main.lua

StartDebug();
local mod = RegisterMod("Spindown dice preview", 1)
local json = require "json"
local spriteCache = {}

---------
-- UTILITY
---
function mod:getPreviousAvailableCollectibleSubType( entity, skipAmount )
  local subType = entity.SubType;
  local itemCfg = nil
  local skipCount = skipAmount - 1

  while itemCfg == nil do
      if subType <= 1 then return nil end
      subType = subType - 1

      itemCfg = Isaac.GetItemConfig():GetCollectible( subType )

      -- If its a valid item, subtract from skip amount
      if itemCfg~= nil and itemCfg.Hidden == false then
        skipAmount = skipAmount - 1
      end

      -- Dont count hidden items
      -- TODO: No way to check for unlocked items
      if (itemCfg ~= nil and itemCfg.Hidden == true) or (skipAmount > 0) then
        itemCfg = nil
      end
  end

  return subType
end

function mod:isItem( entity )
  return entity ~= nil and entity:ToPickup() ~= nil and entity.Variant == 100
end

------------------
-- MOD CALLBACKS
----
function mod:onRender(t)
    local skipAmount = mod:getAvailableSkipAmount()

    if skipAmount == 0 then return nil end

    -- Checking to see if curse of the blind is active
    local curseName = Game():GetLevel():GetCurseName()

    -- Should not be able to display preview if curse of the blind is active
    if curseName ~= nil and curseName == "Curse of the Blind!" then return nil end

    local player = Isaac.GetPlayer( 0 )
    local pickups = Isaac.FindInRadius( player.Position, 600, EntityPartition.PICKUP )

    for i, entity in ipairs( pickups ) do
      if mod:isItem( entity ) then
        mod:renderCollectible( entity,skipAmount )
      end
	end
end

-----------
-- MOD METHODS
------

function mod:getAvailableSkipAmount()
  local playerCount = Game():GetNumPlayers()
  local currentSkipAmount = 0

  for i = 0, playerCount - 1 do
    local p = Isaac.GetPlayer(i)
    local hasCarBattery = p:HasCollectible( CollectibleType.COLLECTIBLE_CAR_BATTERY )
    local skipAmount = 1

    if p ~= nil and ( p:GetActiveItem ( ActiveSlot.SLOT_PRIMARY ) == 723 or p:GetActiveItem ( ActiveSlot.SLOT_POCKET ) == 723 ) then
        if hasCarBattery then
          skipAmount = skipAmount + 1
        end

        currentSkipAmount = math.max( currentSkipAmount, skipAmount )
    end
  end

  return currentSkipAmount
end

function mod:renderCollectible(entity, skipAmount)
  local previousCollectibleSubType = mod:getPreviousAvailableCollectibleSubType(entity, skipAmount)

  if previousCollectibleSubType == nil then return end

  local itemConfig = Isaac.GetItemConfig():GetCollectible( previousCollectibleSubType )

  if itemConfig ~= null then
    descriptor = itemConfig.GfxFileName

    local itemSprite

    -- So we do not have to be constantly creating and reading from spritesheet
    if spriteCache[ descriptor ] == nil then
      itemSprite = Sprite()
      itemSprite:Load("gfx/005.100_Collectible.anm2", true)
      itemSprite:ReplaceSpritesheet(1, itemConfig.GfxFileName )
      itemSprite:LoadGraphics()
      itemSprite.Color = Color(1,1,1,0.45)
      itemSprite:SetFrame("Idle", 8)
      itemSprite.Scale = Vector(0.4, 0.4)

      spriteCache[descriptor] = itemSprite
    else
      itemSprite = spriteCache[descriptor]
    end

    -- Rendering besides item
    local adjustedPosition = Vector(0,0)

    if entity:ToPickup():IsShopItem() then
      adjustedPosition = entity.Position - Vector(-22, 20)
    else
      adjustedPosition = entity.Position - Vector(-22, 38)
    end

    itemSprite:Render( Isaac.WorldToScreen( adjustedPosition ), Vector( 0,0 ), Vector( 0,0 ))
  end
end

mod:AddCallback( ModCallbacks.MC_POST_RENDER , mod.onRender )