[FEATURE] Support custom handler

[spieker]

This enables the user to switch from the default Pipette.Handler to a custom Handler. A custom handler could do some pre- or post-processing to the IP or the given handler definition.

Example:

defmodule MapProtocolHandler do
  alias Pipette.IP

  # Run the handler and assigning the result to the key specified in the
  # arguments
  def handle(handler, %IP{value: %{} = map} = ip) do
    %IP{route: route, value: new_value} = new_ip = Pipette.Handler.handle(handler, ip)
    result_value = compose_result(map, new_value)
    IP.update(new_ip, {route, result_value})
  end

  defp compose_result(%{} = map, new_value, handler) do
    args = get_args(handler)
    case args[:RESULT_KEY] do
      key -> Map.put(map, key, new_value)
      _ -> new_value
    end
  end
end

config :pipette, handler: MapProtocolHandler

[spieker]

@Overbryd Any thoughts on this solution?

[Overbryd]

Yep, I think we need one document in guides/configuration.md that explains the available configuration options.

In general, I think this solution will aid certain implementations. However, I think it might be nice to be able to override this per recipe rather than for a whole application.

On 20. Jul 2018, at 15:38, Hildebrando Rueda notifications@github.com wrote:

@theharq approved this pull request.

LGTM, maybe adding a reference in the README that this configuration is possible will be nice.

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[spieker]

I think we can add a handler configuration on recipe level as another feature.