#!/bin/bash

# Backup a directory, args come from the environment
# $1, if it exists, contains a list of declarations

# Copyright (C) 2019 Carlos Galindo
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

if [ -e "$1" ]; then
    source $1
fi

if [ -z "${outDir}" -o -z "${dir}" -o -z "${maxBackups}" -o -z "${service}" \
       	-o -z "${name}" ]
then
    echo "ERROR: Missing data, you need to declare the following:"
    echo "\toutDir: the directory where the backup will be saved"
    echo "\tdir: the directory to back up"
    echo "\tname: the name of the backup"
    echo "\tservice: the service to be stopped (webserver)"
    echo "\tmaxBackups: the number of backups to keep (0 = infinite)"
    exit 1
fi

if [ "$(id -u)" != "0" ]
then
   echo "ERROR: this script has to be run as root!"
   exit 1
fi

dateDir="${outDir}/$(date +"%Y%m%d_%H%M%S")"

if [ ! -d "${dateDir}" ]
then
    mkdir -p "${dateDir}"
else
    echo "ERROR: the backup directory ${dateDir} already exists!"
    exit 1
fi

echo "Begin backup for ${name}, at ${dateDir}"

echo -n "Stopping service ${service}..."
systemctl stop "${service}"
echo " OK"

trap 'echo -n "Starting service ${service}..."; systemctl start "${service}"; echo " OK"; exit 2' 1 2 3 9 15

echo -n "Backing up ${name}..."
tar --preserve-permissions --absolute-names --create --file "${dateDir}/backup.tar.xz" $dir
pushd "${dateDir}" > /dev/null
sha256sum * > sha256sums
popd > /dev/null
echo " OK"

echo -n "Starting service ${service}..."
systemctl start "${service}"
echo " OK"

if (( ${maxBackups} != 0 ))
then
    nrOfBackups=$(ls -l ${outDir} | grep -c ^d)

    if (( ${nrOfBackups} > ${maxBackups} ))
    then
        echo "Removing old backups..."
        ls -t ${outDir} | tail -$(( nrOfBackups - maxBackups )) | while read dirToRemove; do
            echo -n "Deleting ${dirToRemove}..."
            rm -r ${outDir}/${dirToRemove}
            echo " OK"
        done
    fi
fi

echo "End of backup for ${name}, at ${dateDir}"