defmodule Vuforex do
  @moduledoc """
  HTTP Client for Vuforia Web Services.
  """

  alias Calendar.DateTime.Format

  @api_url Application.compile_env(:vuforex, :base_url)
  @server_access_key Application.compile_env(:vuforex, :server_access_key)

  @spec summary() :: {:ok, map()} | {:error, map()}
  @doc """
  Get a summary of images from a cloud database.

  ## Examples
      iex> Vuforex.summary()
      {:ok,
        %{
          "result_code" => "Success",
          "active_images" => 0,
          "current_month_recos" => 0,
          "failed_images" => 0,
          "inactive_images" => 0,
          "name" => "Vuforex",
          "previous_month_recos" => 0,
          "processing_images" => 0,
          "reco_threshold" => 1000,
          "request_quota" => 100000,
          "request_usage" => 0,
          "target_quota" => 1000,
          "total_recos" => 0,
          "transaction_id" => "659755bdbaf2406dad42f267ef877a7a"
        }
      }
  """
  def summary do
    time = Format.httpdate(DateTime.utc_now())
    signature = Vuforex.Signature.generate("/summary", nil, "GET", time)

    case Tesla.get(tesla_client(signature, time), "#{@api_url}/summary") do
      {:ok, %Tesla.Env{status: status, body: summary}} when status in [200, 201] ->
        {:ok, Jason.decode!(summary)}

      {:ok, %Tesla.Env{status: status, body: body}} when status not in [200, 201] ->
        {:error, Jason.decode!(body)}
    end
  end

  def get_tesla_client(signature, time),
    do: tesla_client(signature, time)

  defp tesla_client(signature, time) do
    middleware = [
      {Tesla.Middleware.BaseUrl, @api_url},
      {Tesla.Middleware.Headers,
       [
         {"Date", time},
         {"Authorization", "VWS #{@server_access_key}:#{signature}"}
       ]}
    ]

    Tesla.client(middleware)
  end
end