Tether improvements and fixes (#89174)

## About The Pull Request

Fixes tether stacking via beacons, you can freely cut your tether while
moving, and cutting/snapping MODsuit tethers now also snaps the beacon
they're connected to if said beacon was generated by a MODsuit
projectile. Retracting the gloves or deactivating your MODsuit also
snaps MODtethers you've created using it.

Closes #88869
Closes #88866
Closes #89170

## Changelog
🆑
qol: Snapping tethers now also removes their beacons
qol: You can now cut tethers that you're attached to while in motion
qol: Tethers now snap when you retract your gloves or disable your
MODsuit
fix: Fixed tether stacking issues
/🆑

code/__DEFINES/dcs/signals/signals_atom/signals_atom_main.dm

@@ -148,3 +148,6 @@
 
 /// From /atom/proc/set_density(new_value) for when an atom changes density
 #define COMSIG_ATOM_DENSITY_CHANGED "atom_density_change"
+
+/// From /datum/component/tether/UnregisterFromParent()
+#define COMSIG_ATOM_TETHER_SNAPPED "atom_tether_snapped"

code/datums/components/tether.dm

@@ -62,6 +62,7 @@
 
 	if (!isnull(parent_module))
 		RegisterSignals(parent_module, list(COMSIG_QDELETING, COMSIG_MOVABLE_MOVED, COMSIG_MOD_TETHER_SNAP), PROC_REF(snap))
+		RegisterSignal(parent_module, COMSIG_MODULE_TRIGGERED, PROC_REF(on_parent_use))
 
 /datum/component/tether/UnregisterFromParent()
 	UnregisterSignal(parent, list(COMSIG_MOVABLE_PRE_MOVE, COMSIG_MOVABLE_MOVED))
@@ -71,11 +72,13 @@
 		UnregisterSignal(tether_target, list(COMSIG_MOVABLE_PRE_MOVE, COMSIG_MOVABLE_MOVED, COMSIG_QDELETING))
 		if (!isnull(tether_trait_source) && !no_target_trait)
 			REMOVE_TRAIT(tether_target, TRAIT_TETHER_ATTACHED, tether_trait_source)
+		SEND_SIGNAL(tether_target, COMSIG_ATOM_TETHER_SNAPPED, tether_trait_source)
 	if (!QDELETED(tether_beam))
 		UnregisterSignal(tether_beam.visuals, list(COMSIG_CLICK, COMSIG_QDELETING))
 		qdel(tether_beam)
 	if (!QDELETED(embed_target))
 		UnregisterSignal(embed_target, list(COMSIG_ITEM_UNEMBEDDED, COMSIG_QDELETING))
+	SEND_SIGNAL(parent, COMSIG_ATOM_TETHER_SNAPPED, tether_trait_source)
 
 /datum/component/tether/proc/check_tether(atom/source, new_loc)
 	SIGNAL_HANDLER
@@ -143,6 +146,12 @@
 	playsound(atom_target, 'sound/effects/snap.ogg', 50, TRUE)
 	qdel(src)
 
+/datum/component/tether/proc/on_parent_use(obj/item/mod/module/module, atom/target)
+	SIGNAL_HANDLER
+
+	if (get_turf(target) == get_turf(tether_target))
+		return MOD_ABORT_USE
+
 /datum/component/tether/proc/on_delete()
 	SIGNAL_HANDLER
 	qdel(src)
@@ -174,7 +183,7 @@
 	var/list/modifiers = params2list(params)
 	if(LAZYACCESS(modifiers, CTRL_CLICK))
 		location.balloon_alert(user, "cutting the tether...")
-		if (!do_after(user, 2 SECONDS, user))
+		if (!do_after(user, 2 SECONDS, user, (user == parent || user == tether_target) ? IGNORE_USER_LOC_CHANGE|IGNORE_TARGET_LOC_CHANGE : NONE))
 			return
 
 		qdel(src)
@@ -190,11 +199,11 @@
 		location.balloon_alert(user, "tether extended")
 		return
 
-	if (cur_dist <= 1)
+	if (cur_dist <= 0)
 		location.balloon_alert(user, "too short!")
 		return
 
