Starbound container diff

function containerDiff(items, itemsCache)
  local events = {}

  for k,v in pairs(itemsCache) do
    if items[k] == nil then
      table.insert(events, {
        type = "remove",
        slot = k,
        item = v
      })
    end
  end

  for k,v in pairs(items) do
    if itemsCache[k] == nil then
      table.insert(events, {
        type = "add",
        slot = k,
        item = v
      })
    elseif not table.equals(v, itemsCache[k]) then
      table.insert(events, {
        type = "remove",
        slot = k,
        item = itemsCache[k]
      })
      table.insert(events, {
        type = "add",
        slot = k,
        item = v
      })
    end
  end

  return events
end