#!/bin/bash -e

FILE=/sys/class/backlight/amdgpu_bl1/brightness
STEPS=7196
MAX=64764

CUR="$(< "$FILE")"

case "$1" in
    +*|-*) CUR=$(((++CUR / STEPS + $1) * STEPS)) ;;
    '') echo "$CUR"; exit ;;
    *) CUR="$1" ;;
esac

if [ "$CUR" -lt 0 ]; then
    CUR=0
elif [ "$CUR" -gt "$MAX" ]; then
    CUR="$MAX"
fi

echo "$CUR" > "$FILE"