#!/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.

# Base configuration.
BACKUP_MOUNTPOINT="/localdata"
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[0]##*/}-$$.log"

# Sanity checks.
(( $# != 1 )) || [[ -z "$1" ]] || [[ "$1" =~ ^(-h|-help|--help)$ ]] && {
  printf "%s: %s <%s>\\n" "Usage" "${BASH_SOURCE[0]}" "backup definition" >&2
  exit 1
}

# Get backup definition specific configuration.
case "$1" in
  'gv0')
    BACKUP_DESTDIR="$BACKUP_MOUNTPOINT/backups/gv0"
    RSYNC_SOURCE="/storage/gv0/"		# The / on the end is required.
    RSYNC_FILTER=()
    ;;
  'mirrors')
    BACKUP_DESTDIR="$BACKUP_MOUNTPOINT/backups/mirrors"
    RSYNC_SOURCE="slackware.uk::mirrors/"	# The / on the end is required.
    RSYNC_FILTER=( \
        '--include=/absolute/***' \
        '--include=/csb/***' \
        '--include=/cumulative/***' \
        '--include=/freeslack/***' \
        '--include=/gfs/***' \
        '--include=/microlinux/***' \
        '--include=/msb/***' \
        '--include=/sarpi/***' \
        '--include=/slackonly/***' \
        '--include=/slackvirt/***' \
        '--include=/slackware/' \
        '--include=/slackware/slackware-pre-1.0-beta/***' \
        '--include=/slackware/slackware-1.01/***' \
        '--include=/slackwarearm/***' \
        '--include=/slacky/***' \
        '--include=/slaxbmc/***' \
        '--include=/slint/***' \
        '--include=/sls/***' \
        '--include=/studioware/***' \
        '--exclude=*' )
    RSYNC_OPTIONS+=( '--contimeout=30' )
    ;;
  *)
    printf "%s: %s: %s\\n" "${BASH_SOURCE[0]##*/}" "$1" "unknown backup definition" >&2
    exit 1
    ;;
esac

# 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[0]##*/}" "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[0]##*/}" "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