#!/bin/bash

set -x
set -eu
set -o pipefail

function usage
{
    retval="$1"
    case "$retval" in
        0)
            ;;
        *)
            exec 1>&2
            ;;
    esac

    echo "Usage: $0 [--normal|--overwrite] --source-dir /source/directory --dest-dir /destination/directory --compressor gzip --help"
    echo
    echo "Normal mode will do a backup with rotation."
    echo
    echo "Overwrite mode will overwrite the last daily backup, without doing any rotation at all.  It's for redoing a backup."
    echo "when a previous one fails."
    echo
    echo "We default to compressing with gzip, but actually pbzip2 is faster - just less common."

	exit "$retval"
}

mode=unknown
source_dir=""
destination_dir=""
compressor=gzip

while [ "$#" -ge 1 ]
do
    case "$1" in
        --normal)
            mode=normal
            ;;
        --overwrite)
            mode=overwrite
            ;;
        --source-dir)
            source_dir="$2"
            shift
            ;;
        --dest-dir)
            destination_dir="$2"
            shift
            ;;
        --compressor)
            compressor="$2"
            shift
            ;;
        -h|--help)
            usage 0
            ;;
	    *)
            usage 1
            ;;
    esac
	shift
done

all_good=True

case "$mode" in
	normal)
		echo "$0: OK, I will do a normal backup with rotation" 1>&2
		;;
	overwrite)
		echo "$0: OK, I will overwrite the most recent backup, without any sort of rotation" 1>&2
		;;
	unknown)
        all_good=False
		echo "$0: You must specify either --normal or --overwrite" 1>&2
		;;
esac

case "$source_dir" in
    "")
        echo "$0: --srcdir is a required option" 1>&2
        all_good=False
esac

case "$destination_dir" in
    "")
        echo "$0: --dstdir is a required option" 1>&2
        all_good=False
esac

case "$all_good" in
    True)
        ;;
    False)
        echo "$0: one or more preflight checks failed" 1>&2
        usage 1
        ;;
    *)
        echo "$0: Internal error: \$all_good has a strange value: $all_good" 1>&2
        exit 1
        ;;
esac

# disabled Wed Nov  3 09:54:46 PST 2004, because $destination_dir exists,
# but is not mounted

# Mon Sep 12 10:23:13 PDT 2005: reenabled, now that we have 3511+QFS
#exit 1

umask 077

PATH=/usr/local/bin:$PATH

mkdir -p "$destination_dir"/backups
if ! cd "$destination_dir"/backups
then
   echo "$destination_dir"/backups does not exit 1>&2
   exit 1
fi

mkdir -p daily.1
mkdir -p daily.2
mkdir -p weekly.1
mkdir -p weekly.2
mkdir -p monthly.1
mkdir -p monthly.2

seven_days=$((60*60*24*7))
thirty_days=$((60*60*24*30))
curtime=$(python3 -c 'import time; t=int(time.time()); print(t)')

if [ "$mode" = normal ]
then
	rm -rf daily.2
	mv daily.1 daily.2

	mkdir -p daily.1
fi

if tty -s
then
	ONTTY=1
else
	ONTTY=0
fi
export ONTTY

# tar likes to exit false if even one file has a problem, but we don't want that to interfere with rotation,
# hence the || true's.
if [ "$ONTTY" = 1 ]
then
	bytes="$(du -skx "$source_dir" | awk ' { print $1 * 1024 }')"
	(cd "$source_dir" && tar cvlSf - . 2> "$destination_dir"/backups/daily.1/tvf) \
        | reblock -e "$bytes" -b $((1024*1024)) -t 300 \
        | eval "$compressor" > daily.1/archive || true
else
	(cd "$source_dir" && tar cvlSf - . 2> daily.1/tvf) | eval "$compressor" > daily.1/archive || true
fi

function mtime_of_file
{
    filename="$1"
    stat -c '%Y' "$filename"
}

function should_do_weekly
{
	if ! [ -f "weekly.1/archive" ]
    then
        return 0
    fi
    
    mtime_of_weekly=$(mtime_of_file weekly.1/archive)
    if [ $((curtime - mtime_of_weekly)) -gt "$seven_days" ]
    then
        return 0
    else
        return 1
    fi
}

function should_do_monthly
{
	if ! [ -f "monthly.1/archive" ]
    then
        return 0
    fi
    
    mtime_of_monthly=$(mtime_of_file monthly.1/archive)
    if [ $((curtime - mtime_of_monthly)) -gt "$thirty_days" ]
    then
        return 0
    else
        return 1
    fi
}

# ln (hardlinking) appears to work even on CIFS now, though our CIFS server is running Samba, so maybe that's why.
if [ "$mode" = normal ]
then
    if should_do_weekly
	then
		rm -rf weekly.2
		mv weekly.1 weekly.2
		mkdir weekly.1
        for file in daily.1/*
        do
            ln "$file" weekly.1/.
        done
	fi

	if should_do_monthly
	then
		rm -rf monthly.2
		mv monthly.1 monthly.2
		mkdir monthly.1
        for file in daily.1/*
        do
            ln "$file" monthly.1/.
        done
	fi
fi