if [ "$(id -u)" -ne 0 ]; then
  echo "This script must be run as root or with sudo privileges."
  exit 1
fi

delete_subvolume_recursively() {
  IFS=$'\n'
  for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
    delete_subvolume_recursively "/mnt/btrfs/$i"
  done
  btrfs subvolume delete "$1"
}

if [[ -e /mnt/btrfs && $(mountpoint -q /mnt/btrfs) ]]; then
  echo "/mnt/btrfs is already mounted. Exiting."
  exit 1
fi

mkdir -p /mnt/btrfs
mount /dev/mapper/luks /mnt/btrfs

if [[ -e /mnt/btrfs/root.bak ]]; then
  if [ "$(ls -A /mnt/btrfs/root.bak)" ]; then
    for i in /mnt/btrfs/root.bak/*; do
      delete_subvolume_recursively "$i"
    done
  else
    echo "/mnt/btrfs/root.bak is empty. Nothing to delete."
  fi
fi

umount /mnt/btrfs
rmdir /mnt/btrfs

nix-collect-garbage -d
nix-store --gc -v