#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  muffle [-n] [--] COMMAND...
		  muffle -h
	EOF
}

help() {
	cat <<-'EOF'


		Options:
		  -n            invert when to do the muffling
		  -h, --help    show this message

		  COMMAND       the COMMAND to be muffled


		Conditionally omit STDOUT and STDERR of COMMAND:
		if command exits with an error, print its original output to the
		corresponding streams, but when there is no error, throw the
		output away, "muffling" the COMMAND.


		Examples:

		  Only print anything if the test fails:

		    $ muffle sh tests/assert-makefile.sh
	EOF
}


for flag in "$@"; do
	case "$flag" in
		(--)
			break
			;;
		(--help)
			usage
			help
			exit
			;;
		(*)
			;;
	esac
done

INVERT=false
while getopts 'nh' flag; do
	case "$flag" in
		(n)
			INVERT=true
			;;
		(h)
			usage
			help
			exit
			;;
		(*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))


OUT="$(mkstemp)"
ERR="$(mkstemp)"
STATUS_F="$(mkstemp)"
trap 'rm -f "$OUT" "$ERR" "$STATUS_F"' EXIT

timed() {
	ts -s -m '%.s'
}

echo 0 > "$STATUS_F"
{
	{ "$@" || echo $? > "$STATUS_F"; } | timed | pre out > "$OUT"
} 2>&1 | timed | pre err > "$ERR"

STATUS="$(cat "$STATUS_F")"
if [ "$INVERT" = false -a "$STATUS" != 0 ] || [ "$INVERT" = true -a "$STATUS" = 0 ]; then
	cat "$OUT" "$ERR" |
	sort -k2  | while read -r line; do
		if [ "$(printf '%s\n' "$line" | cut -d' ' -f1)" = 'out:' ]; then
			printf '%s\n' "$line" | cut -d' ' -f3- >&1
		else
			printf '%s\n' "$line" | cut -d' ' -f3- >&2
		fi
	done
	exit "$STATUS"
fi