#!/bin/bash
#
# shell script to make netcat+tar file transfer similar to scp

printUsage()
{
cat <<EOF
Usage : `basename $0` [SRC_FILES...] [user@ip_addr:destination_dir] [disable or enable compression (0/1)]
EOF
}

if [ $# -lt 3 ]; then
    printUsage
    exit 1
else
    ARGS=("$@")                    # make a copy of the array of args
    enable_compression=${ARGS[-1]} # get last element of the array
    unset ARGS[${#ARGS[@]}-1]      # remove the last element of the array; cannot pass negative index here

    DEST=${ARGS[-1]}               # last element of the remaining array contains the destination info
    user=$(echo $DEST | awk -F'@' '{print $1}')
    ip=$(echo $DEST | awk -F'@' '{print $2}' | awk -F':' '{print $1}')
    dest=$(echo $DEST | awk -F'@' '{print $2}' | awk -F':' '{print $2}')
    unset ARGS[${#ARGS[@]}-1]      # remove the last element of the array

    src=("${ARGS[@]}")             # remaining array contains the src files and directories to be transferred
fi

# sanity checks
echo "sanity checks in progress..."

ping -c 1 -w 10 $ip &>/dev/null
if [ $? -ne 0 ]; then
    echo "ERROR : cannot connect to $ip"
    exit 1
fi

which pv &>/dev/null
if [ $? -ne 0 ]; then
    echo "ERROR : please install 'pv' on src before using this script"
    exit 1
fi

ssh $user@$ip 'which screen' &>/dev/null
if [ $? -ne 0 ]; then
    echo "ERROR : please install 'screen' on destination before using this script"
    exit 1
fi

for i in "${src[@]}"; do
    if [[ (! -d "$i") && (! -f "$i") ]]; then
        echo "ERROR : $i : no such file or directory"
        exit 1
    fi
done

ssh $user@$ip "ls $dest" &>/dev/null
if [ $? -ne 0 ]; then
    ssh $user@$ip "mkdir -p $dest" &>/dev/null
    if [ $? -ne 0 ]; then
        echo "unable to create directory $dest at destination"
        exit 1
    fi
    echo "created directory $dest"
fi
echo "sanity checks complete..."

# transfer data
for i in "${src[@]}"; do
    # start netcat at destination
    if [ $enable_compression -eq 0 ]; then
        echo "nc -l -p 12345 | tar xf - -C $dest" > /tmp/nct.sh
        scp /tmp/nct.sh $user@$ip:/tmp/ &>/dev/null
        ssh -f $user@$ip "screen -dm -S netcat sh /tmp/nct.sh"
    else
        echo "nc -l -p 12345 | tar xzf - -C $dest" > /tmp/nct.sh
        scp /tmp/nct.sh $user@$ip:/tmp/ &>/dev/null
        ssh -f $user@$ip "screen -dm -S netcat sh /tmp/nct.sh"
    fi

    if [ $? -ne 0 ]; then
        echo "ERROR : unable to start netcat at destination"
        exit 1
    fi
    echo "started netcat at destination"
    sleep 2

    # transfer data
    echo "[$i] data transfer in progress..."
    dn=$(dirname "$i")
    bn=$(basename "$i")
    cd "$dn"

    if [ $enable_compression -eq 0 ]; then
        tar cf - "$bn" | pv -s $(du -sb "$bn" | awk '{print $1}') | nc $ip 12345 &>/dev/null
    else
        tar czf - "$bn" | pv -s $(du -sb "$bn" | awk '{print $1}') | nc $ip 12345 &>/dev/null
    fi

    if [ $? -ne 0 ]; then
        echo "ERROR : something went wrong at src"
        ssh $user@$ip "killall nc; killall screen; killall tar" &>/dev/null
        exit 1
    fi
    echo "[$i] data transfer completed..."
    sleep 2
done