#!/bin/sh
# Copyright © 2015-2016 Jonas Smedegaard <dr@jones.dk>
# Description: Synchronize mail using Dovecot tool dsync
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# Depends: dovecot-core
# Recommends: moreutils
#
# FIXME
#  * Generailze account resolving (avoid hardcoded accounts)
#
# TODO
#  * Gracefully serialize (with warning) if parallel not available
#  * Add option to not parallelize (and not warn if parallel missing)
#  * Add global lock
#  * Handle "region" derived from profile:
#    + Avoid parallelize same-region profiles
#    + Lock each region separately
#  * Parse configfile for profiles

set -e

PRG=$(basename "$0")

showhelp() {
	cat <<EOF
Usage: $PRG [--tomuch] [--] PROFILE [PROFILE...]
Synchronize one or more Dovecot Maildir profiles

  --toomuch         Don't update notmuch database after syncronization
  --debug           Enable debugging output
  --alive           Monitor SSH connection that server is alive
  --reset           Clear state tracking to force full sync
  -h, --help        This help text

Examples:
  $PRG jones hb
  $PRG --toomuch jones
EOF
}

exit1() {
	response="${1:+Error: }${1:-Internal error!}"
	echo >&2 "$response"
	exit 1
}

# parse cmdline options
TEMP="`getopt -s sh -o h -l help,toomuch,debug,alive,reset -n "$PRG" -- "$@"`" || exit1 "Internal getopt error."
eval set -- "$TEMP"
while true ; do
	case "$1" in
	-h|--help) showhelp; exit;;
	--toomuch) toomuch=yes; shift;;
	--debug) debug=yes; shift;;
	--alive) alive=yes; shift;;
	--reset) reset=yes; shift;;
	--) shift; break;;
	*) exit1 "Internal error resolving options.";;
	esac
done

[ $# -gt 0 ] || set -- jones debian bb hb lxp5

_nice() {
#	ionice -c 3 chrt --idle 0 /bin/sh -c "$@"
	"$@"
}

_dsync() {
	profile="$1"
	case "$profile" in
		jones) host=mail.jones.dk;;
		debian) host=jonas-debian@mail.jones.dk;;
		bb) host=mail.bitbase.dk;;
		hb) host=mail.homebase.dk;;
#		db) host=db.letsgo.dk;;
#		lb) host=lb.letsgo.dk;;
		lxp5) host=lxp5.free-owl.de;;
		*) exit1 "Wrong account \"$account\"";;
	esac
	for algo in ed25519 ecdsa dsa rsa; do
		key="$HOME/.ssh/id_${algo}_mail_$profile"
		if [ -f "$key" ] && [ -f "$key.pub" ]; then
			break
		fi
		key=
	done
	cachedir="$HOME/.cache/mydsync"
	statefile="$cachedir/$profile"
	[ -z "$reset" ] || rm -f "$statefile" "$statefile"~
	if [ -s "$statefile" ]; then
		cp -f "$statefile" "$statefile"~
	else
		touch "$statefile"
	fi
	state="$(cat "$statefile")"
	if [ -z "$state" ] && [ -f "$statefile"~ ]; then
		state="$(cat "$statefile"~)"
	fi
	mkdir -p "$cachedir"
	[ -n "$key" ] || exit1 "ssh key missing for $profile"
	_nice doveadm ${debug:+-D} \
		-o mail_location=maildir:~/Maildir/"$profile" \
		sync -s "$state" -x spam -x Junk -x Trash \
		ssh -i "$key" -o BatchMode=yes \
			${alive:+-o ServerAliveInterval=10 -o ServerAliveCountMax=5} \
			"$host" doveadm dsync-server \
		> "$statefile"
}

case $# in
    0)
	exit1 "Internal error: no arguments to process";;
    1)
	_dsync "$1";;
    *)
	parallel -i sh -c "$0 --toomuch ${debug:+--debug} ${alive:+--alive} ${reset:+--reset} {}" -- "$@";;
esac
[ -n "$toomuch" ] || _nice notmuch new