#!/bin/bash

################################################################################################################
# Simple backup script for Raspberry Pi 4 hosting Gitea.
#
# Backup file names:
# File names contain the project name and the timestamp (year, month, week, day):
# PROJECT-YYYY-MM-WW-DDatHHMMSS.zip
# Example:
# FocusGitea-2019-11-45-16-at120943.zip has been created on 2019-11-16 (week 45) at 12:09 and 43 seconds for
# project "FocusGitea".
#
# Configuration:
# Backups are created on a daily basis. An amount of those backups can be saved to the device at the same time.
# "Yearlies" are backups which are created once per year. Each time the script detects that the year has changed
# relative to the last backup, it will put the new backup into folder "yearlies".
# "Monthlies", "weeklies" and "yearlies" work the same, except that they are saved in intervals of per month/
# week/day.
#
#
# author: Matthias Paul, FOCUS electronics (Q4/2019)
################################################################################################################



################################################################################################################
######## CONFIGURATION #########################################################################################
################################################################################################################
# amount of yearly backups to keep (set -1 to disable, set 0 for infinite amount of backups)
N_YEARLIES=2
# amount of monthly backups to keep
N_MONTHLIES=3
# amount of weekly backups to keep
N_WEEKLIES=3
# amount of daily backups to keep
N_DAILIES=2
# name of the project (used as filename, so only use valid characters here)
PROJECTNAME=FocusGitea
# main backup folder (incl. ending slash)
BACKUPFOLDER=/home/paule/backup/







################################################################################################################
######## CREATE BACKUP #########################################################################################
################################################################################################################


# current year (integer)
YEAR=$(date +%Y)
# current month (integer)
MONTH=$(date +%m)
# current week (integer)
WEEK=$(date +%U)
# current day (integer)
DAY=$(date +%d)
# current timestamp (string)
TIMESTAMP=$(date +%H%M%S)

# name (excl. folder) of backup file
BACKUPFILE=$PROJECTNAME-$YEAR-$MONTH-$WEEK-$DAY"at"$TIMESTAMP.zip
# length of project string
PROJECTNAMELEN=${#PROJECTNAME}
# length of backup folder sting
BACKUPFOLDERLEN=${#BACKUPFOLDER}


# TODO: remove (debug)
touch $BACKUPFILE

################################################################################################################
######## MOVE BACKUP ###########################################################################################
################################################################################################################

# defines the destination folder of the backup file
DESTFOLDER=
if [ $N_YEARLIES -gt -1 ]
then
	# yearlies are enabled, ensure to put it into that folder
	FOLDER=$BACKUPFOLDER"yearlies/"
	# create folder if not exists
	mkdir -p $FOLDER

	# check if file should be added here, because year changed
	# current backup and latest backup in folder;
	# 1st step: retrieve most up-to-date file by filename
	# ATTENTION: Do not use file properties, becaus there's np
	# file creation property in Linux.
	TOPFILE=$(ls -r $FOLDER$PROJECTNAME*.zip 2>/dev/null | head -n 1)
	echo $FOLDER
	echo $TOPFILE
	if [ -z $TOPFILE ]
	then
		# no previous backups available, put new backup here
		DESTFOLDER=$FOLDER
		mv $BACKUPFILE $DESTFOLDER$BACKUPFILE
		echo "Initial backup "$BACKUPFILE" copied to "$DESTFOLDER
	else
		# there's at least one yearly backup, check if date changed;
		# get substring of length 4 starting 1 character after project name (incl. folder)
		STARTSTR=$((PROJECTNAMELEN+BACKUPFOLDERLEN+10))
		YEARSTR="${TOPFILE:STARTSTR:4}"
		if [ $YEARSTR -lt $YEAR ]
		then
			# backup needs to placed here, because it is newer
			DESTFOLDER=$FOLDER
			mv $BACKUPFILE $FOLDER$BACKUPFILE
			echo "Added backup "$BACKUPFILE" to "$FOLDER
			if [ $N_YEARLIES -gt 0 ]
			then

				# if a maximum amount of backups had been defined,
				# delete previous backups after having copied the file;
				# display all files matching the project name in reverse order
				# (starting at most up-to-date one), then start at n-th entry
				ls -rt $FOLDER$PROJECTNAME*.zip | tail -n +2
			fi
		fi

	fi


	# move backup file into destination folder

fi