require

#!/usr/bin/env sh

# Usage: doc/api.md#require

require(){
	requirement="${1:-}"
	message="${2:-}"

	if [ -n "${requirement}" ] || [ -n "$(command -v "${requirement}")" ]; then
		if [ -f "${requirement}" ]; then
			head -n1 "${requirement}" | grep -q '^#!'

			if [ "${?}" = 0 ]; then
				. "${requirement}"
				[ "${?}" = 0 ] && exit 0 || exit "${?}"
			fi
		fi
	else
	    if [ -z "${requirement}" ]; then
        	echo "require: arguments are missing"
    	else
			echo "Requirement is missing: '${requirement}'"
			[ -n "${message}" ] && echo "${message}"
		fi

		exit 127
	fi
}