Support arbitrary resizing in cover controller

lib/music_library/records/cover.ex

@@ -1,8 +1,8 @@
 defmodule MusicLibrary.Records.Cover do
   @size 600
 
-  def resize(cover_data) do
-    {:ok, thumb} = Vix.Vips.Operation.thumbnail_buffer(cover_data, @size)
+  def resize(cover_data, size \\ @size) do
+    {:ok, thumb} = Vix.Vips.Operation.thumbnail_buffer(cover_data, size)
     Vix.Vips.Image.write_to_buffer(thumb, ".jpg")
   end
 

lib/music_library_web/controllers/cover_controller.ex

@@ -2,6 +2,36 @@ defmodule MusicLibraryWeb.CoverController do
   use MusicLibraryWeb, :controller
 
   alias MusicLibrary.Records
+  alias MusicLibrary.Records.Cover
+
+  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")
+
+      %{cover_data: cover_data} ->
+        {: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)
+        end
+    end
+  end
 
   def show(conn, %{"record_id" => record_id}) do
     case Records.get_cover(record_id) do

test/music_library_web/controllers/cover_controller_test.exs

@@ -2,6 +2,7 @@ defmodule MusicLibraryWeb.CoverControllerTest do
   use MusicLibraryWeb.ConnCase
 
   import MusicLibrary.RecordsFixtures
+  alias MusicLibrary.Records.Cover
 
   defp create_record(_) do
     %{record: record_fixture()}
@@ -55,5 +56,19 @@ defmodule MusicLibraryWeb.CoverControllerTest do
 
       assert conn.resp_body == <<>>
     end
+
+    test "accepts a size attribute for resizing", %{conn: conn, record: record} do
+      conn = get(conn, ~p"/covers/#{record.id}?size=480")
+
+      thumb = File.read!(marbles_thumb_fixture())
+      hash = Cover.hash(thumb)
+
+      assert conn.status == 200
+      assert get_resp_header(conn, "content-type") == ["image/jpeg; charset=utf-8"]
+      assert get_resp_header(conn, "cache-control") == ["public, max-age=86400"]
+      assert get_resp_header(conn, "etag") == [hash]
+
+      assert conn.resp_body == thumb
+    end
   end
 end

test/support/fixtures/records_fixtures.ex

@@ -43,9 +43,11 @@ defmodule MusicLibrary.RecordsFixtures do
   ]
   # While it would be great to have this random, it's ok to use one single image
   @marbles_cover_data_path "#{__DIR__}/marillion-marbles.jpg"
+  @marbles_thumb_data_path "#{__DIR__}/marillion-marbles-thumb.jpg"
   @raven_cover_data_path "#{__DIR__}/steven-wilson-raven.jpg"
 
   def marbles_cover_fixture, do: @marbles_cover_data_path
+  def marbles_thumb_fixture, do: @marbles_thumb_data_path
   def raven_cover_fixture, do: @raven_cover_data_path
 
   def record_fixture(attrs \\ %{}) do