#!/bin/bash
#
# rsyncshot
# Craig Jennings craigmartinjennings@gmail.com
# Inspired by Mike Rubel: http://www.mikerubel.org/computers/rsync_snapshots/

# uncomment next 4 lines for debugging output
# exec 5> >(logger -t $0)
# BASH_XTRACEFD="5"
# PS4='$LINENO: '
# set -x

# default locations for setup
SCRIPTLOC=/usr/local/bin/rsyncshot;
DESTINATION=/home/cjennings/Backup;

INSTALLHOME=/etc/rsyncshot
LOGHOME=/var/log/rsyncshot.log;

INCLUDES="$INSTALLHOME/include.txt";
EXCLUDES="$INSTALLHOME/exclude.txt";

# default cron job entries
# hourly -- hourly on minute 0 from 1am to 11pm
CRON_H="0 1-23 * * * $SCRIPTLOC hourly 22";
# daily -- midnight, Monday - Saturday.
CRON_D="0 0 * * 1-6 $SCRIPTLOC daily 6";
# weekly -- Sundays at midnight
CRON_W="0 0 * * 7 $SCRIPTLOC weekly 51";

# print help
help()
{
    echo ""
    echo "rsyncshot - compact snapshots on Linux using rsync and hard links."
    echo "Usage: "
    echo "rsyncshot <name> <number of backups to retain>"
    echo "          setup (installs rsyncshot and cron jobs)"
    echo "          help  (prints this info)"
    echo "Notes:"
    echo "- install and log locations defined in script."
}

# display error and exit
error()
{
    echo "ERROR: $0: $@" 1>&2;
    echo "See \"rsyncshot help\" for usage."
    exit 1;
}

# copy files, create exclude, and setup cron job
setup()
{
    # copy this file to directory on path
    cp -f $0 /usr/local/bin
    echo "$0 copied to /usr/local/bin"
    
    # make install home if it doesn't exist;
    if [ ! -d $INSTALLHOME ]; then
	mkdir -p $INSTALLHOME;
	"Created install home at $INSTALLHOME.";
    fi

    # create includes file and add default entries
    if [ -f $INCLUDES ]; then rm $INCLUDES; fi
    printf "/home /etc /usr/local/bin" >> $INCLUDES;
    echo "modify include file at $INCLUDES";

    # create excludes file and add default entries
    if [ -f $EXCLUDES ]; then rm $EXCLUDES; fi
    printf "*.pyc\n*.pyo\n*.class\n*.elc\n*.o\n*.tmp\n.cache*" >>  $EXCLUDES;
    echo "modify exclude file at $EXCLUDES";

    # write out current crontab, append default entries, and install
    crontab -l > crontemp;
    echo "$CRON_H >> $LOGHOME 2>&1" >> crontemp;
    echo "$CRON_D >> $LOGHOME 2>&1" >> crontemp;
    echo "$CRON_W >> $LOGHOME 2>&1">> crontemp;
    crontab crontemp;
    rm crontemp;
    echo "hourly, daily, and weekly cron jobs installed.";
}

# if user requested help, display and exit.
if [ "$TYPE" = "HELP" ]; then help; exit; fi

# ensure running as root
if [ "$EUID" -ne 0 ]; then error "This script must be run as root."; fi

# display how the script was started
echo "rsyncshot invoked on `date -u` with: $0 $1 $2";

# validate first arg is alpha chars and make it case insensitive
if ! [[ $1 =~ [a-zA-Z] ]]; then error "snapshot type not recognized."; fi
TYPE=$(tr '[a-z]' '[A-Z]' <<< $1);

# if user requested setup,  and exit.
if [ "$TYPE" = "SETUP" ]; then setup; exit; fi

# Validate second arg is numeric
if ! [[ $2 =~ [0-9] ]]; then error "max snapshots not a number."; fi
MAX=$(($2-1));

# validate include file (source directories)
if [ ! -f "$INCLUDES" ]; then error "include file $INCLUDES not found."; fi
SOURCES=$(<$INCLUDES);
for SOURCE in $SOURCES
do
    if [ ! -d "$SOURCE" ]; then error "source $SOURCE not found"; fi
done

# validate exclude file (exclusion patters)
if [ ! -f "$EXCLUDES" ]; then error "Exclude file $EXCLUDES not found."; fi

# sync each source directories in turn
for SOURCE in $SOURCES
do
    rsync -avh -i --times \
    	  --delete  --delete-excluded \
    	  --exclude-from=$EXCLUDES \
    	  --update $SOURCE $DESTINATION/latest ;
done

# update the time of latest to reflect snapshot time
# touch $DESTINATION/latest;

# delete the last snapshot if it exists
if [ -d $DESTINATION/$TYPE.$MAX ]; then
    rm -rf $DESTINATION/$TYPE.$MAX;
fi

# rotate snapshots descending
for (( start=$(($MAX)); start>=0; start--)); do
    end=$(($start+1));
	if [ -d $DESTINATION/$TYPE.$start ]; then
	    mv $DESTINATION/$TYPE.$start $DESTINATION/$TYPE.$end;
	fi
done

# touch the directory for a timestamp 
touch $DESTINATION/latest

# make a hard-link-only copy into $TYPE.0
cp -al $DESTINATION/latest $DESTINATION/$TYPE.0;

# make the directory $TYPE.0 read-only
chmod -w $DESTINATION/$TYPE.0

# print end time and exit
echo "rsyncshot completed `date -u` ";
exit 0;