#!/bin/bash -l

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

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

conf_only=false
dry_run=false
# mostly for testing
case $1 in
    -c) conf_only=true ;;
    -n) dry_run=true ;;
    ?*) echo "$0: error: unsupported arg"; exit 1 ;;
esac

# background on 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.

target_host=frodo
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


case $HOSTNAME in
    tp|x2)
        if ! timeout -s 9 10 ssh frodo :; then
            target_host=$HOME_DOMAIN
            cat >>/etc/btrbk.conf <<EOF
ssh_port 2222
EOF
        fi
        ;;
esac

if [[ $HOSTNAME != frodo ]]; then
    remote_target="target send-receive ssh://${target_host}/mnt/root/${HOSTNAME}-btrbk"
fi

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

EOF
}

target-section /mnt/iroot i
target-section /mnt/root q

if $conf_only; then
    exit
fi

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