add ban filterer

lib/philomena_web/plugs/current_ban.ex

@@ -4,7 +4,7 @@ defmodule PhilomenaWeb.Plugs.CurrentBan do
 
   ## Example
 
-      plug PhilomenaWeb.Plugs.Ban
+      plug PhilomenaWeb.Plugs.CurrentBan
   """
   alias Philomena.Bans
   alias Plug.Conn

lib/philomena_web/plugs/filter_banned_users.ex

@@ -0,0 +1,33 @@
+defmodule PhilomenaWeb.Plugs.FilterBannedUsers do
+  @moduledoc """
+  This plug redirects back if there is a ban for the current user.
+  CurrentBan must also be plugged, and it must come after it.
+
+  ## Example
+
+      plug PhilomenaWeb.Plugs.FilterBannedUsers
+  """
+  alias Phoenix.Controller
+  alias Plug.Conn
+
+  @doc false
+  @spec init(any()) :: any()
+  def init(opts), do: opts
+
+  @doc false
+  @spec call(Conn.t(), any()) :: Conn.t()
+  def call(conn, _opts) do
+    redirect_url = conn.assigns.referrer
+
+    conn.assigns.current_ban
+    |> maybe_halt(conn, redirect_url)
+  end
+
+  def maybe_halt(nil, conn, _redirect_url), do: conn
+  def maybe_halt(_current_ban, conn, redirect_url) do
+    conn
+    |> Controller.put_flash(:error, "You are currently banned.")
+    |> Controller.redirect(to: redirect_url)
+    |> Conn.halt()
+  end
+end