Handling requests in a controller

At this point, the request is in the controller, which was called by the router according to the logic we described. We'll build the FileController that we saw in the router, and go through the four actions we've created routes for: index, show, new. and create. Let's begin with the index action:

$ cat apps/elixir_drip_web/lib/elixir_drip_web/controllers/
file_controller.ex

defmodule ElixirDripWeb.FileController do
  use ElixirDripWeb, :controller

  alias ElixirDrip.Storage

  def index(conn, %{"path" => path}) do
    with {:ok, media} <- Storage.media_by_folder("hardcoded_user_id", 
    path) do
      render(conn, "index.html", files: media.files, folders: 
      media.folders, current_path: path)
    else
      {:error, :invalid_path} ->
        conn
        |> put_flash(:error, "The path provided is invalid.")
        |> redirect(to: file_path(conn, :index, "path": "$"))
      _ ->
        conn
        |> put_flash(:error, "Unexpected...