brightness

#!/usr/bin/python3

# -*- coding: utf-8 -*-

# Copyright (c) 2018 Jared Daniel Carbonell Recomendable.

# Use visudo to exclude this utility from requiring user/root passwords when
# running with sudo.

import sys
import subprocess

# This is all that has to be changed when porting this program to other computers.
bri_change = 250000
driver_protocol = "intel_backlight"

# Default Commands and Error Messages
max_bri = int(subprocess.check_output('cat /sys/class/backlight/{p}/max_brightness'.format(p=driver_protocol), shell=True).decode())
readcom = 'cat'
com = 'tee /sys/class/backlight/{p}/brightness <<< {s}'
com2 = 'cat /sys/class/backlight/{p}/brightness'
invalid_resp = '\nYou have entered an invalid response.\nExiting...\n'
cannot_get_brightness = '\nUnable to get brightness.\nExiting...\n'

def run(has_input, level=max_bri):
    """Carry out the process of changing the brightness of the display."""
    if has_input == 1:
        to_run = com.format(p=driver_protocol, s=level)
        subprocess.run(['bash', '-c', to_run])
    elif has_input == 2:
        current_brightness = int(subprocess.check_output(com2.format(p=driver_protocol), shell=True).decode().split('\n')[0])
        if level == 'd':
            level = max(current_brightness - bri_change, 0)
        else:
            level = min(current_brightness + bri_change, max_bri)
        run(1, level)
    else:
        temp_level = input('Brightness Level [0-{m}, Default: {m}]: '.format(m=max_bri))
        if temp_level == '':
            run(1)
        elif temp_level.isnumeric():
            if 0 <= int(temp_level) <= max_bri:
                run(1, temp_level)
            else:
                sys.exit(invalid_resp)
        else:
            sys.exit(invalid_resp)

def show_help():
    """Show the help documentation for the program."""
    help_doc = '''Usage: brightness [level/change]

Level:
  0    - lowest
  [...]
  {m} - highest

Change:
  u/up   - Increases the screen brightness by one level.
  d/down - Decreases the screen brightness by one level.'''.format(m=max_bri)
    print(help_doc)

if __name__ == '__main__':
    if len(sys.argv) == 1:
        run(0)
    elif len(sys.argv) == 2:
        if sys.argv[1].isnumeric():
            if 0 <= int(sys.argv[1]) <= max_bri:
                level = sys.argv[1]
                run(1, level)
            else:
                show_help()
        elif sys.argv[1] in ('d', 'u', 'down', 'up'):
            level = sys.argv[1][0]
            run(2, level)
        else:
            show_help()
    else:
        show_help()