#!/bin/bash
# Copyright (C) 2016 Ian Kelling

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


# todo: if we cancel in the middle of a btrfs send, then run again immediately, the received subvolume doesn't get a Received UUID: field, and we won't mount it. Need to figure out a solution that will fix this.

set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR

[[ $EUID == 0 ]] || exec sudo -E "$BASH_SOURCE" "$@"

usage() {
  cat <<'EOF'
btrbk-run [OPTIONS]
usually -t TARGET_HOST or -s SOURCE_HOST

Note, at source location, intentionally not executable, run and read
install-my-scripts.

EOF
  echo "top of script file:"
  sed -n '1,/^[# ]*end command line/{p;b};q' "$0"
  exit $1
}

# latest $MAIL_HOST
if [[ -e /b/bash_unpublished/source-semi-priv ]]; then
  source /b/bash_unpublished/source-semi-priv
fi

# note q is owned by root:1000

mountpoints=()

rsync_mountpoint=/q

# default options
conf_only=false
dry_run=false # mostly for testing
rate_limit=no
verbose=true; verbose_arg=-v
progress_arg="--progress"
pull_reexec=false

default_args_file=/etc/btrbk-run.conf
if [[ -s $default_args_file ]]; then
  set -- $(< $default_args_file) "$@"
  echo "$0: warning: default btrbk-run options set in $default_args_file (sleeping 5 seconds):"
  cat $default_args_file
  sleep 5
fi

orig_args=("$@")
temp=$(getopt -l pull-reexec,help cl:m:nps:t:vh "$@") || usage 1
eval set -- "$temp"
while true; do
  case $1 in
    # only creates the config file, does not run btrbk
    -c) conf_only=true; shift ;;
    # bytes per second, suffix k m g
    -l) rate_limit=$2; shift 2 ;;
    # Comma separated mountpoints to backup. This has defaults set below.
    -m) IFS=, mountpoints=($2); unset IFS; shift 2 ;;
    -n) dry_run=true; dry_run_arg=-n; shift ;;
    -p) progress_arg="--progress"; shift ;;
    --pull-reexec) pull_reexec=true; shift ;;
    -q) verbose=false; verbose_arg=; progress_arg=; shift ;;
    # source host to receive a backup from
    -s) source=$2; shift 2 ;;
    # target hosts to send to. empty is valid for just doing local
    # snapshot. we have default hosts we will populate.
    -t) IFS=, targets=($2); unset IFS; shift 2 ;;
    -v) verbose=true; verbose_arg=-v; shift ;;
    -h|--help) usage ;;
    --) shift; break ;;
    *) echo "$0: Internal error!" ; exit 1 ;;
  esac
done

# usefull commands are resume and archive
cmd_arg=${1:-run}

if [[ -v targets && $source ]]; then
  echo "$0: error: -t and -s are mutually exclusive" >&2
  exit 1
fi

# pull_reexec stops us from getting into an infinite loop if there is some
# kind of weird problem
if ! $pull_reexec && [[ $source ]]; then
  tmpf=$(mktemp)
  scp $source:/a/bin/distro-setup/btrbk-run $tmpf
  if diff -q $tmpf $BASH_SOURCE; then
    echo "$0: found newer version on host $source. reexecing"
    install -T $tmpf /usr/local/bin/btrbk-run
    /usr/local/bin/btrbk-run --pull-reexec "${orig_args[@]}"
  fi
fi


echo -e "$0: options: conf_only=$conf_only\ndry_run=$dry_run\nrate_limit=$rate_limit\nverbose=$verbose\ncmd_arg=$cmd_arg"
### end options parsing


# set default targets
if [[ ! -v targets && ! $source ]]; then
  case $HOSTNAME in
    x2|kw)
      if [[ $HOSTNAME == "$MAIL_HOST" ]]; then
        targets=($HOME_DOMAIN)
      fi
      ;;
    tp)
      targets=(frodo)
      if [[ $HOSTNAME == "$MAIL_HOST" ]]; then
        if timeout -s 9 10 ssh x2 :; then
          targets+=(x2)
        fi
      fi
      ;;
    frodo)
      targets=()
      ;;
    *)
      echo "$0: error: no default targets for this host, use -t"
      exit 1
      ;;
  esac
fi

if [[ -v targets ]]; then
  echo "targets: ${targets[*]}"
fi

if [[ $source ]]; then
  echo "source: $source"
fi


if [[ $mountpoints ]]; then
  for mp in ${mountpoints[@]}; do # default mountpoints to sync
    if [[ -e /nocow/btrfs-stale/$mp ]]; then
      echo "$0: error: $mp is stale, mount-latest-subvol first"
      exit 1
    fi
  done
else
  # set default mountpoints
  case $HOSTNAME in
    # no remote backups atm. note, if we do enable this, configuration below will need some changes.
    #  frodo)
    #    prospective_mps=(/i)
    #    ;;
    *)
      prospective_mps=(/a /q)
      if [[ $HOSTNAME == "$MAIL_HOST" ]]; then
        prospective_mps+=(/o)
      fi
      ;;
  esac
  for mp in ${prospective_mps[@]}; do # default mountpoints to sync
    if [[ -e /nocow/btrfs-stale/$mp ]]; then
      echo "$0: warning: $mp stale, not adding to default mountpoints"
      continue
    fi
    if awk '{print $2}' /etc/fstab | grep -xF $mp &>/dev/null; then
      mountpoints+=($mp)
    fi
  done
fi

echo "mountpoints: ${mountpoints[*]}"

