Small tweak to examine (#1045)

* i didnt tesdt this

* i tested it

Author: Kapu1178

code/game/atoms.dm

@@ -764,17 +764,9 @@
 			else
 				. += span_alert("It looks empty.")
 
-	if(isliving(user) && !ismovable(loc) && !ismob(src))
-		var/mob/living/living_user = user
-		if(living_user.stats.cooldown_finished("examine_forensic_evidence_present_[REF(src)]") && !return_blood_DNA() && (return_fibers() || return_fingerprints() || return_trace_DNA() || return_gunshot_residue()))
-			var/datum/roll_result/result = living_user.stat_roll(15, /datum/rpg_skill/forensics)
-			switch(result.outcome)
-				if(CRIT_SUCCESS, SUCCESS)
-					spawn(0)
-						var/text = isitem(src) ? "someone has held this item in the past" : "someone has been here before"
-						to_chat(living_user, result.create_tooltip("Perhaps it is a stray particle of dust, or a smudge on the surface. Whatever it is, you are certain [text]."))
-
-			living_user.stats.set_cooldown("examine_forensic_evidence_present_[REF(src)]", INFINITY)
+	if(ishuman(user) && !ismovable(loc) && !ismob(src))
+		var/mob/living/carbon/human/human_user = user
+		human_user.forensic_analysis_roll(src)
 
 	SEND_SIGNAL(src, COMSIG_PARENT_EXAMINE, user, .)
 

code/modules/detectivework/detective_work.dm

@@ -195,3 +195,57 @@
  */
 /atom/proc/transfer_gunshot_residue_to(atom/transfer_to)
 	transfer_to.add_gunshot_residue(return_gunshot_residue())
+
+/// On examine, players have a chance to find forensic evidence. This can only happen once per object.
+/mob/living/carbon/human/proc/forensic_analysis_roll(atom/examined)
+	if(!stats.cooldown_finished("examine_forensic_analysis"))
+		return
+
+	// Already gotten the good rng on this one
+	if(stats.examined_object_weakrefs[WEAKREF(examined)])
+		return
+
+	if(examined.return_blood_DNA())
+		return // This is kind of obvious
+
+	var/list/fingerprints = examined.return_fingerprints()?.Copy()
+	var/list/trace_dna = examined.return_trace_DNA()?.Copy()
+	var/list/residue = examined.return_gunshot_residue()
+
+	// Exclude our own prints
+	if(length(fingerprints))
+		var/obj/item/bodypart/arm/left_arm = get_bodypart(BODY_ZONE_L_ARM)
+		var/obj/item/bodypart/arm/right_arm = get_bodypart(BODY_ZONE_R_ARM)
+
+		if(left_arm)
+			fingerprints -= get_fingerprints(TRUE, left_arm)
+		if(right_arm)
+			fingerprints -= get_fingerprints(TRUE, right_arm)
+
+	// Exclude our DNA
+	if(length(trace_dna))
+		trace_dna -= get_trace_dna()
+
+	// Do nothing if theres no evidence.
+	if(!(length(fingerprints) || length(trace_dna) || length(residue)))
+		return
+
+	var/datum/roll_result/result = stat_roll(16, /datum/rpg_skill/forensics)
+
+	switch(result.outcome)
+		if(FAILURE, CRIT_FAILURE)
+			stats.set_cooldown("examine_forensic_analysis", 15 SECONDS)
+			return
+
+	stats.examined_object_weakrefs[WEAKREF(examined)] = TRUE
+	stats.set_cooldown("examine_forensic_analysis", 15 MINUTES)
+
+	// Spawn 0 so this displays *after* the examine block.
+	spawn(0)
+		if(length(residue))
+			to_chat(src, result.create_tooltip("A remnant of past events flashes into your mind, the booming crack of a firearm."))
+
+		else if(length(fingerprints) || length(trace_dna))
+			var/text = isitem(examined) ? "someone else has held this item in the past" : "someone else has been here before"
+			to_chat(src, result.create_tooltip("Perhaps it is a stray particle of dust, or a smudge on the surface. Whatever it may be, you are certain [text]."))
+

code/modules/three_dsix/stats.dm

@@ -10,6 +10,9 @@
 
 	VAR_PRIVATE/list/stat_cooldowns = list()
 
+	/// A list of weakrefs to examined objects. Used for forensic rolls. THIS DOES JUST KEEP GETTING BIGGER, SO, CAREFUL.
+	var/list/examined_object_weakrefs = list()
+
 /datum/stats/New(owner)
 	. = ..()
 	src.owner = owner