backlight

#!/bin/bash

#
# Dank general Backlight Utility
#

#
# Notes: Use a flag to call displayCurrentValue instead of as part of arg parsing
# to avoid argument ordering issues.
#

# CMD Macro
argument_error() { echo "Unrecognized argument: $1"; echo "Try passing --help."; exit 1; };

# File and Directory aliases
BRIGHTNESS_FILE="/sys/class/backlight/intel_backlight/brightness";

# Data
ACTUAL_BRIGHTNESS_RANGE=(0 6000);
EASY_BRIGHTNES_RANGE=(0 10);
TARGET_VALUE=;

# Flags
USE_ACTUAL_VALUE=false;

function throwError() {
	local ERROR_TYPE="$1"

	case "$ERROR_TYPE" in
		argument_count)
			echo "No argument supplied. Try --help.";
			exit 2;;
		non_integer_argument)
			echo "Non integer argument supplied.";
			exit 2;;
		zero_brightness)
			echo "Brightness cannot be set to zero.";
			exit 5;;
		brightness_above_range)
			echo "Simple brightness value must be 1 - 10.";
			exit 5;;
		*)
			echo "Unknown Error.";
			exit 1;;
	esac;
}
function displayHelp() {
	echo displayHelp called.;
	exit "$1";
};
function assertIntegerArgument() {
	local arg_value="$1";
	
	if [[ "$arg_value" == +([0-9]) ]]; then
		return 0;
	fi;
	echo "$arg_value did not pass integer assertion."
	return 1;
};
function convertSimpleValue() {
	local desired_brightness="$TARGET_VALUE";

	if [ "$desired_brightness" == 0 ]; then
		throwError "zero_brightness";
	elif [ "$desired_brightness" -gt 10 ]; then
		echo $desired_brightness
		throwError "brightness_above_range";
	else
		TARGET_VALUE=$(( $desired_brightness * 600 ));
	fi;
};
function setBrightnessValue() {
	if [ -z "$TARGET_VALUE" ]; then
		echo No brightness value supplied.;
		displayHelp "1";
		exit 1;
	fi;

	echo "$TARGET_VALUE" > "$BRIGHTNESS_FILE";

	return 0;
};
function convertActualValue() {
	local actual_value=$1

	echo $(( "$actual_value" / 600 ));
	return 0;
}
function displayCurrentValue() {
	local brightness_value=$(cat $BRIGHTNESS_FILE);
	local simple_value=$(convertActualValue "$brightness_value");

	printf "Current backlight value: ";
	if [ "$USE_ACTUAL_VALUE" == true ]; then
		printf "$brightness_value\n";
		return 0;
	fi;

	printf "$simple_value\n";
	return 0;
};
function main() {
	# Determine argument count
	if [ ${#@} -eq 0 ]; then throwError "argument_count"; fi;

	# Parse arguments
	for argument in ${@}; do
		case $argument in 
			-a|--actual-value) 
				USE_ACTUAL_VALUE=true;;
			-c|--current-value)
				displayCurrentValue;
				exit 0;;
			--help) 
				displayHelp;
				exit 1;;
			*)
				assertIntegerArgument "$argument" && \
				       	TARGET_VALUE="$argument" || \
					throwError "non_integer_argument";;
		esac;	
	done;

	# Determine value type to use (actual or 'easy')
	[ "$USE_ACTUAL_VALUE" == false ] && convertSimpleValue;
	
	# Set brightness value
	setBrightnessValue "$TARGET_VALUE";
        return 0;	
};

main ${@};
exit 0;