Integrated circuits for modular computers (#80530)

## About The Pull Request
This PR integrates circuits for modular computers and a good bits of
their programs.
The peculiarity here is that modular computers have no fixed amount of
unremovable components (except the base one with just a couple ports for
now), instead, they're added and removed along with programs. With a few
exceptions (such as the messenger and signaler), for these program
circuits to work, their associated program has to be either open or in
the background.

For a reason or another, not all programs have a circuit associated to
them, still, however the programs with a circuit are still a handful.
They are:
- Nanotrasen Pay System
- Notepad
- SiliConnect
- WireCarp
- MODsuit Control
- Spectre Meter
- Direct Messenger*
- LifeConnect
- Custodial Locator
- Fission360
- Camera
- Status Display
- SignalCommander

*By the by, sending messages has a cooldown, so it shouldn't be as
spammy. If it turns out to not be enough, I can make it so messages from
circuit will be ignored by other messenger circuits.

The PR is no longer WIP.

## Why It's Good For The Game
I believe modular computers could make for some interesting setups with
circuits, since they're fairly flexible and stocked with features unlike
many other appliances, therefore also a speck more abusable, though
limits, cooldowns, logging and sanitization have been implemented to
keep it in check.

## Changelog

🆑
add: Modular Computers now support integrated circuits. What can be done
with them depends on the programs installed and whether they're running
(open or background).
add: Modular Consoles (the machinery) now have a small backup cell they
draw power from if the power goes out.
/🆑

code/modules/modular_computers/computers/machinery/modular_computer.dm

@@ -1,3 +1,5 @@
+#define CPU_INTERACTABLE(user) (cpu && !HAS_TRAIT_FROM(src, TRAIT_MODPC_INTERACTING_WITH_FRAME, REF(user)))
+
 // Modular Computer - A machinery that is mostly just a host to the Modular Computer item.
 /obj/machinery/modular_computer
 	name = "modular computer"
@@ -9,8 +11,6 @@
 	max_integrity = 300
 	integrity_failure = 0.5
 
-	///The power cell, null by default as we use the APC we're in
-	var/internal_cell = null
 	///A flag that describes this device type
 	var/hardware_flag = PROGRAM_CONSOLE
 	/// Amount of programs that can be ran at once
@@ -41,23 +41,42 @@
 	. = ..()
 	cpu = new(src)
 	cpu.screen_on = TRUE
+	cpu.add_shell_component(SHELL_CAPACITY_LARGE, SHELL_FLAG_USB_PORT)
 	update_appearance()
+	register_context()
 
 /obj/machinery/modular_computer/Destroy()
 	QDEL_NULL(cpu)
 	return ..()
 
+/obj/machinery/modular_computer/add_context(atom/source, list/context, obj/item/held_item, mob/user)
+	. = ..()
+	if(isnull(held_item))
+		context[SCREENTIP_CONTEXT_RMB] = "Toggle processor interaction"
+	return CONTEXTUAL_SCREENTIP_SET
+
+/obj/machinery/modular_computer/attack_hand_secondary(mob/user, list/modifiers)
+	. = ..()
+	if(. == SECONDARY_ATTACK_CANCEL_ATTACK_CHAIN)
+		return
+	if(HAS_TRAIT_FROM(src, TRAIT_MODPC_INTERACTING_WITH_FRAME, REF(user)))
+		REMOVE_TRAIT(src, TRAIT_MODPC_INTERACTING_WITH_FRAME, REF(user))
+		balloon_alert(user, "now interacting with computer")
+	else
+		ADD_TRAIT(src, TRAIT_MODPC_INTERACTING_WITH_FRAME, REF(user))
+		balloon_alert(user, "now interacting with frame")
+	return SECONDARY_ATTACK_CANCEL_ATTACK_CHAIN
+
 /obj/machinery/modular_computer/examine(mob/user)
-	if(cpu)
-		return cpu.examine(user)
-	return ..()
+	. = cpu?.examine(user) || ..()
+	. += span_info("You can toggle interaction between computer and its machinery frame with [EXAMINE_HINT("Right-Click")] while empty-handed.")
+	. += span_info("Currently interacting with [EXAMINE_HINT(HAS_TRAIT_FROM(src, TRAIT_MODPC_INTERACTING_WITH_FRAME, REF(user)) ? "frame" : "computer")].")
 
