#!/bin/bash
#
# A service script to backup the application's storage (with exceptions)
# of a docker-composed Node.JS instance. Creates a tarball in
# $BASE_DIR/storage/backups/tarballs folder (by default). An optional
# parameter may change the target folder.
#
# The contents of the tarball can be refined by setting the SD_BACKUP_*
# environment variables in the docker-compose.yml file.
#
# Call as a Docker manager user (member of the docker Linux group) via cron.
#
# Author: Kovács Zoltán <kovacsz@marcusconsulting.hu>
# License: GNU/GPL 3+ https://www.gnu.org/licenses/gpl-3.0.en.html
# 2024-09-23 v0.1 Initial version.

# Accepted environment variables and their defaults.
#
PAR_BASEDIR=${PAR_BASEDIR:-""}                  # Service's base folder
PAR_BACKUPDIR=${PAR_BACKUPDIR:-""}              # Folder to dump within

# Messages (maybe overridden by configuration).
#
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_NONWRITE="The target directory isn't writable"
MSG_NOLOCATE="Cannot locate the Node.JS container."

# Other initialisations.
#
APPSDIR="/home/node/app"			# Base folder of storage to dump
BACKUPDIR="storage/backups/tarballs"		# Folder to dump within
SERVICENAME="nodejs"				# The composed Node.JS service
USER=${USER:-LOGNAME}                           # Fix for cron enviroment only
YMLFILE="docker-compose.yml"

# Checks the dependencies.
#
TR=$(which tr 2>/dev/null)
if [ -z "$TR" ]; then echo "$MSG_MISSINGDEP tr."; exit 1 ; fi
for item in basename cat cut date dirname docker \
            find grep hostname id pwd tail xargs
do
    if [ -n "$(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.

# 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" "$SOURCE" )" && echo "$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" "$SOURCE" )" && echo "$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.
BACKUPDIR="${PAR_BACKUPDIR:-$BASE_DIR/$BACKUPDIR}"

# The dump target folder must be writable.
#
[[ ! -w "$BACKUPDIR" ]] \
&& echo "$MSG_NONWRITE: $BACKUPDIR" >&2 && exit 1

# The service must be running - silently gives up here if not.
#
[[ -z "$(cd "$BASE_DIR"; "$DOCKER_COMPOSE" $commandstring ps --services --filter "status=running")" ]] \
&& exit 1

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

# Checks and parses the config file for the folder (path)names
# to dump and to exclude.
#
function parse { [[ -z "$1" ]] && return
    # Gets the live lines containing the parameter.
    value=$("$CAT" "$CONFFILE" 2>/dev/null | "$GREP" -ve '^#' | \
            "$GREP" -e " $1:" | "$TR" -d '\r')
    # If multiple the last one to consider.
    value=$(echo -e  "$value" | "$TAIL" -n1)
    # Right side of the equal sign W/O leading and trailing spaces and quotes.
    value=$(echo -ne "$value" | "$CUT" -d':' -f2 | "$XARGS")
    echo -e "$value"; return
}
# Examines the YMLFILE.
CONFFILE="$BASE_DIR/$YMLFILE"
# Gets the list of folders to dump and makes the path relative (some sanitization).
# Sets the app's root if no folders given.
FOLDERS=""
for folder in $(parse "DS_BACKUP_FOLDERS") ''; do [[ -n "$folder" ]] && FOLDERS+=" ./$folder"; done
[[ -z "$FOLDERS" ]] && FOLDERS="."
# Gets the list of excludes as well. Converts them to tar  parameters.
EXCLUDES=""
for exclude in $(parse "DS_BACKUP_EXCLUDES") ''; do [[ -n "$exclude" ]] && EXCLUDES+="--exclude='./$exclude' "; done
# We've folders and excludes prepared.

# Tries the FS backup.
if [ -w "$BACKUPDIR" ]; then
    BACKUP_NAME="storage.$("$DATE" '+%Y%m%d_%H%M%S').$("$HOSTNAME")"
    "$DOCKER" exec $NDCONTAINER sh \
    -c "cd $APPSDIR; tar $EXCLUDES -cz $FOLDERS" \
    >  "$BACKUPDIR/$BACKUP_NAME.tgz" 2>>"$BACKUPDIR/$BACKUP_NAME.log"
fi

# That's all, Folks! :)