[MIRROR] Cuts the number of apply_damage copypaste procs from 3(.5) to 1, fixing a few bugs along the way [MDB IGNORE] (#24619)

* Cuts the number of `apply_damage` copypaste procs from 3(.5) to 1, fixing a few bugs along the way

* Update _species.dm

* Update damage_procs.dm

* Modular adjustments

* Update mutant_species.dm

* Update mutant_species.dm

---------

Co-authored-by: MrMelbert <51863163+MrMelbert@users.noreply.github.com>
Co-authored-by: Bloop <13398309+vinylspiders@users.noreply.github.com>

code/__DEFINES/dcs/signals/signals_mob/signals_mob_main.dm

@@ -90,11 +90,16 @@
 ///from base of mob/set_invis_see(): (new_invis, old_invis)
 #define COMSIG_MOB_SEE_INVIS_CHANGE "mob_see_invis_change"
 
-
-///from base of /mob/living/proc/apply_damage(): (damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
+/// from /mob/living/proc/apply_damage(): (list/damage_mods, damage, damagetype, def_zone, sharpness, attack_direction, attacking_item)
+/// allows you to add multiplicative damage modifiers to the damage mods argument to adjust incoming damage
+/// not sent if the apply damage call was forced
+#define COMSIG_MOB_APPLY_DAMAGE_MODIFIERS "mob_apply_damage_modifiers"
+/// from base of /mob/living/proc/apply_damage(): (damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
 #define COMSIG_MOB_APPLY_DAMAGE "mob_apply_damage"
-///from /mob/living/proc/apply_damage(), works like above but after the damage is actually inflicted: (damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
+/// from /mob/living/proc/apply_damage(): (damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
+/// works like above but after the damage is actually inflicted
 #define COMSIG_MOB_AFTER_APPLY_DAMAGE "mob_after_apply_damage"
+
 ///from base of /mob/living/attack_alien(): (user)
 #define COMSIG_MOB_ATTACK_ALIEN "mob_attack_alien"
 ///from base of /mob/throw_item(): (atom/target)

code/datums/components/explodable.dm

@@ -91,13 +91,16 @@
 		detonate()
 
 ///Called when you attack a specific body part of the thing this is equipped on. Useful for exploding pants.
-/datum/component/explodable/proc/explodable_attack_zone(datum/source, damage, damagetype, def_zone)
+/datum/component/explodable/proc/explodable_attack_zone(datum/source, damage, damagetype, def_zone, ...)
 	SIGNAL_HANDLER
 
 	if(!def_zone)
 		return
 	if(damagetype != BURN) //Don't bother if it's not fire.
 		return
+	if(isbodypart(def_zone))
+		var/obj/item/bodypart/hitting = def_zone
+		def_zone = hitting.body_zone
 	if(!is_hitting_zone(def_zone)) //You didn't hit us! ha!
 		return
 	detonate()

code/datums/components/gunpoint.dm

@@ -172,25 +172,27 @@
 	qdel(src)
 
 ///If the shooter is hit by an attack, they have a 50% chance to flinch and fire. If it hit the arm holding the trigger, it's an 80% chance to fire instead
-/datum/component/gunpoint/proc/flinch(attacker, damage, damagetype, def_zone)
+/datum/component/gunpoint/proc/flinch(mob/living/source, damage_amount, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
 	SIGNAL_HANDLER
 
-	var/mob/living/shooter = parent
-	if(attacker == shooter)
-		return // somehow this wasn't checked for months but no one tried punching themselves to initiate the shot, amazing
+	if(!attack_direction) // No fliching from yourself
+		return
 
 	var/flinch_chance = 50
-	var/gun_hand = LEFT_HANDS
+	var/gun_hand = (source.get_held_index_of_item(weapon) % 2) ? BODY_ZONE_L_ARM : BODY_ZONE_R_ARM
 
-	if(shooter.held_items[RIGHT_HANDS] == weapon)
-		gun_hand = RIGHT_HANDS
+	if(isbodypart(def_zone))
+		var/obj/item/bodypart/hitting = def_zone
+		def_zone = hitting.body_zone
 
-	if((def_zone == BODY_ZONE_L_ARM && gun_hand == LEFT_HANDS) || (def_zone == BODY_ZONE_R_ARM && gun_hand == RIGHT_HANDS))
+	if(def_zone == gun_hand)
 		flinch_chance = 80
 
 	if(prob(flinch_chance))
-		shooter.visible_message(span_danger("[shooter] flinches!"), \
-			span_danger("You flinch!"))
+		source.visible_message(
+			span_danger("[source] flinches!"),
+			span_danger("You flinch!"),
+		)
 		INVOKE_ASYNC(src, PROC_REF(trigger_reaction))
 
 #undef GUNPOINT_DELAY_STAGE_2

code/datums/components/pinata.dm

@@ -33,7 +33,7 @@
 			return
 	return COMPONENT_INCOMPATIBLE
 
-/datum/component/pinata/proc/damage_inflicted(obj/target, damage, damage_type)
+/datum/component/pinata/proc/damage_inflicted(obj/target, damage, damage_type, ...)
 	SIGNAL_HANDLER
 	if(damage < minimum_damage || damage_type == STAMINA || damage_type == OXY)
 		return

code/datums/components/regenerator.dm

@@ -66,7 +66,7 @@
 		deltimer(regeneration_start_timer)
 
 /// When you take damage, reset the cooldown and start processing
-/datum/component/regenerator/proc/on_take_damage(datum/source, damage, damagetype)
+/datum/component/regenerator/proc/on_take_damage(datum/source, damage, damagetype, ...)
 	SIGNAL_HANDLER
 
 	if (damagetype in ignore_damage_types)

code/datums/components/style/style.dm

@@ -456,7 +456,7 @@
 
 
 // Negative effects
-/datum/component/style/proc/on_take_damage()
+/datum/component/style/proc/on_take_damage(...)
 	SIGNAL_HANDLER
 
 	point_multiplier = round(max(point_multiplier - 0.3, 1), 0.1)

code/datums/quirks/negative_quirks/glass_jaw.dm

@@ -34,14 +34,16 @@
 
 /datum/quirk/glass_jaw/proc/punch_out(mob/living/carbon/source, damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
 	SIGNAL_HANDLER
-	if((damagetype != BRUTE) || (def_zone != BODY_ZONE_HEAD))
+
+	if(isbodypart(def_zone))
+		var/obj/item/bodypart/hitting = def_zone
+		def_zone = hitting.body_zone
+	if(damagetype != BRUTE || def_zone != BODY_ZONE_HEAD)
 		return
-	var/actual_damage = damage - (damage * blocked/100)
-	//only roll for knockouts at 5 damage or more
-	if(actual_damage < 5)
+	if(damage < 5)
 		return
 	//blunt items are more likely to knock out, but sharp ones are still capable of doing it
-	if(prob(CEILING(actual_damage * (sharpness & (SHARP_EDGED|SHARP_POINTY) ? 0.65 : 1), 1)))
+	if(prob(CEILING(damage * (sharpness & (SHARP_EDGED|SHARP_POINTY) ? 0.65 : 1), 1)))
 		//don't display the message if little mac is already KO'd
 		if(!source.IsUnconscious())
 			source.visible_message(

code/game/machinery/dna_infuser/organ_sets/roach_organs.dm

@@ -56,11 +56,11 @@
 	greyscale_config = /datum/greyscale_config/mutant_organ
 	greyscale_colors = ROACH_COLORS
 
-	/// Timer ID for resetting the damage resistance applied from attacks from behind
-	var/defense_timerid
 	/// Bodypart overlay applied to the chest the heart is in
 	var/datum/bodypart_overlay/simple/roach_shell/roach_shell
 
