#!/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.


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

source /usr/local/lib/err

usage() {
  cat <<'EOF'
btrbk-run [OPTIONS] [run|resume|archive]
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
}



pre="${0##*/}: "
m() { if $verbose; then printf "$pre%s\n"  "$*"; fi;  "$@"; }
e() { printf "$pre%s\n"  "$*"; }
die() { printf "$pre%s\n" "$*" >&2; echo "exiting with status 1" >&2; exit 1; }
mexit() { echo "$pre: exiting with status $1"; exit $1; }

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

# note q is owned by root:1000

mountpoints=()

rsync_mountpoint=/q

ret=0
# default options
conf_only=false
dry_run=false # mostly for testing
rate_limit=no
verbose=true; verbose_arg=-v
progress_arg="--progress"
incremental_strict=false
pull_reexec=false

default_args_file=/etc/btrbk-run.conf
if [[ -s $default_args_file ]]; then
  set -- $(< $default_args_file) "$@"
  # i havent used this feature yet, so warn about it
  echo "$0: warning: default btrbk-run options set in $default_args_file (sleeping 5 seconds):"
  cat $default_args_file
  sleep 5
fi

early=false
cron=false
orig_args=("$@")
temp=$(getopt -l cron,pull-reexec,help ceil:m:npqrs:t:vh "$@") || usage 1
eval set -- "$temp"
while true; do
  case $1 in
    # some behaviors specific to running under cron:
    # - skip hosts where xprintidle haven't been idle recently
    # - if we can't ssh to 1 or more hosts, still do the rest
    # - if we aren't MAIL_HOST and no -m or -s, just exit
    --cron)
      cron=true
      pre=
      shift
      ;;
    # only creates the config file, does not run btrbk
    -c) conf_only=true; shift ;;
    # quit early, just btrbk, no extra remounting etc.
    -e) early=true; shift ;;
    -i) incremental_strict=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 ;;
    # show progress
    -p) progress_arg="--progress"; shift ;;
    # internal option for rerunning under newer SOURCE_HOST version.
    --pull-reexec) pull_reexec=true; shift ;;
    # quiet
    -q) verbose=false; verbose_arg=; progress_arg=; shift ;;
    # source host to receive a backup from
    -s)
      source=$2
      bbksource=$source
      if [[ $source == *:* ]]; then
        bbksource="[$source]"
      fi
      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 ;;
    # verbose.
    -v) verbose=true; verbose_arg=-v; shift ;;
    -h|--help) usage ;;
    --) shift; break ;;
    *) die "Internal error!" ;;
  esac
done

cmd_arg=${1:-run}


std_preserve="18h 14d 8w 24m"
q_preserve="18h 14d"

case $cmd_arg in
  run|resume) : ;;

  # This works better than the normal archive command. We have to
  # specify the mount points, but that is what we are used to doing and
  # we prefer it. Another difference is that archive works recursively
  # and we don't care about that. Sometimes we may still want to run
  # btrbk archive, but it doesn't even use the config file, so just
  # run it directly, eg:
  # time s btrbk -v archive /mnt/r7/amy/boot/btrbk ssh://bo/mnt/boot2/btrbk
  archive)
    cmd_arg=resume
    std_preserve="999h 999d 999w 999m"
    q_preserve="$std_preserve"
    preserve_arg=-p
    ;;
  *) die "untested command arg" ;;
esac

if (( $# > 1 )); then
  die: "only 1 nonoption arg is supported"
fi

if [[ -v targets && $source ]]; then
  # note, this doesnt need to be the case, but
  # we would need to think about it.
  die "error: -t and -s are mutually exclusive"
fi

if $verbose; then
  printf "options: conf_only=%s\ndry_run=%s\nrate_limit=%s\nverbose=%s\ncmd_arg=%s" "$conf_only" "$dry_run" "$rate_limit" "$verbose" "$cmd_arg"
fi
### end options parsing

# remove path from earlier version of btrbk
rm -f /usr/sbin/btrbk
# note, this still works as intended if there is no /usr/bin/btrbk
if [[ /a/opt/btrbk/btrbk -nt /usr/bin/btrbk ]]; then
  if [[ -e /b/distro-functions/src/package-manager-abstractions ]]; then
    . /b/distro-functions/src/package-manager-abstractions
    pi asciidoctor
  fi
  cd /a/opt/btrbk
  m make install
fi

