#!/bin/sh

if [ -z $NETWORK_IO_INTERFACE ]; then
  if is_osx; then
    NETWORK_IO_INTERFACE="en0"
  else
    NETWORK_IO_INTERFACE="eth0"
  fi
fi

declare -r __network_io_divisor=$[$INTERVAL * 1024]
__network_io_sample=(0 0)

__network_io_calc_kBps() {
  echo $1 $2 | awk -v divisor=$__network_io_divisor \
                '{printf "%.2f", ($1 - $2) / divisor}'
}

if is_osx; then
  __network_io_collect () {
    netstat -bI $NETWORK_IO_INTERFACE | \
                    awk "/$NETWORK_IO_INTERFACE/"'{print $7" "$10; exit}'
  }
else
  __network_io_collect () {
    cat /proc/net/dev | awk -v iface_regex="$NETWORK_IO_INTERFACE:" \
                          '$0 ~ iface_regex {print $2" "$10}'
  }
fi

collect () {
  local sample=( $(__network_io_collect) )
  if [ ${__network_io_sample[0]} -ne 0 ]; then
    report "in" $(__network_io_calc_kBps ${sample[0]} ${__network_io_sample[0]})
    report "out" $(__network_io_calc_kBps ${sample[1]} ${__network_io_sample[1]})
  fi
  __network_io_sample=( "${sample[@]}" )
}

docs () {
  echo "Network traffic in kB/s."
  echo "\$NETWORK_IO_INTERFACE=$NETWORK_IO_INTERFACE"
}