#!/bin/bash
#
# An optional additional backup operation designed to export a
# Time Machine-style, git-based backup for our customers of their data
# we manage. The script compresses the local git backup repository into
# a tarball that can be downloaded from the web.
#
# This script has special naming conventions:
# - If the script file name (without extension) ends in "_w", the script will
#   only run on Sundays.
# - If the script file name (without extension) ends in "_m", the script will
#   only run on the first day of the month.
#
# Author: Kovács Zoltán <kovacsz@marcusconsulting.hu>
# License: GNU/GPL v3+ (https://www.gnu.org/licenses/gpl-3.0.en.html)
# 2026-04-12 v0.1 Initial release

# Accepted environment variables and their defaults.
#
PAR_BASEDIR=${PAR_BASEDIR:-""}			# Service's base folder
PAR_EXPORTDIR=${PAR_EXPORTDIR:-""}		# Absolute path to export dir
PAR_GITDIR=${PAR_GITDIR:-""}			# Absolute path to tgz dumps

# Other initialisations.
#
EXPORTPATH="storage/backups/export"		# Default path to export dir
GITPATH="storage/backups/webcontent"		# Default path to git repository
SERVICENAME="nextcloud"                         # The composed Nextcloud service
USER=${USER:-LOGNAME}				# Fix for cron enviroment only
YMLFILE="docker-compose.yml"

# Messages.
#
MSG_DOCKERGRPNEED="You must be a member of the docker group."
MSG_DOESNOTRUN="This service doesn't run."
MSG_MISSINGDEP="Fatal: missing dependency"
MSG_MISSINGYML="Fatal: didn't find the docker-compose.yml file"
MSG_NOLOCATE="Cannot locate the service container."
MSG_NONWRITE="The target directory isn't writable"

# Checks the dependencies.
#
TR=$(which tr 2>/dev/null)
if [ -z "$TR" ]; then echo "$MSG_MISSINGDEP tr."; exit 1 ; fi
for item in basename cp cut date dirname docker grep hostname id readlink tar
do
    if [ -n "$(which $item)" ]
    then export $(echo $item | "$TR" '[:lower:]' '[:upper:]' | "$TR" '-' '_')=$(which $item)
    else echo "$MSG_MISSINGDEP $item." >&2; exit 1; fi
done
# All dependencies are available via "$THECOMMAND" (upper case) call.
#
# Let's find which version of docker-compose is installed.
if [ $($DOCKER compose version 2>&1 >/dev/null; echo $?) -eq 0 ]; then
    # We'll use v2 if it is available.
    DOCKER_COMPOSE="$DOCKER"
    commandstring="compose"
else
    # Otherwise falling back to v1.
    DOCKER_COMPOSE="$(which docker-compose)"
    commandstring=""
fi
# One of the two is mandatory.
if [ -z "$DOCKER_COMPOSE" ];then echo "$MSG_MISSINGDEP docker-compose" >&2; exit 1; fi
# Below docker-compose should be called as "$DOCKER_COMPOSE" $commandstring sequence.

# Checks the timing conventions.
#
# Last two characters of the filename.
TIMING="$("$BASENAME" "$0")"; TIMING="${TIMING%.*}"; TIMING="${TIMING:0-2}"
# If this "_w" continues only on Sundays.
[ "$TIMING" = "_w" ] && [[ $("$DATE" +%u) -ne 0 ]] && exit 0
# If this "_m" continues only on the 1st day of the month.
[ "$TIMING" = "_m" ] && [[ $("$DATE" +%d) -ne 1 ]] && exit 0
# There is no time limit, go on.

# Where I'm?
# https://gist.github.com/TheMengzor/968e5ea87e99d9c41782
#
SOURCE="$0"
while [ -h "$SOURCE" ]; do
    # resolve $SOURCE until the file is no longer a symlink
    SCRPATH="$( cd -P "$("$DIRNAME" "$SOURCE" )" && pwd )" #"
    SOURCE="$("$READLINK" "$SOURCE")"
    # if $SOURCE was a relative symlink, we need to resolve it
    # relative to the path where the symlink file was located
    [[ $SOURCE != /* ]] && SOURCE="$SCRPATH/$SOURCE"
done; SCRPATH="$( cd -P "$("$DIRNAME" "$SOURCE" )" && pwd )" #"

# Need to be root or a Docker manager user.
#
[[ "$USER" != 'root' ]] \
&& [[ -z "$(echo "$("$ID" -Gn "$USER") " | "$GREP" ' docker ')" ]] \
&& echo "$MSG_DOCKERGRPNEED" >&2 && exit 1 #"

# Searches the base folder, containing a docker-compose.yml file.
#
# Called from the base folder (./)?
BASE_DIR="$PAR_BASEDIR"
TEST_DIR="$SCRPATH"
[[ -z "$BASE_DIR" ]] && [[ -r "$TEST_DIR/$YMLFILE" ]] && BASE_DIR="$TEST_DIR"
# Called from ./tools?
TEST_DIR="$("$DIRNAME" "$TEST_DIR")"
[[ -z "$BASE_DIR" ]] && [[ -r "$TEST_DIR/$YMLFILE" ]] && BASE_DIR="$TEST_DIR"
# Called from ./tools/*.d?
TEST_DIR="$("$DIRNAME" "$TEST_DIR")"
[[ -z "$BASE_DIR" ]] && [[ -r "$TEST_DIR/$YMLFILE" ]] && BASE_DIR="$TEST_DIR"
# On failure gives it up here.
if [ -z "$BASE_DIR" -o ! -r "$BASE_DIR/$YMLFILE" ]; then
    echo "$MSG_MISSINGYML" >&2; exit 1
fi
# Sets the absolute paths.
EXPORTDIR="${PAR_EXPORTDIR:-$BASE_DIR/$EXPORTPATH}"
GITDIR="${PAR_GITDIR:-$BASE_DIR/$GITPATH}"
# Exits silently if EXPORTDIR or GITDIR isn't present.
[[ ! -e "$EXPORTDIR" ]] && exit 0
[[ ! -e "$GITDIR" ]] && exit 0
# EXPORTDIR must be writable.
[[ ! -w "$EXPORTDIR" ]] \
&& echo "$MSG_NONWRITE: $EXPORTDIR" >&2 && exit 1

# Converts the service name to an actual running container's name.
#
MYCONTAINER="$("$DOCKER" inspect -f '{{.Name}}' $(cd "$BASE_DIR"; "$DOCKER_COMPOSE" $commandstring ps -q "$SERVICENAME") | "$CUT" -c2-)"
# Gives up here if failed.
if [ -z "$MYCONTAINER" ]; then echo "$MSG_NOLOCATE" >&2; exit 1; fi

# Tries the backup.
#
pushd "$GITDIR" > /dev/null
    EXPORTNAME=$MYCONTAINER-git.$("$DATE" '+%Y%m%d_%H%M%S').$("$HOSTNAME")
    "$TAR" czf "$EXPORTDIR/$EXPORTNAME.tgz" . 2>"$EXPORTDIR/$EXPORTNAME.log"
popd > /dev/null

# That's all, Folks! :)