bow

defmodule Bow.Download do
  use Tesla, only: [:get]

  plug(Tesla.Middleware.FollowRedirects)

  @doc """
  Download file from given URL
  """
  @spec download(client :: Tesla.Client.t(), url :: String.t()) ::
          {:ok, Bow.t()} | {:error, any}
  def download(client \\ %Tesla.Client{}, url) do
    case get!(client, encode(url)) do
      %{status: 200, url: url, body: body} = env ->
        base =
          url
          |> URI.parse()
          |> case do
            %{path: path} when not is_nil(path) -> path |> Path.basename()
            _ -> ""
          end

        name =
          case Tesla.get_header(env, "content-type") do
            nil ->
              base

            content_type ->
              case MIME.extensions(content_type) do
                [ext | _] -> rootname(base) <> "." <> ext
                _ -> base
              end
          end

        path = Plug.Upload.random_file!("bow-download")

        case File.write(path, body) do
          :ok ->
            {:ok, Bow.new(name: name, path: path)}

          {:error, reason} ->
            {:error, reason}
        end

      env ->
        {:error, env}
    end
  rescue
    ex in Tesla.Error ->
      {:error, ex}
  end

  # If path name is malformed, for example looks like this: ".some-data",
  # we won't be able to extract it and we will treat the name
  # as file extension instead.
  #
  # To handle all kind of problems we simply fallback to auto-generated
  # name if we cannot read it properly.
  defp rootname(base) do
    case Path.rootname(base) do
      "" ->
        Ecto.UUID.generate()

      name ->
        name
    end
  end

  defp encode(url), do: url |> URI.encode() |> String.replace(~r/%25([0-9a-f]{2})/i, "%\\g{1}")
  # based on: https://stackoverflow.com/questions/31825687/how-to-avoid-double-encoding-uri
end