#!/bin/bash
# Version: 0.1.0
# Copyright (c) 2023:
#   Darren 'Tadgy' Austin <darren (at) afterdark.org.uk>
# Licensed under the terms of the GNU General Public License version 3.

BACKUP_MOUNTPOINT="/localdata"
BACKUP_DESTDIR="$BACKUP_MOUNTPOINT/backups/gv0"
RSYNC_SOURCE="/storage/gv0/"		# The / on the end is required.
RSYNC_FILTER=()
RSYNC_OPTIONS=( '-a' '-H' '-A' '--timeout=300' '--partial' '--partial-dir=.rsync-tmp' '--delete-delay' '--delay-updates' )
RSYNC_OPTIONS_VERBOSE=( '--verbose' '--stats' '--human-readable' )
RSYNC_LOG="/tmp/${BASH_SOURCE##*/}-$$.log"

# Only allow one copy of the script to run at any time.
# shellcheck disable=SC2154
if [[ "$FLOCK" != "$0" ]]; then
  exec env FLOCK="$0" flock -e -n "$0" "$0" "$@" || {
    printf "%s: %s\\n" "${BASH_SOURCE##*/}" "flock execution error" >&2
    exit 1
  }
fi

# Source the mail configuration.
source /etc/mail.conf "backups" 2>/dev/null || {
  printf "%s: %s\\n" "${BASH_SOURCE##*/}" "Failed to source /etc/mail.conf" >&2
  exit 1
}

# Make sure BACKUP_MOUNTPOINT is a mountpoint.
mountpoint "$BACKUP_MOUNTPOINT" >/dev/null 2>&1 || {
  CONFIG_FILE="backups" /opt/bin/pushover -T "Backup" -p '-1' -m "Failure: $RSYNC_SOURCE"
  mailx "${MAILX_ARGS[@]}" -S "from='$EMAIL_FROM'" -s "Backup failure: $RSYNC_SOURCE" "${EMAIL_TO[@]}" <<-EOF
	'$BACKUP_MOUNTPOINT' is not a mountpoint.
	EOF
  exit 1
}

# Do the backup.
rsync "${RSYNC_OPTIONS[@]}" "${RSYNC_OPTIONS_VERBOSE[@]}" "${RSYNC_FILTER[@]}" "$RSYNC_SOURCE" "$BACKUP_DESTDIR" >"$RSYNC_LOG" 2>&1
ERR="$?"

# Send a notification and mail a log if there were errors.
(( ERR != 0 )) && (( ERR != 10 ))  && (( ERR != 24 )) && {
  CONFIG_FILE="backups" /opt/bin/pushover -T "Backup" -p '-1' -m "Failure: $RSYNC_SOURCE"
  mailx "${MAILX_ARGS[@]}" -S "from='$EMAIL_FROM'" -s "Backup failure: $RSYNC_SOURCE" "${EMAIL_TO[@]}" <<-EOF
	Exit code: $ERR
	Output:
	$(< "$RSYNC_LOG")
	EOF
  rm -f "$RSYNC_LOG"
  exit 1
}

rm -f "$RSYNC_LOG"

exit 0