#ifdef EXTOOLS_REFERENCE_TRACKING

GLOBAL_LIST_EMPTY(deletion_failures)

/world/proc/enable_reference_tracking()
	if (fexists(EXTOOLS))
		//call(EXTOOLS, "ref_tracking_initialize")()

/proc/get_back_references(datum/D)
	CRASH("/proc/get_back_references not hooked by extools, reference tracking will not function!")

/proc/get_forward_references(datum/D)
	CRASH("/proc/get_forward_references not hooked by extools, reference tracking will not function!")

/proc/clear_references(datum/D)
	return

/datum/admins/proc/view_refs(atom/D in world) //it actually supports datums as well but byond no likey
	set category = "Debug"
	set name = "View References"

	if(!check_rights(R_DEBUG) || !D)
		return

	var/list/backrefs = get_back_references(D)
	if(isnull(backrefs))
		var/datum/browser/popup = new(usr, "ref_view", "<div align='center'>Error</div>")
		popup.set_content("Reference tracking not enabled")
		popup.open(FALSE)
		return

	var/list/frontrefs = get_forward_references(D)
	var/list/dat = list()
	dat += "<h1>References of \ref[D] - [D]</h1><br><a href='?_src_=vars;[HrefToken()];[VV_HK_VIEW_REFERENCES]=TRUE;[VV_HK_TARGET]=[REF(D)]'>\[Refresh\]</a><hr>"
	dat += "<h3>Back references - these things hold references to this object.</h3>"
	dat += "<table>"
	dat += "<tr><th>Ref</th><th>Type</th><th>Variable Name</th><th>Follow</th>"
	for(var/ref in backrefs)
		var/datum/backreference = ref
		if(isnull(backreference))
			dat += "<tr><td>GC'd Reference</td></tr>"
		if(istype(backreference))
			dat += "<tr><td><a href='?_src_=vars;[HrefToken()];Vars=[REF(backreference)]'>[REF(backreference)]</td><td>[backreference.type]</td><td>[backrefs[backreference]]</td><td><a href='?_src_=vars;[HrefToken()];[VV_HK_VIEW_REFERENCES]=TRUE;[VV_HK_TARGET]=[REF(backreference)]'>\[Follow\]</a></td></tr>"
		else if(islist(backreference))
			dat += "<tr><td><a href='?_src_=vars;[HrefToken()];Vars=[REF(backreference)]'>[REF(backreference)]</td><td>list</td><td>[backrefs[backreference]]</td><td><a href='?_src_=vars;[HrefToken()];[VV_HK_VIEW_REFERENCES]=TRUE;[VV_HK_TARGET]=[REF(backreference)]'>\[Follow\]</a></td></tr>"
		else
			dat += "<tr><td>Weird reference type. Add more debugging checks.</td></tr>"
	dat += "</table><hr>"
	dat += "<h3>Forward references - this object is referencing those things.</h3>"
	dat += "<table>"
	dat += "<tr><th>Variable name</th><th>Ref</th><th>Type</th><th>Follow</th>"
	for(var/ref in frontrefs)
		var/datum/backreference = frontrefs[ref]
		dat += "<tr><td>[ref]</td><td><a href='?_src_=vars;[HrefToken()];Vars=[REF(backreference)]'>[REF(backreference)]</a></td><td>[backreference.type]</td><td><a href='?_src_=vars;[HrefToken()];[VV_HK_VIEW_REFERENCES]=TRUE;[VV_HK_TARGET]=[REF(backreference)]'>\[Follow\]</a></td></tr>"
	dat += "</table><hr>"
	dat = dat.Join()

	var/datum/browser/popup = new(usr, "ref_view", "<div align='center'>References of \ref[D]</div>")
	popup.set_content(dat)
	popup.open(FALSE)


/datum/admins/proc/view_del_failures()
	set category = "Debug"
	set name = "View Deletion Failures"

	if(!check_rights(R_DEBUG))
		return

	var/list/dat = list("<table>")
	for(var/t in GLOB.deletion_failures)
		if(isnull(t))
			dat += "<tr><td>GC'd Reference | <a href='byond://?src=[REF(src)];[HrefToken(TRUE)];delfail_clearnulls=TRUE'>Clear Nulls</a></td></tr>"
			continue
		var/datum/thing = t
		dat += "<tr><td>\ref[thing] | [thing.type][thing.gc_destroyed ? " (destroyed)" : ""] [ADMIN_VV(thing)]</td></tr>"
	dat += "</table><hr>"
	dat = dat.Join()

	var/datum/browser/popup = new(usr, "del_failures", "<div align='center'>Deletion Failures</div>")
	popup.set_content(dat)
	popup.open(FALSE)


/datum/proc/find_references()
	testing("Beginning search for references to a [type].")
	var/list/backrefs = get_back_references(src)
	for(var/ref in backrefs)
		if(isnull(ref))
			log_world("## TESTING: Datum reference found, but gone now.")
			continue
		if(islist(ref))
			log_world("## TESTING: Found [type] \ref[src] in list.")
			continue
		var/datum/datum_ref = ref
		if(!istype(datum_ref))
			log_world("## TESTING: Found [type] \ref[src] in unknown type reference: [datum_ref].")
			return
		log_world("## TESTING: Found [type] \ref[src] in [datum_ref.type][datum_ref.gc_destroyed ? " (destroyed)" : ""]")
		message_admins("Found [type] \ref[src] [ADMIN_VV(src)] in [datum_ref.type][datum_ref.gc_destroyed ? " (destroyed)" : ""] [ADMIN_VV(datum_ref)]")
	testing("Completed search for references to a [type].")

