Lurker's scary AI

code/__DEFINES/dcs/signals/atom/mob/living/signals_xeno.dm

@@ -62,3 +62,12 @@
 
 /// For any additional things that should happen when a xeno's melee_attack_additional_effects_self() proc is called
 #define COMSIG_XENO_SLASH_ADDITIONAL_EFFECTS_SELF "xeno_slash_additional_effects_self"
+
+/// From /mob/living/carbon/xenomorph/proc/handle_crit()
+#define COMSIG_XENO_HANDLE_CRIT "xeno_handle_crit"
+
+/// From /datum/action/xeno_action/activable/pounce/use_ability()
+#define COMSIG_XENO_USED_POUNCE "xeno_used_pounce"
+
+/// From /mob/living/carbon/xenomorph/proc/handle_ai_shot()
+#define COMSIG_XENO_HANDLE_AI_SHOT "xeno_handle_ai_shot"

code/__DEFINES/xeno_ai.dm

@@ -28,6 +28,8 @@ PROBABILITY CALCULATIONS ARE HERE
 #define RETREAT_AT_PLASMA_LEVEL 0.2
 #define RETREAT_AT_HEALTH_LEVEL 0.4
 
+#define LURKING_IGNORE_SHOT_CHANCE 75
+
 // Warrior
 
 /// How likely should it be that you lunge when off cooldown?

code/modules/admin/game_master/game_master.dm

@@ -26,7 +26,7 @@ GLOBAL_VAR_INIT(radio_communication_clarity, 100)
 
 // Spawn stuff
 #define DEFAULT_SPAWN_XENO_STRING XENO_CASTE_DRONE
-#define GAME_MASTER_AI_XENOS list(XENO_CASTE_DRONE, XENO_CASTE_RUNNER, XENO_CASTE_CRUSHER)
+#define GAME_MASTER_AI_XENOS list(XENO_CASTE_DRONE, XENO_CASTE_RUNNER, XENO_CASTE_LURKER, XENO_CASTE_CRUSHER)
 
 #define DEFAULT_XENO_AMOUNT_TO_SPAWN 1
 

code/modules/admin/game_master/game_master_submenu/vents.dm

@@ -1,6 +1,6 @@
 
 #define DEFAULT_SPAWN_XENO_STRING XENO_CASTE_DRONE
-#define GAME_MASTER_VENT_AI_XENOS list(XENO_CASTE_DRONE, XENO_CASTE_RUNNER)
+#define GAME_MASTER_VENT_AI_XENOS list(XENO_CASTE_DRONE, XENO_CASTE_RUNNER, XENO_CASTE_LURKER)
 
 #define DEFAULT_XENO_AMOUNT_TO_SPAWN 1
 

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

@@ -446,6 +446,8 @@
 	LM.pass_flags = pounce_pass_flags
 	LM.collision_callbacks = pounce_callbacks
 
+	SEND_SIGNAL(owner, COMSIG_XENO_USED_POUNCE, A)
+
 	X.launch_towards(LM)
 
 	X.update_icons()

code/modules/mob/living/carbon/xenomorph/abilities/lurker/lurker_abilities.dm

@@ -8,7 +8,7 @@
 	// Config options
 	distance = 6
 	knockdown = FALSE
-	knockdown_duration = 2.5
+	knockdown_duration = 1.5
 	freeze_self = TRUE
 	freeze_time = 15
 	can_be_shield_blocked = TRUE

