defmodule UltraPlug.Render do
  @moduledoc """
  Renders the template.

  With status :no_content, send an empty response.

  ## Options

  - **assigns:** overrides conn.assigns in Phoenix.
  - **render:** defaults to [Phoenix.Controller.render/3](https://hexdocs.pm/phoenix/Phoenix.Controller.html#render/3).
  - **status:** calls [Plug.Conn.put_status/2](https://hexdocs.pm/plug/Plug.Conn.html#put_status/2) before rendering.
  - **template:** defaults to "index.html".
  """

  import Plug.Conn

  def init(opts) do
    %{
      assigns: Keyword.get(opts, :assigns, %{}),
      render: Keyword.get(opts, :render, &Phoenix.Controller.render/3),
      status: Keyword.get(opts, :status, :skip),
      template: Keyword.get(opts, :template, "index.html"),
    }
  end

  def call(conn, opts \\ [])

  def call(conn = %{assigns: %{error: error}}, _) do
    {:error, error, conn}
  end

  def call(conn, %{status: :no_content}) do
    send_resp(conn, :no_content, "")
  end

  def call(conn, opts = %{status: status}) when status != :skip do
    conn
    |> put_status(status)
    |> call(%{opts | status: :skip})
  end

  def call(conn, %{assigns: assigns, render: render, template: template}) do
    render.(conn, template, assigns)
  end

  def call(conn, opts) when is_list(opts) do
    call(conn, init(opts))
  end
end