#!/bin/sh

CONFIGDIR="$(dirname $0)/config"

show_help() {
	cat <<-EOF
	usage: ./configure [-c version] [-p version | -x version]

	Options:
	  -c version	Specify the version of ISO/IEC 9899 to conform to
	  -p version	Specify the version of IEEE 1003.1/ISO/IED 9945-1 to
	                conform to
	  -x version	Specify the version of the Single Unix Specification
	                (aka X/Open System Interface) to conform to

	Valid options for -c are:
	$(cat ${CONFIGDIR}/versions.c)

	Valid options for -p are:
	$(cat ${CONFIGDIR}/versions.posix)

	Valid options for -x are:
	$(cat ${CONFIGDIR}/versions.xopen)
	EOF
}

validate_version() {
	versfile="${CONFIGDIR}/versions.$1"

	for ver in $(awk '/^[0-9]/ { print $1 }' "${versfile}"); do
		if [ "$2" = "${ver}" ]; then
			echo $2
			return 0
		fi
	done

	echo 0
}

double_check_version() {
	if [ "$2" = "0" ]; then
		printf 'Invalid version "%s". Valid versions are:\n' $3
		cat "${CONFIGDIR}/versions.$1"
		exit 1
	fi
}

option=
standard_c=
posix=
xopen=

while getopts hc:p:x: option; do
	case ${option} in
	c)	standard_c=$(validate_version c ${OPTARG})
		double_check_version c ${standard_c} ${OPTARG}
		;;

	p)	posix=$(validate_version posix ${OPTARG})
		double_check_version posix ${posix} ${OPTARG}
		;;

	x)	xopen=$(validate_version xopen ${OPTARG})
		double_check_version xopen ${xopen} ${OPTARG}
		;;

	h)	show_help
		exit 0
		;;

	?)	printf 'Unknown option "%c". Try "-h" for help.\n' $option
		exit 1
		;;
	esac
done

if [ -z "${standard_c}" ] && [ -z "${posix}" ] && [ -z "${xopen}" ]; then
	xopen=700
fi

if [ -n "${posix}" ] && [ -n "${xopen}" ]; then
	printf 'Specify only one of "-x" or "-p".\n'
	exit 1
fi

if [ -n "${xopen}" ]; then
	if [ $xopen -eq 700 ]; then
		posix=200809
	elif [ $xopen -eq 600 ]; then
		posix=200112
	elif [ $xopen -eq 500 ]; then
		posix=199506
	else
		posix=2
	fi
fi

if [ -z "${standard_c}" ] && [ -n "${posix}" ]; then
	if [ $posix -ge 200112 ]; then
		standard_c=199901
	else
		standard_c=1
	fi
fi

if [ ${posix:-0} -ge 200112 ] && [ $standard_c -lt 199901 ]; then
	printf 'POSIX.1-2001 and newer require C99 or newer.\n'
	exit 1
fi

printf 'ISO C:  %d\n' ${standard_c}
printf 'POSIX:  %d\n' ${posix}
printf 'X/OPEN: %d\n' ${xopen}