+	COOLDOWN_DECLARE(harden_effect_cd)
+
 /obj/item/organ/internal/heart/roach/Initialize(mapload)
 	. = ..()
 	AddElement(/datum/element/noticable_organ, "has hardened, somewhat translucent skin.")
@@ -78,7 +78,8 @@
 
 	var/mob/living/carbon/human/human_owner = organ_owner
 
-	RegisterSignal(human_owner, COMSIG_MOB_APPLY_DAMAGE, PROC_REF(modify_damage))
+	RegisterSignal(human_owner, COMSIG_MOB_APPLY_DAMAGE_MODIFIERS, PROC_REF(modify_damage))
+	RegisterSignal(human_owner, COMSIG_MOB_AFTER_APPLY_DAMAGE, PROC_REF(do_block_effect))
 	human_owner.physiology.knockdown_mod *= 3
 
 	var/obj/item/bodypart/chest/chest = human_owner.get_bodypart(BODY_ZONE_CHEST)
@@ -92,50 +93,55 @@
 
 	var/mob/living/carbon/human/human_owner = organ_owner
 
-	UnregisterSignal(human_owner, COMSIG_MOB_APPLY_DAMAGE)
+	UnregisterSignal(human_owner, list(COMSIG_MOB_APPLY_DAMAGE_MODIFIERS, COMSIG_MOB_AFTER_APPLY_DAMAGE))
 	human_owner.physiology.knockdown_mod /= 3
 
-	if(defense_timerid)
-		reset_damage(human_owner)
-
 	var/obj/item/bodypart/chest/chest = human_owner.get_bodypart(BODY_ZONE_CHEST)
 	chest.remove_bodypart_overlay(roach_shell)
 	human_owner.update_body_parts()
 
 /**
- * Signal proc for [COMSIG_MOB_APPLY_DAMAGE]
+ * Signal proc for [COMSIG_MOB_APPLY_DAMAGE_MODIFIERS]
  *
- * Being hit with brute damage in the back will impart a large damage resistance bonus for a very short period.
+ * Adds a 0.5 modifier to attacks from the back
  */
-/obj/item/organ/internal/heart/roach/proc/modify_damage(datum/source, damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, obj/item/attacking_item)
+/obj/item/organ/internal/heart/roach/proc/modify_damage(mob/living/carbon/human/source, list/damage_mods, damage_amount, damagetype, def_zone, sharpness, attack_direction, obj/item/attacking_item)
 	SIGNAL_HANDLER
 
-	if(!ishuman(owner) || !attack_direction || damagetype != BRUTE || owner.stat >= UNCONSCIOUS)
+	if(!is_blocking(source, damage_amount, damagetype, attack_direction))
 		return
 
-	var/mob/living/carbon/human/human_owner = owner
+	damage_mods += 0.5
+
+/**
+ * Signal proc for [COMSIG_MOB_AFTER_APPLY_DAMAGE]
+ *
+ * Does a special effect if we blocked damage with our back
+ */
+/obj/item/organ/internal/heart/roach/proc/do_block_effect(mob/living/carbon/human/source, damage_dealt, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, obj/item/attacking_item)
+	SIGNAL_HANDLER
+
+	if(!is_blocking(source, damage_dealt, damagetype, attack_direction))
+		return
+
+	if(COOLDOWN_FINISHED(src, harden_effect_cd))
+		source.visible_message(span_warning("[source]'s back hardens against the blow!"))
+		playsound(source, 'sound/effects/constructform.ogg', 25, vary = TRUE, extrarange = SHORT_RANGE_SOUND_EXTRARANGE)
+
+	COOLDOWN_START(src, harden_effect_cd, 5 SECONDS) // Cooldown resets EVERY time we get hit
+
+/// Checks if the passed mob is in a valid state to be blocking damage with the roach shell
+/obj/item/organ/internal/heart/roach/proc/is_blocking(mob/living/carbon/human/blocker, damage_amount, damagetype, attack_direction)
+	if(damage_amount < 5 || damagetype != BRUTE || !attack_direction)
+		return
+	if(!ishuman(blocker) || blocker.stat >= UNCONSCIOUS)
+		return FALSE
 	// No tactical spinning
-	if(human_owner.flags_1 & IS_SPINNING_1)
-		return
-
-	// If we're lying down, or were attacked from the back, we get armor.
-	var/should_armor_up = (human_owner.body_position == LYING_DOWN) || (human_owner.dir & attack_direction)
-	if(!should_armor_up)
-		return
-
-	// Take 50% less damage from attack behind us
-	if(!defense_timerid)
-		human_owner.physiology.brute_mod /= 2
-		human_owner.visible_message(span_warning("[human_owner]'s back hardens against the blow!"))
-		playsound(human_owner, 'sound/effects/constructform.ogg', 25, vary = TRUE, extrarange = SHORT_RANGE_SOUND_EXTRARANGE)
-
-	defense_timerid = addtimer(CALLBACK(src, PROC_REF(reset_damage), owner), 5 SECONDS, TIMER_UNIQUE|TIMER_OVERRIDE)
-
-/obj/item/organ/internal/heart/roach/proc/reset_damage(mob/living/carbon/human/human_owner)
-	defense_timerid = null
-	if(!QDELETED(human_owner))
-		human_owner.physiology.brute_mod *= 2
-		human_owner.visible_message(span_warning("[human_owner]'s back softens again."))
+	if(blocker.flags_1 & IS_SPINNING_1)
+		return FALSE
+	if(blocker.body_position == LYING_DOWN || (blocker.dir & attack_direction))
+		return TRUE
+	return FALSE
 
 // Simple overlay so we can add a roach shell to guys with roach hearts
 /datum/bodypart_overlay/simple/roach_shell

code/game/objects/items/grenades/flashbang.dm

@@ -112,7 +112,7 @@
 		living_mob.Paralyze(20)
 		living_mob.Knockdown(200)
 		living_mob.soundbang_act(1, 200, 10, 15)
-		if(living_mob.apply_damages(10, 10))
+		if(living_mob.apply_damages(brute = 10, burn = 10))
 			to_chat(living_mob, span_userdanger("The blast from \the [src] bruises and burns you!"))
 
 	// only checking if they're on top of the tile, cause being one tile over will be its own punishment

code/game/objects/items/stacks/golem_food/golem_status_effects.dm

@@ -190,7 +190,7 @@
 	return ..()
 
 /// When we take fire damage (or... technically also cold damage, we don't differentiate), zap a nearby APC
-/datum/status_effect/golem/plasma/proc/on_burned(datum/source, damage, damagetype)
+/datum/status_effect/golem/plasma/proc/on_burned(datum/source, damage, damagetype, ...)
 	SIGNAL_HANDLER
 	if(damagetype != BURN)
 		return

code/modules/antagonists/heretic/magic/shadow_cloak.dm

@@ -190,7 +190,7 @@
 		qdel(src)
 
 /// Signal proc for [COMSIG_MOB_APPLY_DAMAGE], being damaged past a threshold will roll a chance to stop the effect
-/datum/status_effect/shadow_cloak/proc/on_damaged(datum/source, damage, damagetype)
+/datum/status_effect/shadow_cloak/proc/on_damaged(datum/source, damage, damagetype, ...)
 	SIGNAL_HANDLER
 
 	// Stam damage is generally bursty, so we'll half it

code/modules/bitrunning/components/avatar_connection.dm

@@ -108,7 +108,7 @@
 	)
 
 /// Transfers damage from the avatar to the old_body
-/datum/component/avatar_connection/proc/on_linked_damage(datum/source, damage, damage_type, def_zone, blocked, forced)
+/datum/component/avatar_connection/proc/on_linked_damage(datum/source, damage, damage_type, def_zone, blocked, ...)
 	SIGNAL_HANDLER
 
 	var/mob/living/carbon/old_body = old_body_ref?.resolve()
@@ -123,7 +123,7 @@
 	if(damage > 30 && prob(30))
 		INVOKE_ASYNC(old_body, TYPE_PROC_REF(/mob/living, emote), "scream")
 