code/modules/mob/living/carbon/xenomorph/ai/movement/lurking.dm

@@ -0,0 +1,269 @@
+/datum/xeno_ai_movement/linger/lurking
+
+	// Are we currently hiding?
+	var/ai_lurking = FALSE
+
+	// Gradually increases the chance of AI to try and bait marines, annoyance accumulate when we lurk (stand invisible) and aware of our target
+	var/annoyance = 0
+
+	// Total baits this xeno has made
+	var/total_baits = 0
+
+	// Distance at which we want to stay from our spotted target
+	var/stalking_distance = 12
+
+	// List of turfs we see and register while lurking
+	var/list/registered_turfs = list()
+
+	// Let's lower this a little bit cause we do some heavy checks while finding our "home"
+	home_locate_range = 10
+
+	max_distance_from_home = 10
+
+#define AI_CHECK_ANNOYANCE_COOLDOWN 2.5 SECONDS
+
+/datum/xeno_ai_movement/linger/lurking/New(mob/living/carbon/xenomorph/parent)
+	. = ..()
+
+	RegisterSignal(parent, COMSIG_XENO_HANDLE_AI_SHOT, PROC_REF(stop_lurking))
+	RegisterSignal(parent, COMSIG_XENO_HANDLE_CRIT, PROC_REF(stop_lurking))
+	RegisterSignal(parent, COMSIG_XENO_USED_POUNCE, PROC_REF(stop_lurking))
+
+	addtimer(CALLBACK(src, PROC_REF(check_annoyance)), AI_CHECK_ANNOYANCE_COOLDOWN, TIMER_UNIQUE|TIMER_LOOP|TIMER_DELETE_ME)
+
+#undef AI_CHECK_ANNOYANCE_COOLDOWN
+
+/datum/xeno_ai_movement/linger/lurking/ai_move_idle(delta_time)
+	var/mob/living/carbon/xenomorph/idle_xeno = parent
+	if(idle_xeno.throwing)
+		return
+
+	if(home_turf)
+		if(get_dist(home_turf, idle_xeno) <= 0)
+			start_lurking()
+			return
+
+		if(!idle_xeno.move_to_next_turf(home_turf))
+			home_turf = null
+			return
+
+		return
+
+	if(next_home_search > world.time)
+		return
+
+	var/turf/current_turf = get_turf(idle_xeno)
+
+	if(!current_turf)
+		return
+
+	next_home_search = world.time + home_search_delay
+	var/shortest_distance = INFINITY
+	var/turf/non_preferred_turf
+	for(var/turf/potential_home as anything in shuffle(RANGE_TURFS(home_locate_range, current_turf)))
+		if(potential_home.density)
+			continue
+
+		var/blocked = FALSE
+		for(var/atom/potential_blocker as anything in potential_home)
+			if(potential_blocker != idle_xeno && (potential_blocker.can_block_movement || potential_blocker.density))
+				blocked = TRUE
+				break
+
+		if(blocked)
+			continue
+
+		var/preferred = FALSE
+		for(var/turf/closed/touching_turf in orange(1, potential_home))
+			preferred = TRUE
+			break
+
+		var/atom/movable/our_target = idle_xeno.current_target
+		if(our_target)
+			var/potential_home_dir = get_dir(idle_xeno, potential_home)
+			var/current_target_dir = get_dir(idle_xeno, our_target)
+
+			if(current_target_dir == potential_home_dir || current_target_dir == turn(potential_home_dir, 45) || current_target_dir == turn(potential_home_dir, -45))
+				continue
+
+			if(get_dist(potential_home, our_target) > stalking_distance)
+				continue
+
+		var/xeno_to_potential_home_distance = get_dist(idle_xeno, potential_home)
+		if(xeno_to_potential_home_distance > shortest_distance)
+			continue
+
+		if(preferred)
+			home_turf = potential_home
+			shortest_distance = xeno_to_potential_home_distance
+			continue
+
+		if(xeno_to_potential_home_distance < get_dist(idle_xeno, non_preferred_turf))
