Electro-tethers (#10117)

Added a box of eight electro-tethers to the RD's secure locker.

code/game/objects/items/weapons/storage/boxes.dm

@@ -316,6 +316,15 @@
 	desc = "A box of varied assortment of firing pins. Appears to have R&D stickers on all sides of the box. Also seems to have a smiley face sticker on the top of it."
 	starts_with = list(/obj/item/device/firing_pin = 2, /obj/item/device/firing_pin/access = 2, /obj/item/device/firing_pin/implant/loyalty = 2, /obj/item/device/firing_pin/clown = 1, /obj/item/device/firing_pin/dna = 1)
 
+/obj/item/storage/box/tethers
+	name = "box of tethering devices"
+	desc = "A box containing eight electro-tethers, used primarily to keep track of partners during expeditions."
+	starts_with = list(/obj/item/tethering_device = 8)
+
+/obj/item/storage/box/tethers/fill()
+	..()
+	make_exact_fit()
+
 /obj/item/storage/box/teargas
 	name = "box of pepperspray grenades"
 	desc = "A box containing 7 tear gas grenades. A gas mask is printed on the label.<br> WARNING: Exposure carries risk of serious injury or death. Keep away from persons with lung conditions."

code/game/objects/items/weapons/tether.dm

@@ -0,0 +1,86 @@
+var/list/global/all_tethers = list()
+
+/obj/item/tethering_device
+	name = "tethering device"
+	desc = "A device used by explorers to keep track of partners by way of electro-tether."
+	desc_info = "Use in-hand to activate, must be on the same level and within fifteen tiles of another device to latch. Tethers are colour coded by distance."
+	icon = 'icons/obj/device.dmi'
+	icon_state = "locator"
+	w_class = ITEMSIZE_SMALL
+	slot_flags = SLOT_BELT
+	force = 1
+	var/active = FALSE
+	var/list/linked_tethers = list()
+	var/tether_range = 15
+	var/list/active_beams = list()
+
+/obj/item/tethering_device/Initialize(mapload, ...)
+	. = ..()
+	all_tethers += src
+
+/obj/item/tethering_device/Destroy()
+	STOP_PROCESSING(SSprocessing, src)
+	deactivate()
+	all_tethers -= src
+	return ..()
+
+/obj/item/tethering_device/attack_self(mob/user)
+	active = !active
+	var/msg = "You [active ? "activate" : "deactivate"] \the [src]."
+	to_chat(user, SPAN_NOTICE(msg))
+	if(active)
+		activate()
+	else
+		deactivate()
+
+/obj/item/tethering_device/process()
+	var/turf/our_turf = get_turf(src)
+	for(var/tether in all_tethers)
+		var/obj/item/tethering_device/TD = tether
+		if(TD == src)
+			continue
+		if(!TD.active)
+			continue
+		var/turf/target_turf = get_turf(TD)
+		if(our_turf == target_turf)
+			continue
+		if(target_turf.z != our_turf.z)
+			continue
+		if(get_dist(target_turf, our_turf) > tether_range)
+			continue
+		if(TD in linked_tethers)
+			continue
+		if(src in TD.linked_tethers)
+			continue
+		tether(TD)
+
+/obj/item/tethering_device/emp_act()
+	deactivate()
+
+/obj/item/tethering_device/proc/activate()
+	START_PROCESSING(SSprocessing, src)
+
+/obj/item/tethering_device/proc/deactivate()
+	STOP_PROCESSING(SSprocessing, src)
+	for(var/beam in active_beams)
+		var/datum/beam/exploration/B = active_beams[beam]
+		B.End()
+	for(var/tether in all_tethers)
+		var/obj/item/tethering_device/TD = tether
+		TD.untether(src)
+
+/obj/item/tethering_device/proc/tether(var/obj/item/tethering_device/TD)
+	linked_tethers |= TD
+	var/datum/beam/exploration/B = new /datum/beam/exploration(src, TD, beam_icon_state = "explore_beam", time = -1, maxdistance = tether_range)
+	B.owner = src
+	B.Start()
+	active_beams[TD] = B
+
+// untethering logic is primarily dictated by the beam itself, who will end if the max distance is reached, and call this proc
+/obj/item/tethering_device/proc/untether(var/obj/item/tethering_device/TD, var/destroy_beam = TRUE)
+	linked_tethers -= TD
+	if(!destroy_beam)
+		return
+	var/datum/beam/exploration/B = active_beams[TD]
+	if(B)
+		B.End()

code/game/objects/structures/crates_lockers/closets/secure/scientist.dm

@@ -47,6 +47,7 @@
 	new /obj/item/storage/box/firingpinsRD(src)
 	new /obj/item/device/pin_extractor(src)
 	new /obj/item/storage/box/fancy/keypouch/sci(src)
+	new /obj/item/storage/box/tethers(src)
 
 /obj/structure/closet/secure_closet/RD2
 	name = "research director's attire"