SUBSYSTEM_DEF(nightshift)
	name = "Night Shift"
	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_GET(flag/enable_night_shifts))
		can_fire = FALSE
	return ..()

/datum/controller/subsystem/nightshift/fire(resumed = FALSE)
	if(world.time - SSticker.round_start_time < nightshift_first_check)
		return
	check_nightshift()

/datum/controller/subsystem/nightshift/proc/announce(message)
	priority_announce(message, sound='sound/misc/notice2.ogg', sender_override="Automated Lighting System Announcement")

/datum/controller/subsystem/nightshift/proc/check_nightshift()
	var/emergency = GLOB.security_level >= SEC_LEVEL_RED
	var/announcing = TRUE
	var/time = STATION_TIME(FALSE)
	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)
			priority_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.", sound='sound/AI/night.ogg', sender_override="Automated Lighting System Announcement")
		else
			priority_announce("Good morning, crew. As it is now day time, all of the lights aboard the station have been restored to their former brightness.", sound='sound/AI/night2.ogg', sender_override="Automated Lighting System Announcement")
	for(var/A in GLOB.apcs_list)
		var/obj/machinery/power/apc/APC = A
		if (APC.area && (APC.area.type in GLOB.the_station_areas))
			APC.set_nightshift(active)
			CHECK_TICK