Support RSS feeds for specific topics (essentially combining current /feed and /topic functionality)

lib/changelog_web/controllers/feed_controller.ex

@@ -190,5 +190,80 @@ defmodule ChangelogWeb.FeedController do
     |> render("sitemap.xml")
   end
 
+  @doc "A topic's news and podcasts feed"
+  def topic(conn, %{"slug" => slug}) do
+    topic = Repo.get_by!(Topic, slug: slug)
+
+    items =
+      topic
+      |> filter_items_by_topic(:all)
+      |> fetch_items_by_topic()
+
+    render_topic(conn, slug, items)
+  end
+
+  @doc "A topic's news feed"
+  def topic_news(conn, %{"slug" => slug}) do
+    topic = Repo.get_by!(Topic, slug: slug)
+
+    news_items =
+      topic
+      |> filter_items_by_topic(:news)
+      |> fetch_items_by_topic()
+
+    render_topic(conn, topic, news_items)
+  end
+
+  @doc "A topic's podcasts feed"
+  def topic_podcasts(conn, %{"slug" => slug}) do
+    topic = Repo.get_by!(Topic, slug: slug)
+
+    podcasts =
+      topic
+      |> filter_items_by_topic(:podcasts)
+      |> fetch_items_by_topic()
+
+    render_topic(conn, topic, podcasts)
+  end
+
+  defp filter_items_by_topic(topic, :all) do
+    NewsItem
+    |> NewsItem.with_topic(topic)
+  end
+
+  defp filter_items_by_topic(topic, :news) do
+    NewsItem
+    |> NewsItem.with_topic(topic)
+    |> NewsItem.non_audio()
+  end
+
+  defp filter_items_by_topic(topic, :podcasts) do
+    NewsItem
+    |> NewsItem.with_topic(topic)
+    |> NewsItem.audio()
+  end
+
+  defp fetch_items_by_topic(query) do
+    query
+    |> NewsItem.published()
+    |> NewsItem.newest_first()
+    |> NewsItem.preload_all()
+    |> Repo.all()
+  end
+
+  defp render_topic(conn, topic, items) do
+    IO.inspect(topic, label: "TOPIC")
+    IO.inspect(items, label: "ITEMS")
+
+    conn
+    |> put_layout(false)
+    |> put_resp_content_type("application/xml")
+    |> assign(:topic_name, topic.name)
+    |> assign(:topic_description, topic.description)
+    |> assign(:items, items)
+    |> ResponseCache.cache_public(cache_duration())
+    |> render("topic.xml")
+  end
+
   defp cache_duration, do: 2..10 |> Enum.random() |> :timer.minutes()
 end

lib/changelog_web/router.ex

@@ -103,7 +103,10 @@ defmodule ChangelogWeb.Router do
       post "/episodes/:id/transcript", EpisodeController, :transcript, as: :episode
 
       resources "/episode_requests", EpisodeRequestController
-      put "/episode_requests/:id/decline", EpisodeRequestController, :decline, as: :episode_request
+
+      put "/episode_requests/:id/decline", EpisodeRequestController, :decline,
+        as: :episode_request
+
       put "/episode_requests/:id/fail", EpisodeRequestController, :fail, as: :episode_request
       put "/episode_requests/:id/pend", EpisodeRequestController, :pend, as: :episode_request
 
@@ -141,11 +144,18 @@ defmodule ChangelogWeb.Router do
   scope "/", ChangelogWeb do
     pipe_through [:feed]
 
+    get "/sitemap.xml", FeedController, :sitemap
+
     get "/feed", FeedController, :news
     get "/feed/titles", FeedController, :news_titles
+
+    get "/topic/:slug/feed", FeedController, :topic_show
+    get "/topic/:slug/news/feed", FeedController, :topic_news
+    get "/topic/:slug/podcasts/feed", FeedController, :topic_podcasts
+
     get "/posts/feed", FeedController, :posts
-    get "/sitemap.xml", FeedController, :sitemap
     get "/:slug/feed", FeedController, :podcast
+
     get "/plusplus/:slug/feed", FeedController, :plusplus
     get "/metacast/:slug/feed", FeedController, :metacast
   end

