Don't allow empty feed URLs

lib/frenzy_web/controllers/feed_controller.ex

@@ -36,20 +36,38 @@ defmodule FrenzyWeb.FeedController do
   end
 
   def create(conn, %{"feed" => %{"group_id" => group_id, "feed_url" => feed_url}}) do
+    user = conn.assigns[:user]
     group = Repo.get(Group, group_id)
+    feed_url = feed_url |> String.trim()
 
-    changeset =
-      Ecto.build_assoc(group, :feeds, %{
-        feed_url: feed_url,
-        filter: %Filter{
-          mode: "reject",
-          score: 0
-        }
-      })
+    cond do
+      group != nil && group.user_id == user.id ->
+        if String.length(feed_url) > 0 do
+          changeset =
+            Ecto.build_assoc(group, :feeds, %{
+              feed_url: feed_url,
+              filter: %Filter{
+                mode: "reject",
+                score: 0
+              }
+            })
 
-    {:ok, feed} = Repo.insert(changeset)
+          {:ok, feed} = Repo.insert(changeset)
 
-    redirect(conn, to: Routes.group_path(Endpoint, :show, group_id))
+          conn
+          |> put_flash(:info, "Feed created")
+          |> redirect(to: Routes.group_path(Endpoint, :show, group_id))
+        else
+          conn
+          |> put_flash(:error, "Feed URL must not be empty")
+          |> redirect(to: Routes.group_path(Endpoint, :show, group_id))
+        end
+
+      true ->
+        conn
+        |> put_flash(:error, "Invalid group")
+        |> redirect(to: Routes.group_path(Endpoint, :index))
+    end
   end
 
   def edit(conn, _params) do