local Medusa = RegisterMod("Medusa", 1)
local Medusa_item = Isaac.GetItemIdByName("Head of Medusa")

List = {}
function List.new ()
 return {first = 0, last = -1}
end

function List.popleft (list)
	local first = list.first
	if first > list.last then error("list is empty") end
	local value = list[first]
	list[first] = nil
	list.first = first + 1
	return value
end

function List.pushright (list, value)
	local last = list.last + 1
	list.last = last
	list[last] = value
end

local activated = false
local num_stone = 0
local stoney_list = List.new()

function Medusa:use_Medusa()
	activated = true
end

function Medusa:effect_Medusa()
	if activated then
		local player   = Isaac.GetPlayer(0)
		local entities = Isaac.GetRoomEntities()

		if Medusa:hasPlayerJustEnterARoom() and num_stone > 0 then
			num_stone = 0
			activated = false
		end

		for i = 1, #entities do
			if (entities[i]:IsVulnerableEnemy() and entities[i]:IsBoss() == false) then
				local entity = entities[i]
				local pos = entity.Position
				local dist = pos:Distance(player.Position)

				if dist <= 120 then
					entity:Remove()
					local stoney = Isaac.Spawn(EntityType.ENTITY_STONEY, 1, 1, pos, Vector(0, 0), player)
					List.pushright(stoney_list, stoney)
					if num_stone < 3 then
						num_stone = num_stone + 1
					else
						local remove = List.popleft(stoney_list)
						-- remove this reference!
					end
				end
			end
		end
	end
end

function Medusa:hasPlayerJustEnterARoom()
	return Game():GetRoom():GetFrameCount() == 1
end

Medusa:AddCallback(ModCallbacks.MC_USE_ITEM, Medusa.use_Medusa, Medusa_item)
Medusa:AddCallback(ModCallbacks.MC_POST_UPDATE, Medusa.effect_Medusa)