-	old_body.apply_damage(damage, damage_type, def_zone, blocked, forced, wound_bonus = CANT_WOUND)
+	old_body.apply_damage(damage, damage_type, def_zone, blocked, wound_bonus = CANT_WOUND)
 
 	if(old_body.stat > SOFT_CRIT) // KO!
 		full_avatar_disconnect(forced = TRUE)

code/modules/bitrunning/server/util.dm

@@ -58,10 +58,10 @@
 			"health" = creature.health,
 			"name" = creature.name,
 			"pilot" = pilot,
-			"brute" = creature.get_current_damage_of_type(BRUTE),
-			"burn" = creature.get_current_damage_of_type(BURN),
-			"tox" = creature.get_current_damage_of_type(TOX),
-			"oxy" = creature.get_current_damage_of_type(OXY),
+			"brute" = creature.getBruteLoss(),
+			"burn" = creature.getFireLoss(),
+			"tox" = creature.getToxLoss(),
+			"oxy" = creature.getOxyLoss(),
 		))
 
 	return hosted_avatars

code/modules/mining/equipment/monster_organs/brimdust_sac.dm

@@ -141,7 +141,7 @@
 	return COMPONENT_CLEANED
 
 /// When you take brute damage, schedule an explosion
-/datum/status_effect/stacking/brimdust_coating/proc/on_take_damage(datum/source, damage, damagetype)
+/datum/status_effect/stacking/brimdust_coating/proc/on_take_damage(datum/source, damage, damagetype, ...)
 	SIGNAL_HANDLER
 	if(damagetype != BRUTE)
 		return

code/modules/mob/living/basic/lavaland/goliath/goliath.dm

@@ -102,9 +102,7 @@
 // Goliaths can summon tentacles more frequently as they take damage, scary.
 /mob/living/basic/mining/goliath/apply_damage(damage, damagetype, def_zone, blocked, forced, spread_damage, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
 	. = ..()
-	if (!.)
-		return
-	if (damage <= 0)
+	if (. <= 0)
 		return
 	if (tentacles.cooldown_time > 1 SECONDS)
 		tentacles.cooldown_time -= 1 SECONDS

code/modules/mob/living/carbon/damage_procs.dm

@@ -1,44 +1,79 @@
-/mob/living/carbon/apply_damage(damage, damagetype = BRUTE, def_zone = null, blocked = 0, forced = FALSE, spread_damage = FALSE, wound_bonus = 0, bare_wound_bonus = 0, sharpness = NONE, attack_direction = null, attacking_item)
-	SEND_SIGNAL(src, COMSIG_MOB_APPLY_DAMAGE, damage, damagetype, def_zone)
-	var/hit_percent = (100-blocked)/100
-	if(!damage || (!forced && hit_percent <= 0))
-		return 0
+/mob/living/carbon/apply_damage(
+	damage = 0,
+	damagetype = BRUTE,
+	def_zone = null,
+	blocked = 0,
+	forced = FALSE,
+	spread_damage = FALSE,
+	wound_bonus = 0,
+	bare_wound_bonus = 0,
+	sharpness = NONE,
+	attack_direction = null,
+	attacking_item,
+)
+	// Spread damage should always have def zone be null
+	if(spread_damage)
+		def_zone = null
 
-	var/obj/item/bodypart/BP = null
-	if(!spread_damage)
-		if(isbodypart(def_zone)) //we specified a bodypart object
-			BP = def_zone
-		else
-			if(!def_zone)
-				def_zone = get_random_valid_zone(def_zone)
-			BP = get_bodypart(check_zone(def_zone))
-			if(!BP)
-				BP = bodyparts[1]
+	// Otherwise if def zone is null, we'll get a random bodypart / zone to hit.
+	// ALso we'll automatically covnert string def zones into bodyparts to pass into parent call.
+	else if(!isbodypart(def_zone))
+		var/random_zone = check_zone(def_zone || get_random_valid_zone(def_zone))
+		def_zone = get_bodypart(random_zone) || bodyparts[1]
+
+	. = ..()
+	// Taking brute or burn to bodyparts gives a damage flash
+	if(def_zone && (damagetype == BRUTE || damagetype == BURN))
+		damageoverlaytemp += .
+
+	return .
+
+/mob/living/carbon/human/apply_damage(
+	damage = 0,
+	damagetype = BRUTE,
+	def_zone = null,
+	blocked = 0,
+	forced = FALSE,
+	spread_damage = FALSE,
+	wound_bonus = 0,
+	bare_wound_bonus = 0,
+	sharpness = NONE,
+	attack_direction = null,
+	attacking_item,
+)
+
+	// Add relevant DR modifiers into blocked value to pass to parent
+	blocked += physiology?.damage_resistance
+	blocked += dna?.species?.damage_modifier
+	return ..()
+
+/mob/living/carbon/human/get_incoming_damage_modifier(
+	damage = 0,
+	damagetype = BRUTE,
+	def_zone = null,
+	sharpness = NONE,
+	attack_direction = null,
+	attacking_item,
+)
+	var/final_mod = ..()
 
-	var/damage_amount = forced ? damage : damage * hit_percent
 	switch(damagetype)
 		if(BRUTE)
-			if(BP)
-				if(BP.receive_damage(damage_amount, 0, wound_bonus = wound_bonus, bare_wound_bonus = bare_wound_bonus, sharpness = sharpness, attack_direction = attack_direction))
-					update_damage_overlays()
-			else //no bodypart, we deal damage with a more general method.
-				adjustBruteLoss(damage_amount, forced = forced)
+			final_mod *= physiology.brute_mod
 		if(BURN)
-			if(BP)
-				if(BP.receive_damage(0, damage_amount, wound_bonus = wound_bonus, bare_wound_bonus = bare_wound_bonus, sharpness = sharpness, attack_direction = attack_direction))
-					update_damage_overlays()
-			else
-				adjustFireLoss(damage_amount, forced = forced)
+			final_mod *= physiology.burn_mod
 		if(TOX)
-			adjustToxLoss(damage_amount, forced = forced)
+			final_mod *= physiology.tox_mod
 		if(OXY)
-			adjustOxyLoss(damage_amount, forced = forced)
+			final_mod *= physiology.oxy_mod
 		if(CLONE)
-			adjustCloneLoss(damage_amount, forced = forced)
+			final_mod *= physiology.clone_mod
 		if(STAMINA)
-			adjustStaminaLoss(damage_amount, forced = forced)
-	SEND_SIGNAL(src, COMSIG_MOB_AFTER_APPLY_DAMAGE, damage, damagetype, def_zone)
-	return TRUE
+			final_mod *= physiology.stamina_mod
+		if(BRAIN)
+			final_mod *= physiology.brain_mod
+
+	return final_mod
 
 //These procs fetch a cumulative total damage from all bodyparts
 /mob/living/carbon/getBruteLoss()

code/modules/mob/living/carbon/human/_species.dm

@@ -104,10 +104,8 @@ GLOBAL_LIST_EMPTY(features_by_species)
 	///Replaces default appendix with a different organ.
 	var/obj/item/organ/internal/appendix/mutantappendix = /obj/item/organ/internal/appendix
 
-	/**
-	 * Percentage modifier for overall defense of the race, or less defense, if it's negative
-	 * THIS MODIFIES ALL DAMAGE TYPES.
-	 **/
+	/// Flat modifier on all damage taken via [apply_damage][/mob/living/proc/apply_damage] (so being punched, shot, etc.)
+	/// IE: 10 = 10% less damage taken.
 	var/damage_modifier = 0
 	///multiplier for damage from cold temperature
 	var/coldmod = 1
@@ -1072,9 +1070,6 @@ GLOBAL_LIST_EMPTY(features_by_species)
 		affected.log_message("has started overdosing on [chem.name] at [chem.volume] units.", LOG_GAME)
 	return SEND_SIGNAL(affected, COMSIG_SPECIES_HANDLE_CHEMICAL, chem, seconds_per_tick, times_fired)
 
-/datum/species/proc/check_species_weakness(obj/item, mob/living/attacker)
-	return 1 //This is not a boolean, it's the multiplier for the damage that the user takes from the item. The force of the item is multiplied by this value
-
 /**
  * Equip the outfit required for life. Replaces items currently worn.
  */
@@ -1306,30 +1301,36 @@ GLOBAL_LIST_EMPTY(features_by_species)
 						span_userdanger("You block [weapon]!"))
 		return FALSE
 
