# shellcheck shell=bash

if [[ "${EUID}" -ne 0 ]]; then
  echo "Please run the script as root."
  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 && -n $(mountpoint -q /mnt/btrfs) ]]; then
  echo "/mnt/btrfs is already mounted. Exiting."
  exit 1
fi

if [[ -z "$DEVICE" ]]; then
  echo "Error: DEVICE variable is not set."
  exit 1
fi

mkdir -p /mnt/btrfs
mount "/dev/mapper/$DEVICE" /mnt/btrfs

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

umount /mnt/btrfs
rmdir /mnt/btrfs

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