notifbk

#!/usr/bin/env bash
#
# notifbk :: companion backup script for notif.el
# requires: bash 4.0+, tar, gzip, find, sort, rm

trap 'echo -e "\nSIGINT Received... exiting"; exit 130' SIGINT

err() {
  # send errors to standard error
  echo "[${0##*/}] error: $*" >&2
}

show_help() {
  # help option text
  echo "Usage: ${0##*/} -d DIR [OPTION]..."
  echo "Options:"
  echo "  -h, --help    Show this help menu"
  echo "  -d DIR        The directory where to save your backup"
  echo "  -k NUM        When rotating old backups:"
  echo "                  - The NUM most recent backups to keep"
  echo "  -r            Rotate backups only (will not create a backup)"
}

_parse_options() {
  # parse options and assign variables

  # check for long --help
  if [[ "$1" == "--help" ]]; then
    show_help
    showed_help="1"
    return 0
  fi

  # showed_help, backup_directory, keep_backup_files, rotate_backups_only -
  # must be declared in main
  local opt=""
  while getopts ":hd:k:r" opt; do
    case "$opt" in
      h)
        show_help
        showed_help="1"
        return 0
        ;;
      d)
        backup_directory="${OPTARG%/}"
        validate_directories "$backup_directory" || return 1
        ;;
      k)
        keep_backup_files="$OPTARG"
        if ! [[ "$keep_backup_files" -ge 1 ]]; then
          err "value for the -k option must be greater than or equal to 1"
          return 1
        fi
        ;;
      r)
        rotate_backups_only="1"
        ;;
      :)
        err "option -$OPTARG requires an argument"
        return 1
        ;;
      \?)
        err "Invalid option: -$OPTARG"
        show_help
        return 1
        ;;
    esac
  done
}

date() {
  # See: 'man strftime' for format.
  printf "%($1)T\n" "-1"
  # to get YYYY-MM-DD-HH:mm:ss
  # date "%F-%T"
}

validate_directories() {
  # verify that a directory, or list of directories, exist
  #
  # ARG $@: any directory

  local _dir=""
  for _dir in "$@"; do
    if ! [[ -d "$_dir" ]]; then
      err "invalid directory $_dir"
      return 1
    fi
  done
}

create_backup() {
  # create the notif backup, a compressed archive
  #
  # ARG $1: notif directory
  # ARG $2: backup directory

  local notif_dir_name="" notif_dir_parent="" current_date_time=""
  local archive_name=""

  # split the $notif_directory into the dir name, and its parent path
  notif_dir_name="${1##*/}"  # Get the directory name (part after last '/')
  notif_dir_parent="${1%/*}" # Get the parent path (part before last '/')

  # gather the date and time and set the archive name
  current_date_time=$(date "%F-%T") || return 1
  archive_name="notifbk-${current_date_time}.tar.gzip"

  # the archive command
  tar -czv -C "$notif_dir_parent" -f "${2}/${archive_name}" "$notif_dir_name"
}

rotate_old_backups() {
  # removes old notif backups from backup directory
  #
  # ARG $1: destination directory of backups
  # ARG $2: number of backups to keep (recency)

  local -a backup_files=()
  local -a files_to_remove=()
  local n="$2"

  # gather all notif backup file and place them into an array
  readarray -t backup_files < \
            <(find "$1" -maxdepth 1 -type f -name "*notifbk*tar*" | sort -n -r)

  # a check if there are no files found in the destination directory
  [[ "${#backup_files[@]}" -eq 0 ]] && echo "No backup files found in ${1}" && \
    return 0

  # echo all backup files found to the console, with a line indicating
  # which will be kept and removed
  local n="$2"
  echo "----- Files to keep -----"
  for (( i=0; i < ${#backup_files[@]}; i++ )); do
    echo "${backup_files[$i]}"
    if (( i == "$n" - 1 )); then
      echo "---- Files to remove ----"
    fi
  done

  # gather an array of files to remove
  if [[ ${#backup_files[@]} -gt "$n" ]]; then
    files_to_remove=("${backup_files[@]:n}") # slice the array
    echo
    # iterate through and remove each file
    local file=""
    for file in "${files_to_remove[@]}"; do
      rm -i "$file"
    done
  else
    echo
    echo "[${0##*/}]: no files need to be removed"
  fi
}

main() {
  set -eu
  set -o pipefail

  # set constants
  local notif_directory="$HOME/notes"
  validate_directories "$notif_directory"

  # define variables that can be assigned in _parse_options
  local showed_help="" backup_directory="" keep_backup_files=""
  local rotate_backups_only=""
  if [[ $# -gt 0 ]]; then
    _parse_options "$@"
    [[ -n "$showed_help" ]] && exit 0
  else
    show_help
    exit 1
  fi

  # -d option (backup_directory) is always required for any operation
  if [[ -z "$backup_directory" ]]; then
    err "backup directory [-d] required"
    echo "---"
    show_help
    exit 1
  fi

  # if -r was NOT used, we will create a backup
  if [[ -z "$rotate_backups_only" ]]; then
    create_backup "$notif_directory" "$backup_directory"
  fi

  # if -k was used, then run rotate function
  if [[ -n "$keep_backup_files" ]]; then
    rotate_old_backups "$backup_directory" "$keep_backup_files"
  fi

  # if -r was used, but without -k, throw error
  if [[ -n "$rotate_backups_only" ]] && [[ -z "$keep_backup_files" ]]; then
    err "-k option required when using -r option"
    echo "---"
    show_help
    exit 1
  fi
}

main "$@"