#!/bin/bash

err-bash-trace() {
  local -i argc_index=0 frame i start=${1:-0} max_indent=8 indent
  local source
  local extdebug=false
  if [[ $(shopt -p extdebug) == *-s* ]]; then
    extdebug=true
  fi
  for ((frame=0; frame < ${#FUNCNAME[@]}-1; frame++)); do
    argc=${BASH_ARGC[frame]}
    argc_index+=$argc
    ((frame < start)) && continue
    if (( ${#BASH_SOURCE[@]} > 1 )); then
      source="${BASH_SOURCE[frame+1]}:${BASH_LINENO[frame]}:"
    fi
    indent=$((frame-start + 1))
    indent=$((indent < max_indent ? indent : max_indent))
    printf "%${indent}s↳%sin \`%s" '' "$source" "${FUNCNAME[frame]}"
    if $extdebug; then
      for ((i=argc_index-1; i >= argc_index-argc; i--)); do
        printf " %s" "${BASH_ARGV[i]}"
      done
    fi
    echo \'
  done
  return 0
}


err-catch() {
  set -E; shopt -s extdebug
  _err-trap() {
    err=$?
    exec >&2
    set +x
    echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]}: \`$BASH_COMMAND' returned $err"
    err-bash-trace 2
    set -e # err trap does not work within an error trap
    "${_errcatch_cleanup[@]:-:}" # note :-: is to be compatible with set -u
    echo "$0: exiting with code $err"
    exit $err
  }
  trap _err-trap ERR
  set -o pipefail
}
err-catch

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

Turn off mail receiving on OLD_HOST, run btrbk to move mail to NEW_HOST,
turn on mail receiving on NEW_HOST.  Assumes we want to move all
filesystems unless passing -o.

-o         Only btrbk /o, instead of all filesystems.
-h|--help  Print help and exit.

I used to adjust home network dns so NEW_HOST resolves locally if it is
on the local network, but its simpler just not to and just rely
on the internet. Email can wait.

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

restore_new_btrbk=false
restore_old_btrbk=false
cleanup() {
  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
}
_errcatch_cleanup=cleanup

pre="${0##*/}:"
m() { printf "$pre %s\n"  "$*"; "$@"; }
e() { printf "$pre %s\n"  "$*"; }

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

temp=$(getopt -l help owh "$@") || usage 1
mp_args="-m /o,/q,/a"
eval set -- "$temp"
while true; do
  case $1 in
    -o) mp_args="-m /o"; 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-state

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


source /a/bin/bash_unpublished/source-state


new_hostname=$($new_shell hostname)

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

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

btrbk_test="systemctl is-active btrbk.service"
while [[ $($new_shell $btrbk_test) != inactive ]] || [[ $($old_shell $btrbk_test) != inactive ]]; 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

# ensure these are unused before doing anything

e "umounting /m and /o via $new_shell"
$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.

m $old_shell /a/exe/primary-setup $new_hostname

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

m $new_shell /a/exe/primary-setup $new_hostname