config_logger.ex

defmodule Coruscant.ConfigLogger do
  require Logger

  @secret_matcher ~r/key|secret|salt|encryption|password|connection_string|creds/
  defp secrets_masker(k, v) do
    s =
      if is_atom(k) do
        Atom.to_string(k)
      else
        k
      end

    if is_binary(v) &&
         is_binary(s) &&
         Regex.match?(@secret_matcher, s) do
      {k, ((v || "") |> String.first()) <> "*****"}
    else
      {k, v}
    end
  end

  defp deep_transform(data) do
    cond do
      is_tuple(data) && tuple_size(data) == 2 ->
        {k, v} = data

        if is_binary(v) do
          {k, secrets_masker(k, v)}
        else
          {k, deep_transform(v)}
        end

      is_struct(data) && data.__struct__ in [Regex, DateTime, NaiveDateTime, Time] ->
        data

      is_struct(data) ->
        type = data.__struct__

        data
        |> Map.drop([:__struct__])
        |> map_transform()
        |> Map.put(:__struct__, type)

      is_map(data) ->
        map_transform(data)

      is_map(data) || is_struct(data) ->
        Enum.reduce(data, %{}, fn {k, v}, acc ->
          if is_binary(v) do
            Map.put(acc, k, secrets_masker(k, v))
          else
            Map.put(acc, k, deep_transform(v))
          end
        end)

      is_list(data) ->
        Enum.map(data, fn value -> deep_transform(value) end)

      true ->
        data
    end
  end

  defp map_transform(map),
    do:
      Enum.reduce(map, %{}, fn {k, v}, acc ->
        if is_binary(v) do
          Map.put(acc, k, secrets_masker(k, v))
        else
          Map.put(acc, k, deep_transform(v))
        end
      end)

  def log_all_applicaion_config(my_app) do
    try do
      conf =
        ([{my_app, "Top level"}] ++ Application.started_applications())
        |> Enum.map(&elem(&1, 0))
        |> Enum.map(fn app -> {app, Application.get_all_env(app)} end)
        |> Enum.reject(fn {_app, conf} -> Enum.empty?(conf) end)
        |> Enum.map(fn {app, v} -> {app, deep_transform(v)} end)
        |> inspect(pretty: true)

      Logger.info("My configuration is #{conf}")
    rescue
      ex ->
        Logger.warn("Problem logging out config #{Exception.format(:error, ex, __STACKTRACE__)}")
    end
  end
end