#!/bin/bash

INTERVAL=3
# interfaces for desktop and laptop
INTERFACES="enp6s0 wlp0s29u1u1 wlp56s0"

print_bytes() {
  if [ "$1" -eq 0 ] || [ "$1" -lt 1000 ]; then
    bytes="0"
  elif [ "$1" -lt 1000000 ]; then
    bytes="$(echo "scale=0;$1/1000" | bc -l)k"
  else
    bytes="$(echo "scale=1;$1/1000000" | bc -l)M"
  fi

  echo "$bytes"
}

print_bit() {
  if [ "$1" -eq 0 ] || [ "$1" -lt 10 ]; then
    bit="0 B"
  elif [ "$1" -lt 100 ]; then
    bit="$(echo "scale=0;$1*8" | bc -l) B"
  elif [ "$1" -lt 100000 ]; then
    bit="$(echo "scale=0;$1*8/1000" | bc -l) K"
  else
    bit="$(echo "scale=1;$1*8/1000000" | bc -l) M"
  fi

  echo "$bit"
}

declare -A bytes

get_initial_throughput() {
  for interface in $INTERFACES; do

    local dir="/sys/class/net/$interface"
    if [ -d "$dir" ]; then
      bytes[past_rx_$interface]="$(cat "$dir"/statistics/rx_bytes)"
      bytes[past_tx_$interface]="$(cat "$dir"/statistics/tx_bytes)"
    fi

  done
}

get_throughput() {
  while true; do
    down=0
    up=0

    for interface in $INTERFACES; do
      local dir="/sys/class/net/$interface"
      if [ -d "$dir" ]; then
        bytes[now_rx_$interface]="$(cat "$dir"/statistics/rx_bytes)"
        bytes[now_tx_$interface]="$(cat "$dir"/statistics/tx_bytes)"

        bytes_down=$((((${bytes[now_rx_$interface]} - ${bytes[past_rx_$interface]})) / INTERVAL))
        bytes_up=$((((${bytes[now_tx_$interface]} - ${bytes[past_tx_$interface]})) / INTERVAL))

        down=$(((("$down" + "$bytes_down"))))
        up=$(((("$up" + "$bytes_up"))))

        bytes[past_rx_$interface]=${bytes[now_rx_$interface]}
        bytes[past_tx_$interface]=${bytes[now_tx_$interface]}
      fi
    done

    if [ "$down" -gt 1000 ] || [ "$up" -gt 1000 ]; then
      echo " $(print_bytes $down) 祝$(print_bytes $up)"
    else
      echo ""
    fi

    # echo "Download: $(print_bytes $down) / Upload: $(print_bytes $up)"
    # echo "Download: $(print_bit $down) / Upload: $(print_bit $up)"

    sleep $INTERVAL
  done
}

get_initial_throughput
get_throughput