#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  until [-m MAX] [-n SECONDS] [-q] COMMAND...
	EOF
}


_SECONDS=5
QUIET=false
while getopts 'm:n:q' flag; do
	case "$flag" in
		(m)
			MAX="$OPTARG"
			;;
		(n)
			_SECONDS="$OPTARG"
			;;
		(q)
			QUIET=true
			;;
		(*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))


ATTEMPT=1
while true; do
	if [ "$QUIET" = false ]; then
		printf 'Attempt %s.\n' "$ATTEMPT" >&2
	fi
	ATTEMPT=$((ATTEMPT + 1))
	if "$@"; then
		break
	fi
	if [ -n "${MAX:-}" ] && [ "$ATTEMPT" -gt "$MAX" ]; then
		printf 'Maximum number of attempts reached: %s.\n' "$MAX" >&2
		exit 1
	fi
	sleep "$_SECONDS"
done