#!/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.

-o         Only btrbk /o, instead of all filesystems.
-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=$(getopt -l help owh "$@") || usage 1
mp_args=
eval set -- "$temp"
while true; do
  case $1 in
    -o) mp_args="-m /o"; shift ;;
    -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 timeout -s 9 5 ssh-keyscan -p 2220 -t rsa 10.0.0.1 2>/dev/null | grep -qFx '[10.0.0.1]:2220 ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCH+/h1dGEfKEusBblndU2e6QT4wLCm5+yqr/sqh/0X9YfjR7BfWWm8nNmuP55cYc+Wuf5ljB1H1acXEcsl1y8e0j3agHfF0V74FE1N1zz5nn2Ep8NHnmqgEhza38ZxMPh+4p3X7zklEKU7+3SzybKBi8sg0wLzlS2LM0JaUN80zR2sK11Kye3dURUXPk78u5wodOkgcEYRwSYaDMJlUzWP+poRXIDJwFaMQnwmxbl/c84yOyaU0x/d6hFwoRscWecihX+vvBNeSyxR4xr2HDOyUWwJkctyAgt2p7w3tfkXOKcCRzTAjGVIMQLTvo0sG/yJbcyHoEFdFybCsgDvfyYn'; 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=:
else
  wrt_shell="ssh wrt.b8.nz"
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

new_hostname=$($new_shell hostname)

########### 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


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

# previously, I was checking to see if the new mail host
# is on my home network, then changing my home dns
# to resolve on the local network, so that I didnt
# have to send traffic out to the internet or rely
# on that. However, that breaks for a laptop that roams.
# So, we could have a cronjob that updates that dns,
# however, another solution is to just use ipv6,
# and I prefer that.
#
# TODO: enable ipv6 for email. exim config setting disables it.
# need to add vpn support. need to add firewall / routing.
# I think exim will try ipv6 first, so no need to disable
# ipv6 i think.

$old_shell primary-setup $new_hostname

if $localhost_new; then
  btrbk-run -s $old_host $mp_args
else
  btrbk-run -t $new_host $mp_args
fi

$new_shell primary-setup $new_hostname

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