#!/bin/bash

set -o errexit -o errtrace

BORG_HOST="12390@ch-s012.rsync.net"
export BORG_REPO="$BORG_HOST:repos/$(hostname)"
export BORG_PASSPHRASE="$(< ~/.borg_secret)"
export BORG_RSH="ssh -o IdentitiesOnly=yes -o ConnectionAttempts=20 \
                     -o ServerAliveInterval=30 -i ~/.ssh/borg_key"
export LC_COLLATE=C

SNAPSHOT_TARGET="/.snapshots/home-$(date "+%Y-%m-%dT%H:%M:%S")"

cleanup() {
    cd /
    sudo -n /usr/bin/backup-sudo cleanup
}

notify_user() {
    if ! [ -t 1 ]; then
        notify-send "$@"
    fi
}

handle_failure() {
    notify_user -u critical "Backup failed!"

    echo "Backup failed!" >&2
    cleanup
    exit 2
}

trap cleanup EXIT
trap handle_failure INT TERM ERR

cleanup

backup() {
    # borg's caching of 'known' files is really dumb - it takes the full
    # canonical path to check if it has already seen a file. This means that the
    # path of files must never change if you want fast backups.
    # As symlinks won't work, we use mount(8) to ensure the paths stay the same.
    sudo -n backup-sudo mount "$1"

    if [ -t 1 ]; then
        borg_progress="--progress"
    fi

    cd /backup
    borg create --stats $borg_progress \
                --exclude-from ~/.borg_exclude \
                --timestamp . \
                --show-rc \
                ::"$(basename "$1")" . && rc=$? || rc=$?
    if [ $rc -eq 1 ]; then
        # borg defines return code 1 as warning, usually permission stuff
        notify_user "Warning: borgbackup returned 1. Check logs"
    elif [ $rc -gt 1 ]; then
        borg list | grep -q "$(basename "$1")" || handle_failure
    fi

    cleanup
    sudo -n backup-sudo delete_snapshot "$1"
}

if [ ! -d "$SNAPSHOT_TARGET" ]; then
    sudo -n backup-sudo snapshot "$SNAPSHOT_TARGET"
fi

$BORG_RSH "$BORG_HOST" -f -N || rc=$?
if [ ${rc-0} -eq 255 ]; then
    notify_user "Backup: upload skipped"
    echo "SSH server not reachable, skipping upload" >&2
    exit 0
elif [ ${rc-0} -ne 0 ]; then
    handle_failure
fi

# break locks in case the previous run was interrupted
borg break-lock

for d in /.snapshots/*/ ; do
    echo "Now working on: $d"
    backup "$d"
done

echo "Pruning repository."

borg prune --show-rc --list \
           --keep-hourly 72 \
           --keep-daily   7 \
           --keep-weekly  4 \
           --keep-monthly 6

echo "Backup finished."