#!/bin/sh -u
#
# bsed - batch edit with sed
#	- Cameron Simpson <cs@zip.com.au>
#

: ${TMPDIR:=/tmp}
: ${BSEDOPTS=''}
: ${DIFFOPTS='-c'}

cmd=`basename "$0"`
usage="Usage: $cmd [-v] [-i suf] {-f script|{-e sedcmd}...|sedcmd}... [--] files...
	-v		Verbose.
	+v		Not verbose.
	-s		Silent.
	-d diffopt	Option string for diff.
	-i suf		Copy original to original.suf if changed.
	-n		Passed to sed.
	-f script	Passed to sed.
	-e sedcmd	Passed to sed.
	sedcmd		Passed to sed."

diff=diff
fflag=
sedopts=
sedscript=
ecmd=
verbose=
if [ -t 1 ]
then  silent=
else  silent=1
fi
ibak=

set -- $BSEDOPTS ${1+"$@"}

badopts=
while [ $# -gt 0 ]
do
    case $1 in
	--)	shift ; break ;;
	-v)	silent= verbose=1 ;;
	+v)	verbose= ;;
	-s)	silent=1 verbose= ;;
	-d)	DIFFOPTS=$2; shift ;;
	-f)	fflag=1; sedscript=$2; shift ;;
	-i)	ibak=$2; shift ;;
	-i?*)	ibak=`expr "x$1" : 'x-i\(.*\)'` ;;
	-n)	sedopts="$sedopts $1" ;;
	-e)	ecmd="$ecmd
			$2"; shift ;;
	-*)	echo "$cmd: $1: unknown option" >&2
		badopts=1
		;;
	*)	break ;;
    esac
    shift
done

sedf="sed $sedopts"
if [ $fflag ]
then
    sedf="$sedf -f \"\$sedscript\""
else
    if [ -z "$ecmd" ]
    then
	case $# in
	    0)	echo "$cmd: missing sed command" >&2
		badopts=1
		;;
	    *)	ecmd=$1; shift ;;
	esac
    fi
    sedf="$sedf -e \"\$ecmd\""
fi

[ $# = 0 ] && { echo "$cmd: missing filenames" >&2; badopts=1; }

[ $badopts ] && { echo "$usage" >&2; exit 2; }

tmp=$TMPDIR/$cmd.$$
trap 'rm -f "$tmp"; exit 1' 1 2 15

xit=0
ok=1
while	[ $ok ] || xit=1	# catch exit from previous loop
	[ $# -gt 0 ]		# loop condition
do

    file=$1; shift

    if [ "x$file" = x- ]
    then
	[ $verbose ] && echo "reading filenames from stdin..."
	set x `cat` ${1+"$@"}; shift
	continue
    fi

    ok=

    if [ ! -f "$file" ]
    then
	echo "$cmd: $file: not a regular file, skipped" >&2
	continue
    fi

    bakfile= bakdir=
    case "$ibak" in
	'')	;;
	*/)	case "$file" in
			*/*)	bfile=`basename "$file"`
				dfile=`dirname "$file"`
				;;
			*)	bfile=$file
				dfile=.
		esac
		bakdir=$dfile/$ibak
		bakfile=$bakdir/$bfile
		;;
	*)	bakfile=$file.$ibak
		;;
    esac

    if [ -n "$bakfile" ] && [ -f "$bakfile" ]
    then
	echo "$cmd: $file: backup $bakfile already exists, original unchanged" >&2
	continue
    fi

    [ $verbose ] && echo "$file ..."

    # This is a defense against files without newlines:
    # we append a newline and then toss the last line if it's empty.
    # This because sed discards newlineless trailing lines.
    # - Cameron Simpson <cs@zip.com.au> 09nov2001
    #
    if ( cat <"$file"; echo ) \
       | sed -e '$!b notlast' -e '/^$/d' -e ':notlast' \
       | eval "$sedf >\$tmp"
    then
	# check for changes
	if cmp -s "$file" "$tmp"
	then
	    ok=1		# no change
	    continue

# Theoretically the sed should fail if the disc fills.
# Therefore dropping this test, which is a hack and breaks things
# when we really do end up with empty files.
# - Cameron Simpson <cs@zip.com.au> 09nov2001
#
#	else
#	    if [ ! -s "$tmp" ]
#	    then
#		echo "$cmd: warning: tmpfile empty! skipping $file" >&2
#		continue
#	    fi
#


	fi
	[ $silent ] || $diff $DIFFOPTS "$file" "$tmp"

	# ensure we have a backup
	if [ -n "$bakfile" ]
	then
	    if [ -f "$bakfile" ]
	    then
		echo "$cmd: $file: backup $bakfile already exists, original unchanged" >&2
		continue
	    fi
	    if cp "$file" "$bakfile" && cmp -s "$file" "$bakfile"
	    then :
	    else echo "$cmd: $file: can't make backup, original unchanged" >&2
		 continue
	    fi
	fi

	# copy changed version in
	if cat "$tmp" > "$file" && cmp -s "$tmp" "$file"
	then
	    ok=1	# backup & update ok
	    continue
	fi

	echo "$cmd: $file: can't update" >&2
	if [ -n "$bakfile" ]
	then
	    if cat "$bakfile" > "$file"
	    then
		echo "$cmd: $file: original restored" >&2
		rm "$bakfile"
	    else
		echo "$cmd: $file: restore failed; original left in $bakfile" >&2
	    fi
	else
	    echo "$cmd: $file: no backup, may be corrupt" >&2
	fi
    else
	echo "$cmd: $file: edit fails; original unchanged" >&2
    fi
done

rm -f "$tmp"

exit $xit