defmodule Plug.PageCache do
  @moduledoc """
  PageCache Plug
  """

  import Plug.Conn

  alias Plug.PageCache.Config

  @behaviour Plug


  def init(opts), do: opts |> Enum.into(%{})

  def call(conn, opts) do
    cache = Config.cache_id(opts[:cache])

    case GenServer.call(cache, { :load, conn.request_path }) do
      nil  -> conn |> register_before_send( &save(&1, cache) )
      page -> conn |> send_resp(200, page) |> halt()
    end
  end


  @doc """
  Saves a page to the cache.
  """
  @spec save(Plug.Conn.t, atom) :: Plug.Conn.t
  def save(conn, cache) do
    _ = GenServer.call(cache, { :save, conn.request_path, conn.resp_body })

    conn
  end
end