#!/bin/sh

##############################
## Default Options

# The default device should be a non-rewinding tape, so that we can store
# the volume list there.
DEVICE="/dev/nst0"

# Files matching these glob patterns will not be backed up.
EXCLUDE_TYPES="*.wav *.ogg *.mp3 *.rm *.mpg *.mpeg *.asf *.avi *.mov *.qt *.exe *.iso"

# Used to compress the backup before writing to tape.  Use 'cat' if you
# want no compression
COMPRESS="gzip --best"



##############################
## Setup environment

BACKUP_LIST=`mktemp /tmp/backup.XXXXXX`

for type in $EXCLUDE_TYPES; do
	EXCLUDE_ARG="$EXCLUDE_ARG -not -iname $type "
done



##############################
## Backup functions

## find_files generates a list of null terminated filenames and stores
## it in the temp file, "$BACKUP_LIST".  This requires GNU find.
find_files () {
    LIST_TYPE=$1

    case $LIST_TYPE in
	full)
	    for fs in "${FSS[@]}"; do
		find_files_on_fs $fs
	    done
	;;

	partial)
	    # Look for a file under /var/run/backup that will indicate
	    # the last time this fs had a full backup.
	    for fs in "${FSS[@]}"; do
		cleanfs=`slash_out $fs`
		unset FIND_ARGS
		[ -f /var/run/backup/full:$cleanfs ] && \
		    FIND_ARGS="-newer /var/run/backup/full:$cleanfs"
		find_files_on_fs $fs "$FIND_ARGS"
	    done
	;;
    esac
}

find_files_on_fs () {
    SOURCE=$1
    FIND_ARGS=$2

    echo Finding files on $SOURCE...

    find $SOURCE $EXCLUDE_ARG $FIND_ARGS -xdev -print0 >> $BACKUP_LIST
}

mark_fss_full_backup () {
    # Touch a file in /var/run/backup to mark the time an fs
    # last had a full backup.  Partial backups can look for
    # files newer than this one.
    [ -d /var/run/backup ] || mkdir /var/run/backup
    for fs in "${FSS[@]}"; do
	cleanfs=`slash_out $fs`
	touch /var/run/backup/full:$cleanfs
    done
}

## slash_out is a helper function that removes slash characters from a path,
## converting them to dots.
slash_out () {
    echo "$1" | sed -e s:/:.:g
}

## do_backup will store the file list if $DEVICE appears to be a tape.
## It expects $BACKUP_LIST to be a null terminated list of filenames, as generated
## by GNU find.
do_backup () {
    echo -n "$TYPE backup of ${FSS[@]} began on "
    date

    [ -c $DEVICE ] && {
	# Set the tape device parameters: variable block size, compression off
	mt -f $DEVICE setblk 0
	mt -f $DEVICE compression 0

	# Write the file list to the beginning of the tape, as a volume list
	dd of=$DEVICE if=$BACKUP_LIST bs=5k
    }

    # Long cpio options are:
    # cpio -o --format=newc --null --reset-access-time --verbose
    cpio -oc0av < $BACKUP_LIST | $COMPRESS | dd of=$DEVICE bs=5k

    [ -c $DEVICE ] && {
	# Rewind if this is a tape device
	mt -f $DEVICE rewind
    }

    rm -f $BACKUP_LIST

    echo -n "$TYPE backup of ${FSS[@]} finished on "
    date
}

## Print the number of bytes, uncompressed, this backup will probably
## compose.
estimate_size_bytes () {
    xargs --null ls -ld < $BACKUP_LIST | \
	awk 'BEGIN { EST=0 }
		   { EST=EST + $5 }
	     END   { print EST }'
}

## Print readable information based on estimate_size_bytes
estimate_size () {
    ESIZE=`estimate_size_bytes`
    echo "Backup of ${FSS[@]} will be about $ESIZE bytes, uncompressed."

    rm -f $BACKUP_LIST
}


##############################
## View volume list function

view_volume_list () {
    if [ -c $DEVICE ]; then
	# For a tape device, rewind to the beginning, where the volume
	# list will be stored, read it out to the pager, and rewind again.
	mt -f $DEVICE rewind
	dd if=$DEVICE bs=5k | tr '\000' '\n'
	mt -f $DEVICE rewind
    else
	# For non-tape devices, get the list from cpio
	dd if=$DEVICE bs=5k | $COMPRESS -d | cpio -it
    fi
}



##############################
## Restore function

restore_files () {
    # If the backup was uncompressed, then use "cat" to "decompress".  This
    # special case is required, because cat does not accept the -d flag.
    # Everything else has to.
    if [ "$COMPRESS" = "cat" ] ; then
	UNCOMPRESS=cat
    else
	UNCOMPRESS="$COMPRESS -d"
    fi

    echo -n "restore of ${FSS[@]} began on "
    date

    [ -c $DEVICE ] && {
	# For a tape device, move forward, beyond the volume list.
	mt -f $DEVICE rewind
	mt -f $DEVICE fsf 1
    }

    [ -n "$RESTORE_ROOT" ] && {
	# Restore files to alternate root directory
	[ -d $RESTORE_ROOT ] || mkdir $RESTORE_ROOT
	cd $RESTORE_ROOT
    }

    # Long cpio options are:
    # cpio -o --format=newc --make-directories --preserve-modification-time --verbose
    dd if=$DEVICE bs=5k | $UNCOMPRESS | cpio -icdmv --no-absolute-filenames "${FSS[@]}"

    echo -n "restore of ${FSS[@]} finished on "
    date

    [ -c $DEVICE ] && {
	mt -f $DEVICE rewind
    }
}



##############################
## General functions

print_help () {
cat <<EOF
For backups:
  backup [full|partial] <-dev device> <-comp compressor> <-prune dir> filesystem ...
Estimate the uncompressed size of a backup:
  backup [estimate_full|estimate_partial] <-prune dir> filesystem ...
View the volume list on a tape:
  backup view <-dev device>
Restore files from tape:
  backup restore <-dev device> <-comp compressor> <-root alt-restore-root> pattern ...
EOF
}



##############################
## Parse command line options

TYPE=$1
shift

unset FSS
while [ -n "$*" ]; do
    case "$1" in
	-comp*)
	    shift
	    COMPRESS="$1"
	    shift
	    ;;

	-dev*)
	    shift
	    DEVICE="$1"
	    shift
	    ;;

	-prune)
	    shift
	    EXCLUDE_ARG="-path $1 -prune -o $EXCLUDE_ARG"
	    shift
	    ;;

	-root)
	    shift
	    RESTORE_ROOT="$1"
	    shift
	    ;;

	*)
	    FSS[${#FSS[@]}]="$1"
	    shift
	    ;;
    esac
done



##############################
## Validate options

case $TYPE in
    full|partial|estimate_full|estimate_partial)
	if [ -z "$FSS" ]; then
	    print_help
	    exit
	fi
	;;

    view)
	;;

    restore)
	;;

    *)
	print_help
	exit
	;;
esac



##############################
## Do it
case $TYPE in
    full)
	find_files full
	mark_fss_full_backup
	do_backup
	;;

    partial)
	find_files partial
	do_backup
	;;

    estimate_full)
	find_files full
	estimate_size
	;;

    estimate_partial)
	find_files partial
	estimate_size
	;;

    view)
	view_volume_list
	;;

    restore)
	restore_files
	;;
esac