#!/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)


		Examples:

		  Roll a dice of size 6:

		    $ dice

		  Roll a D20:

		    $ dice 20
	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}"
echo $(((RANDOM % SIZE) + 1))