#!/bin/bash

# ZSC - zfs snapshot cron

CONFIG_FILE="$HOME/.zsc"

FORMAT='+%Y-%m-%d'
DATE=$(date $FORMAT)


### LOCK ###
echo "Locking $0"
if ! lockfile-create -p -r 2 "$0"; then
	echo "Another backup is running, aborting"
	exit 49
fi


split_date() {
	echo "$1" | sed -E 's/([0-9]{4})-([0-9]{2})-([0-9]{2})/\1\n\2\n\3/'
}

handle_dataset() {
	DATASET=$1
	AUTO_CREATE=$2
	D=$3
	W=$4
	M=$5
	Y=$6

	PREFIX=$7
	if test -z "$PREFIX"; then
		PREFIX="zsc-"
	fi

	if test "!no_prefix!" = "$PREFIX"; then
		PREFIX=""
	fi


	echo "--- $DATASET --- $D $W $M $Y $PREFIX"


	# Create new snapshot
	if [ $(zfs list -t snapshot -o name "$DATASET" | grep "$DATE" | head -n1 | wc -l) -eq 0 ]; then
		echo -e
		if [ $AUTO_CREATE == "true" ]; then
			echo -e "Creating snapshot $DATASET@$PREFIX$DATE"
			zfs snapshot "$DATASET@$PREFIX$DATE"
		else
			echo -e "Skip snapshot creation"
		fi
		echo -e
	fi


	# Delete old snapshots
	SNAPSHOTS=($(zfs list -t snapshot -o name "$DATASET" | grep "@$PREFIX" | sort -r))
	for s in "${SNAPSHOTS[@]}"; do
		sdate=$(echo "$s" | awk 'match($0, /.+@'"$PREFIX"'(.+)/, a) {print a[1]}')

		scomp=($(split_date "$sdate") $(date -d "$sdate" "+%u %W"))

		echo -n "${scomp[3]} ${scomp[4]} | "
		
		echo -n "${sdate}: "

		if [ $D -gt 0 ]; then
			D=$(( D-1 ))
			echo "KEEP; D: $D"
		elif [ $W -gt 0 ] && [ ${scomp[3]#0} -eq 1 ]; then
			W=$(( W-1 ))
			echo "KEEP; W: $W"
		elif [ $M -gt 0 ] && [ ${scomp[3]#0} -eq 1 ] && [ $(( ${scomp[4]#0} % 4 )) -eq 0 ]; then
			M=$(( M-1 ))
			echo "KEEP; M: $M"
		elif [ $Y -gt 0 ] && [ ${scomp[3]#0} -eq 1 ] && [ ${scomp[4]#0} -eq 4 ]; then
			Y=$(( Y-1 ))
			echo "KEEP; Y: $Y"
		else
			zfs destroy "$s"
			echo "DISCARD"
		fi
	done
}

cat "$CONFIG_FILE" | while IFS=: read dataset recursive auto_create d w m y prefix; do
	echo "| ##### Dataset: $dataset Recursive: $recursive Auto create: $auto_create Prefix: $prefix d: $d w: $w m: $m y: $y #####"

	if [ $recursive = "true" ]; then
		SUBDATASETS=($(zfs list -o name | grep "$dataset/"))
		echo -e "| Subdatasets: ${SUBDATASETS[@]}"
		echo -e '|'
		for p in "${SUBDATASETS[@]}"; do
			handle_dataset $p $auto_create $d $w $m $y $prefix | awk '{print "| " $0}'
			echo -e '|'
		done
	fi

	handle_dataset $dataset $auto_create $d $w $m $y $prefix | awk '{print "| " $0}'

	echo -e "----------------------------------------------------------------------"
done


### UNLOCK ###
echo "Unlocking $0"
lockfile-remove "$0"