spannex

defmodule Spannex.Interceptors.Auth do
  @moduledoc """
  A gRPC interceptor that adds authentication headers to outgoing requests. Requires `Goth` to fetch the latest auth token.
  """

  @behaviour GRPC.Client.Interceptor

  @doc """
  Requires a `:goth` option that is the name of the `Goth` instance to fetch tokens from.
  """
  @impl GRPC.Client.Interceptor
  def init(opts), do: Keyword.fetch!(opts, :goth)

  @impl GRPC.Client.Interceptor
  def call(stream, req, next, goth) do
    %{type: type, token: token} = Goth.fetch!(goth)
    stream = GRPC.Client.Stream.put_headers(stream, %{"authorization" => "#{type} #{token}"})
    next.(stream, req)
  end
end