-	var/hit_area
-	if(!affecting) //Something went wrong. Maybe the limb is missing?
-		affecting = human.bodyparts[1]
-
-	hit_area = affecting.plaintext_zone
-	var/def_zone = affecting.body_zone
-
-	var/armor_block = human.run_armor_check(affecting, MELEE, span_notice("Your armor has protected your [hit_area]!"), span_warning("Your armor has softened a hit to your [hit_area]!"),weapon.armour_penetration, weak_against_armour = weapon.weak_against_armour)
-	armor_block = min(ARMOR_MAX_BLOCK, armor_block) //cap damage reduction at 90%
-	var/Iwound_bonus = weapon.wound_bonus
+	affecting ||= human.bodyparts[1] //Something went wrong. Maybe the limb is missing?
+	var/hit_area = affecting.plaintext_zone
+	var/armor_block = min(human.run_armor_check(
+		def_zone = affecting,
+		attack_flag = MELEE,
+		absorb_text = span_notice("Your armor has protected your [hit_area]!"),
+		soften_text = span_warning("Your armor has softened a hit to your [hit_area]!"),
+		armour_penetration = weapon.armour_penetration,
+		weak_against_armour = weapon.weak_against_armour,
+	), ARMOR_MAX_BLOCK) //cap damage reduction at 90%
 
+	var/modified_wound_bonus = weapon.wound_bonus
 	// this way, you can't wound with a surgical tool on help intent if they have a surgery active and are lying down, so a misclick with a circular saw on the wrong limb doesn't bleed them dry (they still get hit tho)
 	if((weapon.item_flags & SURGICAL_TOOL) && !user.combat_mode && human.body_position == LYING_DOWN && (LAZYLEN(human.surgeries) > 0))
-		Iwound_bonus = CANT_WOUND
-
-	var/weakness = check_species_weakness(weapon, user)
+		modified_wound_bonus = CANT_WOUND
 
 	human.send_item_attack_message(weapon, user, hit_area, affecting)
+	var/damage_dealt = human.apply_damage(
+		damage = weapon.force,
+		damagetype = weapon.damtype,
+		def_zone = affecting,
+		blocked = armor_block,
+		wound_bonus = modified_wound_bonus,
+		bare_wound_bonus = weapon.bare_wound_bonus,
+		sharpness = weapon.get_sharpness(),
+		attack_direction = get_dir(user, human),
+		attacking_item = weapon,
+	)
 
-
-	var/attack_direction = get_dir(user, human)
-	apply_damage(weapon.force * weakness, weapon.damtype, def_zone, armor_block, human, wound_bonus = Iwound_bonus, bare_wound_bonus = weapon.bare_wound_bonus, sharpness = weapon.get_sharpness(), attack_direction = attack_direction, attacking_item = weapon)
-
-	if(!weapon.force)
+	if(damage_dealt <= 0)
 		return FALSE //item force is zero
 	var/bloody = FALSE
 	if(weapon.damtype != BRUTE)
@@ -1399,61 +1400,6 @@ GLOBAL_LIST_EMPTY(features_by_species)
 
 	return TRUE
 
-/datum/species/proc/apply_damage(damage, damagetype = BRUTE, def_zone = null, blocked, mob/living/carbon/human/H, forced = FALSE, spread_damage = FALSE, wound_bonus = 0, bare_wound_bonus = 0, sharpness = NONE, attack_direction = null, attacking_item)
-	SEND_SIGNAL(H, COMSIG_MOB_APPLY_DAMAGE, damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
-	var/hit_percent = (100-(damage_modifier+blocked))/100
-	hit_percent = (hit_percent * (100-H.physiology.damage_resistance))/100
-	if(!damage || (!forced && hit_percent <= 0))
-		return 0
-
-	var/obj/item/bodypart/BP = null
-	if(!spread_damage)
-		if(isbodypart(def_zone))
-			BP = def_zone
-		else
-			if(!def_zone)
-				def_zone = H.get_random_valid_zone(def_zone)
-			BP = H.get_bodypart(check_zone(def_zone))
-			if(!BP)
-				BP = H.bodyparts[1]
-
-	switch(damagetype)
-		if(BRUTE)
-			H.damageoverlaytemp = 20
-			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.brute_mod
-			if(BP)
-				if(BP.receive_damage(damage_amount, 0, forced = forced, wound_bonus = wound_bonus, bare_wound_bonus = bare_wound_bonus, sharpness = sharpness, attack_direction = attack_direction, damage_source = attacking_item))
-					H.update_damage_overlays()
-			else//no bodypart, we deal damage with a more general method.
-				H.adjustBruteLoss(damage_amount, forced = forced)
-			INVOKE_ASYNC(H, TYPE_PROC_REF(/mob/living/carbon/human, adjust_pain), damage_amount) // SKYRAT EDIT ADDITION - ERP Pain
-		if(BURN)
-			H.damageoverlaytemp = 20
-			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.burn_mod
-			if(BP)
-				if(BP.receive_damage(0, damage_amount, forced = forced, wound_bonus = wound_bonus, bare_wound_bonus = bare_wound_bonus, sharpness = sharpness, attack_direction = attack_direction, damage_source = attacking_item))
-					H.update_damage_overlays()
-			else
-				H.adjustFireLoss(damage_amount, forced = forced)
-			INVOKE_ASYNC(H, TYPE_PROC_REF(/mob/living/carbon/human, adjust_pain), damage_amount) // SKYRAT EDIT ADDITION - ERP Pain
-		if(TOX)
-			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.tox_mod
-			H.adjustToxLoss(damage_amount, forced = forced)
-		if(OXY)
-			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.oxy_mod
-			H.adjustOxyLoss(damage_amount, forced = forced)
-		if(CLONE)
-			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.clone_mod
-			H.adjustCloneLoss(damage_amount, forced = forced)
-		if(STAMINA)
-			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.stamina_mod
-			H.adjustStaminaLoss(damage_amount, forced = forced)
-		if(BRAIN)
-			var/damage_amount = forced ? damage : damage * hit_percent * H.physiology.brain_mod
-			H.adjustOrganLoss(ORGAN_SLOT_BRAIN, damage_amount)
-	SEND_SIGNAL(H, COMSIG_MOB_AFTER_APPLY_DAMAGE, damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
-	return TRUE
-
 //////////////////////////
 // ENVIRONMENT HANDLERS //
 //////////////////////////
@@ -1741,11 +1687,12 @@ GLOBAL_LIST_EMPTY(features_by_species)
 	switch(adjusted_pressure)
 		// Very high pressure, show an alert and take damage
 		if(HAZARD_HIGH_PRESSURE to INFINITY)
-			if(!HAS_TRAIT(H, TRAIT_RESISTHIGHPRESSURE))
-				H.adjustBruteLoss(min(((adjusted_pressure / HAZARD_HIGH_PRESSURE) - 1) * PRESSURE_DAMAGE_COEFFICIENT, MAX_HIGH_PRESSURE_DAMAGE) * H.physiology.pressure_mod * seconds_per_tick, required_bodytype = BODYTYPE_ORGANIC)
-				H.throw_alert(ALERT_PRESSURE, /atom/movable/screen/alert/highpressure, 2)
-			else
+			if(HAS_TRAIT(H, TRAIT_RESISTHIGHPRESSURE))
 				H.clear_alert(ALERT_PRESSURE)
+			else
+				var/pressure_damage = min(((adjusted_pressure / HAZARD_HIGH_PRESSURE) - 1) * PRESSURE_DAMAGE_COEFFICIENT, MAX_HIGH_PRESSURE_DAMAGE) * H.physiology.pressure_mod * H.physiology.brute_mod * seconds_per_tick
+				H.adjustBruteLoss(pressure_damage, required_bodytype = BODYTYPE_ORGANIC)
+				H.throw_alert(ALERT_PRESSURE, /atom/movable/screen/alert/highpressure, 2)
 
