#!/bin/bash

# Useful to delete a docker runtime diretory. In case of btrfs storage driver, handles deletion of btrfs
# subvolumes used to store image layers. Similarly, in caes of zfs storage driver, handles deletion of
# zfs datasets used to store image layers. Assumes dockerd is not running.

# Note: If the $target diretory is spit across multiple volumes, this operation is a no-op.

# Caution: in case of 'native' zfs storage driver which uses datasets to store layers, $target is irrelevant
# because datasets are not listed under directories.  This script will destroy *all* legacy datasets in the
# volume.  For example, consider two directories on same volume:

#  /mnt/cache/docker
#  /mnt/cache/docker-backup

# Each directory holds a valid docker tree structure, maybe 'docker' is current and 'docker-backup' is
# a backup.  User decides he no loner needs 'docker-backup' so he invokes this script.  The result will be
# that not only will /mnt/cache/docker-backup be deleted, but all datasets belonging to /mnt/cache/docker
# will also be deleted.  This is because we cannot tell which datasets belong with which docker instance.

# If /mnt/cache/docker and /mnt/cache/docker-backup were themselves datasets, then we would be able to, but
# this is not implemented here.

dereference() {
  local DIR=$1
  # if directory is on user share, attempt to dereference
  if [[ "$DIR" == /mnt/user/* ]]; then
    # getfattr would return blank if /mnt/user/<share> is a bind-mount
    local DISK=$(getfattr -n system.LOCATIONS --absolute-names --only-values "$DIR" 2>/dev/null)
    if [[ -n "$DISK" ]]; then
      # whitespace in $DISK would exist if $target is split across multiple volumes
      [[ ! "$DISK" =~ [[:space:]] ]] && DIR="${DIR/user/$DISK}" || DIR=""
    fi
  fi
  echo "$DIR"
}

rm_docker() {
  local target="${1%/}"

  # sanity check that this is a docker folder
  if [[ ! -d "$target/containerd" ]]; then
    echo "docker_rm: $target is not a docker folder"
    exit 1
  fi

  # dereference folder on user share
  target=$(dereference "$target")
  if [[ -z "$target" ]]; then
    echo "docker_rm: $target is split across multiple volumes"
    exit 1
  fi

  if [[ -d "$target/btrfs/subvolumes" ]]; then
    # delete btrfs subvolumes
    for subvol in "$target/btrfs/subvolumes/"*; do
      btrfs subvolume delete -cR "$subvol"
    done
  elif [[ -d "$target/zfs" ]]; then
    # destroy zfs 'legacy' datasets
    zfs list -rHo name,mountpoint "$target" 2>/dev/null | awk '$2 == "legacy" {print $1}' | while read -r dataset; do
      echo "docker_rm: zfs destroy -R $dataset"
      zfs destroy -R "$dataset"
    done
  fi

  # delete files and directories
  echo "docker_rm: rm -rf $target"
  rm -rf "$target"
}

# delete the docker image file or folder
if [[ -f /boot/config/docker.cfg ]]; then
  rm -f /var/local/emhttp/plugins/dynamix.docker.manager/docker.json
  . /boot/config/docker.cfg
  if  [[ -f $DOCKER_IMAGE_FILE ]]; then
    echo "Deleting $DOCKER_IMAGE_FILE ..."
    rm -f "$DOCKER_IMAGE_FILE"
  elif [[ -d $DOCKER_IMAGE_FILE ]]; then
    echo "Deleting $DOCKER_IMAGE_FILE ..."
    rm_docker "$DOCKER_IMAGE_FILE"
  fi
fi