outdir=${OUTDIR:-.build}
srcdir=${SRCDIR:-$(dirname "$0")}
AR=${AR:-ar}
AS=${AS:-as}
CC=${CC:-cc}
CFLAGS=${CFLAGS:-}
LD=${LD:-ld}
SCDOC=${SCDOC:-scdoc}

for arg
do
	case "$arg" in
		--bindir=*)
			BINDIR=${arg#*=}
			;;
		--libdir=*)
			LIBDIR=${arg#*=}
			;;
		--mandir=*)
			MANDIR=${arg#*=}
			;;
		--prefix=*)
			PREFIX=${arg#*=}
			;;
	esac
done

subdir() {
	eval ". $srcdir/$1/configure"
}

genrules() {
	target="$1"
	shift
	printf '# Begin generated rules for %s\n' "$target"
	for file in "$@"
	do
		ext="${file#*.}"
		file="${file%.*}"
		deps=
		printf '%s.o: %s.%s%s\n' "$file" "$file" "$ext" "$deps"
	done
	printf '%s_objects=\\\n' "$target"
	n=0
	for file in "$@"
	do
		file="${file%.*}"
		n=$((n+1))
		if [ $n -eq $# ]
		then
			printf '\t%s.o\n' "$file"
		else
			printf '\t%s.o \\\n' "$file"
		fi
	done
	printf '# End generated rules for %s\n' "$target"
}

append_cflags() {
	for flag
	do
		CFLAGS="$(printf '%s \\\n\t%s' "$CFLAGS" "$flag")"
	done
}

test_cflags() {
	[ ! -e "$outdir"/check.c ] && cat <<-EOF > "$outdir"/check.c
	int main(void) { return 0; }
	EOF
	werror=""
	case "$CFLAGS" in
		*-Werror*)
			werror="-Werror"
			;;
	esac
	if $CC $werror "$@" -o "$outdir"/check "$outdir"/check.c >/dev/null 2>&1
	then
		append_cflags "$@"
	else
		return 1
	fi
}

find_library() {
	name="$1"
	pc="$2"
	printf "Checking for %s... " "$name"
	if ! command -v pkg-config >/dev/null
	then
		printf "ERROR: pkg-config not found\n"
		return 1
	fi
	if ! pkg-config "$pc" 2>/dev/null
	then
		printf "NOT FOUND\n"
		printf "Tried pkg-config %s\n" "$pc"
		return 1
	fi
	printf "OK\n"
	CFLAGS="$CFLAGS $(pkg-config --cflags "$pc")"
	LIBS="$LIBS $(pkg-config --libs "$pc")"
}

docs() { true; }

run_configure() {
	mkdir -p $outdir

	for flag in -g -std=c11 -D_XOPEN_SOURCE=700 -Wall -Wextra -Werror -pedantic
	do
		printf "Checking for %s... " "$flag"
		if test_cflags "$flag"
		then
			echo yes
		else
			echo no
		fi
	done

	# XXX: Asked the maintainer to provide a .pc file
	LIBS="$LIBS -lbearssl"

	printf "Checking for scdoc... "
	if scdoc -v >/dev/null 2>&1
	then
		echo yes
		all="$all docs"
		install_docs="
	mkdir -p \$(MANDIR)/man1
	install -m644 doc/gmni.1 \$(MANDIR)/man1/gmni.1
	install -m644 doc/gmnlm.1 \$(MANDIR)/man1/gmnlm.1"
	else
		echo no
	fi

	printf "Creating $outdir/config.mk... "
	cat <<-EOF > "$outdir"/config.mk
	CC=$CC
	SCDOC=$SCDOC
	LIBS=$LIBS
	PREFIX=${PREFIX:-/usr/local}
	OUTDIR=${outdir}
	_INSTDIR=\$(DESTDIR)\$(PREFIX)
	BINDIR?=${BINDIR:-\$(_INSTDIR)/bin}
	LIBDIR?=${LIBDIR:-\$(_INSTDIR)/lib}
	INCLUDEDIR?=${INCLUDEDIR:-\$(_INSTDIR)/include}
	MANDIR?=${MANDIR:-\$(_INSTDIR)/share/man}
	CACHE=\$(OUTDIR)/cache
	CFLAGS=${CFLAGS}
	CFLAGS+=-Iinclude -I\$(OUTDIR)
	CFLAGS+=-DPREFIX='"\$(PREFIX)"'
	CFLAGS+=-DLIBDIR='"\$(LIBDIR)"'

	all: ${all}
	install_docs: ${install_docs}
	EOF

	for target in $(printf '%s\n' $all | tr '.' '_')
	do
		$target
	done >>"$outdir"/config.mk
	echo done

	touch $outdir/cppcache

	if [ "$srcdir" = "." ]
	then
		return
	fi

	populate() (
		path="$1"
		mkdir -p "${path#$srcdir/}"
		fullpath() ( cd "$1" && pwd )
		for orig in "$path"/*
		do
			link="${orig#$srcdir/}"
			if [ -d "$orig" ]
			then
				mkdir -p $link
				populate "$orig"
			elif [ -f "$orig" ]
			then
				ln -sf "$(fullpath "$path")"/"$(basename "$orig")" "$link"
			fi
		done
	)

	printf "Populating build dir... "
	populate "$srcdir/include"
	populate "$srcdir/src"
	populate "$srcdir/doc"
	ln -sf "$srcdir"/Makefile ./
	echo done
}