 		// High pressure, show an alert
 		if(WARNING_HIGH_PRESSURE to HAZARD_HIGH_PRESSURE)
@@ -1769,7 +1716,8 @@ GLOBAL_LIST_EMPTY(features_by_species)
 			if(HAS_TRAIT(H, TRAIT_RESISTLOWPRESSURE))
 				H.clear_alert(ALERT_PRESSURE)
 			else
-				H.adjustBruteLoss(LOW_PRESSURE_DAMAGE * H.physiology.pressure_mod * seconds_per_tick, required_bodytype = BODYTYPE_ORGANIC)
+				var/pressure_damage = LOW_PRESSURE_DAMAGE * H.physiology.pressure_mod * H.physiology.brute_mod * seconds_per_tick
+				H.adjustBruteLoss(pressure_damage, required_bodytype = BODYTYPE_ORGANIC)
 				H.throw_alert(ALERT_PRESSURE, /atom/movable/screen/alert/lowpressure, 2)
 
 

code/modules/mob/living/carbon/human/damage_procs.dm

@@ -1,4 +0,0 @@
-
-/// depending on the species, it will run the corresponding apply_damage code there
-/mob/living/carbon/human/apply_damage(damage = 0, damagetype = BRUTE, def_zone = null, blocked = 0, forced = FALSE, spread_damage = FALSE, wound_bonus = 0, bare_wound_bonus = 0, sharpness = NONE, attack_direction = null, attacking_item)
-	return dna.species.apply_damage(damage, damagetype, def_zone, blocked, src, forced, spread_damage, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)

code/modules/mob/living/carbon/human/physiology.dm

@@ -1,18 +1,33 @@
 //Stores several modifiers in a way that isn't cleared by changing species
 /datum/physiology
-	var/brute_mod = 1 // % of brute damage taken from all sources
-	var/burn_mod = 1 // % of burn damage taken from all sources
-	var/tox_mod = 1 // % of toxin damage taken from all sources
-	var/oxy_mod = 1 // % of oxygen damage taken from all sources
-	var/clone_mod = 1 // % of clone damage taken from all sources
-	var/stamina_mod = 1 // % of stamina damage taken from all sources
-	var/brain_mod = 1 // % of brain damage taken from all sources
+	/// Multiplier to brute damage received.
+	/// IE: A brute mod of 0.9 = 10% less brute damage.
+	/// Only applies to damage dealt via [apply_damage][/mob/living/proc/apply_damage] unless factored in manually.
+	var/brute_mod = 1
+	/// Multiplier to burn damage received
+	var/burn_mod = 1
+	/// Multiplier to toxin damage received
+	var/tox_mod = 1
+	/// Multiplier to oxygen damage received
+	var/oxy_mod = 1
+	/// Multiplier to clone damage received
+	var/clone_mod = 1
+	/// Multiplier to stamina damage received
+	var/stamina_mod = 1
+	/// Multiplier to brain damage received
+	var/brain_mod = 1
 
-	var/pressure_mod = 1 // % of brute damage taken from low or high pressure (stacks with brute_mod)
-	var/heat_mod = 1 // % of burn damage taken from heat (stacks with burn_mod)
-	var/cold_mod = 1 // % of burn damage taken from cold (stacks with burn_mod)
+	/// Multiplier to damage taken from high / low pressure exposure, stacking with the brute modifier
+	var/pressure_mod = 1
+	/// Multiplier to damage taken from high temperature exposure, stacking with the burn modifier
+	var/heat_mod = 1
+	/// Multiplier to damage taken from low temperature exposure, stacking with the toxin modifier
+	var/cold_mod = 1
 
-	var/damage_resistance = 0 // %damage reduction from all sources
+	/// Flat damage reduction from taking damage
+	/// Unlike the other modifiers, this is not a multiplier.
+	/// IE: DR of 10 = 10% less damage.
+	var/damage_resistance = 0
 
 	var/siemens_coeff = 1 // resistance to shocks
 

code/modules/mob/living/carbon/human/species_types/flypeople.dm

@@ -32,10 +32,19 @@
 		BODY_ZONE_CHEST = /obj/item/bodypart/chest/fly,
 	)
 
-/datum/species/fly/check_species_weakness(obj/item/weapon, mob/living/attacker)
-	if(istype(weapon, /obj/item/melee/flyswatter))
-		return 30 //Flyswatters deal 30x damage to flypeople.
-	return 1
+/datum/species/fly/on_species_gain(mob/living/carbon/human/human_who_gained_species, datum/species/old_species, pref_load)
+	. = ..()
+	RegisterSignal(human_who_gained_species, COMSIG_MOB_APPLY_DAMAGE_MODIFIERS, PROC_REF(damage_weakness))
+
+/datum/species/fly/on_species_loss(mob/living/carbon/human/C, datum/species/new_species, pref_load)
+	. = ..()
+	UnregisterSignal(C, COMSIG_MOB_APPLY_DAMAGE_MODIFIERS)
+
+/datum/species/fly/proc/damage_weakness(datum/source, list/damage_mods, damage_amount, damagetype, def_zone, sharpness, attack_direction, obj/item/attacking_item)
+	SIGNAL_HANDLER
+
+	if(istype(attacking_item, /obj/item/melee/flyswatter))
+		damage_mods += 30 // Yes, a 30x damage modifier
 
 /datum/species/fly/get_physical_attributes()
 	return "These hideous creatures suffer from pesticide immensely, eat waste, and are incredibly vulnerable to bright lights. They do have wings though."

code/modules/mob/living/carbon/human/species_types/mothmen.dm

@@ -47,10 +47,19 @@
 
 	return randname
 
-/datum/species/moth/check_species_weakness(obj/item/weapon, mob/living/attacker)
-	if(istype(weapon, /obj/item/melee/flyswatter))
-		return 10 //flyswatters deal 10x damage to moths
-	return 1
+/datum/species/moth/on_species_gain(mob/living/carbon/human/human_who_gained_species, datum/species/old_species, pref_load)
+	. = ..()
+	RegisterSignal(human_who_gained_species, COMSIG_MOB_APPLY_DAMAGE_MODIFIERS, PROC_REF(damage_weakness))
+
+/datum/species/moth/on_species_loss(mob/living/carbon/human/C, datum/species/new_species, pref_load)
+	. = ..()
+	UnregisterSignal(C, COMSIG_MOB_APPLY_DAMAGE_MODIFIERS)
+
+/datum/species/moth/proc/damage_weakness(datum/source, list/damage_mods, damage_amount, damagetype, def_zone, sharpness, attack_direction, obj/item/attacking_item)
+	SIGNAL_HANDLER
+
+	if(istype(attacking_item, /obj/item/melee/flyswatter))
+		damage_mods += 10 // Yes, a 10x damage modifier
 
 /datum/species/moth/randomize_features(mob/living/carbon/human/human_mob)
 	human_mob.dna.features["moth_markings"] = pick(GLOB.moth_wings_list)

code/modules/mob/living/carbon/human/species_types/vampire.dm

@@ -40,6 +40,11 @@
 	new_vampire.skin_tone = "albino"
 	new_vampire.update_body(0)
 	new_vampire.set_safe_hunger_level()
+	RegisterSignal(new_vampire, COMSIG_MOB_APPLY_DAMAGE_MODIFIERS, PROC_REF(damage_weakness))
+
+/datum/species/vampire/on_species_loss(mob/living/carbon/human/C, datum/species/new_species, pref_load)
+	. = ..()
+	UnregisterSignal(C, COMSIG_MOB_APPLY_DAMAGE_MODIFIERS)
 
 /datum/species/vampire/spec_life(mob/living/carbon/human/vampire, seconds_per_tick, times_fired)
 	. = ..()
@@ -64,10 +69,11 @@
 		vampire.adjust_fire_stacks(3 * seconds_per_tick)
 		vampire.ignite_mob()
 
