#!/bin/bash


function chksum (){
        echo -n "$1" | md5sum | awk '{print $1}'
}

function rx_data (){
        Filename="$1"

        if [ -f $Filename.b64 ] ; then
                rm $Filename.b64
        fi

        echo > /dev/ttyUSB0
        (sleep 1 && echo "/bin/sh /xfer.sh $Filename" > /dev/ttyUSB0) &

        read MD5Sum
        MD5Sum=$(echo $MD5Sum | tr -d '\r')
        echo "Expected sum is $MD5Sum"

        (sleep 1 && echo > /dev/ttyUSB0) &
        while read x ; do
                x=$(echo $x | tr -d '\r')
                if [[ "$x" == "EOF" ]] ; then
                        break
                fi

                Payload=$(echo "$x" | awk -F: '{print $1}')
                SumActual=$(echo "$x" | awk -F: '{print $2}' )
                Sum=$(chksum "$Payload")

                if [[ "$Sum" == "$SumActual" ]] ; then
                        # Valid data, write it somewhere
                        echo $Payload >> $Filename.b64
                        # Ack data
                        echo $Sum > /dev/ttyUSB0
                        echo -n "."
                else
                        echo "FAIL" > /dev/ttyUSB0
                        echo -n 'x'
                fi
        done  < /dev/ttyUSB0

        cat $Filename.b64 | base64 -d > $Filename
        rm $Filename.b64

        ActualSum=$(md5sum $Filename | awk '{print $1}')
        if [[ "$ActualSum" == "$MD5Sum" ]] ; then
                return 0
        else
                return 1
        fi
}


File="$1"

if rx_data "$File" ; then
        echo "File transferred OK!"
else
        echo "File appears corrupt."
        echo "Retry?"
fi