Donor Card

local Mod = RegisterMod("YourFolderName", 1)
local game = Game()

local donorcard = {
	SPAWN_CHANCE = 50,		-- chance to spawn a blood donation machine.
	MaggieStart = true   	-- should Maggie start with the Trinket?
}

TrinketType.TRINKET_DONOR_CARD = Isaac.GetTrinketIdByName("Donor Card")

-- console commands
function Mod:costumizeMaggie(consol,para)
	if consol == "betterMaggie" then
		if donorcard.MaggieStart == false then
			donorcard.MaggieStart = true
			Isaac.ConsoleOutput("Maggie will start with the Donor Card")
		else
			donorcard.MaggieStart = false
			Isaac.ConsoleOutput("Maggie won't start with the Donor Card")
		end
	end
end
SuperBum:AddCallback(ModCallbacks.MC_EXECUTE_CMD, Mod.costumizeMaggie)

-- on post peffect update
function Mod:onInit(player)

    -- stuff, which happens on frame 1
	if game:GetFrameCount() == 1 then

		-- let Maggie start with the trinket
		if player:GetPlayerType() == PlayerType.PLAYER_MAGDALENA
		and donorcard.MaggieStart == true then

		    -- player gets the donor card trinket
	    	player:GetTrinket(TrinketType.TRINKET_DONOR_CARD)
		end
	end
end
Mod:AddCallback(ModCallbacks.MC_POST_PEFFECT_UPDATE, Mod.onInit)


-- on new room
function Mod:onNewRoom(_)
	local player = Isaac.GetPlayer(0)
	local roomType = game:GetRoom():GetType()

    -- check if the player has the trinket
	if player:HasTrinket(TrinketType.TRINKET_DONOR_CARD)
    or player:GetEffects():HasTrinketEffect(TrinketType.TRINKET_DONOR_CARD) then

        -- check if the player already visited room and if the room is a shop
		if game:GetRoom():IsFirstVisit() == true
		and roomType == RoomType.ROOM_SHOP then

			-- get RNG if needed
			local rng = player:GetTrinketRNG(TrinketType.TRINKET_DONOR_CARD)
            local roll = rng:RandomInt(100)

			if roll < donorcard.SPAWN_CHANCE then

				-- spawn the blood donation machine
				Isaac.Spawn(EntityType.ENTITY_SLOT, 8, 0, Vector(250, 250), Vector(0, 0), player)    -- position needs adjustment
			end
		end
	end
end
Mod:AddCallback(ModCallbacks.MC_POST_NEW_ROOM, Mod.onNewRoom)