#!/usr/bin/env bash

set -eo pipefail

if ssh takyon sudo -u bingus test -e /opt/bingus-files/files_snapshots/current; then
	echo 'Error: an operation is already ongoing' >&2
	exit 1
fi

mkdir -p baks

ssh takyon sudo -u bingus btrfs subvol snapshot -r \
	/opt/bingus-files/files \
	/opt/bingus-files/files_snapshots/current

if ssh takyon sudo -u bingus test -e /opt/bingus-files/files_snapshots/last; then
	echo "taking incremental backup" >&2
	out=baks/"$(date --rfc-3339=seconds)"
	ssh takyon sudo btrfs send \
		-p /opt/bingus-files/files_snapshots/last \
		/opt/bingus-files/files_snapshots/current \
		--compressed-data > "$out"
	du -h "$out"
	echo "removing parent" >&2
	ssh takyon sudo -u bingus btrfs property set -ts /opt/bingus-files/files_snapshots/last ro false
	ssh takyon sudo -u bingus btrfs subvol delete /opt/bingus-files/files_snapshots/last
else
	echo "taking first copy" >&2
	ssh takyon sudo btrfs send \
		/opt/bingus-files/files_snapshots/current \
		--compressed-data > baks/epoch
	du -h baks/epoch
fi

echo "renaming current to last" >&2

ssh takyon sudo -u bingus mv \
	/opt/bingus-files/files_snapshots/current \
	/opt/bingus-files/files_snapshots/last

echo "backup complete" >&2