#!/bin/bash

#
# Copyright © 2017 Sébastien Luttringer
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

# display what to run and run it quietly
run() {
	echo "==> $*"
	"$@" > /dev/null
}

# check kernel is valid for action
# it means kernel and its headers are installed
# $1: kernel version
check_kernel() {
	local kver="$1"; shift
	if [[ ! -d "$install_tree/$kver/kernel" ]]; then
		echo "==> No kernel $kver modules. You must install them to use DKMS!"
		return 1
	elif [[ ! -e "$install_tree/$kver/build/Makefile" ]]; then
		echo "==> No kernel $kver headers. You must install them to use DKMS!"
		return 1
	fi
	return 0
}

# handle actions on module addition/upgrade/removal
# $1: module name
# $2: module version
# $3: dkms action
parse_module() {
	pushd "$install_tree" >/dev/null
	local path
	for path in */build/; do
		local kver="${path%%/*}"
		dkms_register "$1" "$2" "$kver" "$3"
	done
	popd >/dev/null
}

# handle actions on kernel addition/upgrade/removal
# $1: kernel version
# $2: dkms action
parse_kernel() {
	local path
	for path in "$source_tree"/*-*/dkms.conf; do
		if [[ -f "$path" && "$path" =~ ^$source_tree/([^/]+)-([^/]+)/dkms\.conf$ ]]; then
			dkms_register "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}" "$1" "$2"
		fi
	done
}

# register a dkms call
# this function suppress echo call for a module
# $1: module name, $2: module version, $3: kernel version, $4: action
dkms_register() {
	DKMS_ACTION["$1/$2/$3"]="$4"
}

# check whether the dependencies of a module are installed
# $1: module name/module version
# $2: kernel version
check_dependency() {
	local BUILD_DEPENDS
	mod_name=${1%/*}
	mod_ver=${1#*/}
	readarray -t BUILD_DEPENDS <<<$(source "$source_tree/$mod_name-$mod_ver/dkms.conf"; printf '%s\n' "${BUILD_DEPENDS[@]}")
	[ "$BUILD_DEPENDS" = "" ] && unset BUILD_DEPENDS
	for dep in "${BUILD_DEPENDS[@]}"; do
		if [ ! "$(dkms status -m "$dep" -k "$2" | grep -o installed)" = "installed" ]; then
			return 1
		fi
	done
	return 0
}

# run registered dkms commands
dkms_run() {
	local nvk mod kver cont
	cont=y
	while [ "$cont" = "y" ]; do
		cont=n
		for nvk in "${!DKMS_ACTION[@]}"; do
			mod=${nvk%/*}
			kver=${nvk##*/}
			check_kernel "$kver" || continue
			if [ "${DKMS_ACTION[$nvk]}" = "install" ]; then
				check_dependency "$mod" "$kver" || continue
			fi
			run dkms "${DKMS_ACTION[$nvk]}" "$mod" -k "$kver"
			cont=y
			unset DKMS_ACTION[$nvk]
		done
	done
	# show warning for modules not installed
	for nvk in "${!DKMS_ACTION[@]}"; do
		[ "${DKMS_ACTION[$nvk]}" = "install" ] || continue
		mod=${nvk%/*}
		kver=${nvk##*/}
		check_kernel "$kver" || continue
		echo "==> WARNING: Cannot resolve dependencies for module $mod, kernel version $kver"
	done
}

# emulated program entry point
main() {
	[[ -n "$DKMS_ALPM_HOOK_DEBUG" ]] && set -x

	# prevent to have all each dkms call to fail
	if (( EUID )); then
		echo 'You must be root to use this hook' >&2
		exit 1
	fi

	# check args count
	if (( $# < 1 )); then
		echo "usage: ${0##*/} dkms-arguments" >&2
		exit 1
	fi

	# dkms path from framework config
	# note: the alpm hooks which trigger this script use static path
	source_tree='/usr/src'
	install_tree='/usr/lib/modules'
	source /etc/dkms/framework.conf

	# check source_tree and install_tree exists
	local path
	for path in "$source_tree" "$install_tree"; do
		if [[ ! -d "$path" ]]; then
			echo "==> Missing mandatory directory: $path. Exiting!"
			return 1
		fi
	done

	# Storage for DKMS action to run
	declare -A DKMS_ACTION

	# parse stdin paths to guess what do do
	while read -r path; do
		if [[ "/$path" =~ ^$source_tree/([^/]+)-([^/]+)/dkms\.conf$ ]]; then
			parse_module "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}" "$@"
		elif [[ "/$path" =~ ^$install_tree/([^/]+)/ ]]; then
			parse_kernel "${BASH_REMATCH[1]}" "$@"
		fi
	done

	dkms_run

	return 0
}

main "$@"