#! @BASH@

set -e

# File: backup-files.sh

# Copyright (C) 2006 Steve Langasek <vorlon@debian.org>
# portions Copyright (C) 2003, 2004, 2005, 2006 Andreas Gruenbacher
# <agruen@suse.de>, SuSE Labs

# 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; version 2 dated June, 1991.

# 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, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
# MA 02110-1301, USA.


# Create backup files of a list of files similar to GNU patch. A path
# name prefix for the backup files must be specified with the -B option.

usage () {
	echo "Usage: $0 [-B prefix] [-f {file|-}] [-s] [-k] [-t] [-L] [-b|-r|-x] {file|-} ...

	Create hard linked backup copies of a list of files
	read from standard input.

	-b	Create backup
	-r	Restore the backup
	-x	Remove backup files and empty parent directories
	-k	When doing a restore, keep the backup files
	-B	Path name prefix for backup files
	-s	Silent operation; only print error messages
	-f	Read the filenames to process from file (- = standard input)
	-t	Touch original files after restore (update their mtimes)

	-L	Ensure that when finished, the source file has a link count of 1
"
}

ensure_nolinks() {
	local filename="$1"
	local link_count tmpname

	link_count=$(stat @STAT_HARDLINK@ "$filename")
	if [ $link_count -gt 1 ]; then
		tmpname=$(mktemp "$filename.XXXXXX")
		cp -p "$filename" "$tmpname"
		mv "$tmpname" "$filename"
	fi
}

backup() {
	local file="$1"
	local backup="${OPT_PREFIX}${file}"
	local dir

	dir=$(dirname "$backup")
	[ -d "$dir" ] || mkdir -p "$dir"

	if [ ! -e "$file" ]; then
		$ECHO "New file $file"
		: > "$backup"
	else
		$ECHO "Copying $file"
		if [ -n "$OPT_NOLINKS" -a "$(stat @STAT_HARDLINK@ "$file")" = 1 ]; then
			cp -p "$file" "$backup"
		else
			ln "$file" "$backup" 2> /dev/null || cp -p "$file" "$backup"
			if [ -n "$OPT_NOLINKS" ]; then
				ensure_nolinks "$file"
			fi
		fi
	fi
}

restore()
{
	local file="$1"
	local backup="${OPT_PREFIX}${file}"

	if [ ! -e "$backup" ]; then
		return 1
	fi
	if [ ! -s "$backup" ]; then
		$ECHO "Removing $file"
		if [ -e "$file" ]; then
			rm "$file"
		fi
	else
		$ECHO "Restoring $file"
		if [ -e "$file" ]; then
			rm "$file"
		else
			mkdir -p "$(dirname "$file")"
		fi
		if [ -n "$OPT_NOLINKS" ]; then
			cp -p "$backup" "$file"
		else
			ln "$backup" "$file" 2> /dev/null || cp -p "$backup" "$file"
		fi

		if [ -n "$OPT_TOUCH" ]; then
			touch "$file"
		fi
	fi

	if [ -z "$OPT_KEEP_BACKUP" ]; then
		rm "$backup"
		rmdir -p "${backup%/*}" 2> /dev/null || true
	fi
}

remove()
{
	local file="$1"
	local backup="${OPT_PREFIX}${file}"

	if [ -e "$backup" ]; then
		rm "$backup"
	fi
	rmdir -p "${backup%/*}" 2> /dev/null || true
}

noop()
{
	local file="$1"

	if [ -e "$file" ] && [ -n "$OPT_NOLINKS" ]; then
		ensure_nolinks "$file"
	fi
}


ECHO=echo
OPT_WHAT=noop
while [ $# -gt 0 ]; do
	case $1 in
	-b)	OPT_WHAT=backup
		;;
	-r)	OPT_WHAT=restore
		;;
	-x)	OPT_WHAT=remove
		;;
	-B)	OPT_PREFIX=$2
		shift
		;;
	-f)	OPT_FILE=$2
		shift
		;;
	-s)	ECHO=:
		;;
	-k)	OPT_KEEP_BACKUP=1
		;;
	-L)	OPT_NOLINKS=1
		;;
	-t)	OPT_TOUCH=1
		;;
	-?*)	usage
		exit 0
		;;
	*)	break
		;;
	esac

	shift
done

if [ -z "$OPT_PREFIX" ]; then
	usage
	exit 1
fi

if [ "${OPT_PREFIX:(-1)}" != / ]; then
	echo "Prefix must be a directory" >&2
	exit 1
fi

if [ -n "$OPT_FILE" ]; then
	cat "$OPT_FILE" \
	| while read nextfile; do
		$OPT_WHAT "$nextfile"
	done
fi

while [ $# -gt 0 ]; do
	case $1 in
	-)
		# No backup directory? We're done
		[ -d "$OPT_PREFIX" ] || exit 0

		find "$OPT_PREFIX" -type f -print \
		| while read
		do
			$OPT_WHAT "${REPLY#$OPT_PREFIX}"
		done
		if [ ${PIPESTATUS[0]} != 0 ]; then
			exit 1
		fi
		;;
	*)
		$OPT_WHAT "$1"
		;;
	esac

	shift
done