-/datum/species/vampire/check_species_weakness(obj/item/weapon, mob/living/attacker)
-	if(istype(weapon, /obj/item/nullrod/whip))
-		return 2 //Whips deal 2x damage to vampires. Vampire killer.
-	return 1
+/datum/species/vampire/proc/damage_weakness(datum/source, list/damage_mods, damage_amount, damagetype, def_zone, sharpness, attack_direction, obj/item/attacking_item)
+	SIGNAL_HANDLER
+
+	if(istype(attacking_item, /obj/item/nullrod/whip))
+		damage_mods += 2
 
 /datum/species/vampire/get_physical_attributes()
 	return "Vampires are afflicted with the Thirst, needing to sate it by draining the blood out of another living creature. However, they do not need to breathe or eat normally. \

code/modules/mob/living/damage_procs.dm

@@ -1,58 +1,149 @@
 
 /**
- * Applies damage to this mob
+ * Applies damage to this mob.
  *
  * Sends [COMSIG_MOB_APPLY_DAMAGE]
  *
  * Arguuments:
- * * damage - amount of damage
- * * damagetype - one of [BRUTE], [BURN], [TOX], [OXY], [CLONE], [STAMINA]
- * * def_zone - zone that is being hit if any
- * * blocked - armor value applied
- * * forced - bypass hit percentage
- * * spread_damage - used in overrides
+ * * damage - Amount of damage
+ * * damagetype - What type of damage to do. one of [BRUTE], [BURN], [TOX], [OXY], [CLONE], [STAMINA], [BRAIN].
+ * * def_zone - What body zone is being hit. Or a reference to what bodypart is being hit.
+ * * blocked - Percent modifier to damage. 100 = 100% less damage dealt, 50% = 50% less damage dealt.
+ * * forced - "Force" exactly the damage dealt. This means it skips damage modifier from blocked.
+ * * spread_damage - For carbons, spreads the damage across all bodyparts rather than just the targeted zone.
+ * * wound_bonus - Bonus modifier for wound chance.
+ * * bare_wound_bonus - Bonus modifier for wound chance on bare skin.
+ * * sharpness - Sharpness of the weapon.
+ * * attack_direction - Direction of the attack from the attacker to [src].
+ * * attacking_item - Item that is attacking [src].
  *
- * Returns TRUE if damage applied
+ * Returns the amount of damage dealt.
  */
-/mob/living/proc/apply_damage(damage = 0, damagetype = BRUTE, def_zone = null, blocked = 0, forced = FALSE, spread_damage = FALSE, wound_bonus = 0, bare_wound_bonus = 0, sharpness = NONE, attack_direction = null, attacking_item)
-	SEND_SIGNAL(src, COMSIG_MOB_APPLY_DAMAGE, damage, damagetype, def_zone)
-	var/hit_percent = (100-blocked)/100
-	if(!damage || (!forced && hit_percent <= 0))
-		return FALSE
-	var/damage_amount = forced ? damage : damage * hit_percent
-	switch(damagetype)
-		if(BRUTE)
-			adjustBruteLoss(damage_amount, forced = forced)
-		if(BURN)
-			adjustFireLoss(damage_amount, forced = forced)
-		if(TOX)
-			adjustToxLoss(damage_amount, forced = forced)
-		if(OXY)
-			adjustOxyLoss(damage_amount, forced = forced)
-		if(CLONE)
-			adjustCloneLoss(damage_amount, forced = forced)
-		if(STAMINA)
-			adjustStaminaLoss(damage_amount, forced = forced)
-	SEND_SIGNAL(src, COMSIG_MOB_AFTER_APPLY_DAMAGE, damage, damagetype, def_zone)
-	return TRUE
+/mob/living/proc/apply_damage(
+	damage = 0,
+	damagetype = BRUTE,
+	def_zone = null,
+	blocked = 0,
+	forced = FALSE,
+	spread_damage = FALSE,
+	wound_bonus = 0,
+	bare_wound_bonus = 0,
+	sharpness = NONE,
+	attack_direction = null,
+	attacking_item,
+)
+	SHOULD_CALL_PARENT(TRUE)
+	var/damage_amount = damage
+	if(!forced)
+		damage_amount *= ((100 - blocked) / 100)
+		damage_amount *= get_incoming_damage_modifier(damage_amount, damagetype, def_zone, sharpness, attack_direction, attacking_item)
+	if(damage_amount <= 0)
+		return 0
 
-///like [apply_damage][/mob/living/proc/apply_damage] except it always uses the damage procs
-/mob/living/proc/apply_damage_type(damage = 0, damagetype = BRUTE)
+	SEND_SIGNAL(src, COMSIG_MOB_APPLY_DAMAGE, damage_amount, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
+
+	var/damage_dealt = 0
 	switch(damagetype)
 		if(BRUTE)
-			return adjustBruteLoss(damage)
+			if(isbodypart(def_zone))
+				var/obj/item/bodypart/actual_hit = def_zone
+				var/delta = actual_hit.get_damage()
+				if(actual_hit.receive_damage(
+					brute = damage_amount,
+					burn = 0,
+					forced = forced,
+					wound_bonus = wound_bonus,
+					bare_wound_bonus = bare_wound_bonus,
+					sharpness = sharpness,
+					attack_direction = attack_direction,
+					damage_source = attacking_item,
+				))
+					update_damage_overlays()
+				damage_dealt = actual_hit.get_damage() - delta // Unfortunately bodypart receive_damage doesn't return damage dealt so we do it manually
+			else
+				damage_dealt = adjustBruteLoss(damage_amount, forced = forced)
+			INVOKE_ASYNC(src, TYPE_PROC_REF(/mob/living, adjust_pain), damage_amount) // SKYRAT EDIT ADDITION - ERP Pain
 		if(BURN)
-			return adjustFireLoss(damage)
+			if(isbodypart(def_zone))
+				var/obj/item/bodypart/actual_hit = def_zone
+				var/delta = actual_hit.get_damage()
+				if(actual_hit.receive_damage(
+					brute = 0,
+					burn = damage_amount,
+					forced = forced,
+					wound_bonus = wound_bonus,
+					bare_wound_bonus = bare_wound_bonus,
+					sharpness = sharpness,
+					attack_direction = attack_direction,
+					damage_source = attacking_item,
+				))
+					update_damage_overlays()
+				damage_dealt = delta - actual_hit.get_damage() // See above
+			else
+				damage_dealt = adjustFireLoss(damage_amount, forced = forced)
+			INVOKE_ASYNC(src, TYPE_PROC_REF(/mob/living, adjust_pain), damage_amount) // SKYRAT EDIT ADDITION - ERP Pain
 		if(TOX)
-			return adjustToxLoss(damage)
+			damage_dealt = adjustToxLoss(damage_amount, forced = forced)
 		if(OXY)
-			return adjustOxyLoss(damage)
+			damage_dealt = adjustOxyLoss(damage_amount, forced = forced)
 		if(CLONE)
-			return adjustCloneLoss(damage)
+			damage_dealt = adjustCloneLoss(damage_amount, forced = forced)
 		if(STAMINA)
-			return adjustStaminaLoss(damage)
+			damage_dealt = adjustStaminaLoss(damage_amount, forced = forced)
+		if(BRAIN)
+			damage_dealt = adjustOrganLoss(ORGAN_SLOT_BRAIN, damage_amount)
+
+	SEND_SIGNAL(src, COMSIG_MOB_AFTER_APPLY_DAMAGE, damage_dealt, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
+	return damage_dealt
+
+/**
+ * Used in tandem with [/mob/living/proc/apply_damage] to calculate modifier applied into incoming damage
+ */
+/mob/living/proc/get_incoming_damage_modifier(
+	damage = 0,
+	damagetype = BRUTE,
+	def_zone = null,
+	sharpness = NONE,
+	attack_direction = null,
+	attacking_item,
+)
+	SHOULD_CALL_PARENT(TRUE)
+	SHOULD_BE_PURE(TRUE)
+
+	var/list/damage_mods = list()
+	SEND_SIGNAL(src, COMSIG_MOB_APPLY_DAMAGE_MODIFIERS, damage_mods, damage, damagetype, def_zone, sharpness, attack_direction, attacking_item)
+
+	var/final_mod = 1
+	for(var/new_mod in damage_mods)
+		final_mod *= new_mod
+	return final_mod
+
+/**
+ * Simply a wrapper for calling mob adjustXLoss() procs to heal a certain damage type,
+ * when you don't know what damage type you're healing exactly.
+ */
+/mob/living/proc/heal_damage_type(heal_amount = 0, damagetype = BRUTE)
+	heal_amount = abs(heal_amount) * -1
+
+	switch(damagetype)
+		if(BRUTE)
+			return adjustBruteLoss(heal_amount)
+		if(BURN)
+			return adjustFireLoss(heal_amount)
+		if(TOX)
+			return adjustToxLoss(heal_amount)
+		if(OXY)
+			return adjustOxyLoss(heal_amount)
+		if(CLONE)
+			return adjustCloneLoss(heal_amount)
+		if(STAMINA)
+			return adjustStaminaLoss(heal_amount)
 
