#!/bin/sh

Version='diffdir-0.1'

diffdir() {
	[ -f "/etc/backup/ignore" ] && xf=--exclude-from=/etc/backup/ignore || xf=
	rsync -aDSnivx "$xf" --delete "$2/" "$1" |
	awk -v OptF="${OptF#./}" -v prefix="$prefix" '
	NF == 0 {exit}
	NR < 2 || /\/*\.dv$/ || /\/$/ {next}
	# Match an itemized status for all versions of rsync -i
	$1 !~ /^[<>ch.*][fdLDS+][.+?cstpoguaxz]+$/ {next}
	{key = $1; file = substr($0, length(key) + 2)}
	OptF && OptF != file {next}
	key == "*deleting" {print "deleted " prefix file; next}
	substr(key, 3, 7) == "+++++++" {print "created " prefix file; next}
	{	# Avoid false positive if only mtime is changed.
		of = "'"$1"'/" file; gsub("'\''", "'\'\\\\\'\''", of)
		nf = "'"$2"'/" file; gsub("'\''", "'\'\\\\\'\''", nf)
		if (substr(key, 2, 1) == "L") {	# Symlink
			src = target = file
			sub(/.* -> /, "", target);
			sub(/ -> .*/, "", src);
			"readlink '"$2"'/" src | getline otarget
			if (target != otarget)
				print "changed " src
		} else if (system("cmp -s '\''" of "'\'\ \''" nf "'\''"))
			print "changed " file
	}'
	# Or: scan key for file/link size, checksum or permission change
	#     rsync -c is required
	#key ~ /[cps]/ { print "changed " prefix file }'
}

last() {
	i=0 m=0
	case $1 in
		([0-9]|[1-9][0-9]) m=$((m + $1)) ;;
		("") ;;
		(*) echo "$1"; return ;;
	esac
	for l in $vlist; do
		[ $i -ge $m ] && break
		i=$((i + 1))
	done
	echo "$dest/$l"
}

while getopts :V opt; do
	case $opt in
	(V) echo "$Version"; exit ;;
	(*) echo "Usage: $0 [-V] old new"; exit 1 ;;
	esac
done
shift $((OPTIND - 1))

dest=/.history
vlist=$(rsync --list-only "$dest/" 2>/dev/null | cut -b 47- | tac)

old=$(last "$1") new=$(last "${2:-/}")
echo "diffdir" "$old" "$new"
diffdir "$old" "$new"