Nightshifts & Randomized Station Time

This commit adds the Nightshift lighting mode from /tg/. From 19:00 to
07:00 in station time, the station will go into a reduced-lighting mode,
with dimmed lights across the station.

In conjunction with this, there is a new configuration option to start
the shift time at a random time other than 12:00, so that players are
more likely to experience a night shift (as opposed to having to have a
7 hour round).

code/controllers/configuration.dm

@@ -199,6 +199,10 @@
 	var/high_pop_mc_mode_amount = 65
 	var/disable_high_pop_mc_mode_amount = 60
 
+	// Nightshift
+	var/randomize_shift_time = FALSE
+	var/enable_night_shifts = FALSE
+
 /datum/configuration/New()
 	var/list/L = subtypesof(/datum/game_mode)
 	for(var/T in L)
@@ -605,19 +609,18 @@
 					shutdown_shell_command = value
 
 				if("disable_karma")
-					disable_karma = 1
+					config.disable_karma = 1
 
 				if("tick_limit_mc_init")
-					tick_limit_mc_init = text2num(value)
+					config.tick_limit_mc_init = text2num(value)
 				if("base_mc_tick_rate")
-					base_mc_tick_rate = text2num(value)
+					config.base_mc_tick_rate = text2num(value)
 				if("high_pop_mc_tick_rate")
-					high_pop_mc_tick_rate = text2num(value)
+					config.high_pop_mc_tick_rate = text2num(value)
 				if("high_pop_mc_mode_amount")
-					high_pop_mc_mode_amount = text2num(value)
+					config.high_pop_mc_mode_amount = text2num(value)
 				if("disable_high_pop_mc_mode_amount")
-					disable_high_pop_mc_mode_amount = text2num(value)
-
+					config.disable_high_pop_mc_mode_amount = text2num(value)
 				else
 					diary << "Unknown setting in configuration: '[name]'"
 
@@ -680,6 +683,10 @@
 					MAX_EX_FLAME_RANGE = BombCap
 				if("default_laws")
 					config.default_laws = text2num(value)
+				if("randomize_shift_time")
+					config.randomize_shift_time = TRUE
+				if("enable_night_shifts")
+					config.enable_night_shifts = TRUE
 				else
 					diary << "Unknown setting in configuration: '[name]'"
 

code/controllers/subsystem/nightshift.dm

@@ -0,0 +1,59 @@
+SUBSYSTEM_DEF(nightshift)
+	name = "Night Shift"
+	init_order = INIT_ORDER_NIGHTSHIFT
+	priority = FIRE_PRIORITY_NIGHTSHIFT
+	wait = 600
+	flags = SS_NO_TICK_CHECK
+
+	var/nightshift_active = FALSE
+	var/nightshift_start_time = 702000		//7:30 PM, station time
+	var/nightshift_end_time = 270000		//7:30 AM, station time
+	var/nightshift_first_check = 30 SECONDS
+
+	var/high_security_mode = FALSE
+
+/datum/controller/subsystem/nightshift/Initialize()
+	if(!config.enable_night_shifts)
+		can_fire = FALSE
+	if(config.randomize_shift_time)
+		GLOB.gametime_offset = rand(0, 23) HOURS
+	return ..()
+
+/datum/controller/subsystem/nightshift/fire(resumed = FALSE)
+	if(world.time - round_start_time < nightshift_first_check)
+		return
+	check_nightshift()
+
+/datum/controller/subsystem/nightshift/proc/announce(message)
+	priority_announcement.Announce(message, new_sound = 'sound/misc/notice2.ogg', new_title = "Automated Lighting System Announcement")
+
+/datum/controller/subsystem/nightshift/proc/check_nightshift()
+	var/emergency = security_level >= SEC_LEVEL_RED
+	var/announcing = TRUE
+	var/time = station_time()
+	var/night_time = (time < nightshift_end_time) || (time > nightshift_start_time)
+	if(high_security_mode != emergency)
+		high_security_mode = emergency
+		if(night_time)
+			announcing = FALSE
+			if(!emergency)
+				announce("Restoring night lighting configuration to normal operation.")
+			else
+				announce("Disabling night lighting: Station is in a state of emergency.")  
+	if(emergency)
+		night_time = FALSE
+	if(nightshift_active != night_time)
+		update_nightshift(night_time, announcing)
+
+/datum/controller/subsystem/nightshift/proc/update_nightshift(active, announce = TRUE)
+	nightshift_active = active
+	if(announce)
+		if (active)
+			announce("Good evening, crew. To reduce power consumption and stimulate the circadian rhythms of some species, all of the lights aboard the station have been dimmed for the night.")
+		else
+			announce("Good morning, crew. As it is now day time, all of the lights aboard the station have been restored to their former brightness.")
+	for(var/A in apcs)
+		var/obj/machinery/power/apc/APC = A
+		if(is_station_level(APC.z))
+			APC.set_nightshift(active)
+			CHECK_TICK