#!/bin/bash

#
# Copyright Emil Karlson 2012, freely distributable
#

set -u
set -e

sendLevel=""
sendTarget=""
configFile=""
failLog=""
compression="xz"

IFS=$'\n'
shopt -s nullglob

die() {
	[[ $1 != 0 ]] && echo "Failed:"
	echo "$2"
	exit $1
}

case "$compression" in
	xz)
		compressor="compressor_xz"
		;;
	lzo)
		compressor="compressor_lzo"
		;;
	*)
		die 1 "unsupported compressor"
		;;
esac

compressor_xz() {
	xz -T 2 -c "$@"
}
compressor_lzo() {
	lzop -c "$@"
}

getNum() {
	echo "$1" | sed 's/^.*N\([0-9a-f]\{6\}\)\(-sent\)\?$/0x\1/g'
}

getSnapshots() {
	local retval=(snapshot-[0-9][0-9][0-9][0-9]-[0-1][0-9]-[0-3][0-9]T[0-2][0-9].[0-5][0-9].[0-5][0-9]N[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]{,-sent})
	printf "%s\n" ${retval[*]} | sort -r
}

delSnapshot() {
	btrfs subvolume delete "${1}" > /dev/null || \
		die 1 "btrfs subvolume delete ${1}"
}

sendSnapshot() {
	local sendSubvolFull="${@: -1}"
	local sendImage sendSubvol=$(basename "$sendSubvolFull")
	local sendSubvolDir=$(dirname "$sendSubvolFull") sendSubvolTmp="$(perl -MURI::Escape -e 'print uri_escape shift, , q{^A-Za-z0-9\-._~:}' -- "${root}/${sendSubvol}@$(hostname)")" sftpPart="${sendTarget##sftp://}"
	local sftpHost="${sftpPart%%/*}" sftpPath="/${sftpPart#*/}"
	case "${sendTarget}" in
		/*)
			btrfs send "$@" | btrfs receive "${sendTarget}" || \
				die 1 "btrfs subvolume send ${1}"
			;;
		sftp://*)
			sendImage=$(mktemp)
			if ! [[ -f "/var/cache/backup-btrfs/${sendSubvolTmp}.far.${compression}" ]]; then
				btrfs send "$@" | $compressor -c > "$sendImage"
				if [[ "${PIPESTATUS[0]}" != "0" ]]; then
					rm "$sendImage"
					die 1 "btrfs subvolume send ${1}"
				fi
				mv "$sendImage" "/var/cache/backup-btrfs/${sendSubvolTmp}.far.${compression}.tmp"
				sync
				mv "/var/cache/backup-btrfs/${sendSubvolTmp}.far.${compression}.tmp" "/var/cache/backup-btrfs/${sendSubvolTmp}.far.${compression}"
			fi
			sftp -b <(printf '%s\n' "reput /var/cache/backup-btrfs/${sendSubvolTmp}.far.${compression} ${sftpPath}/${sendSubvol}.far.${compression}") "$sftpHost" || \
				sftp -b <(printf '%s\n' "put /var/cache/backup-btrfs/${sendSubvolTmp}.far.${compression} ${sftpPath}/${sendSubvol}.far.${compression}") "$sftpHost" || \
				exit 0
			;;
		*)
			echo Invalid send target
			exit 1
			;;
	esac
}

genmask() {
	local base x
	x=$1
	base=$((2**x - 1))
	printf "%x" $base
	for ((i=1; i<$(( 2 ** ( ( 4 - x % 4 ) % 4) )); i++)); do
		printf "\\|%x" $(( $base + $i * ( $base +1 ) ))
	done
}

localSend() {
	local mask operand parent
	mask="$(genmask $sendLevel)"
	operand="$(printf "%s\n" ${snapshots[*]} | grep "\\(${mask}\\)\$" | tail -n 1)"
	parent="$(printf "%s\n" ${snapshots[*]} | grep '-sent$' | head -n 1)"

	if [[ -n "${operand}" ]]; then
		[[ -d "${sendTarget}/${operand}" ]] && delSnapshot "${sendTarget}/${operand}"
		if [[ -n "${parent}" ]]; then
			sendSnapshot -p "${snapshotPath}/${parent}" "${snapshotPath}/${operand}"
		else
			sendSnapshot "${snapshotPath}/${operand}"
		fi
		if [[ -n "${failLog}" ]]; then
			echo "Sent ${operand}, diff: ======" >> "${failLog}"
			rsync -cvan --delete "${snapshotPath}/${operand}/" "${sendTarget}/${operand}/" >> "${failLog}"
			echo "End diff ${operand} =========" >> "${failLog}"
		fi
		mv "${snapshotPath}/${operand}" "${snapshotPath}/${operand}-sent"
	fi

}

usage="usage: $0 <number of levels> <level size> <volume root> [snapshot dir]
usage: $0 <volume root|configfile>"

case $# in
	1)
		if [[ "-h" == "$1" ]] || [[ "--help" == "$1" ]]; then
			die 0 "$usage"
		elif [[ -f "${1}/.backup-btrfsrc" ]]; then
			root="$1"
			configFile="${1}/.backup-btrfsrc"
		elif [[ -f "${1}" ]]; then
			configFile="${1}"
		else
			die 1 "${0}: '${1}/.backup-btrfsrc' not found and '${1}' is not a configfile"
		fi
		. "${configFile}"
		;;	
	4)
		snapshotPath="$4"
		nLevels="$1"
		levelSize="$2"
		root="$3"
		;;
	3)
		nLevels="$1"
		levelSize="$2"
		root="$3"
		snapshotPath="${root}/.snapshots/"
		;;

	*)
		die 1 "$usage"
esac


mkdir -p "${snapshotPath}"
cd "${snapshotPath}"
snapshots=($(getSnapshots))
if [[ ${#snapshots[*]} -lt 1 ]]; then
	thisNum=0
else
	thisNum=$(( ($(getNum ${snapshots[0]}) + 1) % 0x1000000 ))
fi

thisSnapshot="${snapshotPath}/snapshot-$(date +%Y-%m-%dT%H.%M.%S)N$(printf %.6x $thisNum)"
btrfs "fi" sync "${root}" > /dev/null
btrfs subvolume snapshot -r "$root" "${thisSnapshot}" > /dev/null &
sleep 0.01
btrfs "fi" sync "${root}" > /dev/null
wait
btrfs "fi" sync "${root}" > /dev/null
[[ -d "${thisSnapshot}" ]] || \
	die 1 "btrfs subvolume snapshot -r $root ${thisSnapshot}"

for ((i=1;i<$nLevels;i++)); do
	for ((j=0;j<$levelSize;j++)); do
		snapshots=($(getSnapshots))
		index=$((${i}*${levelSize}+${j}))
		[[ ${index} -ge ${#snapshots[*]} ]] && break 2
		thisSnapshot="${snapshots[ ${index} ]}"
		if (( $(getNum "$thisSnapshot")%2**${i} < 2**(${i}-1) )); then
			delSnapshot "$thisSnapshot"
		fi
	done
done

snapshots=($(getSnapshots))
[[ ${#snapshots[*]} -gt $(( ${nLevels} * ${levelSize} )) ]] && \
	delSnapshot "${snapshots[-1]}"

snapshots=($(getSnapshots))
if [[ -n "$sendLevel" ]] && [[ -n "$sendTarget" ]] && [[ -n "${configFile}" ]]; then
	( flock -x -n 3 || exit 0; localSend; ) 3<"${configFile}"
fi

exit $?