#!/bin/bash
set -x
set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR

usage() {
    cat <<EOF
Usage: ${0##*/} OLD_HOST NEW_HOST

Adjust home network dns so NEW_HOST resolves locally if it is on the
local network.  Turn off mail receiving on OLD_HOST, run btrbk to move
mail to NEW_HOST, turn on mail receiving on NEW_HOST.

-w         Don't try to ssh to wrt. Should only be used in unusual network situation.
-h|--help  Print help and exit.

Note: Uses GNU getopt options parsing style
EOF
    exit $1
}

##### begin command line parsing ########

update_wrt=true # default
temp=$(getopt -l help wh "$@") || usage 1
eval set -- "$temp"
while true; do
    case $1 in
        -w) update_wrt=false; shift ;;
        -h|--help) usage ;;
        --) shift; break ;;
        *) echo "$0: Internal error! unexpected args: $*" ; exit 1 ;;
    esac
done


(( $# == 2 )) || usage 1

old_host=$1
new_host=$2
source /a/bin/bash_unpublished/source-semi-priv

if [[ $old_host != $MAIL_HOST ]]; then
    read -p "warning: \$old_host != \$MAIL_HOST: $old_host != $MAIL_HOST, proceed? y/N "
    if [[ $REPLY != [yY] ]]; then
        exit 1
    fi
fi

if [[ $new_host == "$HOSTNAME" ]]; then
    localhost_new=true
    new_shell=
else
    localhost_new=false
    new_shell="ssh $new_host"
fi

old_shell="ssh $old_host"
if [[ $old_host == "$HOSTNAME" ]]; then
    old_shell=
fi

if [[ ! $new_host || ! $old_host ]]; then
    echo "$0: bad args. see script"
    exit 1
fi

at_home=false
if [[ $HOSTNAME == tp ]] || [[ $HOSTNAME == frodo ]] || timeout -s 9 5 ssh wrt.b8.nz :; then
    at_home=true
fi
echo "$0: at_home = $at_home"

source /a/bin/bash_unpublished/source-semi-priv
#### begin convert private hostnames to public hostnames ####
if ! $at_home; then
    for var in old_host new_host; do
        case ${!var} in
            tp)
                eval $var=$HOME_DOMAIN
                ;;
        esac
    done
fi
####  end convert private hostnames to public hostnames ####


# because our port forward is not robust enough, we can't use proxy command,
# todo: setup vpn so this is all taken care of.
if ! $update_wrt; then
    wrt_shell=:
elif $at_home; then
    wrt_shell="ssh wrt.b8.nz"
else
    if [[ $old_host == iank.vpn.office.fsf.org || $new_host == iank.vpn.office.fsf.org ]]; then
        wrt_shell="ssh iank.vpn.office.fsf.org ssh wrt.b8.nz"
    else
        wrt_shell="ssh $HOME_DOMAIN ssh wrt.b8.nz"
    fi
fi

btrbk_test="systemctl is-active btrbk.service"
while $new_shell $btrbk_test || $old_shell $btrbk_test; do
    echo "$0: btrbk is running on new or old host. sleeping for 8 seconds"
    sleep 6
    echo "$0: testing for btrbk activity in 2 seconds"
    sleep 2
done

########### end initial processing, begin actually modifying things ##########

restore_new_btrbk=false
if $new_shell systemctl is-active btrbk.timer; then
    $new_shell sudo systemctl stop btrbk.timer
    restore_new_btrbk=true
fi
restore_old_btrbk=false
if $old_shell systemctl is-active btrbk.timer; then
    $old_shell sudo systemctl stop btrbk.timer
    restore_old_btrbk=true
fi

for ((i=0; i<10; i++)); do
    $old_shell killall arbtt-capture || break
    sleep 1
    if [[ i == 9 ]]; then
        warn="WARNING!!! failed to kill arbtt-capture"
        fi
    done


$new_shell bash -s <<'EOF'
set -eE
if mountpoint /m; then sudo umount /m; fi
if mountpoint /o; then sudo umount /o; fi
EOF

# if new_host is not on home network, make mail.iankelling.org not resolve
# on the home network.
if [[ $new_host == $HOSTNAME ]] && ! $at_home; then
    echo | $wrt_shell cedit mail_host /etc/hosts || [[ $? == 1 ]] # 1 means file changed.
else
    $wrt_shell bash -s <<EOFOUTER
    cedit mail_host /etc/hosts <<EOF || /etc/init.d/dnsmasq restart
\$(grep "\b$new_host\b" /etc/hosts | awk '{print \$1}') mail.iankelling.org
EOF
EOFOUTER
fi

mail-setup() {
    shell="$1"
    $shell sed -ri "s/MAIL_HOST=.*/MAIL_HOST=$new_host/" /a/bin/bash_unpublished/source-semi-priv
    $shell /a/bin/distro-setup/mail-setup exim4
}

mail-setup "$old_shell"

sudo dd of=/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

# 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


EOF


if $localhost_new; then
    btrbk_src=ssh://$old_host/mnt/root
    btrbk_dst=/mnt/root/btrbk
else
    btrbk_src=/mnt/root
    btrbk_dst=ssh://$new_host/mnt/root/btrbk
fi

sudo tee -a /etc/btrbk.conf <<EOF
volume $btrbk_src
subvolume o
target send-receive $btrbk_dst
EOF


sudo btrbk -l debug --progress run
$new_shell mount-latest-subvol

mail-setup "$new_shell"

if $restore_new_btrbk; then
    $new_shell sudo systemctl start btrbk.timer
fi
if $restore_old_btrbk; then
    $old_shell sudo systemctl start btrbk.timer
fi

$new_shell DISPLAY=:0 arbtt-capture --sample-rate=10 &

echo $warn