local M = {victims={}}

local LOUD_DEBUG 	= false
local DEBUG 		= false
local INB4_DAMAGE	= false

function pr(...)
	local txt = strformat(...)
	if LOUD_DEBUG then 
		tasks_chimera_scan.message_by_id(0,txt)
	end
	if DEBUG then
		printf('gameplay_silent_kills: %s', txt)
	end
	return true
end

function feature_enabled()
	local val = ui_options.get("gameplay/silent_kills/sk_enabled")
	-- pr('enabled: %s', val)
	return val
end
function all_melee_ok()
	local val = ui_options.get("gameplay/silent_kills/sk_all_melee_ok")
	pr('all melee ok: %s', val)
	return val
end
function melee_enabled()
	local val = ui_options.get("gameplay/silent_kills/sk_melee_enabled")
	pr('melee enabled: %s', val)
	return val
end
function gun_enabled()
	local val = ui_options.get("gameplay/silent_kills/sk_gun_enabled")
	pr('gun enabled: %s', val)
	return val
end
function headshot_only()
	local val = ui_options.get("gameplay/silent_kills/sk_headshot_only")
	pr('headshot only: %s', val)
	return val
end

function get_fresh_time() 
	local val = ui_options.get("gameplay/silent_kills/sk_fresh_time")
	pr('fresh time: %s', val)
	return (tonumber(val) or 5) * level.get_time_factor() 
end


function get_suspect_dist() 
	local val = ui_options.get("gameplay/silent_kills/sk_suspect_dist")
	pr('fresh time: %s', val)
	return (tonumber(val) or 10)
end

function backstab_hear_range()
	local val = ui_options.get("gameplay/silent_kills/sk_melee_hear_dist")
	pr('melee hear range: %s', val)
	val = tonumber(val) or 5
	return val - val * 0.5 * level.rain_factor()
end

function silent_weapon_hear_range(obj)
	local val = ui_options.get("gameplay/silent_kills/sk_gun_hear_dist")
	pr('gun hear range: %s', val)
	val = tonumber(val) or 10
	return val - val * 0.5 * level.rain_factor()
end

function on_game_start()
	RegisterScriptCallback("npc_on_before_hit",npc_on_before_hit)
	RegisterScriptCallback("npc_on_update",npc_on_update)
	RegisterScriptCallback("save_state",save_state)
	RegisterScriptCallback("load_state",load_state)
end


function tss()
	return game.get_game_time():diffSec(level.get_start_time())
end

function anybody_see(obj)
	for i=1, #db.OnlineStalkers do
		local npc = level.object_by_id(db.OnlineStalkers[i])
		if (npc and IsStalker(npc,npc:clsid()) and npc:alive()) then
			if (npc:see(obj or db.actor)) then
				pr('%s can see %s', npc:name(), obj and obj:name() or 'actor')
				return npc
			end
		end
	end
	return false
end

function closest_npc_dist(obj, victim)
	local testp = obj and obj:position() or db.actor:position()
	local closest = 99999999999
	for i=1, #db.OnlineStalkers do
		local npc = not (db.OnlineStalkers[i] == victim:id() or db.OnlineStalkers[i] == obj:id()) and level.object_by_id(db.OnlineStalkers[i])
		if npc and IsStalker(npc) and npc:alive() then
			local dist = npc:position():distance_to(testp)
			closest = closest > dist and dist or closest
		end
	end
	return closest
end


function save_state(md)
	md.stealth_kills = M
end
function load_state(md) 
	M = md.stealth_kills or {
		victims = {
			-- id = death time
		}
	}
end

function are_enemies(a,b)
	return game_relations.is_factions_enemies(a:character_community(), b:character_community())
end

function npc_on_update(npc)
	if not feature_enabled() then return end
	if not npc then return end
	if not npc:alive() then return end
	
	if npc:see(db.actor) then
		local now = tss()
		for id,ktime in pairs(M.victims) do
			local ded = level.object_by_id(id)
			if 
				ded
				and not are_enemies(npc, ded)
				and now < ktime
				and npc:see(ded)
				and db.actor:position():distance_to(ded:position()) < get_suspect_dist()
			then
				pr('%s is triggered by seeing the corpse of %s!', npc and npc:name(), ded and ded:name())
				