 /// return the damage amount for the type given
+/**
+ * Simply a wrapper for calling mob getXLoss() procs to get a certain damage type,
+ * when you don't know what damage type you're getting exactly.
+ */
 /mob/living/proc/get_current_damage_of_type(damagetype = BRUTE)
 	switch(damagetype)
 		if(BRUTE)
@@ -72,26 +163,34 @@
 /mob/living/proc/get_total_damage(precision = DAMAGE_PRECISION)
 	return round(getBruteLoss() + getFireLoss() + getToxLoss() + getOxyLoss() + getCloneLoss(), precision)
 
-/// applies multiple damages at once via [/mob/living/proc/apply_damage]
-/mob/living/proc/apply_damages(brute = 0, burn = 0, tox = 0, oxy = 0, clone = 0, def_zone = null, blocked = FALSE, stamina = 0, brain = 0)
-	if(blocked >= 100)
-		return 0
+/// Applies multiple damages at once via [apply_damage][/mob/living/proc/apply_damage]
+/mob/living/proc/apply_damages(
+	brute = 0,
+	burn = 0,
+	tox = 0,
+	oxy = 0,
+	clone = 0,
+	def_zone = null,
+	blocked = 0,
+	stamina = 0,
+	brain = 0,
+)
+	var/total_damage = 0
 	if(brute)
-		apply_damage(brute, BRUTE, def_zone, blocked)
+		total_damage += apply_damage(brute, BRUTE, def_zone, blocked)
 	if(burn)
-		apply_damage(burn, BURN, def_zone, blocked)
+		total_damage += apply_damage(burn, BURN, def_zone, blocked)
 	if(tox)
-		apply_damage(tox, TOX, def_zone, blocked)
+		total_damage += apply_damage(tox, TOX, def_zone, blocked)
 	if(oxy)
-		apply_damage(oxy, OXY, def_zone, blocked)
+		total_damage += apply_damage(oxy, OXY, def_zone, blocked)
 	if(clone)
-		apply_damage(clone, CLONE, def_zone, blocked)
+		total_damage += apply_damage(clone, CLONE, def_zone, blocked)
 	if(stamina)
-		apply_damage(stamina, STAMINA, def_zone, blocked)
+		total_damage += apply_damage(stamina, STAMINA, def_zone, blocked)
 	if(brain)
-		apply_damage(brain, BRAIN, def_zone, blocked)
-	return 1
-
+		total_damage += apply_damage(brain, BRAIN, def_zone, blocked)
+	return total_damage
 
 /// applies various common status effects or common hardcoded mob effects
 /mob/living/proc/apply_effect(effect = 0,effecttype = EFFECT_STUN, blocked = 0)
@@ -432,11 +531,11 @@
 
 ///heal up to amount damage, in a given order
 /mob/living/proc/heal_ordered_damage(amount, list/damage_types)
-	. = FALSE //we'll return the amount of damage healed
+	. = 0 //we'll return the amount of damage healed
 	for(var/damagetype in damage_types)
 		var/amount_to_heal = min(abs(amount), get_current_damage_of_type(damagetype)) //heal only up to the amount of damage we have
 		if(amount_to_heal)
-			. += apply_damage_type(-amount_to_heal, damagetype)
+			. += heal_damage_type(amount_to_heal, damagetype)
 			amount -= amount_to_heal //remove what we healed from our current amount
 		if(!amount)
 			break

code/modules/mob/living/silicon/damage_procs.dm

@@ -1,17 +1,3 @@
-
-/mob/living/silicon/apply_damage(damage = 0, damagetype = BRUTE, def_zone = null, blocked = 0, forced = FALSE, spread_damage = FALSE, wound_bonus = 0, bare_wound_bonus = 0, sharpness = NONE, attack_direction = null, attacking_item)
-	var/hit_percent = (100-blocked)/100
-	if((!damage || (!forced && hit_percent <= 0)))
-		return 0
-	var/damage_amount = forced ? damage : damage * hit_percent
-	switch(damagetype)
-		if(BRUTE)
-			adjustBruteLoss(damage_amount, forced = forced)
-		if(BURN)
-			adjustFireLoss(damage_amount, forced = forced)
-	return 1
-
-
 /mob/living/silicon/apply_effect(effect = 0,effecttype = EFFECT_STUN, blocked = FALSE)
 	return FALSE //The only effect that can hit them atm is flashes and they still directly edit so this works for now. (This was written in at least 2016. Help)
 

code/modules/mob/living/simple_animal/bot/medbot.dm

@@ -658,10 +658,10 @@
 						healies *= 1.1
 					if(bot_cover_flags & BOT_COVER_EMAGGED)
 						patient.reagents.add_reagent(/datum/reagent/toxin/chloralhydrate, 5)
-						patient.apply_damage_type((healies*1),treatment_method)
+						patient.apply_damage((healies * 1), treatment_method, spread_damage = TRUE)
 						log_combat(src, patient, "pretended to tend wounds on", "internal tools", "([uppertext(treatment_method)]) (EMAGGED)")
 					else
-						patient.apply_damage_type((healies*-1),treatment_method) //don't need to check treatment_method since we know by this point that they were actually damaged.
+						patient.heal_damage_type((healies * 1), treatment_method) //don't need to check treatment_method since we know by this point that they were actually damaged.
 						log_combat(src, patient, "tended the wounds of", "internal tools", "([uppertext(treatment_method)])")
 					C.visible_message(span_notice("[src] tends the wounds of [patient]!"), \
 						"<span class='infoplain'>[span_green("[src] tends your wounds!")]</span>")

code/modules/research/xenobiology/crossbreeding/_status_effects.dm

@@ -995,7 +995,7 @@
 		healing_types += CLONE
 
 	if(length(healing_types))
-		owner.apply_damage_type(-heal_amount, damagetype = pick(healing_types))
+		owner.heal_damage_type(heal_amount, damagetype = pick(healing_types))
 
 	owner.adjust_nutrition(3)
 	drained.apply_damage(heal_amount * DRAIN_DAMAGE_MULTIPLIER, damagetype = BRUTE, spread_damage = TRUE)

code/modules/surgery/organs/internal/heart/heart_ethereal.dm

@@ -139,7 +139,7 @@
 	return
 
 ///Lets you stop the process with enough brute damage
-/obj/item/organ/internal/heart/ethereal/proc/on_take_damage(datum/source, damage, damagetype, def_zone)
+/obj/item/organ/internal/heart/ethereal/proc/on_take_damage(datum/source, damage, damagetype, def_zone, ...)
 	SIGNAL_HANDLER
 	if(damagetype != BRUTE)
 		return

code/modules/surgery/organs/internal/lungs/_lungs.dm

@@ -264,7 +264,7 @@
 		return
 
 	var/ratio = (breath.gases[/datum/gas/oxygen][MOLES] / safe_oxygen_max) * 10
-	breather.apply_damage_type(clamp(ratio, oxy_breath_dam_min, oxy_breath_dam_max), oxy_damage_type)
+	breather.apply_damage(clamp(ratio, oxy_breath_dam_min, oxy_breath_dam_max), oxy_damage_type, spread_damage = TRUE)
 	breather.throw_alert(ALERT_TOO_MUCH_OXYGEN, /atom/movable/screen/alert/too_much_oxy)
 
