#!/usr/bin/env sh

# TROUBLESHOOTING:
# If /bin/echo doesn't exist _and_ echo -n doesn't work, then this
# script fails. A more graceful fallback to not dropping the trailing
# newline in pipes would also work, but this hasn't been necessary yet.

usage () { cat <<'EOF' 1>&2
lsowners [OPTIONS] [--] [DIRS...]

lsowners searches for OWNERS files in the given DIRS. If no DIRS are
named, it searches the current working directory. Unless --no-recursive
is passed, it will also search directories above each dir for OWNERS
files.

If you pass both --recursive and --no-recursive (or both --printlf and
--print0), the last flag in the arguments list is used.

Options:
-r, --recursive      walk parent directories for OWNERS files (default)
-R, --no-recursive   disable --recursive
-n, --printlf        print output names separated by \n bytes (default)
-0, --print0         print output names separated by NUL bytes. this is
                     useful if passing the output to xargs (or similar).
EOF
}

# globals
owners=''
recursive=1
zerosep=0
parsed=0

while test $# -gt 0
do
	case "$1" in
	-h|--help) usage; exit 2;;
	-R|--no-recursive) recursive=0 ;; # disable walk up the tree
	-r|--recursive) recursive=1 ;; # default
	-0|--print0) zerosep=1 ;; # print output with zero separators
	-n|--printlf) zerosep=0 ;; # print output with \n separators
	--) shift; parsed=1 ;; # remaining arguments are directories
	*) break;;
	esac

	if test $parsed -eq 1
	then
		break
	fi
	shift
done

# make sure echo builtin actually supports the -n flag -- if it doesn't,
# fall back to /bin/echo -- if /bin/echo doesn't exist, then give up.
if test "$(echo -n test)" = "-n test"
then
	if test -e /bin/echo && test -x /bin/echo
	then
		puts () { /bin/echo "$@"; }
	else
		echo '/bin/echo does not exist' 2>&1
		exit 1
	fi
else
	puts () { echo "$@"; }
fi

strip_empty () {
	sed -e '/^[[:space:]]*#/d;/^[[:space:]]*$/d;s/^[[:space:]]*//;s/[[:space:]]*$//' |
	tr -s $'\n'
}

owners_in () {
	local dir="$1"

	while :
	do
		if test -f "$dir/OWNERS"
		then
			owners="$({ echo "$owners"; cat "$dir/OWNERS"; } | strip_empty | sort | uniq)"
		fi

		if test $recursive -eq 0
		then
			break
		fi

		if test "$dir" = /
		then
			break
		fi
		dir="$(cd -P "$(dirname "$dir")" && pwd)"
	done
}

if test $# -eq 0
then
	set -- "$PWD"
fi

for argdir in "$@"
do
	owners_in "$argdir"
done

if test $zerosep -eq 1
then
	puts -n "$owners" | tr -s '\n' '\0'
	exit
fi

if ! test -t 1
then
	puts -n "$owners"
	exit
fi

puts "$owners"