#!/bin/sh
# vim: set noexpandtab

die() { printf '%s\n' "$*" >&2; exit 1; }

do_help() {
	cat <<-END
	Manage kernel modules links

	Usage: ${0} <command>

	<command> is one of:
	copy:  copy modules of the current kernel to /run/modules
	link:  link the copied kernel modules into /usr/lib/modules
	gc:    remove dangling links in /usr/lib/modules
	clean: remove everything from akulm, that it looks like
	       a usual ArchLinux system
	help:  Show this help
	END
}

do_copy() {
	rsync -r \
		"/usr/lib/modules/$(uname -r)/" \
		"/run/modules/$(uname -r)/"
}

do_clean() {
	rm -rf /run/modules/*
	do_gc_links
}

do_gc() {
	do_gc_links && do_gc_modules
}

do_gc_modules() {
	find /run/modules \
		-mindepth 1 \
		-maxdepth 1 \
		-not -name "$(uname -r)" \
		-exec rm -rf '{}' ';'
}
do_gc_links() {
	find /usr/lib/modules \
		-mindepth 1 \
		-maxdepth 1 \
		-xtype l \
		-exec rm '{}' ';'
}

do_link() {
	[ -e "/usr/lib/modules/$(uname -r)" ] \
		|| ln -sT "/run/modules/$(uname -r)" "/usr/lib/modules/$(uname -r)"
}

case "${1}" in
	copy) do_copy;;
	gc) do_gc;;
	link) do_link;;
	clean) do_clean;;
	hook-pre)  do_copy && do_gc;;
	hook-post) do_link;;
	help) do_help;;
	*) die "Invalid command: '${1}'. Valid commands: copy gc link clean help";;
esac