Cain & Abel no longer forces dual-wielding and instead requires an empty offhand (#94661)

## About The Pull Request

Instead of forcing the player to dual wield it, Cain & Abel can now be
held with one hand, although doing so prohibits you from using it to
attack, throw/spin daggers or send out wisps.

## Why It's Good For The Game

Forcing dual wielding on a small pocketable item is a bit weird and
feels bad in gameplay, as it essentially prohibits you from being able
to use any healing items unless you keep an empty pocket, in which case
quick storage on all other items will default to it which is rather
impractical. Requiring an empty offhand essentially keeps the wielding
requirement without UX issues coming from inhand usage swapping modes or
inventory jank.

## Changelog
🆑
balance: Cain & Abel no longer forces dual-wielding and instead requires
an empty offhand
/🆑

code/modules/mining/lavaland/cain_and_abel/_cain_and_abel.dm

@@ -6,7 +6,7 @@
 	desc = "I cry I pray mon Dieu."
 	icon = 'icons/obj/mining_zones/artefacts.dmi'
 	lefthand_file = 'icons/mob/inhands/equipment/kitchen_lefthand.dmi'
-	righthand_file = 'icons/mob/inhands/equipment/kitchen_lefthand.dmi' //same sprite as lefthand
+	righthand_file = 'icons/mob/inhands/equipment/kitchen_righthand.dmi'
 	icon_state = "cain_and_abel"
 	inhand_icon_state = "cain_and_abel"
 	attack_verb_continuous = list("attacks", "saws", "slices", "tears", "lacerates", "rips", "dices", "cuts")
@@ -36,12 +36,13 @@
 	var/throw_mode = THROW_MODE_CRYSTALS
 	/// Flames we have up!
 	var/list/current_wisps = list()
+	/// Have we thrown the second dagger yet?
+	var/dagger_thrown = FALSE
 	/// Cooldown till we can throw blades again
 	COOLDOWN_DECLARE(throw_cooldown)
 
 /obj/item/cain_and_abel/Initialize(mapload)
 	. = ..()
-	AddComponent(/datum/component/two_handed, require_twohands = TRUE, force_unwielded = force, force_wielded = force)
 	if (length(animation_steps))
 		return
 
@@ -64,11 +65,10 @@
 		source.RemoveElement(/datum/element/relay_attackers)
 
 	set_combo(new_value = 0, user = source)
-	UnregisterSignal(source, list(COMSIG_ATOM_WAS_ATTACKED))
+	UnregisterSignal(source, list(COMSIG_ATOM_WAS_ATTACKED, COMSIG_MOB_UPDATE_HELD_ITEMS))
 
 /obj/item/cain_and_abel/equipped(mob/user, slot)
 	. = ..()
-
 	if(!(slot & ITEM_SLOT_HANDS))
 		unset_user(user)
 		return
@@ -77,6 +77,7 @@
 		user.AddElement(/datum/element/relay_attackers)
 
 	RegisterSignal(user, COMSIG_ATOM_WAS_ATTACKED, PROC_REF(on_attacked))
+	RegisterSignal(user, COMSIG_MOB_UPDATE_HELD_ITEMS, PROC_REF(on_updated_held_items))
 
 /obj/item/cain_and_abel/proc/on_attacked(datum/source, atom/attacker, attack_flags)
 	SIGNAL_HANDLER
@@ -86,6 +87,10 @@
 	if(get_dist(interacting_with, user) > 9 || interacting_with.z != user.z)
 		return NONE
 
+	if(!check_wield(user))
+		user.balloon_alert(user, "offhand busy!")
+		return ITEM_INTERACT_BLOCKING
+
 	if(!length(current_wisps))
 		user.balloon_alert(user, "no wisps!")
 		return ITEM_INTERACT_BLOCKING
@@ -94,6 +99,14 @@
 		addtimer(CALLBACK(src, PROC_REF(fire_wisp), user, interacting_with), index * 0.15 SECONDS)
 	return ITEM_INTERACT_SUCCESS
 