				local h = hit()
				h.type = hit.fire_wound
				h.power = 0.0
				h.impulse = 0.0
				h.direction = VEC_Y
				h.draftsman = db.actor
				npc:hit(h)
				M.victims[id] = nil
			elseif not ded then
				pr('%s no longer online', ded and ded:name())
				M.victims[id] = nil
			elseif now > ktime then
				pr('%s forgot the death of %s', npc and npc:name(), ded and ded:name())
				M.victims[id] = nil
			end
		end
	end
end

local _section_cache = {}
function valid_backstab_weapon(obj)
	if not obj then return false end
	if all_melee_ok() then return true end
	if not _section_cache[obj:section()] then
		_section_cache[obj:section()] = ini_sys:r_bool_ex(obj:section(),"can_stealth_stab", false)
	end
	return _section_cache[obj:section()]
end

function valid_silent_weapon(obj)
	return obj and obj:weapon_is_silencer()
end

local dtype = {
	[hit.light_burn]    = "light_burn",
	[hit.burn]          = "burn",
	[hit.strike]        = "strike",
	[hit.shock]         = "shock",
	[hit.wound]         = "wound",
	[hit.radiation]     = "radiation",
	[hit.telepatic]     = "telepatic",
	[hit.chemical_burn] = "chemical_burn",
	[hit.explosion]     = "explosion",
	[hit.fire_wound]    = "fire_wound",
}


function npc_on_before_hit(npc,shit,bone_id,flags)
	if not feature_enabled() then return end
	if not (melee_enabled() or gun_enabled()) then return end
	
	_ = INB4_DAMAGE and pr(
		'%s about to be hit by %s at %s at distance %s damage type %s', 
		npc and npc:name(), 
		shit and shit.draftsman and shit.draftsman:name(), 
		bone_id, 
		db.actor:position():distance_to(npc:position()),
		dtype[shit.type]
	)
	
	-- skip if it wasnt a hit by the player (skips also fake lethal hits because draftsman is weapon)
	if not (shit.draftsman and shit.draftsman:id() == 0) then return end
	
	-- skip if player has no weapon out (it wasn't damage dealt directly eg. grenade)
	local weapon = db.actor:active_item()
	if not weapon then 
		pr("no active weapon")
		return 
	end
	
	-- not effective vs npc fighting with player
	local in_combat	= npc:best_enemy() and npc:best_enemy():id() == 0
	if in_combat then 
		pr("victim in combat with player")
		return 
	end
	
	-- skip if anybody seen the victim or the player when it happened
	
	local actor_seen	= anybody_see(db.actor) 
	if actor_seen then  
		pr('player seen')
		return
	end
	
	local victim_seen	= anybody_see(npc)		
	if victim_seen then  
		pr('victim seen')
		return
	end
	
	-- find distance of closest non victim npc
	local closest_npc_to_player = closest_npc_dist(db.actor,npc)
	pr('closest to player: %s', closest_npc_to_player)
	
	local closest_npc_to_victim = closest_npc_dist(npc,db.actor)
	pr('closest to victim: %s', closest_npc_to_victim)
	
	if 
		melee_enabled()
		and valid_backstab_weapon(weapon)  								and not printf('stab weapon ok')
		and shit.type == hit.wound        							and not printf('stab damage type ok')
		and closest_npc_to_player > backstab_hear_range()           and not printf('stab distance others ok')
		and closest_npc_to_victim > backstab_hear_range()           and not printf('stab distance others ok')
	then
		local h = hit(shit)
		h.draftsman = weapon
		h.power = 100
		npc:hit(h)
		M.victims[npc:id()] = tss() + get_fresh_time()

		pr('%s stealth stabbed', npc:name())
		
		flags.ret_value = false
		return
	end
	
	-- skip if it wasnt a hit to the head
	if headshot_only() then
		if not (bone_id == 15) then 
			pr("it wasn't a headshot")
			return 
		end
	end
	
	if 
		gun_enabled()
		and shit.type == hit.fire_wound 								and not printf('shot damage type ok')
		and valid_silent_weapon(weapon)									and not printf('shot weapon ok')
		and closest_npc_to_player > silent_weapon_hear_range(weapon)	and not printf('shot distance others ok')
		and closest_npc_to_victim > silent_weapon_hear_range(weapon)	and not printf('shot distance others ok')
	then
		local h = hit(shit)
		h.draftsman = weapon
		h.power = 100
		npc:hit(h)
		M.victims[npc:id()] = tss() + get_fresh_time()
		
		pr('%s stealth shot', npc:name())
		
		flags.ret_value = false
	end
end