#!/bin/bash

set -eu

path=$1
uuid=$(jq -r .client_uuid < /etc/backup/config.json)
server=$(jq -r .server_hostname < /etc/backup/config.json)
ssh="ssh -o ConnectTimeout=5 backup-receiver@$server"

source_dataset=$(zfs list -H -o mountpoint,name | grep -P "^$path\t" | cut -d $'\t' -f 2)
target_dataset="tank/$uuid/$source_dataset"
target_dataset_parent=$(echo $target_dataset | rev | cut -d / -f 2- | rev)
bookmark_prefix="auto-backup_"
new_bookmark="$bookmark_prefix$(date +"%Y-%m-%d_%H:%M:%S")"

for var in path uuid server ssh source_dataset target_dataset target_dataset_parent new_bookmark
do
  [[ -z "${!var}" ]] && echo "ERROR - $var is empty" && exit 96
done

$ssh true || (echo "ERROR - cant ssh connect to $server" && exit 97)

echo "BACKUP ZFS DATASET - PATH: $path, SERVER: $server, UUID: $uuid, SOURCE_DATASET: $source_dataset, TARGET_DATASET: $target_dataset"

if ! $ssh sudo zfs list -t filesystem -H -o name | grep -q "^$target_dataset_parent$"
then
  echo "CREATING PARENT DATASET..."
  $ssh sudo zfs create -p -o mountpoint=none "$target_dataset_parent"
fi

zfs snap "$source_dataset@$new_bookmark"

if zfs list -t bookmark -H -o name | grep "^$source_dataset#$bookmark_prefix" | wc -l | grep -q "^0$"
then
  echo "INITIAL BACKUP"
  # do in subshell, otherwise ctr+c will lead to 0 exitcode
  $(zfs send -v "$source_dataset@$new_bookmark" | $ssh sudo zfs recv -F "$target_dataset")
else
  echo "INCREMENTAL BACKUP"
  last_bookmark=$(zfs list -t bookmark -H -o name | grep "^$source_dataset#$bookmark_prefix" | sort | tail -1 | cut -d '#' -f 2)
  [[ -z "$last_bookmark" ]] && echo "ERROR - last_bookmark is empty" && exit 98
  $(zfs send -v -L -i "#$last_bookmark" "$source_dataset@$new_bookmark" | $ssh sudo zfs recv "$target_dataset")
fi

if [[ "$?" == "0" ]]
then

  # delete old local bookmarks
  for destroyable_bookmark in $(zfs list -t bookmark -H -o name "$source_dataset" | grep "^$source_dataset#$bookmark_prefix")
  do
    zfs destroy "$destroyable_bookmark"
  done

  # delete remote snapshots from bookmarks (except newest, even of not necessary; maybe for resuming tho)
  for destroyable_snapshot in $($ssh sudo zfs list -t snapshot -H -o name "$target_dataset" | grep "^$target_dataset@$bookmark_prefix" | grep -v "$new_bookmark")
  do
    $ssh sudo zfs destroy "$destroyable_snapshot"
  done

  zfs bookmark "$source_dataset@$new_bookmark" "$source_dataset#$new_bookmark"
  zfs destroy "$source_dataset@$new_bookmark" # keep snapshots?
  echo "SUCCESS"
else
  zfs destroy "$source_dataset@$new_bookmark"
  echo "ERROR"
  exit 99
fi