#!/bin/sh
. libsb

CACHE="${XDG_RUNTIME_DIR}/nettrafcache"

get_physical_devices() {
    nmcli -t -f STATE,DEVICE device | awk -F: '$1=="connected" { print $2 }'
}

get_bytes() {
    cat "/sys/class/net/${1}/statistics/${2}_bytes" || echo 0
}

update() {
    device=$1 cache=$2

    rx_old=$(awk '$1=="rx" { print $2 }' "$cache" || echo 0)
    tx_old=$(awk '$1=="tx" { print $2 }' "$cache" || echo 0)

    rx_new=$(get_bytes "$device" rx)
    tx_new=$(get_bytes "$device" tx)

    printf "rx %s\n" "$rx_new" >"$cache"
    printf "tx %s\n" "$tx_new" >>"$cache"

    printf "rx=%s tx=%s" "$((rx_new - rx_old))" "$((tx_new - tx_old))"
}

rx_sum=0 tx_sum=0
for device in $(get_physical_devices); do
    cache=${CACHE}-${device}

    rx=0 tx=0
    eval "$(update "$device" "$cache")"

    rx_sum=$((rx_sum + rx))
    tx_sum=$((tx_sum + tx))
done

printf " %5sB  %5sB" "$(numfmt --to=iec "$rx_sum")" "$(numfmt --to=iec "$tx_sum")"