#!/bin/bash
#
# WizBackup 2.0 - Simple rsync backup
# Based on incremental-backup 0.1 by Matteo Mattei
#
# Copyright 2006 Matteo Mattei <matteo.mattei@gmail.com>
# Copyright 2007, 2008, 2009, 2010, 2011 Bernie Innocenti <bernie@codewiz.org>
#
#  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 of the License,
#  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/>.
#

if [ $# -lt 2 ]; then
	echo "Usage: $0 SOURCE DEST [RSYNC_OPTS]"
	exit 1
fi

# Treat undefined variables as errors
set -u

#####################################################################
# CONFIGURATION
#####################################################################

# Source rsync URL
SRC=$1; shift

# Destination directory (will be created if it doesn't exist)
DEST=$1; shift

# NOTE: --timeout needs to be large enough: if a large dir tree don't change a lot of time can pass without I/O
# NOTE: --inplace will clobber linked files in older snapshots. DON'T USE IT!
RSYNC_OPTS="-HAXa --stats --timeout 1800 --numeric-ids --delete --delete-excluded --ignore-errors $@"

# Number of saved snapshots
SNAPSHOTS=45

# Abort backup if the destination volume has less than these GBs free
MIN_FREE_GB=10

RESULT=500
DATE=`date +"%Y%m%d"`
DEST="`echo $DEST | sed -e 's/\/$//'`"


# Use "backup" ssh key with ssh protocol, or password file for rsync protocol
if [ "${SRC%:*}" == "rsync" ]; then
	RSYNC_OPTS="$RSYNC_OPTS --password-file=/etc/wizbackup/rsync_password --contimeout 10"
else
	export RSYNC_RSH="ssh -i /etc/wizbackup/ssh_id -c arcfour -x -o VerifyHostKeyDNS=yes -o StrictHostKeyChecking=no"
fi

# Error tolerant grep
tgrep()
{
	grep "$@"
	return 0
}

do_backup()
{
	set -o pipefail
	echo "$(date): rsync $RSYNC_OPTS $SRC $DEST/tmp/"
	rsync $RSYNC_OPTS "$SRC" "$DEST/tmp/" 2>&1 | tgrep -v -E 'vanished|some files'
	RESULT=$?
	case "$RESULT" in
	0|24)
		RESULT=0 # Ignore error 24 (Partial transfer due to vanished source files)
		# Cleanup old incomplete backups
		if [ -d "$DEST/$DATE" ]; then
			echo "$(date): Removing existing backup $DEST/$DATE"
			rm -rf "$DEST/$DATE"
		fi
		mv "$DEST/tmp" "$DEST/$DATE"
		;;
	*)
		echo "$(date): rsync failed: $RESULT"
		echo "$(date): Leaving incomplete backup in $DEST/tmp"
		;;
	esac
	set +o pipefail
}


do_init()
{
	# Safety net (4 slashes just in case)
	case "$DEST" in
		/|//|///|////) exit 666 ;;
	esac

	if [ ! -d "$DEST" ]; then
		echo "$(date): Creating missing destination directory $DEST."
		mkdir -p "$DEST" || exit 667
	fi

	cd "$DEST" || exit 668
}

do_prune()
{
	local old="`ls | grep -v tmp | head -n -$SNAPSHOTS`"
	if [ ! -z "$old" ]; then
		echo "$(date): Removing oldest snapshot(s): $old..."
		rm -rf "$old" || exit 669
	fi
}

do_link()
{
	local newest=`ls | grep  -v tmp | tail -n 1`
	if [ -d "$DEST/tmp" ]; then
		echo "$(date): Continuing with pre-existing snapshot $DEST/tmp"
	elif [ -z "$newest" ]; then
		echo "$(date): No previous snapshot found, performing a full backup!"
	else
		echo "$(date): Linking snapshot $DEST/$newest to $DEST/tmp"
		# TODO: Creating the hardlinks takes a lot of time.
		# Perhaps we could save time by recycling the oldest snapshot
		cp -la "$DEST/$newest" "$DEST/tmp"
		RESULT=$?
		if [ $RESULT -ne 0 ]; then
			echo "$(date): Failed to setup tmp snapshot: $RESULT. Cleaning up."
			rm -rf "$DEST/tmp"
			exit $RESULT
		fi
	fi
}

do_test()
{
	# TODO: test for free space and free inodes in the $DEST filesystem
	block_size=`stat --file-system --format "%S" "$DEST"`
	free_blocks=`stat --file-system --format "%f" "$DEST"`
	free_inodes=`stat --file-system --format "%d" "$DEST"`
	free_gb=$((block_size * free_blocks / 1024 / 1024 / 1024))

	if [ "$free_gb" -lt "$MIN_FREE_GB" ]; then
		echo "$(date): Aborting due to insufficient free space ${free_gb}GB."
		exit 670
	fi

	# Avoid clobbering the latest snapshot if the remote host does
	# not allow us to connect
	# --contimeout: sometimes hangs on connection...
	rsync $RSYNC_OPTS --dry-run --no-recursive "$SRC" >/dev/null
	RESULT=$?
	if [ $RESULT -ne 0 ]; then
		echo "$(date): rsync test failed: $RESULT.  Aborting."
		exit $RESULT
	fi
}

######################################
# Main
######################################

# make sure to be root
if (( `id -u` != 0 )); then { echo "Sorry, must be root.  Exiting..."; exit; } fi

echo "$(date): START backup: $SRC -> $DEST"
do_init
do_prune
do_test
do_link
do_backup
echo "$(date): END backup: $SRC -> $DEST"

exit $RESULT