# TODO: i wonder if there should be an option to send to the default
# targets, plus any given on the command line.


amy=false
# set default targets
if [[ ! -v targets && ! $source ]]; then
  if [[ $HOSTNAME != "$MAIL_HOST" ]] && $cron ; then
    echo "MAIL_HOST=$MAIL_HOST, nothing to do"
    mexit 0
  else
    amy=true
  fi

  at_work=false

  targets=(frodo.b8.nz)
  case $HOSTNAME in
    x2|kw)
      at_work=true
      ;;&
    x2|x3|sy|bo)
      if ping -q -c1 -w1 hal.office.fsf.org \
          && ip n show 192.168.0.26 | grep . &>/dev/null; then
        at_work=true
      fi
      ;;&
    kw|x2|x3|sy|bo)
      if $at_work; then
        if ping -q -c1 -w1 iank.vpn.office.fsf.org &>/dev/null; then
          home=iank.vpn.office.fsf.org
        else
          home=i.b8.nz
        fi
      else
        home=b8.nz
      fi
      ;;&
    kw)
      targets+=($home x2.office.fsf.org)
      ;;
    x2|x3|sy|bo)
      targets+=($home)
      if $at_work; then
        targets+=(x2.office.fsf.org x2.b8.nz)
      else
        targets+=(x2wg.b8.nz)
      fi
      ;;
    kd)
      targets+=(x2wg.b8.nz x3.b8.nz)
      if ping -q -c1 -w1 sy.b8.nz &>/dev/null; then
        targets+=(sy.b8.nz)
      else
        targets+=(syw.b8.nz)
      fi
      ;;
    frodo)
      # no targets
      targets=()
      ;;
    *)
      die "error: no default targets for this host, use -t"
      ;;
  esac
fi

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

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

if [[ ${mountpoints[0]} ]]; then
  for mp in ${mountpoints[@]}; do
    if [[ -e /nocow/btrfs-stale/$mp ]]; then
      die "error: $mp is stale, mount-latest-subvol first"
    fi
  done
else
  # set default mountpoints
  if [[ ${targets[0]} == tp ]]; then
    prospective_mps=(/a)
  else
    case $HOSTNAME in
      frodo)
        prospective_mps=(/i)
        ;;
      *)
        prospective_mps=()
        if [[ $source ]]; then
          source_state="$(ssh $source cat /a/bin/bash_unpublished/source-state)"
          eval "$source_state"
          source_host="$(ssh $source cat /etc/hostname)"
          if [[ $source_host == "$MAIL_HOST" ]]; then
            prospective_mps+=(/o)
          fi
        else
          if [[ $HOSTNAME == "$MAIL_HOST" ]]; then
            # HOST2 is really the mail host if it exists
            if [[ $HOST2 && $HOST2 != "$HOSTNAME" ]]; then
              echo "skipping /o because HOST2 is not us"
            else
              prospective_mps+=(/o)
            fi
          fi
        fi
        # note: put q last just in case its specific retention options were to
        # affect other config sections. I havent tested if that is the case.
        prospective_mps+=(/a /ar /qr /q)
        ;;
    esac
  fi
  for mp in ${prospective_mps[@]}; do # default mountpoints to sync
    if [[ -e /nocow/btrfs-stale/$mp ]]; then
      e "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 ########

if [[ $source ]]; then
  if [[ $(ssh $source ps --no-headers -o comm 1) == systemd ]]; then
    status=$(ssh $source systemctl is-active btrbk.service) || : # normally returns 3
    case $status in
      inactive|failed) : ;;
      *)
        echo "$0: error: cron btrbk is running on source. exiting out of caution"
        mexit 1
    esac
  fi
fi

# pull_reexec stops us from getting into an infinite loop if there is some
# kind of weird problem
pulla=false
for m in "${mountpoints[@]}"; do
  if [[ $m == /a ]]; then
    pulla=true
    break
  fi
done
if ! $pull_reexec && [[ $source ]] && $pulla ; then
  tmpf=$(mktemp)
  m rsync -ra $source:/usr/local/bin/{mount-latest-subvol,check-subvol-stale} /usr/local/bin
  m rsync -ra $source:/usr/local/lib/err /usr/local/lib
  m scp $source:/a/bin/distro-setup/btrbk-run $tmpf
  if ! diff -q $tmpf ${BASH_SOURCE[0]}; then
    e "found different version on host $source. reexecing"
    install -T $tmpf /usr/local/bin/btrbk-run
    m /usr/local/bin/btrbk-run --pull-reexec "${orig_args[@]}"
    mexit 0
  fi
fi


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

# for an initial run, btrbk requires the dir to exist.
mkdir -p /mnt/{root,o}/btrbk
local_zone=$(date +%z)

if [[ $source ]]; then
  if ! zone=$(ssh root@$source date +%z); then
    if $conf_only; then
      echo "$0: warning: failed to ssh to root@$source"
    else
      die failed to ssh to root@$source
    fi
  fi
  if [[ $zone != "$local_zone" ]]; then
    die "error: dont confuse yourself with multiple time zones. $h has different timezone than localhost"
  fi

else

  sshable=()
  sshfail=()
  min_idle_ms=$((1000 * 60 * 15))
  for h in ${targets[@]}; do
    if remote_info=( $(timeout -s 9 6 ssh root@$h "mkdir -p /mnt/root/btrbk /mnt/o/btrbk && date +%z && df --output=size,pcent / | tail -n1") ); then
      zone=${remote_info[0]}
      root_size=${remote_info[1]}
      percent_used=${remote_info[2]%%%}

      if (( ${#remote_info[@]} != 3 )); then
        die "error: didnt get 3 fields in test ssh to target $h. investigate"
      fi
    elif $conf_only; then
      # Use some typical values in this case
      root_size=$(( 1024 * 1024 * 2000 )) #2tb
      percent_used=10
      zone=$(date +%z)
    else
      sshfail+=($h)
      continue
    fi

