/datum/event/carp_migration
	announceWhen	= 50
	endWhen 		= 900

	var/list/spawned_carp = list()

	var/list/despawn_turfs = list(
		/turf/space,
		/turf/unsimulated/floor/asteroid,
		/turf/simulated/open,
		/turf/simulated/floor/reinforced/airless	// Station roof.
	)

	ic_name = "biological entities"

/datum/event/carp_migration/setup()
	announceWhen = rand(40, 60)
	endWhen = rand(600, 1200)
	despawn_turfs = typecacheof(despawn_turfs)

/datum/event/carp_migration/announce()
	var/announcement = ""
	var/soundfile = 'sound/AI/spacecarp.ogg'
	if(severity == EVENT_LEVEL_MAJOR)
		announcement = "Massive migration of unknown biological entities has been detected near [station_name()], please stand-by. The NDV Icarus has dispatched combat drones to assist."
		soundfile = 'sound/AI/massivespacecarp.ogg'
	else
		announcement = "Unknown biological [length(spawned_carp) == 1 ? "entity has" : "entities have"] been detected near [station_name()], please stand-by.[severity == EVENT_LEVEL_MODERATE ? " The NDV Icarus has dispatched combat drones to assist." : ""]"
	command_announcement.Announce(announcement, "Lifesign Alert", new_sound = soundfile)

/datum/event/carp_migration/start()
	if(severity == EVENT_LEVEL_MAJOR)
		spawn_fish(length(landmarks_list), spawn_drones = TRUE)
		spawn_caverndweller(length(landmarks_list), spawn_drones = TRUE)
	else if(severity == EVENT_LEVEL_MODERATE)
		spawn_fish(rand(4, 6), spawn_drones = TRUE)			//12 to 30 carp, in small groups
		spawn_caverndweller(rand(1, 2), spawn_drones = TRUE) //less of those, also don't happen in the regular event
	else
		spawn_fish(rand(1, 3), 1, 2)	//1 to 6 carp, alone or in pairs

/datum/event/carp_migration/proc/spawn_fish(var/num_groups, var/group_size_min = 3, var/group_size_max = 5, var/spawn_drones = FALSE)
	set waitfor = FALSE
	var/list/spawn_locations = list()

	for(var/obj/effect/landmark/C in landmarks_list)
		if(C.name == "carpspawn")
			spawn_locations.Add(C.loc)
	spawn_locations = shuffle(spawn_locations)
	num_groups = min(num_groups, spawn_locations.len)

	var/i = 1
	while (i <= num_groups)
		var/group_size = rand(group_size_min, group_size_max)
		if(spawn_drones && prob(25))
			var/drone_num = rand(1, 2)
			for(var/d = 1, d <= drone_num, d++)
				new /mob/living/simple_animal/hostile/icarus_drone(get_random_turf_in_range(spawn_locations[i], 10, 6, TRUE))
		for(var/j = 1, j <= group_size, j++)
			if(prob(95))
				var/mob/living/simple_animal/hostile/carp/carp = new(spawn_locations[i])
				spawned_carp += WEAKREF(carp)
			else if(prob(80))
				var/mob/living/simple_animal/carp/baby/carp = new(spawn_locations[i])
				spawned_carp += WEAKREF(carp)
			else
				var/mob/living/simple_animal/hostile/carp/shark/carp = new(spawn_locations[i])
				spawned_carp += WEAKREF(carp)
			CHECK_TICK
		i++

/datum/event/carp_migration/proc/spawn_caverndweller(var/num_groups, var/group_size_min=2, var/group_size_max=3, var/spawn_drones = FALSE)
	set waitfor = FALSE
	var/list/spawn_locations = list()

	for(var/obj/effect/landmark/C in landmarks_list)
		if(C.name == "cavernspawn")
			spawn_locations.Add(C.loc)
	spawn_locations = shuffle(spawn_locations)
	num_groups = min(num_groups, spawn_locations.len)

	var/i = 1
	while (i <= num_groups)
		var/group_size = rand(group_size_min, group_size_max)
		if(spawn_drones && prob(25))
			var/drone_num = rand(1, 2)
			for(var/d = 1, d <= drone_num, d++)
				new /mob/living/simple_animal/hostile/icarus_drone(get_random_turf_in_range(spawn_locations[i], 10, 6, TRUE))
		for (var/j in 1 to group_size)
			new /mob/living/simple_animal/hostile/retaliate/cavern_dweller(spawn_locations[i])
			CHECK_TICK
		i++

/datum/event/carp_migration/end()
	for (var/carp_ref in spawned_carp)
		var/datum/weakref/carp_weakref = carp_ref
		var/mob/living/simple_animal/hostile/carp/fish = carp_weakref.resolve()
		if (fish && prob(50) && is_type_in_typecache(fish.loc, despawn_turfs))
			qdel(fish)