#!/bin/bash

REMOTE_HOST=localhost
REMOTE_BASE=/tmp/backmeupscotty
ARCHIVE_KEEPNBACKUPS=30
ARCHIVE_KEEPNDAYS=30
BACKUP_RUNEVERYNTHDAY=1

function upperme {
    echo $(basename $0) | tr '[:lower:]' '[:upper:]'
}

function scottyinfo {
    echo $(upperme): $@ 
}

function scottyerror {
    echo $(upperme): $@ >&2 
}

if [ $(pidof -x $(basename $0) | wc -w) -gt 2 ]; then 
    scottyerror Another instance of $(basename $0) is already running!
    exit 1
fi

while getopts "qn:" opt; do
    case $opt in
	q)
	    exec > /dev/null
	    ;;
	n)
	    BACKUP_RUNEVERYNTHDAY=$OPTARG
	    ;;
    esac
done

function grepbackups {
    ssh $REMOTE_HOST "ls $REMOTE_BASE/$1" | grep -E '[0-9]+-[0-9]+'
}

function isIncomplete {
    if ( ssh $REMOTE_HOST '[ -d '$REMOTE_BASE/$1/incomplete' ]' ); then
	return 0
    else
	return 1
    fi
}

function isIncompleteOrNthDay {
    if isIncomplete $1 || \
	[ $(( ( $(date +%s) / (60*60*24) ) % $BACKUP_RUNEVERYNTHDAY )) -eq 0 ]; 
    then
	return 0
    else
	return 1
    fi
	
}

function scottysync {
    timestamp=$(date +%s)

    scottyinfo Syncing $1 to $REMOTE_HOST:$REMOTE_BASE/$2 @$timestamp

    if [ ! -d "$1" ]; then
	scottyerror Source dir $1 does not exist. Not syncing!
	return 1
    fi

    if [ $(ls -A "$1" | wc -l) -eq 0 ]; then
	scottyerror Source dir $1 is empty. Not syncing!
	return 1
    fi

    dir_current=$REMOTE_BASE/$2/current
    dir_incomplete=$REMOTE_BASE/$2/incomplete
    dir_timestamped=$REMOTE_BASE/$2/$timestamp-$(date -d @$timestamp +%Y%m%d%H%M%S)

    if [ -z $3 ]; then
	rsync_exclude=""
    else
	rsync_exclude=$(eval echo --exclude={$3} | tr -d {})
    fi

    if (ssh $REMOTE_HOST '[ ! -d '$REMOTE_BASE/$2' ]'); then
	scottyinfo Creating destination directory $REMOTE_HOST:$REMOTE_BASE/$2
	ssh $REMOTE_HOST "mkdir $REMOTE_BASE/$2"
    fi

    if isIncomplete $2; then
	scottyerror Continuing old incomplete backup
    fi

    scottyinfo Starting rsync
    rsync -e ssh \
	-v -aHAX --numeric-ids --delete --delete-excluded \
	--link-dest=$dir_current \
	$rsync_exclude \
	$1/ $REMOTE_HOST:$dir_incomplete/
    
    if [ $? -eq 0 ]; then
	scottyinfo Timestamping completed backup and linking to current backup
	ssh $REMOTE_HOST \
	    "mv $dir_incomplete $dir_timestamped && rm -f $dir_current && ln -s $(basename $dir_timestamped) $dir_current"
    fi

    while [ $(grepbackups $2 | wc -l) -gt $ARCHIVE_KEEPNBACKUPS ]; do
	oldestbackup=$(grepbackups $2 | head -1)
	oldestbackuptstamp=$(echo $oldestbackup | cut -d'-' -f1)

	if [ $oldestbackuptstamp -lt $(( $(date +%s) - $ARCHIVE_KEEPNDAYS*60*60*24 )) ]; then
	    scottyinfo Removing old backup $oldestbackup
	    ssh $REMOTE_HOST rm -r "$REMOTE_BASE/$2/$oldestbackup"
	else
	    break
	fi
    done
}