# -----------------------------------------------------------------------------
#
# Copyright (c) 2014 - OpenSLX GmbH
#
# This program is free software distributed under the GPL version 2.
# See http://openslx.org/COPYING
#
# If you have any feedback please consult http://openslx.org/feedback and
# send your suggestions, praise, or complaints to feedback@openslx.org
#
# General information about OpenSLX can be found at http://openslx.org/
# -----------------------------------------------------------------------------
#
#			Common functions for chrooting
#
# -----------------------------------------------------------------------------

CHROOT_TEMPDIR="${ROOT_DIR}/remote/chroot.tmp"
CHROOT_MOUNTDIR="${CHROOT_TEMPDIR}/rootmount"
CHROOT_BINDDIR="${CHROOT_TEMPDIR}/rootbind"
CHROOT_LOWERDIR="/"
CHROOT_BINDMOUNTS="/dev /proc /sys /run"

# Helper function to setup the directory structure
chroot_prepare_dirs() {
	# first check if CHROOT_TEMPDIR exists
	if [ -d "${CHROOT_TEMPDIR}" ]; then
		# try to umount and rmdir CHROOT_MOUNTDIR
		umount "${CHROOT_MOUNTDIR}" 2>/dev/null
		rmdir "${CHROOT_MOUNTDIR}" || perror "Could not remove '${CHROOT_MOUNTDIR}', meaning it has stuff in it. Aborting..."

		# try to umount and rmdir CHROOT_BINDDIR
		umount "${CHROOT_BINDDIR}" 2>/dev/null
		rmdir "${CHROOT_BINDDIR}" || perror "Could not remove '${CHROOT_BINDDIR}', meaning it has stuff in it. Aborting..."

		# try to rmdir CHROOT_TEMPDIR
		rmdir "${CHROOT_TEMPDIR}" || perror "Could not remove '${CHROOT_TEMPDIR}', meaning it has stuff in it. Aborting..."
	fi

	mkdir -p "${CHROOT_TEMPDIR}"	|| perror "Could not create base directory for mount directories $CHROOT_TEMPDIR."
	for DIR in "${CHROOT_BINDDIR}" "${CHROOT_MOUNTDIR}"; do
		mkdir -p "${DIR}"			|| perror "Could not create directory for mount directory $DIR."
	done
}

# Helper to mount the overlay structure:
#	- bind mount system / to CHROOT_BINDDIR and make it read-only
#	- make an overlay from CHROOT_LOWERDIR CHROOT_UPPERDIR
#	- bind mount additional pseudo-fs (as given in CHROOT_BINDMOUNTS)
chroot_prepare_mounts() {

	# first mount / on CHROOT_BINDDIR and remount read-only
	mount -o bind "${CHROOT_LOWERDIR}" "${CHROOT_BINDDIR}"	|| perror "Could not bind-mount '$CHROOT_LOWERDIR' to '$CHROOT_BINDDIR'."
	mount -o remount,ro,bind "${CHROOT_BINDDIR}"		|| perror "Could not remount '$CHROOT_BINDDIR' read-only."

	# check that it really is read-only
	[ "x$(mount | grep -E "^/ on ${CHROOT_BINDDIR}" | grep -v '\(.*ro.*\)')" != "x" ] && perror "'${CHROOT_BINDDIR}' is not read-only! Aborting..."

	# safe, go on to make the overlay
	mount -t overlayfs overlayfs -o lowerdir="${CHROOT_BINDDIR}",upperdir="${CHROOT_UPPERDIR}" "${CHROOT_MOUNTDIR}"  \
		|| perror "Could not mount (overlayfs) $CHROOT_LOWERDIR, $CHROOT_UPPERDIR to $CHROOT_BINDDIR."

	# mount pseudo-filesystems
	for DIR in $CHROOT_BINDMOUNTS; do
		mount -o bind "${DIR}" "${CHROOT_MOUNTDIR}/${DIR}" \
			|| perror "Could not bind mount '$DIR' into '$CHROOT_MOUNTDIR/$DIR'."
	done
}

# Helper to generate the mighty autoexec.bat
chroot_gen_autoexec() {
	# create the script to be automatically executed.
	cat >"${CHROOT_MOUNTDIR}/autoexec.bat"<<-EOF
		#!/bin/bash
		#######################################################
		#						      #
		#		    Warning!			      #
		#						      #
		#  This	file is only meant to be executed within      #
		#  the specially chrooted mltk building environment.  # 
		#						      #
		#  Do NOT execute it if you are not sure what you do, #
		#  it may be very harmful if being run in a normal    #
		#  system environment!				      #
		#						      #
		#######################################################
		echo "chroot started successfully."
	EOF

