#!/bin/bash
# Title:        Incremental Back-up script
# Description:  Create back-ups of dirs and dbs by copying them to Perfacilis' back-up servers
#               We strongly recommend to put this in /etc/cron.hourly
# Version:      0.5
# Usage:        bash /etc/cron.hourly/backup

readonly BACKUP_LOCAL_DIR=/ext/local-backup
readonly BACKUP_DIRS=(/etc /home /ext $BACKUP_LOCAL_DIR)

readonly RSYNC_PROFILE="/mnt/nas-backup"
readonly RSYNC_DEFAULTS="-trlqz4 --delete --delete-excluded --prune-empty-dirs"
readonly RSYNC_EXCLUDE=(pvc-ab1fbe1d-fb06-4bfb-a4bd-b73c664d7a9f_nzbget_store-data-ssd/ temp/ tmp/ .cache/ log/ logs/ *.log)

readonly INCREMENTS=14

log() {
  MSG=`echo $1`
  logger -p local0.notice -t `basename $0` -- $MSG

  # Interactive shell
  if tty -s; then
    echo $MSG
  fi
}

prepare_local_dir() {
  if [ ! -d $BACKUP_LOCAL_DIR ]; then
    mkdir -p $BACKUP_LOCAL_DIR
    touch -d "January 1 1990" $BACKUP_LOCAL_DIR
  fi
}

prepare_remote_dir() {
  local RSYNC_OPTS=$(get_rsync_opts)
  local EMPTYDIR=$(mktemp -d)

  rsync ${RSYNC_OPTS//--delete* /} $EMPTYDIR/ $RSYNC_PROFILE/current
  rm -rf $EMPTYDIR
}

get_next_increment() {
  local LAST NEXT

  if [ -f $BACKUP_LOCAL_DIR/last ]; then
    LAST=$(cat $BACKUP_LOCAL_DIR/last | tr -d "\n")
  fi

  if [ -z "$LAST" ]; then
    echo 0
    return
  fi

  NEXT=$(($LAST+1))
  if [ "$NEXT" -gt "$INCREMENTS" ]; then
    echo 0
    return
  fi

  echo $NEXT
}

get_rsync_opts() {
  local EXCLUDE=`dirname $0`/rsync.exclude

  if [ ! -f $EXCLUDE ]; then
    printf '%s\n' "${RSYNC_EXCLUDE[@]}" > $EXCLUDE
  fi

  echo "$RSYNC_DEFAULTS --exclude-from=$EXCLUDE"
}

backup_packagelist() {
  log "Back-up list of installed packages"
  dpkg --get-selections > $BACKUP_LOCAL_DIR/packagelist.txt
}

backup_folders() {
  local RSYNC_OPTS=$(get_rsync_opts)
  local DIR TARGET RSYNC
  local INC=$(get_next_increment)
  local VANISHED='^(file has vanished: |rsync warning: some files vanished before they could be transferred)'

  log "Moving back-up to target: ${INC/#0/current}"
  for DIR in ${BACKUP_DIRS[@]}; do
    TARGET=${DIR/#\//}
    TARGET=${TARGET//\//_}

    RSYNC="rsync $RSYNC_OPTS"
    if [ "$INC" -gt 0 ]; then
      RSYNC="rsync $RSYNC_OPTS --backup --backup-dir=/$INC/$TARGET"
    fi

    log "- $DIR"
    $RSYNC $DIR/ $RSYNC_PROFILE/current/$TARGET 2>&1 | (egrep -v "$VANISHED" || true)
  done
}

signoff_increment() {
  echo $(get_next_increment) > $BACKUP_LOCAL_DIR/last
}

cleanup() {
  rm -f `dirname $0`/rsync.exclude
  rm -f `dirname $0`/rsync.secret
}

main() {
  log "Backup initiated at `date`"

  trap "cleanup" EXIT

  prepare_local_dir
  prepare_remote_dir

  backup_packagelist
  backup_folders

  signoff_increment

  log "Backup completed at `date`"
}

main