Implements lighting rags on fire

Rags can be lit on fire if soaked with welder fuel. While lit, the rag provides light, starts fires, and attacking mobs will ignite them.
Rags can be put out by clicking in hand.
Rags will burn out after a short time, turning into ash.

code/modules/detectivework/footprints_and_rag.dm

@@ -25,23 +25,51 @@
 	can_be_placed_into = null
 	flags = OPENCONTAINER | NOBLUDGEON
 
+	var/on_fire = 0
+	var/burn_time = 20 //if the rag burns for too long it turns to ashes
+
 /obj/item/weapon/reagent_containers/glass/rag/New()
 	..()
 	update_name()
 
-/obj/item/weapon/reagent_containers/glass/rag/attack_self(mob/user as mob)
-	remove_contents(user)
+/obj/item/weapon/reagent_containers/glass/rag/Destroy()
+	processing_objects -= src //so we don't continue turning to ash while gc'd
+	..()
+
+/obj/item/weapon/reagent_containers/glass/rag/attack_self(mob/user as mob)
+	if(on_fire)
+		user.visible_message("<span class='warning'>\The [user] stamps out [src].</span>", "<span class='warning'>You stamp out [src].</span>")
+		user.unEquip(src)
+		extinguish()
+	else
+		remove_contents(user)
+
+/obj/item/weapon/reagent_containers/glass/rag/attackby(obj/item/W, mob/user)
+	var/obj/item/weapon/flame/F = W
+	if(!on_fire && istype(F) && F.lit)
+		ignite()
+		if(on_fire)
+			visible_message("<span class='warning'>\The [user] lights [src] with [W].</span>")
+		else
+			user << "<span class='warning'>You manage to singe [src], but fail to light it.</span>"
 
-/obj/item/weapon/reagent_containers/glass/rag/attackby()
 	. = ..()
 	update_name()
 
 /obj/item/weapon/reagent_containers/glass/rag/proc/update_name()
-	if(reagents.total_volume)
+	if(on_fire)
+		name = "burning [initial(name)]"
+	else if(reagents.total_volume)
 		name = "damp [initial(name)]"
 	else
 		name = "dry [initial(name)]"
 
+/obj/item/weapon/reagent_containers/glass/rag/update_icon()
+	if(on_fire)
+		icon_state = "raglit"
+	else
+		icon_state = "rag"
+
 /obj/item/weapon/reagent_containers/glass/rag/proc/remove_contents(mob/user, atom/trans_dest = null)
 	if(!trans_dest && !user.loc)
 		return
@@ -70,18 +98,28 @@
 			A.clean_blood()
 
 /obj/item/weapon/reagent_containers/glass/rag/attack(atom/target as obj|turf|area, mob/user as mob , flag)
-	if(ismob(target) && reagents.total_volume)
-		if(user.zone_sel.selecting == "mouth")
-			user.visible_message(
-				"<span class='danger'>\The [user] smothers [target] with [src]!</span>", 
-				"<span class='warning'>You smother [target] with [src]!</span>", 
-				"You hear some struggling and muffled cries of surprise"
-				)
-			reagents.trans_to_mob(target, amount_per_transfer_from_this, CHEM_INGEST) //it's inhaled, really... maybe this should be CHEM_BLOOD?
-			update_name()
-		else
-			wipe_down(target, user)
+	if(isliving(target))
+		var/mob/living/M = target
+		if(on_fire)
+			user.visible_message("<span class='danger'>\The [user] hits [target] with [src]!</span>",)
+			user.do_attack_animation(src)
+			M.IgniteMob()
+		else if(reagents.total_volume)
+			if(user.zone_sel.selecting == "mouth")
+				user.do_attack_animation(src)
+				user.visible_message(
+					"<span class='danger'>\The [user] smothers [target] with [src]!</span>", 
+					"<span class='warning'>You smother [target] with [src]!</span>", 
+					"You hear some struggling and muffled cries of surprise"
+					)
+				
+				//it's inhaled, so... maybe CHEM_BLOOD doesn't make a whole lot of sense but it's the best we can do for now
+				reagents.trans_to_mob(target, amount_per_transfer_from_this, CHEM_BLOOD)
+				update_name()
+			else
+				wipe_down(target, user)
 		return
+	
 	return ..()
 	
 /obj/item/weapon/reagent_containers/glass/rag/afterattack(atom/A as obj|turf|area, mob/user as mob, proximity)
@@ -97,11 +135,78 @@
 			user.visible_message("<span class='notice'>\The [user] soaks [src] using [A].</span>", "<span class='notice'>You soak [src] using [A].</span>")
 			update_name()
 		return
-	
-	if(istype(A) && (src in user))
+
+	if(!on_fire && istype(A) && (src in user))
 		if(A.is_open_container())
 			remove_contents(user, A)
 		else if(!ismob(A)) //mobs are handled in attack() - this prevents us from wiping down people while smothering them.
 			wipe_down(A, user)
 		return
 
+/obj/item/weapon/reagent_containers/glass/rag/fire_act(datum/gas_mixture/air, exposed_temperature, exposed_volume)
+	if(exposed_temperature >= 50 + T0C)
+		ignite()
+
+//rag must have a minimum of 2 units welder fuel and at least 80% of the reagents must be welder fuel.
+//maybe generalize flammable reagents someday
+/obj/item/weapon/reagent_containers/glass/rag/proc/can_ignite()
+	var/fuel = reagents.get_reagent_amount("fuel")
+	return (fuel >= 2 && fuel >= reagents.total_volume*0.8)
+
+/obj/item/weapon/reagent_containers/glass/rag/proc/ignite()
+	if(on_fire)
+		return
+	if(!can_ignite())
+		return
+	
+	//also copied from matches
+	if(reagents.get_reagent_amount("phoron")) // the phoron explodes when exposed to fire
+		visible_message("<span class='danger'>\The [src] conflagrates violently!</span>")
+		var/datum/effect/effect/system/reagents_explosion/e = new()
+		e.set_up(round(reagents.get_reagent_amount("phoron") / 2.5, 1), get_turf(src), 0, 0)
+		e.start()
+		qdel(src)
+		return
+	
+	processing_objects += src
+	set_light(2, null, "#E38F46")
+	on_fire = 1
+	update_name()
+	update_icon()
+
+/obj/item/weapon/reagent_containers/glass/rag/proc/extinguish()
+	processing_objects -= src
+	set_light(0)
+	on_fire = 0
+	
+	//rags sitting around with 1 second of burn time left is dumb.
+	//ensures players always have a few seconds of burn time left when they light their rag
+	if(burn_time <= 5)
+		visible_message("<span class='warning'>\The [src] falls apart!</span>")
+		new /obj/effect/decal/cleanable/ash(get_turf(src))
+		qdel(src)
+	update_name()
+	update_icon()
+
+/obj/item/weapon/reagent_containers/glass/rag/process()
+	if(!can_ignite())
+		visible_message("<span class='warning'>\The [src] burns out.</span>")
+		extinguish()
+
+	//copied from matches
+	if(isliving(loc))
+		var/mob/living/M = loc
+		M.IgniteMob()
+	var/turf/location = get_turf(src)
+	if(location)
+		location.hotspot_expose(700, 5)
+	
+	if(burn_time <= 0)
+		processing_objects -= src
+		new /obj/effect/decal/cleanable/ash(location)
+		qdel(src)
+		return
+
+	reagents.remove_reagent("fuel", reagents.maximum_volume/25)
+	update_name()
+	burn_time--