#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  clamp NUMBER MIN MAX
		  clamp -h
	EOF
}

help() {
	cat <<-'EOF'

		Options:
		  -h, --help    show this message

		Clamp the NUMBER between MIN and MAX.
	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))

assert_arg() {
	if [ -z "$1" ]; then
		printf 'Missing %s\n\n' "$2" >&2
		usage >&2
		exit 2
	fi
}

NUMBER="${1:-}"
MIN="${2:-}"
MAX="${3:-}"

assert_arg "$NUMBER" 'NUMBER'
assert_arg "$MIN"    'MIN'
assert_arg "$MAX"    'MAX'


if [ "$MIN" -gt "$MAX" ]; then
	printf 'MIN (%s) is greater then MAX (%s).\n' "$MIN" "$MAX" >&2
	exit 2
fi

min -- "$(max -- "$NUMBER" "$MIN")" "$MAX"