defmodule CCXT.WS.Subscription.MethodTopics do
  @moduledoc """
  Exmo-style subscribe frame.

      %{"method" => "subscribe", "topics" => ["spot/ticker:BTC_USDT"]}

  Config keys: `:op_field` (default `"method"`), `:args_field`
  (default `"topics"`).
  """

  @behaviour CCXT.WS.Subscription.Behaviour

  @impl true
  def subscribe(channels, config) when is_list(channels) do
    build(channels, config, "subscribe")
  end

  @impl true
  def unsubscribe(channels, config) when is_list(channels) do
    build(channels, config, "unsubscribe")
  end

  defp build(channels, config, action) do
    method = Map.get(config, :op_field, "method")
    topics = Map.get(config, :args_field, "topics")
    %{method => action, topics => channels}
  end
end