#!/usr/bin/env bash

set -o pipefail  ## trace ERR through pipes
set -o errtrace  ## trace ERR through 'time command' and other functions
set -o nounset   ## set -u : exit the script if you try to use an uninitialised variable
set -o errexit   ## set -e : exit the script if any statement returns a non-true return value

if [[ "$#" -ne 1 ]]; then
    echo "Usage: $0 <file>"
    exit 1
fi

SOURCE_FILE="$1"
BACKUP_FILE="$(dirname "$1")/.$(basename "$1").bak"

if [[ -f "$BACKUP_FILE" ]]; then
    ## Backup file exists
    ## -> container was restarted
    ## -> restoring configuration
    cp -a -- "$BACKUP_FILE" "$SOURCE_FILE"
else
    ## Backup file DOESN'T exists
    ## -> container first startup
    ## -> backup configuration
    cp -a -- "$SOURCE_FILE" "$BACKUP_FILE"
fi