#!/bin/bash

# initiate a staged mirror update from sync-source for a component.
#
# if we have a serial file and we got a serial on the command line, only sync if the serial is different

# Copyright (c) 2012 Peter Palfrader
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


set -e
set -u

NAME="$(basename "$0")"

usage() {
	echo "Usage: $0 [--one-stage] <componentdir> <sync-source> [<serial>]"
}

if [ "${1:-}" = "-h" ] || [ "${1:-}" = "--help" ]; then usage; exit 0; fi

one_stage=0
while :; do
	case "${1:-}" in
		--)
			shift
			break;
			;;
		--one-stage)
			shift
			one_stage=1
			;;
		-*)	usage >&2
			exit 1
			;;
		*)
			break
			;;
	esac
done

COMPONENTDIR=${1:-}; shift
SYNC_SOURCE=${1:-}; shift
SYNC_SERIAL=${1:-}; shift || true
if [ -z "$COMPONENTDIR" ]; then usage >&2; exit 1; fi
if [ -z "$SYNC_SOURCE" ]; then usage >&2; exit 1; fi
COMPONENT="$(basename "${COMPONENTDIR}")"

RSYNC="rsync"
RSYNC_BASE_OPTIONS="-rtvz --delete --links --hard-links --safe-links"
RSYNC_SSH_OPTIONS="ssh -o BatchMode=yes"

LOGDIR="$HOME/logs"
LOGFILE="$LOGDIR/$NAME-run-${COMPONENT}.log"


ALPHA="tree-a"
BRAVO="tree-b"
ACTIVE="cur"

CNF_FILE="$HOME/etc/$NAME.conf"
! [ -e "$CNF_FILE" ] || . "$CNF_FILE"

SOURCE="${SYNC_SOURCE}/"
COMPONENTDIR="${COMPONENTDIR}/"

###############################################

# point stdout and stderr to the logfile if it's not a tty.
# save stdout to fd5 for communications with the master

log_setup() {
	mkdir -p "$LOGDIR"
	if ! [ -t 1 ]; then
		# move current stdout to fd5 and reopen to logfile
		exec 5>&1-
		exec 1>> "$LOGFILE"
	else
		# duplicate stdout to fd5
		exec 5>&1
	fi
	if ! [ -t 2 ]; then
		exec 2>> "$LOGFILE"
	fi
}

log() {
	echo "[$(date)][$NAME][$$] $1"
}

lock() {
	mkdir -p "$COMPONENTDIR"
	exec 200< "$COMPONENTDIR"
	if ! flock -e 200; then
		log "Cannot acquire lock."
		echo >&5 "[MSM] LOCK-ERROR"
		exit 1
	fi
	log "Got the lock."
}

###############################################


log_setup
log "called with $*"
lock

if [ -e "${COMPONENTDIR}${ACTIVE}" ] && [ "$(readlink "${COMPONENTDIR}${ACTIVE}")" = "$ALPHA" ] ; then
	staging="$BRAVO"
	active="$ALPHA"
elif [ -e "${COMPONENTDIR}${ACTIVE}" ] && [ "$(readlink "${COMPONENTDIR}${ACTIVE}")" != "$BRAVO" ] ; then
	echo >&5 "Invalid state of ${COMPONENTDIR}${ACTIVE}."
	exit 1
else
	staging="$ALPHA"
	active="$BRAVO"
fi
log "active is $active; staging is $staging"

rsync_source="${SOURCE}"
rsync_curactive="${COMPONENTDIR}${active}/"
rsync_target="${COMPONENTDIR}${staging}/"

if [ -e "$rsync_curactive/.serial" ] && [ -n "$SYNC_SERIAL" ] && [ "$(cat $rsync_curactive/.serial)" = "$SYNC_SERIAL" ]; then
	log "active is already at serial $SYNC_SERIAL.  No action required."
	echo >&5 "[MSM] ALREADY-CURRENT"
	exit 0
fi

echo >&5 "[MSM] STAGE1-START"
log "Running $RSYNC $RSYNC_BASE_OPTIONS -e $RSYNC_SSH_OPTIONS --link-dest $rsync_curactive $rsync_source $rsync_target"
$RSYNC $RSYNC_BASE_OPTIONS -e "$RSYNC_SSH_OPTIONS" --link-dest "$rsync_curactive" "$rsync_source" "$rsync_target"
log "rsync done."
echo >&5 "[MSM] STAGE1-DONE"
if [ "$one_stage" -gt 0 ]; then
	action="go"
else
	read action
fi

case "$action" in
	go)
		ln --symbolic --force --no-target-directory "$staging" "${COMPONENTDIR}$ACTIVE"
		rm -rf "$rsync_curactive"
		echo >&5 "[MSM] STAGE2-DONE"
		log "stage2 done"
		;;
	abort)
		echo >&5 "[MSM] STAGE2-ABORT"
		log "stage2 abort"
		;;
	*)
		echo >&5 "[MSM] STAGE2-UNKNOWN-ACTION $action"
		log "stage2 unknown action $action"
		exit 1
		;;
esac

savelog "$LOGFILE"