Oxygen tank supplier

local component = require("component")
local pi = component.playerinterface
local chest = component.chest
local chatbox = nil

------ CONFIG SECTION STARTS HERE -------

pi.setOutputSide("south") -- Hopper side
pi.setInputSide("west") -- Oxygen supply chest side

local playername = "Subtixx" -- (Your) Playername to chat to
local delay = 5 -- Delay between checks
local tankToKeepInInv = 3 -- Amount of tanks to keep supplied in your inventory
local shouldSmallTanksCount = false -- Count small tanks to tank keep in inv
local stockSmallTanks = false -- Should small tanks be transferred to player
local stockHotbar = false -- Should the hotbar counted in when searching for a free inventory spot?
local enableChatBox = true --

------ DO NOT MODIFY BEYOND THIS POINT -------
if(enableChatBox) then
  chatbox = component.peripheralsplusplus_chatbox
end

local player = pi.getPlayerInv(playername).value

local cooldown = {}

function outputCooldown(text)
  if(cooldown[text] ~= nil) then
    if(cooldown[text] <= (os.time() * 1000/60/60) - 6000) then
      cooldown[text] = nil
    end
  else
    if(enableChatbox) then
      chatbox.tell(playername, tostring(text))
    end
    print(tostring(text))
    cooldown[text] = (os.time() * 1000/60/60) + 6000 -- 12000 (-6000)
  end
end

function findFirstFreeInventorySlot()
  for i=0, 36, 1 do
    local itemStack = player.getStackInSlot(i)
    if(itemStack == nil) then
      return i
    end
  end
  outputCooldown("NO ROOM! YOUR INVENTORY IS FULL!")
end

function findFirstOxygenChestSlot()
  for i=1, chest.getInventorySize() do
    local itemStack = chest.getStackInSlot(i)
    if(itemStack ~= nil) then
      if(itemStack.id == "GalacticraftCore:item.oxygenTankHeavyFull" or
          (stockSmallTanks and (itemStack.id == "GalacticraftCore:item.oxygenTankMedFull" or
            itemStack.id == "GalacticraftCore:item.oxygenTankLightFull"))) then
        if(i <= 9 and stockHotbar) or (i > 9) then
           return i - 1
        end
      end
    end
  end
  outputCooldown("NO OXYGEN TANKS LEFT! CHECK THE OXYGEN CHEST!")
end

function replaceTanks()
  local totalTanks = 0
  for i=0, 36, 1 do
    local itemStack = player.getStackInSlot(i)
    if(itemStack ~= nil) then
      if(itemStack.name == "GalacticraftCore:item.oxygenTankHeavyFull") then
        if(itemStack.meta >= 2700) then
          -- Extract
          player.retrieveFromSlot(i, 1)
        else
          totalTanks = totalTanks + 1
        end
      elseif(itemStack.name == "GalacticraftCore:item.oxygenTankMedFull") then
        if(itemStack.meta >= 1800) then
          player.retrieveFromSlot(i, 1)
        elseif(shouldSmallTanksCount) then
          totalTanks = totalTanks + 1
        end
      elseif(itemStack.name == "GalacticraftCore:item.oxygenTankLightFull") then
        if(itemStack.meta >= 900) then
          player.retrieveFromSlot(i, 1)
        elseif(shouldSmallTanksCount) then
          totalTanks = totalTanks + 1
        end
      end
    end
  end

  while totalTanks < tankToKeepInInv do
    local oxygenSlot = findFirstOxygenChestSlot()
    local inventorySlot = findFirstFreeInventorySlot()

    player.push(oxygenSlot, inventorySlot)
    totalTanks = totalTanks + 1
  end
end

while true do
  replaceTanks()
  os.sleep(delay)
end