    # we may be booted into a bootstrap fs or something
    min_root_kb=$(( 1024 * 1024 * 200 )) # 200 gb
    if (( root_size < min_root_kb )); then
      continue
    fi

    if (( percent_used >= 98 )); then
      die "error: filesystem on target $h is $percent_used % full"
    fi

    # This is a separate ssh because xprintidle can fail and thats ok.
    if $cron && idle_ms=$(timeout -s 9 6 ssh $h DISPLAY=:0 xprintidle); then
      if (( idle_ms < min_idle_ms )); then

        # Ignore this host. i sometimes use a non-main machine for
        # testing or web browsing, knowing that everything will be wiped
        # by the next backup, but I dont want it to happen as Im using
        # it from cronjob.
        e "warning: $h: active X session in the last 15 minutes, skipping for now"
        continue
      fi
    fi
    sshable+=($h)
    if [[ $zone != "$local_zone" ]]; then
      die "error: dont confuse yourself with multiple time zones. $h has different timezone than localhost"
    fi
  done
  if [[ ! ${sshable[*]} ]] || { ! $cron && [[ ${sshfail[*]} ]]; }; then
    die "failed to ssh to hosts: ${sshfail[*]}"
  else
    if [[ ${sshfail[*]} ]]; then
      ret=1
      e "error: failed to ssh to ${sshfail[*]} but continuing with other hosts"
    fi
    targets=(${sshable[@]})
  fi
fi


cat >/etc/btrbk.conf <<EOF
ssh_identity /q/root/h
#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

# trying this out
stream_compress zstd

# 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 $std_preserve
snapshot_preserve_min 2h
snapshot_dir btrbk
# so, total backups = ~58
target_preserve $std_preserve
target_preserve_min 2h

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

rate_limit $rate_limit
EOF

if $incremental_strict; then
  cat >>/etc/btrbk.conf <<EOF
incremental strict
EOF
fi

for m in ${mountpoints[@]}; do
  case $m in
    /o)
      vol=/mnt/o
      ;;
    *)
      vol=/mnt/root
      ;;
  esac

  sub=${m#/}
  if [[ $source ]]; then
    cat >>/etc/btrbk.conf <<EOF
volume ssh://$bbksource$vol
subvolume $sub
target send-receive $vol/btrbk
EOF
  fi
  if (( ${#targets[@]} )); then
    cat >>/etc/btrbk.conf <<EOF
volume $vol
subvolume $sub
EOF
    case $sub in
      q)
        # q has sensitive data i dont want to backup for so long
        cat >>/etc/btrbk.conf <<EOF
snapshot_preserve $std_preserve
snapshot_preserve_min 2h
snapshot_dir btrbk
target_preserve $std_preserve
target_preserve_min 2h
EOF
        ;;
    esac
    for tg in ${targets[@]}; do
      # handle ipv6
      if [[ $tg == *:* ]]; then
        tg="[$tg]"
      fi
      cat >>/etc/btrbk.conf <<EOF
target send-receive ssh://$tg$vol/btrbk
EOF
    done
  fi
done

# if $amy; then
#   # to manually backup amy,
#   # bbk -e -s amy -m root_ubuntubionic
#   cat >>/etc/btrbk.conf <<'EOF'
# volume ssh://amy/mnt/root
# subvolume root_ubuntubionic
# target send-receive /mnt/root/btrbk
# EOF
# fi

# 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
  mexit 0
fi



if $dry_run; then
  m btrbk -v -n $cmd_arg
  mexit 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 $preserve_arg $verbose_arg $progress_arg $cmd_arg

# todo: tp not valid anymore.
# 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
      tp)
        dirs=(/p/c/machine_specific/tp)
        for x in /p/c/machine_specific/*.hosts; do
          if grep -qxF $tg $x; then
            dirs+=(${x%.hosts})
          fi
        done
        m rsync -aSAXPH --specials --devices --delete --relative ${dirs[@]} root@$tg:/
        ;;
    esac
  done
fi

if [[ $source ]]; then
  m mount-latest-subvol
else
  m /a/exe/mount-latest-remote ${targets[@]}
fi

if [[ $ret == 0 ]]; then
  for tg in ${targets[@]}; do
    :
    #ssh root@$tg /a/exe/mail-backup-clean
  done
fi

mexit $ret

# 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