	# dump the piped input to it
	cat >> "${CHROOT_MOUNTDIR}/autoexec.bat"

	# make it executable
	chmod +x "${CHROOT_MOUNTDIR}/autoexec.bat" || perror "Failed to make '${CHROOT_MOUNTDIR}/autoexec.bat' exeutable."
}

chroot_handle_whiteouts() {
	local WHITEOUT_LIST="${CHROOT_UPPERDIR}/overlay.whiteout.list"
	rm -f -- "$WHITEOUT_LIST="
	#mkdir -p "$(dirname "$WHITEOUT_LIST")" || perror "Could not create $(dirname "$WHITEOUT_LIST")"
	pdebug "Searching for overlayfs-whiteouts ..."
	for WHITEOUT in $(find "$CHROOT_UPPERDIR" -lname "(overlay-whiteout)"); do
		pdebug "Whiteout found: $WHITEOUT"
		echo "/./${WHITEOUT#$CHROOT_UPPERDIR}" >> "$WHITEOUT_LIST"
		rm -f -- "$WHITEOUT" || perror "Could not delete whiteout $WHITEOUT!"
	done
	pinfo "Whiteout list dumped to '${CHROOT_UPPERDIR}/overlay.whiteout.list'"
}

###############################################################################
#
#				MAIN FUNCTION
#
# Main function to be called from the outside
# Usage:
#	chroot_run <build_dir> < <code_to_exec_in_chroot>
#
# Example:
#	chroot_run /tmp/chroot_build <<-EOF
#		echo "This will be executed inside the chroot"
#	EOF
#
# It will run:
#	- chroot_prepare
#	- chroot $CHROOT_TEMPDIR/rootmount
#	- executes $CHROOT_TEMPDIR/rootmount/autoexec.bat
#	- chroot_cleanup
chroot_run() {
	# check args
	[ $# -eq 1 ] || perror "'chroot_run' requires exactly 1 parameter. Given $#.  Use 'chroot_run <build_dir>'"

	local CHROOT_UPPERDIR="$1"
	mkdir -p "$1" 

	# first prepare the dir structure
	chroot_prepare_dirs || perror "'chroot_prepare_dirs' failed with $?."
	chroot_prepare_mounts || perror "'chroot_prepare_mounts' failed with $?."

	# generate the code to be executed when chroot'ing
	chroot_gen_autoexec || perror "'chroot_gen_autoexec' failed with $?."

	# do the chroot
	exec 0>&8		# This redirection is used for debugging within a chroot
	chroot --userspec root:root "${CHROOT_MOUNTDIR}" /autoexec.bat
	local RET=$?
	if [ "$RET" -eq 0 ]; then
		pinfo "chroot executed '${CHROOT_MOUNTDIR}/autoexec.bat' succeeded."
	else
		perror "Failed to run '$CHROOT_MOUNTDIR/autoexec.bat' inside the chroot to '$CHROOT_MOUNTDIR' with error code: $RET"
	fi

	# handle whiteouts
	chroot_handle_whiteouts || perror "'chroot_handle_whiteouts' failed with error code: $?"

	# finally cleanup all the mounting stuff we did previously
	chroot_cleanup_mounts			|| perror "'chroot_cleanup' failed with $?."
}

###############################################################################
#
#				CLEANUP FUNCTIONS
#
# Helper to check if the given path is mounted
chroot_check_mount_point() {
	[ "$#" -eq 1 ] || perror "'chroot_check_mount_point' called with $# arguements, only 1 accepted."
	local MOUNT="$1"	
	if [ "x$(mount | grep "$(readlink -f $MOUNT)")" != "x" ]; then
		# still mounted
		pdebug "'$MOUNT' is mounted!"
		return 1
	else
		pdebug "'$MOUNT' is not mounted."
		return 0
	fi
}

# Helper to umount the given path
chroot_umount() {
	[ "$#" -eq 1 ] || perror "'chroot_umount' called with $# arguments, only 1 accepted."
	local MOUNT="$1"

	# check if MOUNT is mounted
	if ! chroot_check_mount_point "${MOUNT}"; then
		# still mounted
		if umount -l "${MOUNT}"; then
			pdebug "Successfully umounted '${MOUNT}'."
		else
			pwarning "Could not umount '${MOUNT}'! Trying again..."
			# now it gets ugly
			for i in `seq 1 5`; do
				umount -l "${MOUNT}" && return 0
			done
			perror "Could not umount '${MOUNT}' after 5 tries! This shouldn't happen. Check your scripts."
		fi
	else
		pdebug "'${MOUNT}' is not mounted."
	fi

	# better be safe than sorry
	chroot_check_mount_point "$MOUNT" || perror "'$MOUNT' is still mounted, exiting before something bad happens..."
}

# Helper to cleanup the temporary mounts
chroot_cleanup_mounts() {
	if [[ "$(mount | grep -c $CHROOT_TEMPDIR)" -gt 0 ]]; then	# No point in unmounting then...
		for DIR in $CHROOT_BINDMOUNTS; do
			chroot_umount "${CHROOT_MOUNTDIR}/${DIR}"
		done
		chroot_umount "${CHROOT_MOUNTDIR}"
		chroot_umount "${CHROOT_BINDDIR}"
	else
		pinfo "Nothing chroot-related is mounted - exiting."
	fi
}