 /obj/machinery/modular_computer/attack_ghost(mob/dead/observer/user)
 	. = ..()
 	if(.)
 		return
-	if(cpu)
-		cpu.attack_ghost(user)
+	cpu?.attack_ghost(user)
 
 /obj/machinery/modular_computer/emag_act(mob/user, obj/item/card/emag/emag_card)
 	if(!cpu)
@@ -98,17 +117,14 @@
 
 /obj/machinery/modular_computer/AltClick(mob/user)
 	. = ..()
-	if(!can_interact(user))
+	if(CPU_INTERACTABLE(user) || !can_interact(user))
 		return
-	if(cpu)
-		cpu.AltClick(user)
+	cpu.AltClick(user)
 
 //ATTACK HAND IGNORING PARENT RETURN VALUE
 // On-click handling. Turns on the computer if it's off and opens the GUI.
 /obj/machinery/modular_computer/interact(mob/user)
-	if(cpu)
-		return cpu.interact(user)
-	return ..()
+	return CPU_INTERACTABLE(user) ? cpu.interact(user) : ..()
 
 // Modular computers can have battery in them, we handle power in previous proc, so prevent this from messing it up for us.
 /obj/machinery/modular_computer/power_change()
@@ -118,30 +134,33 @@
 		return
 	return ..()
 
+///Try to recharge our internal cell if it isn't fully charged.
+/obj/machinery/modular_computer/process(seconds_per_tick)
+	var/obj/item/stock_parts/cell/cell = get_cell()
+	if(isnull(cell) || cell.percent() >= 100)
+		return
+	var/power_to_draw = idle_power_usage * seconds_per_tick * 0.5
+	if(!use_power_from_net(power_to_draw))
+		return
+	cell.give(power_to_draw)
+
+/obj/machinery/modular_computer/get_cell()
+	return cpu?.internal_cell
+
 /obj/machinery/modular_computer/screwdriver_act(mob/user, obj/item/tool)
-	if(cpu)
-		return cpu.screwdriver_act(user, tool)
-	return ..()
+	return CPU_INTERACTABLE(user) ? cpu.screwdriver_act(user, tool) : ..()
 
 /obj/machinery/modular_computer/wrench_act_secondary(mob/user, obj/item/tool)
-	if(cpu)
-		return cpu.wrench_act_secondary(user, tool)
-	return ..()
+	return CPU_INTERACTABLE(user) ? cpu.wrench_act_secondary(user, tool) : ..()
 
 /obj/machinery/modular_computer/welder_act(mob/user, obj/item/tool)
-	if(cpu)
-		return cpu.welder_act(user, tool)
-	return ..()
+	return CPU_INTERACTABLE(user) ? cpu.welder_act(user, tool) : ..()
 
-/obj/machinery/modular_computer/attackby(obj/item/W as obj, mob/living/user)
-	if (cpu && !user.combat_mode && !(obj_flags & NO_DECONSTRUCTION))
-		return cpu.attackby(W, user)
-	return ..()
+/obj/machinery/modular_computer/attackby(obj/item/weapon, mob/living/user)
+	return (CPU_INTERACTABLE(user) && !user.combat_mode) ? cpu.attackby(weapon, user) : ..()
 
 /obj/machinery/modular_computer/attacked_by(obj/item/attacking_item, mob/living/user)
-	if (cpu)
-		return cpu.attacked_by(attacking_item, user)
-	return ..()
+	return CPU_INTERACTABLE(user) ? cpu.attacked_by(attacking_item, user) : ..()
 
 // Stronger explosions cause serious damage to internal components
 // Minor explosions are mostly mitigitated by casing.
@@ -170,6 +189,6 @@
 // "Burn" damage is equally strong against internal components and exterior casing
 // "Brute" damage mostly damages the casing.
 /obj/machinery/modular_computer/bullet_act(obj/projectile/Proj)
-	if(cpu)
-		return cpu.bullet_act(Proj)
-	return ..()
+	return cpu?.bullet_act(Proj) || ..()
+
+#undef CPU_INTERACTABLE