/datum/disease
	//Flags
	var/visibility_flags = 0
	var/disease_flags = CURABLE|CAN_CARRY|CAN_RESIST
	var/spread_flags = DISEASE_SPREAD_AIRBORNE | DISEASE_SPREAD_CONTACT_FLUIDS | DISEASE_SPREAD_CONTACT_SKIN

	//Fluff
	var/form = "Virus"
	var/name = "No disease"
	var/desc = ""
	var/agent = "some microbes"
	var/spread_text = ""
	var/cure_text = ""

	//Stages
	var/stage = 1
	var/max_stages = 0
	var/stage_prob = 4

	//Other
	var/list/viable_mobtypes = list() //typecache of viable mobs
	var/mob/living/carbon/affected_mob = null
	var/list/cures = list() //list of cures if the disease has the CURABLE flag, these are reagent ids
	var/infectivity = 65
	var/cure_chance = 8
	var/carrier = FALSE //If our host is only a carrier
	var/bypasses_immunity = FALSE //Does it skip species virus immunity check? Some things may diseases and not viruses
	var/permeability_mod = 1
	var/severity = DISEASE_SEVERITY_NONTHREAT
	var/list/required_organs = list()
	var/needs_all_cures = TRUE
	var/list/strain_data = list() //dna_spread special bullshit
	var/infectable_biotypes = MOB_ORGANIC //if the disease can spread on organics, synthetics, or undead
	var/process_dead = FALSE //if this ticks while the host is dead
	var/copy_type = null //if this is null, copies will use the type of the instance being copied

/datum/disease/New(make_typecache = TRUE)
	if(make_typecache && length(viable_mobtypes))
		viable_mobtypes = typecacheof(viable_mobtypes)

/datum/disease/Destroy()
	. = ..()
	if(affected_mob)
		remove_disease()
	SSdisease.active_diseases.Remove(src)

//add this disease if the host does not already have too many
/datum/disease/proc/try_infect(var/mob/living/infectee, make_copy = TRUE)
	infect(infectee, make_copy)
	return TRUE

//add the disease with no checks
/datum/disease/proc/infect(var/mob/living/infectee, make_copy = TRUE)
	var/datum/disease/D = make_copy ? Copy() : src
	infectee.diseases += D
	D.affected_mob = infectee
	SSdisease.active_diseases += D //Add it to the active diseases list, now that it's actually in a mob and being processed.

	D.after_add()
	infectee.med_hud_set_status()

	var/turf/source_turf = get_turf(infectee)
	log_virus("[key_name(infectee)] was infected by virus: [src.admin_details()] at [loc_name(source_turf)]")

//Return a string for admin logging uses, should describe the disease in detail
/datum/disease/proc/admin_details()
	return "[src.name] : [src.type]"

/datum/disease/proc/stage_act()
	var/cure = has_cure()

	if(carrier && !cure)
		return

	stage = min(stage, max_stages)

	if(!cure)
		if(prob(stage_prob))
			update_stage(min(stage + 1,max_stages))
	else
		if(prob(cure_chance))
			update_stage(max(stage - 1, 1))

	if(disease_flags & CURABLE)
		if(cure && prob(cure_chance))
			cure()

/datum/disease/proc/update_stage(new_stage)
	stage = new_stage

/datum/disease/proc/has_cure()
	if(!(disease_flags & CURABLE))
		return FALSE

	. = cures.len
	for(var/C_id in cures)
		if(!affected_mob.reagents.has_reagent(C_id))
			.--
	if(!. || (needs_all_cures && . < cures.len))
		return FALSE

//Airborne spreading
/datum/disease/proc/spread(force_spread = 0)
	if(!affected_mob)
		return

	if(!(spread_flags & DISEASE_SPREAD_AIRBORNE) && !force_spread)
		return

	if(affected_mob.reagents.has_reagent(/datum/reagent/medicine/spaceacillin) || (affected_mob.satiety > 0 && prob(affected_mob.satiety/10)))
		return

	var/spread_range = 2

	if(force_spread)
		spread_range = force_spread

	var/turf/T = affected_mob.loc
	if(istype(T))
		for(var/mob/living/carbon/C in oview(spread_range, affected_mob))
			var/turf/V = get_turf(C)
			if(disease_air_spread_walk(T, V))
				C.AirborneContractDisease(src, force_spread)

/proc/disease_air_spread_walk(turf/start, turf/end)
	if(!start || !end)
		return FALSE
	while(TRUE)
		if(end == start)
			return TRUE
		var/turf/Temp = get_step_towards(end, start)
		if(!CANATMOSPASS(end, Temp))
			return FALSE
		end = Temp


/datum/disease/proc/cure(add_resistance = TRUE)
	if(affected_mob)
		if(add_resistance && (disease_flags & CAN_RESIST))
			affected_mob.disease_resistances |= GetDiseaseID()
	qdel(src)

/datum/disease/proc/IsSame(datum/disease/D)
	if(istype(src, D.type))
		return TRUE
	return FALSE


/datum/disease/proc/Copy()
	//note that stage is not copied over - the copy starts over at stage 1
	var/static/list/copy_vars = list("name", "visibility_flags", "disease_flags", "spread_flags", "form", "desc", "agent", "spread_text",
									"cure_text", "max_stages", "stage_prob", "viable_mobtypes", "cures", "infectivity", "cure_chance",
									"bypasses_immunity", "permeability_mod", "severity", "required_organs", "needs_all_cures", "strain_data",
									"infectable_biotypes", "process_dead")

	var/datum/disease/D = copy_type ? new copy_type() : new type()
	for(var/V in copy_vars)
		var/val = vars[V]
		if(islist(val))
			var/list/L = val
			val = L.Copy()
		D.vars[V] = val
	return D

/datum/disease/proc/after_add()
	return


/datum/disease/proc/GetDiseaseID()
	return "[type]"

/datum/disease/proc/remove_disease()
	affected_mob.diseases -= src		//remove the datum from the list
	affected_mob.med_hud_set_status()
	affected_mob = null