#!/bin/bash

save_database() {
  echo "Saving database contents to file \"$1\" ..."
  # some database dump command goes here.
}
restore_database() {
  echo "Restoring database contents from file \"$1\" ..."
  # some database restore command goes here.
}
save_files() {
  echo "Saving files to tarball \"$1\" ..."
  # This would have the application-level knowledge of which
  # files should be backed up - for this example, we'll try
  # to archive file1.txt and file2.txt from the /tmp directory
  # eg: tar cf ${1} /tmp/file1.txt /tmp/file2.txt
}
restore_files() {
  echo "Restoring files from tarball \"$1\" ..."
  # eg: tar xf ${1}
}

usage()
{
  echo "Usage: $0 [-s|-r] [ -d DB_DUMP ] [ -f TARBALL ]"
  exit 2
}

set_variable()
{
  local varname=$1
  shift
  if [ -z "${!varname}" ]; then
    eval "$varname=\"$@\""
  else
    echo "Error: $varname already set"
    usage
  fi
}

####################################################################
# Main script starts here

unset DB_DUMP TARBALL ACTION

while getopts 'srd:f:?h' c
do
  case $c in
    s) set_variable ACTION SAVE ;;
    r) set_variable ACTION RESTORE ;;
    d) set_variable DB_DUMP $OPTARG ;;
    f) set_variable TARBALL $OPTARG ;;
    h|?) usage ;; esac
done

[ -z "$ACTION" ] && usage
[ -z "$DB_DUMP" ] && [ -z "$TARBALL" ] && usage

if [ -n "$DB_DUMP" ]; then
  case $ACTION in
    SAVE) save_database $DB_DUMP ;;
    RESTORE) restore_database $DB_DUMP ;;
  esac
fi

if [ -n "$TARBALL" ]; then
  case $ACTION in
    SAVE) save_files $TARBALL ;;
    RESTORE) restore_files $TARBALL ;;
  esac
fi