#!/bin/sh

DATASET=$1
if test -z "$DATASET"; then
	echo "Missing dataset argument"
	exit 1
fi

TARGET=$2
if test -z "$TARGET"; then
	echo "Missing target"
	exit 1
fi

TARGET_PATH=$3
if test -z "$TARGET_PATH"; then
	echo "Missing target path"
	exit 1
fi

DATE=$4
if test -z "$DATE"; then
	DATE=$(date +%Y-%m-%d_%H-%M)
fi

REMOTE_NAME="$TARGET_PATH/"$(echo -e $DATASET | sed -r "s/\//_/g")


### Resume existing transfer ###
RESUME_TOKEN=$(ssh $TARGET zfs get -H -p receive_resume_token -o value "$REMOTE_NAME")
if [ "$RESUME_TOKEN" != "" ] && [ "$RESUME_TOKEN" != "-" ]; then
	echo "Resuming interrupted transfer..."
	zfs send -v -t "$RESUME_TOKEN" | ssh $TARGET zfs receive -F -s "$REMOTE_NAME" || exit 1
	echo "Resumed transfer finished."
	exit 0
fi


### Sync existing snapshots ###
REMOTE_SNAPSHOTS=($(ssh $TARGET zfs list -H -t snapshot -o name -s creation $REMOTE_NAME | cut -d"@" -f 2))
LOCAL_SNAPSHOTS=($(zfs list -H -t snapshot -o name -s creation $DATASET | cut -d"@" -f 2))

echo "Remote snapshots: $REMOTE_SNAPSHOTS"

for local_snapshot in "${LOCAL_SNAPSHOTS[@]}"; do
	echo "Syncing local snapshot $local_snapshot ..."
	found=false
	for remote_snapshot in "${REMOTE_SNAPSHOTS[@]}"; do
		if [ "$remote_snapshot" = "$local_snapshot" ] ; then
			found=true
			break
		fi
	done

	if [ $found = true ] ; then
		echo "> Found remotely, setting as last snapshot"
		LAST_SNAPSHOT=$local_snapshot
		EXISTING_SNAPSHOT=""
	else
		echo "> Needs sync"
		EXISTING_SNAPSHOT=$local_snapshot
	fi
done


### New snapshot ###
if [ "$EXISTING_SNAPSHOT" = "" ]; then
	NAME=$DATE
else
	NAME=$EXISTING_SNAPSHOT
fi
SNAPSHOT="$DATASET@$NAME"
echo "New snapshot name is: $NAME"
echo "New snapshot is: $SNAPSHOT"


### Last snapshot ###
echo "Last snapshot is: $LAST_SNAPSHOT"


## Perform transfer
echo "Starting backup with args $DATASET $NAME $LAST_SNAPSHOT"
$HOME/scripts/zfs_backup.sh $DATASET $NAME "$LAST_SNAPSHOT" $TARGET $TARGET_PATH || exit 1


## Destroy last snapshot
echo "Destroying last snapshot..."
zfs destroy "$DATASET@$LAST_SNAPSHOT" || exit 1


echo "Backup finished."