+			non_preferred_turf = potential_home
+			continue
+
+	if(!home_turf)
+		home_turf = non_preferred_turf
+		return
+
+/datum/xeno_ai_movement/linger/lurking/ai_move_target(delta_time)
+	var/mob/living/carbon/xenomorph/moving_xeno = parent
+	if(moving_xeno.throwing)
+		return
+
+	var/incapacitated_check = TRUE
+	if(istype(moving_xeno.current_target, /mob))
+		var/mob/current_target_mob = moving_xeno.current_target
+		incapacitated_check = current_target_mob.is_mob_incapacitated()
+
+	if(incapacitated_check)
+		return ..()
+
+	var/turf/target_turf = get_turf(moving_xeno.current_target)
+	if(ai_lurking || get_dist(moving_xeno, target_turf) > world.view + 1)
+		if(get_dist(moving_xeno, target_turf) > stalking_distance)
+			home_turf = null
+			return moving_xeno.move_to_next_turf(target_turf)
+		return ai_move_idle(delta_time)
+
+	annoyance = 0
+	check_for_travelling_turf_change(moving_xeno)
+
+	if(!moving_xeno.move_to_next_turf(travelling_turf))
+		travelling_turf = target_turf
+		return TRUE
+
+/datum/xeno_ai_movement/linger/lurking/proc/check_annoyance()
+	var/mob/living/carbon/xenomorph/annoyed_xeno = parent
+	if(!annoyed_xeno.current_target || !ai_lurking)
+		return
+
+	var/target_distance = get_dist(annoyed_xeno, annoyed_xeno.current_target)
+
+	if(target_distance < world.view)
+		return
+
+	if(target_distance > 10)
+		annoyance = 0
+		total_baits = 0
+		return
+
+	annoyance++
+
+	if(prob(annoyance))
+		try_bait()
+
+#define LURKER_BAIT_TYPES list("Taunt","Emote","Interact")
+#define LURKER_BAIT_EMOTES list("growl","roar","hiss","needshelp")
+#define LURKER_BAIT_TAUNTS list("Come here, little host","I won't bite","I see you","Safe to go, little one")
+#define LURKER_BAITS_BEFORE_AMBUSH 3
+
+/datum/xeno_ai_movement/linger/lurking/proc/try_bait(no_interact)
+	var/mob/living/carbon/xenomorph/baiting_xeno = parent
+	if(baiting_xeno.throwing)
+		return
+
+	if(total_baits >= LURKER_BAITS_BEFORE_AMBUSH)
+		stop_lurking()
+		total_baits = 0
+		return
+
+	var/bait_types = LURKER_BAIT_TYPES
+	if(no_interact)
+		bait_types -= "Interact"
+
+	var/bait = pick(bait_types)
+	switch(bait)
+		if("Emote")
+			baiting_xeno.emote(pick(LURKER_BAIT_EMOTES))
+		if("Taunt")
+			baiting_xeno.say(pick(LURKER_BAIT_TAUNTS))
+		if("Interact")
+			if(!interact_random(baiting_xeno))
+				return try_bait(no_interact = TRUE)
+
+	total_baits++
+	annoyance = 0
+	return bait
+
+#undef LURKER_BAIT_TYPES
+#undef LURKER_BAIT_EMOTES
+#undef LURKER_BAIT_TAUNTS
+#undef LURKER_BAITS_BEFORE_AMBUSH
+
+/datum/xeno_ai_movement/linger/lurking/proc/interact_random(mob/living/carbon/xenomorph/X)
+	for(var/obj/potential_interaction in orange(1, X))
+		if(istype(potential_interaction, /obj/structure/window_frame))
+			continue
+		if(istype(potential_interaction, /obj/structure/pipes))
+			continue
+		if(istype(potential_interaction, /obj/structure/sign))
+			continue
+		if(!potential_interaction.xeno_ai_act(X))
+			continue
+		return TRUE
+	return FALSE
+
+/datum/xeno_ai_movement/linger/lurking/proc/start_lurking()
+	SIGNAL_HANDLER
+	if(ai_lurking)
+		return
+
+	var/mob/living/carbon/xenomorph/lurking_xeno = parent
