#!/usr/bin/bash

# dracut-lib to use debugging functions
command -v warn >/dev/null || . /lib/dracut-lib.sh
command -v emergency_shell >/dev/null || . /lib/dracut-lib.sh

###############################################################################
# GLOBALS
#
# TODO make this configurable
[ -f /opt/openslx/config ] && . /opt/openslx/config
[ -z $SLX_DNBD3_SERVER ] && SLX_DNBD3_SERVER="132.230.4.1"
[ -z $SLX_STAGE4 ] && SLX_STAGE4="stage4/joe/centos7"
[ -z $SLX_STAGE4_RID ] && SLX_STAGE4_RID="4"
declare -rg DNBD3_SERVER="$SLX_DNBD3_SERVER"
declare -rg DNBD3_IMAGE="$SLX_STAGE4"
declare -rg DNBD3_RID="$SLX_STAGE4_RID"
declare -rg DNBD3_DEVICE="/dev/dnbd0"
declare -rg QCOW_CONTAINER="/opt/openslx/system/system.qcow2"
#
# END GLOBALS
###############################################################################

###############################################################################
# FUNCTION DEFINITIONS
#
# helper to do some sanity checks
check_dnbd3() {
	if [ ! command -v "dnbd3-client" >/dev/null ]; then
		warn "No 'dnbd3-client' found. Was the initramfs built correctly?"
		emergency_shell -n "Error in $0"
		return 1
	fi
	return 0
}

# helper to connect to the dnbd3-server
connect_dnbd3() {
	# check if it already connected
	local current_image_name="$(cat /sys/block/${DNBD3_DEVICE#/dev/}/net/image_name)"
	[ "x${current_image_name}" != "x(null)" ] && return 0

	# not connected yet, do it
	if ! dnbd3-client -h "${DNBD3_SERVER}" \
							-i "${DNBD3_IMAGE}" \
							-r "${DNBD3_RID}" \
							-d "${DNBD3_DEVICE}" ; then
		warn "Failed to mount $DNBD3_IMAGE from $DNBD3_SERVER to $DNBD3_DEVICE"
		emergency_shell -n "Error in $0"
		return 1
	fi
	return 0
}

# helper to create the qcow2 container file using
# DNBD3_DEVICE as the base of the filesystem
# QCOW_CONTAINER as the writable file
# (our future rootfs)
create_qcow() {
	# check if we already created the qcow2-container
	[ -e "$QCOW_CONTAINER" ] && return 0

	# check if we have our target directory, if not create it
	[ ! -d "$(busybox dirname $QCOW_CONTAINER)" ] && \
		mkdir -p "$(busybox dirname $QCOW_CONTAINER)"

	# we did not, let's create it
	if ! qemu-img create -f qcow2 -o \
		backing_file="$DNBD3_DEVICE",backing_fmt=qcow2 "$QCOW_CONTAINER"; then
		warn "Failed to create qcow2-Container from $DNBD3_DEVICE"
		emergency_shell -n "Error in $0"
		rm -f -- "$QCOW_CONTAINER"
		return 1
	fi
	return 0
}
# helper to start qemu-nbd on localhost:2000
# use our wrapper to set argv[0][0] to '@'
# this keeps qemu-nbd running after switching root
export_qcow() {
	# check if we already have a qemu-nbd
	if [ -e /tmp/qemu-nbd.pid ]; then
			kill -0 $(cat /tmp/qemu-nbd.pid) && return 0
	fi
	# since we use the wrapper, we need a little more logic to see if it runs
	/usr/bin/systemd-preserve-process-marker \
		/usr/bin/qemu-nbd -t -p 2000 "$QCOW_CONTAINER" &
	# the wrapper returns 255 if the qemu-nbd binary is missing
	local qemu_nbd_pid="$!"
	for i in 0.5 1 2; do
		sleep $i
		if ! kill -0 $qemu_nbd_pid; then
			# not running
			wait $qemu_nbd_pid
			local ret_wrapper="$?"
			if [ "${ret_wrapper}" -eq 127 ]; then
				# wrapper was not found by bash
				warn "No such file or directory: /usr/bin/systemd-preserve-process-marker"
			elif [ "${ret_wrapper}" -eq 255 ]; then
				# qemu-nbd was not found
				warn "No such file or directory: /usr/bin/qemu-nbd"
			fi
			emergency_shell -n "Error in $0"
			return 1
		else
			# all good, qemu-nbd is running, remember its pid
			echo $qemu_nbd_pid > /tmp/qemu-nbd.pid
			return 0
		fi
	done
	# fallback
	return 1
}
# helper to mount the qcow2-container per nbd
connect_qcow() {
	# try to mount the locally exported qcow2-container using nbd-client
	if nbd-client --systemd-mark --persist 127.0.0.1 2000 /dev/nbd0; then
		# it worked, lets set the symlink to /dev/root as dracut needs it
		# later on to mount that device to the future root (/sysroot)
		ln -sf /dev/nbd0 /dev/root
		return 0
	else
		# this is pretty bad, dracut would spawn an emergency later on
		# since there is no /dev/root to mount.
		# For debugging purposes, we drop an emergency shell ourselves
		# if the mount fails.
		warn "Could not mount /dev/nbd0 from 127.0.0.1:2000."
		emergency_shell -n "Error in $0"
		return 1
	fi
}
#
# END FUNCTION DEFINITIONS
###############################################################################

# No main, use functions!