brightness.nim

import strutils

proc parseFile(filename: string): int =
  result = filename.staticRead.strip.parseInt

# define the brightness file
const file = "/sys/class/backlight/intel_backlight/brightness"

# define thresholds for on and off
const brightnessOff = 0
const offThreshold = 20
const brightnessDefault = 12000
const oldBrightnessFile = "/home/basti/scripts/old_brightness"

# read the current brightness
let brightness = parseFile file
# get the input argument. Either "on" or "off"
let args = paramCount()
let toOn = paramStr(args)

if toOn notin @["on", "off", "toggle"]:
  echo toOn
  quit()
elif toOn == "on":
  # write brightness from current_brightness
  let oldBrightness = parseFile oldBrightnessFile
elif toOn == "toggle":
  # write the current `brightness` to `old_brightness` if
  # it's different from 0, then write 0. Otherwise read
  # `old_brightness` and write that
  if brightness < offThreshold:
    # display is off -> read current_brightness
    let oldBrightness = parseFile oldBrightnessFile
    if oldBrightness > offThreshold:
      # simply write `oldBrightness`
      echo "Writing oldBrightness ", oldBrightness, " to file ", file
      writeFile(file, $oldBrightness)
    else:
      # write default brightness
      echo "Writing brightnessDefault ", brightnessDefault, " to file ", file
      writeFile(file, $brightnessDefault)
  elif brightness > offThreshold:
    # means we turn off display
    # first write current brightness file
    echo "Writing brightness ", brightness, " to oldBrightnessFile ", oldBrightnessFile
    writeFile(oldBrightnessFile, $brightness)
    # now write brightness zero
    echo "Writing brightnessOff ", brightnessOff, " to file ", file
    writeFile(file, $brightnessOff & "\n")