+/obj/item/cain_and_abel/pre_attack(atom/target, mob/living/user, list/modifiers, list/attack_modifiers)
+	. = ..()
+	if (.)
+		return
+	if(!check_wield(user))
+		user.balloon_alert(user, "offhand busy!")
+		return TRUE
+
 /obj/item/cain_and_abel/attack(mob/living/target, mob/living/carbon/human/user)
 	if(!istype(target) || target.mob_size < MOB_SIZE_LARGE || target.stat == DEAD)
 		attack_speed = CLICK_CD_MELEE
@@ -129,6 +142,13 @@
 
 	combo_count = new_value
 
+/obj/item/cain_and_abel/proc/on_updated_held_items(mob/living/source)
+	SIGNAL_HANDLER
+	update_dagger_icon()
+
+/obj/item/cain_and_abel/proc/update_dagger_icon()
+	inhand_icon_state = "[src::inhand_icon_state][(dagger_thrown || !check_wield(loc)) ? "_thrown" : ""]"
+
 /obj/item/cain_and_abel/proc/add_wisp(mob/living/user)
 	var/obj/effect/overlay/blood_wisp/new_wisp = new(src)
 	current_wisps += new_wisp
@@ -181,6 +201,18 @@
 	animate(wisp_to_remove, alpha = 0, time = 0.2 SECONDS)
 	QDEL_IN(wisp_to_remove, 0.2 SECONDS)
 
+/obj/item/cain_and_abel/proc/check_wield(mob/living/user)
+	if (!istype(user))
+		return TRUE
+	var/active_item = (src == user.get_active_held_item())
+	var/obj/item/other_held = active_item ? user.get_inactive_held_item() : user.get_active_held_item()
+	if (!isnull(other_held))
+		return FALSE
+	var/obj/item/bodypart/hand = active_item ? user.get_inactive_hand() : user.get_active_hand()
+	if (!hand || hand.bodypart_disabled)
+		return FALSE
+	return TRUE
+
 /// Frame data for cain & abel wisps so we don't have to make list monstrocities
 /datum/abel_wisp_frame
 	var/x = 0

code/modules/mining/lavaland/cain_and_abel/dagger_abilities.dm

@@ -10,12 +10,16 @@
 
 /datum/action/cooldown/dagger_swing/Activate(atom/target_atom)
 	var/mob/living/living_owner = owner
-	var/obj/item/cain_and_abel = target
+	var/obj/item/cain_and_abel/cain_and_abel = target
 
 	if(!living_owner.is_holding(cain_and_abel))
 		owner.balloon_alert(owner, "must be held")
 		return FALSE
 
+	if(!cain_and_abel.check_wield(owner))
+		owner.balloon_alert(owner, "offhand busy!")
+		return TRUE
+
 	living_owner.apply_status_effect(/datum/status_effect/dagger_swinging)
 
 	var/static/list/possible_sounds = list(

code/modules/mining/lavaland/cain_and_abel/dagger_throw.dm

@@ -11,6 +11,10 @@
 		user.balloon_alert(user, "unable!")
 		return
 
+	if(!check_wield(user))
+		user.balloon_alert(user, "offhand busy!")
+		return
+
 	if(get_dist(target, user) > 9)
 		user.balloon_alert(user, "too far away!")
 		return
@@ -52,7 +56,8 @@
 	set_dagger_icon(thrown = FALSE)
 
 /obj/item/cain_and_abel/proc/set_dagger_icon(thrown = FALSE)
-	inhand_icon_state = "[src::inhand_icon_state][thrown ? "_thrown" : ""]"
+	dagger_thrown = thrown
+	update_dagger_icon()
 	update_inhand_icon()
 
 /obj/item/cain_and_abel/proc/reset_dagger_icon(datum/source)