 /// Handles NOT having too much o2. only relevant if safe_oxygen_max has a value
@@ -320,10 +320,10 @@
 		breather.throw_alert(ALERT_TOO_MUCH_CO2, /atom/movable/screen/alert/too_much_co2)
 		breather.Unconscious(6 SECONDS)
 		// Lets hurt em a little, let them know we mean business.
-		breather.apply_damage_type(3, co2_damage_type)
+		breather.apply_damage(3, co2_damage_type, spread_damage = TRUE)
 		// They've been in here 30s now, start to kill them for their own good!
 		if((world.time - breather.co2overloadtime) > 30 SECONDS)
-			breather.apply_damage_type(8, co2_damage_type)
+			breather.apply_damage(8, co2_damage_type, spread_damage = TRUE)
 
 /// Handles NOT having too much co2. only relevant if safe_co2_max has a value
 /obj/item/organ/internal/lungs/proc/safe_co2(mob/living/carbon/breather, datum/gas_mixture/breath, old_co2_pp)
@@ -364,7 +364,7 @@
 		breather.throw_alert(ALERT_TOO_MUCH_PLASMA, /atom/movable/screen/alert/too_much_plas)
 
 	var/ratio = (breath.gases[/datum/gas/plasma][MOLES] / safe_plasma_max) * 10
-	breather.apply_damage_type(clamp(ratio, plas_breath_dam_min, plas_breath_dam_max), plas_damage_type)
+	breather.apply_damage(clamp(ratio, plas_breath_dam_min, plas_breath_dam_max), plas_damage_type, spread_damage = TRUE)
 
 /// Resets plasma side effects
 /obj/item/organ/internal/lungs/proc/safe_plasma(mob/living/carbon/breather, datum/gas_mixture/breath, old_plasma_pp)
@@ -754,11 +754,11 @@
 	if(!HAS_TRAIT(breather, TRAIT_RESISTCOLD)) // COLD DAMAGE
 		var/cold_modifier = breather.dna.species.coldmod
 		if(breath_temperature < cold_level_3_threshold)
-			breather.apply_damage_type(cold_level_3_damage*cold_modifier, cold_damage_type)
+			breather.apply_damage(cold_level_3_damage*cold_modifier, cold_damage_type, spread_damage = TRUE)
 		if(breath_temperature > cold_level_3_threshold && breath_temperature < cold_level_2_threshold)
-			breather.apply_damage_type(cold_level_2_damage*cold_modifier, cold_damage_type)
+			breather.apply_damage(cold_level_2_damage*cold_modifier, cold_damage_type, spread_damage = TRUE)
 		if(breath_temperature > cold_level_2_threshold && breath_temperature < cold_level_1_threshold)
-			breather.apply_damage_type(cold_level_1_damage*cold_modifier, cold_damage_type)
+			breather.apply_damage(cold_level_1_damage*cold_modifier, cold_damage_type, spread_damage = TRUE)
 		if(breath_temperature < cold_level_1_threshold)
 			if(prob(20))
 				to_chat(breather, span_warning("You feel [cold_message] in your [name]!"))
@@ -766,11 +766,11 @@
 	if(!HAS_TRAIT(breather, TRAIT_RESISTHEAT)) // HEAT DAMAGE
 		var/heat_modifier = breather.dna.species.heatmod
 		if(breath_temperature > heat_level_1_threshold && breath_temperature < heat_level_2_threshold)
-			breather.apply_damage_type(heat_level_1_damage*heat_modifier, heat_damage_type)
+			breather.apply_damage(heat_level_1_damage*heat_modifier, heat_damage_type, spread_damage = TRUE)
 		if(breath_temperature > heat_level_2_threshold && breath_temperature < heat_level_3_threshold)
-			breather.apply_damage_type(heat_level_2_damage*heat_modifier, heat_damage_type)
+			breather.apply_damage(heat_level_2_damage*heat_modifier, heat_damage_type, spread_damage = TRUE)
 		if(breath_temperature > heat_level_3_threshold)
-			breather.apply_damage_type(heat_level_3_damage*heat_modifier, heat_damage_type)
+			breather.apply_damage(heat_level_3_damage*heat_modifier, heat_damage_type, spread_damage = TRUE)
 		if(breath_temperature > heat_level_1_threshold)
 			if(prob(20))
 				to_chat(breather, span_warning("You feel [hot_message] in your [name]!"))

modular_skyrat/modules/modular_items/lewd_items/code/lewd_arousal/pain.dm

@@ -2,7 +2,10 @@
 
 /// Adds or removes pain, this should be used instead of the modifying the var, due to quirk logic.
 /// Makes the human scream and shiver when pain hits the soft limit, provided autoemote is enabled.
-/mob/living/carbon/human/proc/adjust_pain(change_amount = 0)
+/mob/living/proc/adjust_pain(change_amount = 0)
+	return
+
+/mob/living/carbon/human/adjust_pain(change_amount = 0)
 	if(stat >= DEAD || !client?.prefs?.read_preference(/datum/preference/toggle/erp))
 		return
 

modular_skyrat/modules/mutants/code/mutant_species.dm

@@ -74,9 +74,14 @@
 	/// The cooldown before the mutant can start regenerating
 	COOLDOWN_DECLARE(regen_cooldown)
 
-/datum/species/mutant/infectious/on_species_gain(mob/living/carbon/C, datum/species/old_species)
+/datum/species/mutant/infectious/on_species_gain(mob/living/carbon/human/human_who_gained_species, datum/species/old_species, pref_load)
 	. = ..()
-	C.AddComponent(/datum/component/mutant_hands, mutant_hand_path = hands_to_give)
+	human_who_gained_species.AddComponent(/datum/component/mutant_hands, mutant_hand_path = hands_to_give)
+	RegisterSignal(human_who_gained_species, COMSIG_MOB_AFTER_APPLY_DAMAGE, PROC_REF(queue_regeneration))
+
+/datum/species/mutant/infectious/on_species_loss(mob/living/carbon/human/human_who_lost_species, datum/species/new_species, pref_load)
+	. = ..()
+	UnregisterSignal(human_who_lost_species, COMSIG_MOB_AFTER_APPLY_DAMAGE)
 
 /obj/item/bodypart/leg/left/mutant_zombie/infectious
 	speed_modifier = 0.5
@@ -137,9 +142,11 @@
 /datum/species/mutant/infectious/spec_stun(mob/living/carbon/human/H,amount)
 	. = min(20, amount)
 
-/datum/species/mutant/infectious/apply_damage(damage, damagetype = BRUTE, def_zone = null, blocked, mob/living/carbon/human/H, forced = FALSE, spread_damage = FALSE, wound_bonus = 0, bare_wound_bonus = 0, sharpness = NONE, attack_direction = null, attacking_item)
-	. = ..()
-	if(.)
+/// Start the cooldown to regenerate - 5 seconds after taking damage
+/datum/species/mutant/infectious/proc/queue_regeneration()
+	SIGNAL_HANDLER
+
+	if(COOLDOWN_FINISHED(src, regen_cooldown))
 		COOLDOWN_START(src, regen_cooldown, REGENERATION_DELAY)
 
 /datum/species/mutant/infectious/spec_life(mob/living/carbon/carbon_mob, seconds_per_tick, times_fired)

tgstation.dme

@@ -4732,7 +4732,6 @@
 #include "code\modules\mob\living\carbon\alien\special\alien_embryo.dm"
 #include "code\modules\mob\living\carbon\alien\special\facehugger.dm"
 #include "code\modules\mob\living\carbon\human\_species.dm"
-#include "code\modules\mob\living\carbon\human\damage_procs.dm"
 #include "code\modules\mob\living\carbon\human\death.dm"
 #include "code\modules\mob\living\carbon\human\dummy.dm"
 #include "code\modules\mob\living\carbon\human\emote.dm"