lib/changelog_web/templates/feed/topic.xml.eex

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd">
+  <channel>
+    <title>Changelog: <%= @topic_name %></title>
+    <copyright>All rights reserved</copyright>
+    <link><%= Routes.root_url(@conn, :index) %></link>
+    <atom:link href="<%= Routes.feed_url(@conn, :news) %>" rel="self" type="application/rss+xml" />
+    <atom:link href="<%= Routes.root_url(@conn, :index) %>" rel="alternate" type="text/html" />
+    <language>en-us</language>
+    <description><%= @topic_description %></description>
+  <%= for item <- @items do %>
+    <item>
+      <%= render_item(item, assigns) %>
+    </item>
+  <% end %>
+  </channel>
+</rss>

test/changelog_web/controllers/feed_controller_test.exs

@@ -140,4 +140,93 @@ defmodule ChangelogWeb.FeedControllerTest do
     refute conn.resp_body =~ p2.title
     assert conn.resp_body =~ p3.title
   end
+
+  describe "Topic feed" do
+    setup [:setup_topic_feed_tests]
+
+    test "the topic feed", %{
+      conn: conn,
+      topics: topics,
+      news_items_with_topics: news_items_with_topics,
+      posts_with_topics: posts_with_topics,
+      podcast_episodes_with_topics: podcast_episodes_with_topics
+    } do
+      topic_slug = "rust"
+      conn = get(conn, Routes.feed_path(conn, :topic, topic_slug))
+
+      assert conn.status == 200
+      assert valid_xml(conn)
+    end
+
+    test "the topic's news feed", %{
+      conn: conn,
+      topics: topics,
+      news_items_with_topics: news_items_with_topics,
+      posts_with_topics: posts_with_topics,
+      podcast_episodes_with_topics: podcast_episodes_with_topics
+    } do
+      topic_slug = "rust"
+      conn = get(conn, Routes.feed_path(conn, :topic_news, topic_slug))
+
+      assert conn.status == 200
+      assert valid_xml(conn)
+    end
+
+    test "the topic's podcasts feed", %{
+      conn: conn,
+      topics: topics,
+      news_items_with_topics: news_items_with_topics,
+      posts_with_topics: posts_with_topics,
+      podcast_episodes_with_topics: podcast_episodes_with_topics
+    } do
+      topic_slug = "rust"
+      conn = get(conn, Routes.feed_path(conn, :topic_podcasts, topic_slug))
+
+      assert conn.status == 200
+      assert valid_xml(conn)
+
+      topic = topics[topic_slug]
+      assert conn.resp_body =~ topic.name
+      assert conn.resp_body =~ topic.description
+
+      Enum.each(posts_with_topics, fn post_with_topic ->
+        assert conn.resp_body =~ post_with_topic.post.title
+        assert conn.resp_body =~ post_with_topic.post.body
+      end)
+
+      Enum.each(podcast_episodes_with_topics, fn podcast_episode_with_topic ->
+        assert conn.resp_body =~ podcast_episode_with_topic.episode.title
+        assert conn.resp_body =~ podcast_episode_with_topic.episode.summary
+      end)
+    end
+  end
+
+  defp setup_topic_feed_tests(context) do
+    # Add some topics
+    t1 = insert(:topic, slug: "rust", name: "Rust", description: "Rust is a systems programming language created by Mozilla.")
+    # Create some news items
+    ni1 = insert(:published_news_item, headline: "Rust is pretty cool", story: "Use it or lose it")
+    # Associate those news items with topics
+    nit1 = insert(:news_item_topic, topic: t1, news_item: ni1)
+
+    # Add a post
+    post1 = insert(:published_post, body: "Can you believe this Rust thing?!")
+    pt1 = insert(:post_topic, post: post1, topic: t1)
+
+    # Add a podcast
+    pod1 = insert(:podcast, name: "Rust Crust", slug: "rustcrust", description: "Rust is neat")
+    # Add a podcast episode
+    e1 = insert(:published_episode, podcast: pod1)
+    # Associate that episode with a topic
+    et1 = insert(:episode_topic, episode: e1, topic: t1)
+
+    %{
+      topics: %{
+        "rust" => t1
+      },
+      news_items_with_topics: [nit1],
+      posts_with_topics: [pt1],
+      podcast_episodes_with_topics: [et1]
+    }
+  end
 end