#!/bin/sh
set -eu

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

help() {
	cat <<-'EOF'


		Options:
		  -h, --help    show this message

		  NUMBER        the number to be clamped
		  MIN           lower bound
		  MAX           upper bound


		Clamp the NUMBER between MIN and MAX.


		Examples:

		  Assert the number is within the interval:

		    $ clamp 5 3 9
		    5


		  When a number is below MIN it gets clamped:

		    $ clamp 1 3 9
		    3


		  When a number is above MAX it gets clamped:

		    $ clamp 15 3 9
		    9
	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))


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

eval "$(assert-arg -- "$NUMBER" 'NUMBER')"
eval "$(assert-arg -- "$MIN"    'MIN')"
eval "$(assert-arg -- "$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"