#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  dice [SIZE]
		  dice -h
	EOF
}

help() {
	cat <<-'EOF'


		Options:
		  -h, --help    show this message

		  SIZE          the size of the dice (default: 6)


		Roll a dice of SIZE.  Caveat: rolling a dice more than once in
		the same second will give you the same number.


		Examples:

		  Roll a dice of size 6:

		    $ dice
		    3


		  Roll a D20:

		    $ dice 20
		    15
	EOF
}


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

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


SIZE="${1:-6}"
RAND="$(awk 'BEGIN { srand(); print int(rand()*32768) }' /dev/null)"
echo $(((RAND % SIZE) + 1))