##### end command line parsing ########

rsync-dirs() {
  local host=$1
  local path=$2
  m rsync $dry_run_arg -ahi --relative --delete "$path" "root@$host:/"
}


m() { printf "%s: %s\n" "${0##*/}" "$*";  "$@"; }


if ! which btrbk &>/dev/null; then
  echo "$0: error: no btrbk binary found"
  exit 1
fi
# if our mountpoints are from stale snapshots,
# it doesn't make sense to do a backup.
check-subvol-stale ${mountpoints[@]} || exit 1


cat >/etc/btrbk.conf <<EOF
ssh_identity /root/.ssh/home
# Just a guess that local7 is a good facility to pick.
# It's a bit odd that the transaction log has to be logged to
# a file or syslog, while other output is sent to std out.
# The man does not mention a way for them to be together, but
# I dunno if setting a log level like warn might also output
# transaction info.
transaction_syslog local7

# 20%ish speedup[]
stream_buffer 512m

# so we only run one at a time
lockfile                   /var/lock/btrbk.lock

# default format of short does not accomidate hourly preservation setting
timestamp_format long-iso

# only make a snapshot if things have changed
snapshot_create onchange
# I could make this different from target_preserve,
# if one disk had less space.
# for now, keeping them equal.
snapshot_preserve 36h 14d 8w 24m
snapshot_preserve_min 4h
snapshot_dir btrbk

# so, total backups = ~89
target_preserve 36h 14d 8w 24m
target_preserve_min 4h

# if something fails and it's not obvious, try doing
# btrbk -l debug -v dryrun

rate_limit $rate_limit
EOF



for tg in ${targets[@]:-$HOSTNAME}; do
  # for an initial run, btrbk requires the dir to exist.
  ssh root@$tg mkdir -p /mnt/root/btrbk
done



vol=/mnt/root
for m in ${mountpoints[@]}; do
  sub=${m##*/}
  if [[ $source ]]; then
    cat >>/etc/btrbk.conf <<EOF
volume ssh://$source$vol
subvolume $sub
target send-receive $vol/btrbk
EOF
  else
    cat >>/etc/btrbk.conf <<EOF
volume $vol
subvolume $sub
EOF
    for tg in ${targets[@]}; do
      cat >>/etc/btrbk.conf <<EOF
target send-receive ssh://$tg$vol/btrbk
EOF
    done
  fi
done


# todo: umount first to ensure we don't have any errors
# todo: do some kill fuser stuff to make umount more reliable


if $conf_only; then
  exit
fi



if $dry_run; then
  m btrbk -v -n $cmd_arg
  exit 0
elif [[ $cmd_arg == archive ]]; then
  if [[ $source ]]; then
    m btrbk $verbose_arg $progress_arg $cmd_arg ssh://$source$vol $vol
  else
    for tg in ${targets[@]}; do
      m btrbk $verbose_arg $progress_arg $cmd_arg $vol ssh://$tg$vol
    done
  fi
  exit 0
fi
# -q and just using the syslog option seemed nice,
# but it doesn't show when a send has a parent and when it doesn't.
m btrbk $verbose_arg $progress_arg $cmd_arg

# if we have it, sync to systems which don't
if mountpoint $rsync_mountpoint >/dev/null; then
  for tg in ${targets[@]}; do
    case $tg in
      li|lk)
        for x in /p/c/machine_specific/*.hosts; do
          if grep -qxF $tg $x; then
            dir=${x%.hosts}
            rsync-dirs $tg $dir
          fi
        done
        ;;
    esac
  done
fi

/a/bin/distro-setup/install-my-scripts
if [[ $source ]]; then
  m mount-latest-subvol
else
  m /a/exe/mount-latest-remote ${targets[@]}
fi

# todo: move variable data we don't care about backing up
# to /nocow and symlink it.


# background on btrbk timezones. with short/long, timestamps use local time.
# for long, if your local time moves backwards, by moving timezones or
# for an hour when daylight savings changes it, you will temporarily get
# a more aggressive retention policy for the overlapping period, and
# vice versa for the opposite timezone move. The alternative is using
# long-iso, which puts timezone info into the timestamp, which means
# that instead of shifting time, you shift the start of day/week/month
# which is used for retention to your new local time, which means for
# example, if you moved forward by 8 hours, the daily/weekly/monthly
# retention will be 8 hours more aggressive since midnight is at a new
# time, unless you fake the timzeone using the TZ env variable.
# However, in the short term, there will be no inconsistencies.
# I don't see any problem with shifting when the day starts for
# retention, so I'm using long-iso.

# note to create a long-iso timestamp: date +%Y%m%dT%H%M%S%z