[Fix] Xenos scuttle + Allied Xenos Using Doors (#3915)

# About the pull request

Reviving #3128 since I finally
have time to work on these again

Fixing scuttle code and incidentally, allied xenos opening doors

# Explain why it's good for the game

Playable facehuggers were intended to scuttle but the code wasn't
updated to handle them.

This refactors the code so that all small xenos ( larva, facehugger,
future small castes?) can scuttle properly and removes duplicate code
from both the updated facehugger code and old larva scuttle code that
wasn't up to date in code style ( one letter var names for example )

Incidentally, I fix allied xenos using hive's doors. So allied xenos can
toggle hive doors and allied small xenos can scuttle hive's doors

# Changelog

:cl:
fix: Xenos allied to the hive can now open hive's doors
fix: Huggers can now scuttle doors
code: Combined hugger + larva code to allow for any small castes to
scuttle
/:cl:

Co-authored-by: harryob <[email protected]>

code/modules/cm_aliens/XenoStructures.dm

@@ -394,11 +394,13 @@
 		return attack_hand(user)
 
 /obj/structure/mineral_door/resin/TryToSwitchState(atom/user)
-	if(islarva(user))
-		var/mob/living/carbon/xenomorph/larva/L = user
-		if (L.hivenumber == hivenumber)
-			L.scuttle(src)
-		return
+	if(isxeno(user))
+		var/mob/living/carbon/xenomorph/xeno_user = user
+		if (xeno_user.hivenumber != hivenumber && !xeno_user.ally_of_hivenumber(hivenumber))
+			return
+		if(xeno_user.scuttle(src))
+			return
+		return ..()
 	if(iscarbon(user))
 		var/mob/living/carbon/C = user
 		if (C.ally_of_hivenumber(hivenumber))

code/modules/mob/living/carbon/xenomorph/Embryo.dm

@@ -314,20 +314,3 @@
 		victim.death(cause) // Certain species were still surviving bursting (predators), DEFINITELY kill them this time.
 		victim.chestburst = 2
 		victim.update_burst()
-
-// Squeeze thru dense objects as a larva, as airlocks
-/mob/living/carbon/xenomorph/larva/proc/scuttle(obj/structure/target)
-	var/move_dir = get_dir(src, loc)
-	for(var/atom/movable/AM in get_turf(target))
-		if(AM != target && AM.density && AM.BlockedPassDirs(src, move_dir))
-			to_chat(src, SPAN_WARNING("\The [AM] prevents you from squeezing under \the [target]!"))
-			return
-	// Is it an airlock?
-	if(istype(target, /obj/structure/machinery/door/airlock))
-		var/obj/structure/machinery/door/airlock/selected_airlock = target
-		if(selected_airlock.locked || selected_airlock.welded) //Can't pass through airlocks that have been bolted down or welded
-			to_chat(src, SPAN_WARNING("\The [selected_airlock] is locked down tight. You can't squeeze underneath!"))
-			return
-	visible_message(SPAN_WARNING("\The [src] scuttles underneath \the [target]!"), \
-	SPAN_WARNING("You squeeze and scuttle underneath \the [target]."), null, 5)
-	forceMove(target.loc)

code/modules/mob/living/carbon/xenomorph/Xenomorph.dm

@@ -1092,3 +1092,23 @@
 	. = ..()
 	if(behavior_delegate)
 		behavior_delegate.on_collide(movable_atom)
+
+/mob/living/carbon/xenomorph/proc/scuttle(obj/structure/current_structure)
+	if (mob_size != MOB_SIZE_SMALL)
+		return FALSE
+
+	var/move_dir = get_dir(src, loc)
+	for(var/atom/movable/atom in get_turf(current_structure))
+		if(atom != current_structure && atom.density && atom.BlockedPassDirs(src, move_dir))
+			to_chat(src, SPAN_WARNING("[atom] prevents you from squeezing under [current_structure]!"))
+			return FALSE
+	// Is it an airlock?
+	if(istype(current_structure, /obj/structure/machinery/door/airlock))
+		var/obj/structure/machinery/door/airlock/current_airlock = current_structure
+		if(current_airlock.locked || current_airlock.welded) //Can't pass through airlocks that have been bolted down or welded
+			to_chat(src, SPAN_WARNING("[current_airlock] is locked down tight. You can't squeeze underneath!"))
+			return FALSE
+	visible_message(SPAN_WARNING("[src] scuttles underneath [current_structure]!"), \
+	SPAN_WARNING("You squeeze and scuttle underneath [current_structure]."), max_distance = 5)
+	forceMove(current_structure.loc)
+	return TRUE

code/modules/mob/living/carbon/xenomorph/castes/Facehugger.dm

@@ -221,22 +221,6 @@
 /mob/living/carbon/xenomorph/facehugger/add_xeno_shield(added_amount, shield_source, type = /datum/xeno_shield, duration = -1, decay_amount_per_second = 1, add_shield_on = FALSE, max_shield = 200)
 	return
 
-/mob/living/carbon/xenomorph/facehugger/proc/scuttle(obj/structure/current_structure)
-	var/move_dir = get_dir(src, loc)
-	for(var/atom/movable/atom in get_turf(current_structure))
-		if(atom != current_structure && atom.density && atom.BlockedPassDirs(src, move_dir))
-			to_chat(src, SPAN_WARNING("\The [atom] prevents you from squeezing under \the [current_structure]!"))
-			return
-	// Is it an airlock?
-	if(istype(current_structure, /obj/structure/machinery/door/airlock))
-		var/obj/structure/machinery/door/airlock/current_airlock = current_structure
-		if(current_airlock.locked || current_airlock.welded) //Can't pass through airlocks that have been bolted down or welded
-			to_chat(src, SPAN_WARNING("\The [current_airlock] is locked down tight. You can't squeeze underneath!"))
-			return
-	visible_message(SPAN_WARNING("\The [src] scuttles underneath \the [current_structure]!"), \
-	SPAN_WARNING("You squeeze and scuttle underneath \the [current_structure]."), null, 5)
-	forceMove(current_structure.loc)
-
 /mob/living/carbon/xenomorph/facehugger/emote(act, m_type, message, intentional, force_silence)
 	playsound(loc, "alien_roar_larva", 15)