_ability/perform(seconds_per_tick, datum/ai_controller/controller, ability_key, target_key)
-	var/datum/weakref/weak_ability = controller.blackboard[ability_key]
-	var/datum/action/cooldown/ability = weak_ability?.resolve()
-
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/mob/living/target = weak_target?.resolve()
-	if(!ability || QDELETED(target))
+	var/datum/action/cooldown/ability = controller.blackboard[ability_key]
+	var/mob/living/target = controller.blackboard[target_key]
+	if(QDELETED(ability) || QDELETED(target))
 		finish_action(controller, FALSE, ability_key, target_key)
 		return
 	var/mob/pawn = controller.pawn
@@ -19,16 +16,15 @@
 
 /datum/ai_behavior/targeted_mob_ability/finish_action(datum/ai_controller/controller, succeeded, ability_key, target_key)
 	. = ..()
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/atom/target = weak_target?.resolve()
+	var/atom/target = controller.blackboard[target_key]
 	if (QDELETED(target))
-		controller.blackboard[target_key] = null
+		controller.clear_blackboard_key(target_key)
 		return
 	if (!isliving(target))
 		return
 	var/mob/living/living_target = target
 	if(living_target.stat >= UNCONSCIOUS)
-		controller.blackboard[target_key] = null
+		controller.clear_blackboard_key(target_key)
 
 /**
  * # Try Mob Ability and plan execute
@@ -38,7 +34,7 @@
 /datum/ai_behavior/targeted_mob_ability/and_plan_execute
 
 /datum/ai_behavior/targeted_mob_ability/and_plan_execute/finish_action(datum/ai_controller/controller, succeeded, ability_key, target_key)
-	controller.blackboard[BB_BASIC_MOB_EXECUTION_TARGET] = controller.blackboard[target_key]
+	controller.set_blackboard_key(BB_BASIC_MOB_EXECUTION_TARGET, controller.blackboard[target_key])
 	return ..()
 
 /**
@@ -49,4 +45,4 @@
 
 /datum/ai_behavior/targeted_mob_ability/and_clear_target/finish_action(datum/ai_controller/controller, succeeded, ability_key, target_key)
 	. = ..()
-	controller.blackboard[target_key] = null
+	controller.clear_blackboard_key(target_key)

code/datums/ai/basic_mobs/basic_ai_behaviors/targetting.dm

@@ -13,13 +13,12 @@
 	if(!targetting_datum)
 		CRASH("No target datum was supplied in the blackboard for [controller.pawn]")
 
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/atom/current_target = weak_target?.resolve()
+	var/atom/current_target = controller.blackboard[target_key]
 	if (targetting_datum.can_attack(living_mob, current_target))
 		finish_action(controller, succeeded = FALSE)
 		return
 
-	controller.blackboard[target_key] = null
+	controller.clear_blackboard_key(target_key)
 	var/list/potential_targets = hearers(vision_range, controller.pawn) - living_mob //Remove self, so we don't suicide
 
 	for(var/HM in typecache_filter_list(range(vision_range, living_mob), hostile_machines)) //Can we see any hostile machines?
@@ -42,12 +41,12 @@
 		return
 
 	var/atom/target = pick_final_target(controller, filtered_targets)
-	controller.blackboard[target_key] = WEAKREF(target)
+	controller.set_blackboard_key(target_key, target)
 
 	var/atom/potential_hiding_location = targetting_datum.find_hidden_mobs(living_mob, target)
 
 	if(potential_hiding_location) //If they're hiding inside of something, we need to know so we can go for that instead initially.
-		controller.blackboard[hiding_location_key] = WEAKREF(potential_hiding_location)
+		controller.set_blackboard_key(hiding_location_key, potential_hiding_location)
 
 	finish_action(controller, succeeded = TRUE)
 

code/datums/ai/basic_mobs/basic_ai_behaviors/tipped_reaction.dm

@@ -33,5 +33,5 @@
 /datum/ai_behavior/tipped_reaction/finish_action(datum/ai_controller/controller, succeeded, tipper_key, reacting_key)
 	. = ..()
 	//I'VE SAID MY PEACE...
-	controller.blackboard[reacting_key] = FALSE
-	controller.blackboard[tipper_key] = null
+	controller.set_blackboard_key(reacting_key, FALSE)
+	controller.clear_blackboard_key(tipper_key)

code/datums/ai/basic_mobs/basic_ai_behaviors/travel_towards.dm

@@ -9,9 +9,8 @@
 
 /datum/ai_behavior/travel_towards/setup(datum/ai_controller/controller, target_key)
 	. = ..()
-	var/datum/weakref/weak_target = controller.blackboard[target_key]
-	var/atom/target = weak_target?.resolve()
-	if(isnull(target))
+	var/atom/target = controller.blackboard[target_key]
+	if(QDELETED(target))
 		return FALSE
 	set_movement_target(controller, target)