#endif

#ifdef REFERENCE_TRACKING

/datum/proc/find_references(skip_alert)
	running_find_references = type
	if(usr?.client)
		if(usr.client.running_find_references)
			log_reftracker("CANCELLED search for references to a [usr.client.running_find_references].")
			usr.client.running_find_references = null
			running_find_references = null
			//restart the garbage collector
			SSgarbage.can_fire = TRUE
			SSgarbage.update_nextfire(reset_time = TRUE)
			return

		if(!skip_alert && tgui_alert(usr,"Running this will lock everything up for about 5 minutes.  Would you like to begin the search?", "Find References", list("Yes", "No")) != "Yes")
			running_find_references = null
			return

	//this keeps the garbage collector from failing to collect objects being searched for in here
	SSgarbage.can_fire = FALSE

	if(usr?.client)
		usr.client.running_find_references = type

	log_reftracker("Beginning search for references to a [type].")

	var/starting_time = world.time

	//Time to search the whole game for our ref
	DoSearchVar(GLOB, "GLOB") //globals
	log_reftracker("Finished searching globals")

	for(var/datum/thing in world) //atoms (don't beleive its lies)
		DoSearchVar(thing, "World -> [thing.type]", search_time = starting_time)
	log_reftracker("Finished searching atoms")

	for(var/datum/thing) //datums
		DoSearchVar(thing, "Datums -> [thing.type]", search_time = starting_time)
	log_reftracker("Finished searching datums")

	//Warning, attempting to search clients like this will cause crashes if done on live. Watch yourself
	for(var/client/thing) //clients
		DoSearchVar(thing, "Clients -> [thing.type]", search_time = starting_time)
	log_reftracker("Finished searching clients")

	log_reftracker("Completed search for references to a [type].")

	if(usr?.client)
		usr.client.running_find_references = null
	running_find_references = null

	//restart the garbage collector
	SSgarbage.can_fire = TRUE
	SSgarbage.update_nextfire(reset_time = TRUE)

/datum/proc/DoSearchVar(potential_container, container_name, recursive_limit = 64, search_time = world.time)
	#ifdef REFERENCE_TRACKING_DEBUG
	if(!found_refs && SSgarbage.should_save_refs)
		found_refs = list()
	#endif

	if(usr?.client && !usr.client.running_find_references)
		return

	if(!recursive_limit)
		log_reftracker("Recursion limit reached. [container_name]")
		return

	//Check each time you go down a layer. This makes it a bit slow, but it won't effect the rest of the game at all
	#ifndef FIND_REF_NO_CHECK_TICK
	CHECK_TICK
	#endif

	if(istype(potential_container, /datum))
		var/datum/datum_container = potential_container
		if(datum_container.last_find_references == search_time)
			return

		datum_container.last_find_references = search_time
		var/list/vars_list = datum_container.vars

		for(var/varname in vars_list)
			#ifndef FIND_REF_NO_CHECK_TICK
			CHECK_TICK
			#endif
			if (varname == "vars" || varname == "vis_locs") //Fun fact, vis_locs don't count for references
				continue
			var/variable = vars_list[varname]

			if(variable == src)
				#ifdef REFERENCE_TRACKING_DEBUG
				if(SSgarbage.should_save_refs)
					found_refs[varname] = TRUE
				#endif
				log_reftracker("Found [type] \ref[src] in [datum_container.type]'s \ref[datum_container] [varname] var. [container_name]")
				continue

			if(islist(variable))
				DoSearchVar(variable, "[container_name] \ref[datum_container] -> [varname] (list)", recursive_limit - 1, search_time)

	else if(islist(potential_container))
		var/normal = IS_NORMAL_LIST(potential_container)
		var/list/potential_cache = potential_container
		for(var/element_in_list in potential_cache)
			#ifndef FIND_REF_NO_CHECK_TICK
			CHECK_TICK
			#endif
			//Check normal entrys
			if(element_in_list == src)
				#ifdef REFERENCE_TRACKING_DEBUG
				if(SSgarbage.should_save_refs)
					found_refs[potential_cache] = TRUE
				#endif
				log_reftracker("Found [type] \ref[src] in list [container_name].")
				continue

			var/assoc_val = null
			if(!isnum(element_in_list) && normal)
				assoc_val = potential_cache[element_in_list]
			//Check assoc entrys
			if(assoc_val == src)
				#ifdef REFERENCE_TRACKING_DEBUG
				if(SSgarbage.should_save_refs)
					found_refs[potential_cache] = TRUE
				#endif
				log_reftracker("Found [type] \ref[src] in list [container_name]\[[element_in_list]\]")
				continue
			//We need to run both of these checks, since our object could be hiding in either of them
			//Check normal sublists
			if(islist(element_in_list))
				DoSearchVar(element_in_list, "[container_name] -> [element_in_list] (list)", recursive_limit - 1, search_time)
			//Check assoc sublists
			if(islist(assoc_val))
				DoSearchVar(potential_container[element_in_list], "[container_name]\[[element_in_list]\] -> [assoc_val] (list)", recursive_limit - 1, search_time)

/proc/qdel_and_find_ref_if_fail(datum/thing_to_del, force = FALSE)
	thing_to_del.qdel_and_find_ref_if_fail(force)

/datum/proc/qdel_and_find_ref_if_fail(force = FALSE)
	SSgarbage.reference_find_on_fail["\ref[src]"] = TRUE
	qdel(src, force)

#endif