Realtime market-data updates - full channel - calculating the rate

client.ex

defmodule Coinbase.Client do
  use WebSockex

  @url "wss://ws-feed.pro.coinbase.com"

  def start_link(products \\ []) do
    {:ok, pid} = WebSockex.start_link(@url, __MODULE__, %{})
    subscribe(pid, products)
    {:ok, pid}
  end

  def handle_connect(_conn, state) do
    IO.puts("connected!")
    {:ok, state}
  end

  def handle_disconnect(_conn, state) do
    IO.puts("disconnected")
    {:ok, state}
  end

  def handle_frame({:text, msg}, state) do
    handle_msg(Poison.decode!(msg), state)
  end

  def handle_msg(%{"time" => time}=event, seconds_counts) when is_binary(time) do
    {:ok, time, _} = DateTime.from_iso8601(event["time"])
    key = {time.year, time.month, time.day, time.hour, time.minute, time.second}
    seconds_counts = Map.update(seconds_counts, key, 0, fn v -> v + 1 end)
    {:ok, seconds_counts}
  end

  def handle_msg(_,state), do: {:ok,state}


  def subscribe(pid, products) do
    frame = subscription_frame(products)
    WebSockex.send_frame(pid, frame)
  end

  defp subscription_frame(products) do
    subscription_json =
      %{
        type: "subscribe",
        product_ids: products,
        channels: ["full"]
      }
      |> Poison.encode!()

    {:text, subscription_json}
  end
end