Refactor cover controller to reuse common pieces

lib/music_library_web/controllers/cover_controller.ex

@@ -7,28 +7,16 @@ defmodule MusicLibraryWeb.CoverController do
   def show(conn, %{"record_id" => record_id, "size" => size}) do
     case Records.get_cover(record_id) do
       nil ->
-        conn
-        |> put_status(:not_found)
-        |> text("Not found")
+        not_found(conn)
 
       %{cover_data: cover_data} ->
+        # TODO: find a way to cache computation, or pre-compute thumb and store it
         {:ok, thumb_data} = Cover.resize(cover_data, String.to_integer(size))
         hash = :crypto.hash(:sha256, thumb_data) |> Base.encode16()
 
         case get_req_header(conn, "if-none-match") do
-          [^hash] ->
-            conn
-            # 24 hours
-            |> put_resp_header("cache-control", "public, max-age=86400")
-            |> send_resp(304, "")
-
-          _ ->
-            conn
-            |> put_resp_content_type("image/jpeg", "utf-8")
-            # 24 hours
-            |> put_resp_header("cache-control", "public, max-age=86400")
-            |> put_resp_header("etag", hash)
-            |> send_resp(200, thumb_data)
+          [^hash] -> extend_cache(conn)
+          _ -> respond_with_cache(conn, thumb_data, hash)
         end
     end
   end
@@ -36,26 +24,35 @@ defmodule MusicLibraryWeb.CoverController do
   def show(conn, %{"record_id" => record_id}) do
     case Records.get_cover(record_id) do
       nil ->
-        conn
-        |> put_status(:not_found)
-        |> text("Not found")
+        not_found(conn)
 
       %{cover_data: cover_data, cover_hash: etag} ->
         case get_req_header(conn, "if-none-match") do
-          [^etag] ->
-            conn
-            # 24 hours
-            |> put_resp_header("cache-control", "public, max-age=86400")
-            |> send_resp(304, "")
-
-          _ ->
-            conn
-            |> put_resp_content_type("image/jpeg", "utf-8")
-            # 24 hours
-            |> put_resp_header("cache-control", "public, max-age=86400")
-            |> put_resp_header("etag", etag)
-            |> send_resp(200, cover_data)
+          [^etag] -> extend_cache(conn)
+          _ -> respond_with_cache(conn, cover_data, etag)
         end
     end
   end
+
+  defp not_found(conn) do
+    conn
+    |> put_status(:not_found)
+    |> text("Not found")
+  end
+
+  # 24 hours
+  defp extend_cache(conn) do
+    conn
+    |> put_resp_header("cache-control", "public, max-age=86400")
+    |> send_resp(304, "")
+  end
+
+  # 24 hours
+  defp respond_with_cache(conn, cover_data, etag) do
+    conn
+    |> put_resp_content_type("image/jpeg", "utf-8")
+    |> put_resp_header("cache-control", "public, max-age=86400")
+    |> put_resp_header("etag", etag)
+    |> send_resp(200, cover_data)
+  end
 end