#!/bin/bash -l

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

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

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

conf_only=false
dry_run=false # mostly for testing

temp=$(getopt -l help,long-opt hcnt "$@") || usage 1
eval set -- "$temp"
while true; do
    case $1 in
        -c) conf_only=true; shift ;;
        -n) dry_run=true; dry_run_arg=-n; shift ;;
        -t) IFS=, targets=($2); shift 2 ;;
        -h|--help) usage ;;
        --) shift; break ;;
        *) echo "$0: Internal error!" ; exit 1 ;;
    esac
done
read primary <<<"$@"

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

sed="sed -r --follow-symlinks"
last_snaps=()

target-section() {
    local root=$1
    local subvol=$2
    mountpoint $root &>/dev/null || return
    cat >>/etc/btrbk.conf <<EOF
volume $root
subvolume $subvol
$remote_target

EOF
}

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

last-snap() {
    vol=${1##*/}
    cd /mnt/root
    last_snap=$(
        for f in $vol.20*; do
            printf "%s %s\n" $(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s) $f
        done | sort -r | head -n 1 | awk '{print $2}'
             )
    last_snaps+=($last_snap)
}

# note q is owned by root:1000
# note p is owned 1000:1000 and chmod 700
mountpoints=(/q)
if mountpoint /p; then
    mountpoints+=(/p)
fi

if [[ ! $targets ]]; then
    case $HOSTNAME in
        tp|x2)
            if ! timeout -s 9 10 ssh frodo :; then
                targets=($HOME_DOMAIN)
            fi
            ;;
    esac
    targets=(frodo)
fi


# umount first to ensure we don't have any errors
# todo: do some kill fuser stuff to make umount more reliable
# todo: setup sync systemd timer on $primary, once per hour.
# todo: setup lock so that if this is already running, we exit out, so
# that manual runs don't interfere with cronjobs.
if [[ $primary ]] && ! $dry_run; then
    for m in ${mountpoints[@]}; do
        # note, this won't work for /i, due to path being /mnt/iroot
        # todo: include /i for treetowl/frodo
        btrfs property set -ts /mnt/root$m ro true
        ssh root@$primary bash <<EOF
set -ex
umount $m
[[ -e /mnt/root$m ]] || exit 0
btrfs sub del /mnt/root$m
EOF
    done
fi

for tg in ${targets[@]}; do
    cat >/etc/btrbk.conf <<'EOF'
ssh_identity /root/.ssh/id_rsa
transaction_syslog daemon

# 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
# much less snapshots because I have less space on the
# local filesystem.
snapshot_preserve 2h 2d

# so, total backups = ~89
target_preserve 48h 14d 8w 24m
target_preserve_min 6h

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

    remote_target="target send-receive ssh://${tg}/mnt/root"

    if [[ $tg == frodo && $HOSTNAME == treetowl ]]; then
        target-section /mnt/iroot i
    fi
    for m in ${mountpoints[@]}; do
        target-section /mnt/root ${m##*/}
    done
done

if $conf_only; then
    exit
fi

if $dry_run; then
    btrbk -n run
else
    btrbk -q run
fi

# if we have /p, rsync to targets without /p
if mountpoint /p; then
    for tg in ${targets[@]}; do
        case $tg in
            tp|li|lk)
                # todo, test this
                for x in /p/c/machine_specific/*.hosts; do
                    if grep -qxF $tg $x; then
                        dir=${x%.hosts}
                        rsync-dirs ${dir##*/} $dir
                    fi
                done
                ;;
        esac
    done
fi

first_root=$(awk '$2 == "/mnt/root" {print $1}' /etc/mtab)

# make $primary have the rw snapshot
if [[ $primary ]] && ! $dry_run; then
    fstab=()
    for m in ${mountpoints[@]}; do
        last-snap $m
        fstab+=("$first_root  $m  btrfs  noatime,subvol=$last_snap  0 0")
    done

    printf "%s\n" "${fstab[@]}" | cedit /etc/fstab
    for d in ${mountpoints[@]}; do
        mount $d
        btrfs sub del /mnt/root$d
    done
    ssh root@primary bash -s "${mountpoints[*]}" "${last_snaps[*]}" <<'EOF'
set -xe
mountpoints=($1)
last_snaps=($2)
first_root=$(awk '$2 == "/mnt/root" {print $1}' /etc/mtab)
for ((i=0; i < ${#mountpoints[@]}; i++)); do
  m=${mountpoints[i]}
  vol=${m##*/}
  fstab+=("$first_root $m  btrfs  noatime,subvol=$vol  0 0")
  cd /mnt/root
  btrfs sub snapshot ${last_snaps[i]} $vol
  mount $m
done
EOF
fi


# 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.