local function padLeft(str, w)
  return string.rep(" ", w - #str) .. str
end

local function findPeripheral(_type)
  for _,name in pairs(peripheral.getNames()) do
    if peripheral.getType(name) == _type then
      return peripheral.wrap(name)
    end
  end

  error("Cannot find ".._type.." attached to this computer", 0) --# may as well put the error here
end

local m = findPeripheral("monitor")
local powerUnit = findPeripheral("mfsu") or findPeripheral("batbox") --# have the larger unit take priority, if an mfsu is found then a search will not be performed for a batbox

m.setTextScale(0.5)

local w, h = m.getSize()
local total = (powerUnit.getCapacity or powerUnit.getEUCapacity)() --# a compatible call, it will find the function pointer and invoke it, whichever it may be

os.startTimer(1)

while true do
  local stored = (powerUnit.getStored or powerUnit.getEUStored)() --# a compatible call, it will find the function pointer and invoke it, whichever it may be

  m.clear()
  m.setCursorPos(1, 2)
  m.setTextColour(colours.orange)
  m.write("Energy:")
  m.setTextColour(colours.white)
  m.write(padLeft(tostring(stored), w - 7))

  m.setCursorPos(1, 4)
  m.setTextColour(colours.orange)
  m.write("Total:")
  m.setTextColour(colours.white)
  m.write(padLeft(tostring(total), w - 6))

  local p = (w-2) * stored / total

  m.setBackgroundColour(colours.lightGrey)
  m.setCursorPos(2, 8)
  m.write(string.rep(" ", w-2))
  m.setBackgroundColour(colours.grey)
  m.setCursorPos(2, 8)
  m.write(string.rep(" ", p))
  m.setBackgroundColour(colours.black)

  os.pullEvent("timer")
  os.startTimer(1)
end