startup

rednet.open("top")
local mon = peripheral.wrap("monitor_38")
monX, monY = mon.getSize()

function drawText(x, y, text, color_txt, color_bg)
  mon.setTextScale(2)
  mon.setBackgroundColor(color_bg)
  mon.setTextColor(color_txt)
  mon.setCursorPos(x, y)
  mon.write(text)
end

function drawLine(x, y, length, size, color_bg)
  for yPos = y, y+size-1 do
    mon.setBackgroundColor(color_bg)
    mon.setCursorPos(x, yPos)
    mon.write(string.rep(" ", length))
  end
end

function drawProg(x, y, txt, length, size, color_bg, color_bar, minVal, maxVal)
  drawLine(x, y, length, size, color_bg)

  local barSize = math.floor((minVal/maxVal)*length)
  drawLine(x, y, barSize, size, color_bar)

  local text = txt.." ".. math.floor((minVal/maxVal)*100).."%"
  if barSize > length/2+#text/2 then
    drawText(x+length/2-#text/2, y+size/2, text, colors.black, color_bar)
  elseif barSize > #text then
    drawText((x+barSize)-#text, y+size/2, text, colors.black, color_bar)
  else
    drawText(x+length/2-#text/2, y+size/2, text, colors.black, color_bg)
  end
end

function clear()
  mon.setBackgroundColor(colors.black)
  mon.clear()
end

while true do
  id, cmd = rednet.receive()
  clear()
  drawProg(2, 1, "Energy", monX-2, 1, colors.gray, colors.green, cmd, 100)
  sleep(0.75)
end