-	if (cur_dist > get_dist(parent, tether_target))
+	if (cur_dist > CEILING(get_dist(parent, tether_target), 1))
 		cur_dist -= 1
 		location.balloon_alert(user, "tether shortened")
 		return

code/modules/mod/modules/modules_engineering.dm

@@ -114,8 +114,10 @@
 	.["cut_tethers"] = add_ui_configuration("Cut Tethers", "button", "scissors")
 
 /obj/item/mod/module/tether/configure_edit(key, value)
-	if (key != "cut_tethers")
-		return
+	if (key == "cut_tethers")
+		SEND_SIGNAL(src, COMSIG_MOD_TETHER_SNAP)
+
+/obj/item/mod/module/tether/on_deactivation(display_message, deleting)
 	SEND_SIGNAL(src, COMSIG_MOD_TETHER_SNAP)
 
 /obj/projectile/tether
@@ -197,6 +199,7 @@
 	anchor.pixel_x = hitx
 	anchor.pixel_y = hity
 	anchor.anchored = TRUE
+	anchor.parent_module = parent_module
 	firer.AddComponent(/datum/component/tether, anchor, 7, "MODtether", parent_module = parent_module, tether_trait_source = REF(parent_module))
 
 /obj/projectile/tether/Destroy()
@@ -210,6 +213,17 @@
 	icon = 'icons/obj/clothing/modsuit/mod_modules.dmi'
 	max_integrity = 60
 	interaction_flags_atom = INTERACT_ATOM_ATTACK_HAND | INTERACT_ATOM_UI_INTERACT
+	/// MODsuit tether module that created our projectile
+	var/obj/item/mod/module/tether/parent_module
+
+/obj/item/tether_anchor/Initialize(mapload)
+	. = ..()
+	RegisterSignal(src, COMSIG_ATOM_TETHER_SNAPPED, PROC_REF(tether_snapped))
+
+/obj/item/tether_anchor/Destroy(force)
+	// We don't need to worry about hanging refs in case our parent gets destroyed because then it snaps all tethers, which in turn destroys us
+	parent_module = null
+	return ..()
 
 /obj/item/tether_anchor/examine(mob/user)
 	. = ..()
@@ -229,6 +243,10 @@
 		balloon_alert(user, "already tethered!")
 		return
 
+	if (parent_module && HAS_TRAIT_FROM(user, TRAIT_TETHER_ATTACHED, REF(parent_module)))
+		balloon_alert(user, "already tethered!")
+		return
+
 	balloon_alert(user, "attached tether")
 	user.AddComponent(/datum/component/tether, src, 7, "tether", tether_trait_source = REF(src))
 	return SECONDARY_ATTACK_CANCEL_ATTACK_CHAIN
@@ -244,6 +262,10 @@
 		balloon_alert(user, "already tethered!")
 		return
 
+	if (parent_module && HAS_TRAIT_FROM(user, TRAIT_TETHER_ATTACHED, REF(parent_module)))
+		balloon_alert(user, "already tethered!")
+		return
+
 	if (target == user)
 		balloon_alert(user, "attached tether")
 		user.AddComponent(/datum/component/tether, src, 7, "tether", tether_trait_source = REF(src), no_target_trait = TRUE)
@@ -258,10 +280,24 @@
 		balloon_alert(user, "already tethered!")
 		return
 
+	if (parent_module && HAS_TRAIT_FROM(user, TRAIT_TETHER_ATTACHED, REF(parent_module)))
+		balloon_alert(user, "already tethered!")
+		return
+
 	balloon_alert(user, "attached tether")
 	to_chat(target, span_userdanger("[user] attaches a tether to you!"))
 	target.AddComponent(/datum/component/tether, src, 7, "tether", tether_trait_source = REF(src), no_target_trait = TRUE)
 
+/obj/item/tether_anchor/proc/tether_snapped(datum/component/tether/tether, tether_source)
+	SIGNAL_HANDLER
+
+	if (!parent_module || tether_source != REF(parent_module))
+		return
+
+	// Destroy self if we've been created by a tether module
+	do_sparks(3, TRUE, src)
+	qdel(src)
+
 /datum/embedding/tether_projectile
 	embed_chance = 65 //spiky
 	fall_chance = 2