Cache transformations

lib/music_library_web/controllers/cover_controller.ex

@@ -2,36 +2,58 @@ defmodule MusicLibraryWeb.CoverController do
   use MusicLibraryWeb, :controller
 
   alias MusicLibrary.Assets
-  alias MusicLibrary.Assets.Transform
+  alias MusicLibrary.Assets.{Cache, Transform}
   alias MusicLibrary.Records.Cover
 
   # 1 year in seconds
   @cache_duration 60 * 60 * 24 * 365
 
   def show(conn, %{"transform_payload" => payload}) do
+    format = pick_format(conn)
     transform = Transform.decode!(payload)
 
-    case Assets.get(transform.hash) do
+    case cached_get(payload, transform, format) do
       nil ->
         not_found(conn)
 
-      %{content: content} ->
-        image_data =
-          if transform.width do
-            # TODO: find a way to cache computation, or pre-compute thumb and store it
-            {:ok, thumb_data} = Cover.resize(content, transform.width)
-            thumb_data
-          else
-            content
-          end
-
+      content when is_binary(content) ->
         case get_req_header(conn, "if-none-match") do
           [^payload] -> extend_cache(conn)
-          _ -> respond_with_cache(conn, image_data, payload)
+          _ -> respond_with_cache(conn, content, format, payload)
         end
     end
   end
 
+  defp cached_get(payload, transform, format) do
+    case Cache.get(payload, format) do
+      :not_found ->
+        if asset = Assets.get(transform.hash) do
+          image_data =
+            if transform.width do
+              # TODO: find a way to cache computation, or pre-compute thumb and store it
+              {:ok, data} = Cover.resize(asset.content, transform.width, format)
+              data
+            else
+              {:ok, data} = Cover.convert(asset.content, asset.format, format)
+              data
+            end
+
+          Cache.set(payload, format, image_data)
+          image_data
+        end
+
+      {:found, content} ->
+        content
+    end
+  end
+
+  defp pick_format(conn) do
+    case get_req_header(conn, "accept") do
+      ["image/webp" <> _] -> "image/webp"
+      _ -> "image/jpeg"
+    end
+  end
+
   defp not_found(conn) do
     conn
     |> put_status(:not_found)
@@ -44,9 +66,9 @@ defmodule MusicLibraryWeb.CoverController do
     |> send_resp(304, "")
   end
 
-  defp respond_with_cache(conn, data, etag) do
+  defp respond_with_cache(conn, data, format, etag) do
     conn
-    |> put_resp_content_type("image/jpeg", "utf-8")
+    |> put_resp_content_type(format, "utf-8")
     |> put_resp_header("cache-control", "public, max-age=#{@cache_duration}")
     |> put_resp_header("etag", etag)
     |> send_resp(200, data)