#!/bin/sh

set -e

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

show_help() {
	cat <<-EOF
	usage: ./configure [options...]

	Options:
	   -a arch	Choose the underlying architecture to build for:
	$(awk '{ printf("\t%s\n", $0); }' ${CONFIGDIR}/architecture)

	   -c version	Conform to:
	$(awk '{ printf("\t%s\n", $0); }' ${CONFIGDIR}/versions.c)

	   -p version	Conform to:
	$(awk '{ printf("\t%s\n", $0); }' ${CONFIGDIR}/versions.posix)

	   -w wordsize	Choose a word size for the architecuture:
	$(awk '{ printf("\t%s\n", $0); }' ${CONFIGDIR}/wordsize)

	   -x version	Conform to:
	$(awk '{ printf("\t%s\n", $0); }' ${CONFIGDIR}/versions.xopen)

	EOF
}

validate_option() {
	option="${CONFIGDIR}/$1"

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

	printf 'Invalid option '%s'. Valid options are:\n' "$2" >&2
	cat "${option}" >&2
	exit 1
}

option=

architecture=x86
wordsize=64

standard_c=
posix=
xopen=

while getopts hc:p:x: option; do
	case ${option} in
	a)	architecture=$(validate_option architecture ${OPTARG})
		;;

	c)	standard_c=$(validate_option c ${OPTARG})
		;;

	p)	posix=$(validate_option posix ${OPTARG})
		;;

	x)	xopen=$(validate_option 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 'C library configured to conform to the following standards:\n'
printf 'ISO C:  %d\n' ${standard_c}
test -n "${posix}" && printf 'POSIX:  %d\n' ${posix}
test -n "${xopen}" && printf 'X/OPEN: %d\n' ${xopen}

printf 'Building for %d-bit %s architecture\n' "${wordsize}" "${architecture}"

exec > Makefile

cat <<-EOF
	.POSIX:
	.DEFAULT:;\$(MAKE) all

	ARCHITECTURE=${architecture}
	WORDSIZE=${WORDSIZE}
	SRCDIR=$(dirname $0)/src
	INCDIR=$(dirname $0)/include
	OBJDIR=$(pwd)/obj

EOF

if [ ${standard_c:-1} -lt 199901 ]; then
	printf 'CC=c89\n'
else
	printf 'CC=c%02d\n' $(( (standard_c / 100) % 100 ))
fi

if [ -n "${xopen}" ]; then
	if [ $xopen -eq 400 ]; then
		printf 'CFLAGS=-D_XOPEN_SOURCE -D_XOPEN_SOURCE_EXTENDED=1\n'
	else
		printf 'CFLAGS=-D_XOPEN_SOURCE=%d\n' "${xopen}"
	fi
elif [ -n "${posix}" ]; then
	printf 'CFLAGS=-D_POSIX_C_SOURCE=%d\n' "${posix}"
fi

cat <<EOF

all: .deps.mk include
	@mkdir -p \$(OBJDIR)
	\$(MAKE) -f .deps.mk $@

deps: .headers.mk .deps.mk

.deps.mk: mk.sh
	sh -c '. ./mk.sh; make_deps_mk'

.headers.mk: mk.sh
	sh -c '. ./mk.sh; make_headers_mk'

headers include: .headers.mk mkh.sh
	\$(MAKE) -f .headers.mk headers

ctags:
	ctags \$\$(find src -name \*.c)

clean:
	rm -rf \$(OBJDIR) *.a

extra-clean: clean
	rm -rf .deps .*.mk \$(INCDIR)
EOF