Item caching thing for reddit

-- Context: https://www.reddit.com/r/ComputerCraft/comments/1enbvku/comment/lhd6j9h/

local cache = {}

--- Cache info about a single slot in the inventory.
---@param inventory Inventory The inventory to cache from.
---@param slot number The slot to cache.
---@param item item The item in the slot. This allows the function to skip if the item is already cached.
local function cache_slot(inventory, slot, item)
  -- If we have already cached info about this item...
  if cache[item.name] then
    -- ...then we don't need to do it again.
    return
  end

  local data = inventory.getItemDetail(slot)

  if data then
    cache[data.name] = data
  end
end

-- Initialize the peripherals
local chest = peripheral.find("minecraft:chest") --[[@as Inventory?]]
local monitor = peripheral.find("monitor") --[[@as Monitor?]]

-- Throw an error if the peripherals are not found
if not chest then
  error("No chest found.", 0)
end

if not monitor then
  error("No monitor found.", 0)
end

-- Get the size of the chest
local size = chest.size()

-- and set up the monitor.
monitor.setTextScale(0.5)
monitor.setBackgroundColor(colors.white)
monitor.setTextColor(colors.black)
monitor.clear()

local w, h = monitor.getSize()
local spaces = (' '):rep(w)

-- Main loop:
while true do
  -- First, get the list of items in the chest.
  local list = chest.list()

  -- Initialize the items counter
  local items = 0

  -- For each slot in the chest...
  for i = 1, size do
    -- Get the item in the slot.
    local item = list[i]

    -- If there is an item in the slot...
    if item then
      -- Cache the item info.
      cache_slot(chest, i, item)

      -- Then increment our items counter, and set the cursor position to the start of the correct line.
      items = items + 1
      monitor.setCursorPos(1, items)

      -- Set the color depending on how full the slot is.
      if item.count >= 64 then
        monitor.setTextColor(colors.red)
      elseif item.count >= 32 then
        monitor.setTextColor(colors.pink)
      else
        monitor.setTextColor(colors.white)
      end


      -- Before finally writing the item name and count to the monitor.
      monitor.write(("%d x %s in slot %d%s"):format(item.count, cache[item.name].displayName, i, spaces))
    end
  end

  sleep() -- Wait for the next tick.
end