+	animate(lurking_xeno, alpha = 20, time = 0.5 SECONDS, easing = QUAD_EASING)
+	lurking_xeno.set_movement_intent(MOVE_INTENT_WALK)
+	register_turf_signals()
+	ai_lurking = TRUE
+
+	RegisterSignal(parent, COMSIG_MOVABLE_MOVED, PROC_REF(lurking_parent_moved))
+
+	var/datum/action/xeno_action/activable/pounce/lurker/LPA = get_xeno_action_by_type(lurking_xeno, /datum/action/xeno_action/activable/pounce/lurker)
+	if(LPA && istype(LPA))
+		LPA.knockdown = TRUE
+		LPA.freeze_self = TRUE
+
+	INVOKE_ASYNC(lurking_xeno, TYPE_PROC_REF(/mob, stop_pulling))
+
+/datum/xeno_ai_movement/linger/lurking/proc/stop_lurking()
+	SIGNAL_HANDLER
+	if(!ai_lurking)
+		return
+
+	var/mob/living/carbon/xenomorph/lurking_xeno = parent
+	animate(lurking_xeno, alpha = initial(lurking_xeno.alpha), time = 0.2 SECONDS, easing = QUAD_EASING)
+	lurking_xeno.set_movement_intent(MOVE_INTENT_RUN)
+	unregister_turf_signals()
+	ai_lurking = FALSE
+
+	UnregisterSignal(parent, COMSIG_MOVABLE_MOVED)
+
+	INVOKE_ASYNC(lurking_xeno, TYPE_PROC_REF(/mob, stop_pulling))
+
+/datum/xeno_ai_movement/linger/lurking/proc/register_turf_signals()
+	for(var/turf/open/cycled_open_turf in view(world.view, parent))
+		RegisterSignal(cycled_open_turf, COMSIG_TURF_ENTERED, PROC_REF(set_target))
+		registered_turfs += cycled_open_turf
+
+		var/mob/living/carbon/human/possible_target = locate() in cycled_open_turf
+		if(possible_target && (!parent.current_target || get_dist(parent, possible_target) < get_dist(parent, parent.current_target)))
+			parent.current_target = possible_target
+
+/datum/xeno_ai_movement/linger/lurking/proc/unregister_turf_signals()
+	for(var/turf/open/cycled_open_turf in registered_turfs)
+		UnregisterSignal(cycled_open_turf, COMSIG_TURF_ENTERED)
+	registered_turfs.Cut()
+
+/datum/xeno_ai_movement/linger/lurking/proc/set_target(turf/hooked, atom/movable/entering_atom)
+	SIGNAL_HANDLER
+
+	if(!istype(entering_atom, /mob/living/carbon/human))
+		return
+
+	if(!parent.current_target || get_dist(parent, entering_atom) < get_dist(parent, parent.current_target))
+		parent.current_target = entering_atom
+
+/datum/xeno_ai_movement/linger/lurking/proc/lurking_parent_moved(atom/movable/moving_atom, atom/oldloc, direction, Forced)
+	SIGNAL_HANDLER
+
+	unregister_turf_signals()
+	register_turf_signals()

code/modules/mob/living/carbon/xenomorph/ai/xeno_ai.dm

@@ -37,12 +37,16 @@ GLOBAL_LIST_INIT(ai_target_limbs, list(
 	return new /datum/xeno_ai_movement(src)
 
 /mob/living/carbon/xenomorph/proc/handle_ai_shot(obj/projectile/P)
-	if(!current_target && P.firer)
-		var/distance = get_dist(src, P.firer)
-		if(distance > max_travel_distance)
-			return
+	SEND_SIGNAL(src, COMSIG_XENO_HANDLE_AI_SHOT, P)
 
-		SSxeno_pathfinding.calculate_path(src, P.firer, distance, src, CALLBACK(src, PROC_REF(set_path)), list(src, P.firer))
+	if(current_target || !P.firer)
+		return
+
+	var/distance = get_dist(src, P.firer)
+	if(distance > max_travel_distance)
+		return
+
+	SSxeno_pathfinding.calculate_path(src, P.firer, distance, src, CALLBACK(src, PROC_REF(set_path)), list(src, P.firer))
 
 /mob/living/carbon/xenomorph/proc/register_ai_action(datum/action/xeno_action/XA)
 	if(XA.owner != src)