#!/bin/bash

set -e

usage()
{
	echo "usage: $0 <kernel source tree>" >&2
	exit 1
}

[ "$#" -eq 1 ] || usage
KERNEL_DIR="$(readlink --canonicalize-existing "$1")"

MODULES=()
for MODULE_DIR in module/*
do
	[ -d "$MODULE_DIR" ] || continue
	MODULES+=("${MODULE_DIR##*/}")
done

if ! [ -e 'spl_config.h' ]
then
	echo >&2
	echo "    $0: you did not run configure, or you're not in the SPL source directory." >&2
	echo "    $0: run configure with --with-linux=$KERNEL_DIR and --enable-linux-builtin." >&2
	echo >&2
	exit 1
fi

make clean || true

rm -rf "$KERNEL_DIR/include/spl" "$KERNEL_DIR/spl"
cp --recursive include "$KERNEL_DIR/include/spl"
cp --recursive module "$KERNEL_DIR/spl"
cp spl_config.h "$KERNEL_DIR/"
cp spl.release.in "$KERNEL_DIR/"

adjust_obj_paths()
{
	local FILE="$1"
	local LINE OBJPATH

	while IFS='' read -r LINE
	do
		OBJPATH="${LINE#\$(MODULE)-objs += }"
		if [ "$OBJPATH" = "$LINE" ]
		then
			echo "$LINE"
		else
			echo "\$(MODULE)-objs += ${OBJPATH##*/}"
		fi
	done < "$FILE" > "$FILE.new"
	mv "$FILE.new" "$FILE"
}

for MODULE in "${MODULES[@]}"
do
	adjust_obj_paths "$KERNEL_DIR/spl/$MODULE/Makefile"
	sed -i.bak '/obj =/d' "$KERNEL_DIR/spl/$MODULE/Makefile"
	sed -i.bak '/src =/d' "$KERNEL_DIR/spl/$MODULE/Makefile"
done

cat > "$KERNEL_DIR/spl/Kconfig" <<"EOF"
config SPL
	tristate "Solaris Porting Layer (SPL)"
	help
	  This is the SPL library from the ZFS On Linux project.

	  See http://zfsonlinux.org/

	  To compile this library as a module, choose M here.

	  If unsure, say N.
EOF

{
	cat <<-"EOF"
	SPL_MODULE_CFLAGS  = -I$(srctree)/include/spl
	SPL_MODULE_CFLAGS += -include $(srctree)/spl_config.h
	export SPL_MODULE_CFLAGS

	obj-$(CONFIG_SPL) :=
	EOF

	for MODULE in "${MODULES[@]}"
	do
		echo 'obj-$(CONFIG_SPL) += ' "$MODULE/"
	done
} > "$KERNEL_DIR/spl/Kbuild"

echo 'source "spl/Kconfig"' >>"$KERNEL_DIR/Kconfig"
# We must take care to build SPL before ZFS, otherwise the symbols required
# to link ZFS will not be available.
sed -i 's~mm/ fs/~mm/ spl/ fs/~' "$KERNEL_DIR/Makefile"

echo >&2
echo "    $0: done." >&2
echo "    $0: now you can build the kernel with SPL support." >&2
echo "    $0: make sure you enable SPL support (CONFIG_SPL) before building." >&2
echo >&2