From 12af10423819f0381d35e9d238fc32d9bf2b016e Mon Sep 17 00:00:00 2001
From: Marcin Kulik <m@ku1ik.com>
Date: Sat, 4 May 2024 20:53:04 +0200
Subject: [PATCH] Enable SVG preview caching

---
 lib/asciinema_web.ex                            |  1 +
 lib/asciinema_web/caching.ex                    | 17 +++++++++++++++++
 .../controllers/recording/thumbnail.html.heex   |  2 +-
 .../controllers/recording_controller.ex         | 11 +++++++++--
 lib/asciinema_web/controllers/recording_html.ex |  3 +++
 5 files changed, 31 insertions(+), 3 deletions(-)
 create mode 100644 lib/asciinema_web/caching.ex

diff --git a/lib/asciinema_web.ex b/lib/asciinema_web.ex
index eaa801ec7..d07181c08 100644
--- a/lib/asciinema_web.ex
+++ b/lib/asciinema_web.ex
@@ -52,6 +52,7 @@ defmodule AsciinemaWeb do
       import AsciinemaWeb.Auth, only: [require_current_user: 2]
       import AsciinemaWeb.Plug.ReturnTo
       import AsciinemaWeb.Plug.Authz
+      import AsciinemaWeb.Caching
 
       unquote(verified_routes())
 
diff --git a/lib/asciinema_web/caching.ex b/lib/asciinema_web/caching.ex
new file mode 100644
index 000000000..978b188d3
--- /dev/null
+++ b/lib/asciinema_web/caching.ex
@@ -0,0 +1,17 @@
+defmodule AsciinemaWeb.Caching do
+  import Plug.Conn
+
+  def put_etag(conn, content) do
+    etag = Crypto.md5(to_string(content))
+
+    conn
+    |> put_resp_header("etag", etag)
+    |> register_before_send(fn conn ->
+      if etag in get_req_header(conn, "if-none-match") do
+        send_resp(conn, 304, "")
+      else
+        conn
+      end
+    end)
+  end
+end
diff --git a/lib/asciinema_web/controllers/recording/thumbnail.html.heex b/lib/asciinema_web/controllers/recording/thumbnail.html.heex
index 5ae18794c..42a29b02b 100644
--- a/lib/asciinema_web/controllers/recording/thumbnail.html.heex
+++ b/lib/asciinema_web/controllers/recording/thumbnail.html.heex
@@ -2,5 +2,5 @@
   class="thumbnail"
   style={"background-color: #{theme(@asciicast).bg}; border-right: 1ch solid #{theme(@asciicast).bg}"}
 >
-  <img src={~p"/a/#{@asciicast}" <> ".svg?v=t"} />
+  <img src={~p"/a/#{@asciicast}" <> ".svg?f=t&v=#{svg_cache_key(@asciicast)}"} />
 </div>
diff --git a/lib/asciinema_web/controllers/recording_controller.ex b/lib/asciinema_web/controllers/recording_controller.ex
index 0de4e1339..3ca7f0b0b 100644
--- a/lib/asciinema_web/controllers/recording_controller.ex
+++ b/lib/asciinema_web/controllers/recording_controller.ex
@@ -3,6 +3,7 @@ defmodule AsciinemaWeb.RecordingController do
   alias Asciinema.{Recordings, PngGenerator}
   alias Asciinema.Recordings.Asciicast
   alias AsciinemaWeb.PlayerOpts
+  alias AsciinemaWeb.RecordingHTML
 
   plug :clear_main_class
   plug :load_asciicast when action in [:show, :edit, :update, :delete, :iframe]
@@ -102,6 +103,9 @@ defmodule AsciinemaWeb.RecordingController do
     end
   end
 
+  # 1 hour
+  @svg_max_age 3600
+
   def do_show(conn, "svg", asciicast) do
     if asciicast.archived_at do
       path = Application.app_dir(:asciinema, "priv/static/images/archived.png")
@@ -112,12 +116,15 @@ defmodule AsciinemaWeb.RecordingController do
       |> send_file(200, path)
     else
       variant =
-        case conn.params["v"] do
+        case conn.params["f"] do
           "t" -> :thumbnail
           _ -> :show
         end
 
-      render(conn, variant, asciicast: asciicast)
+      conn
+      |> put_resp_header("cache-control", "public, max-age=#{@svg_max_age}, must-revalidate")
+      |> put_etag(RecordingHTML.svg_cache_key(asciicast))
+      |> render(variant, asciicast: asciicast)
     end
   end
 
diff --git a/lib/asciinema_web/controllers/recording_html.ex b/lib/asciinema_web/controllers/recording_html.ex
index ec9f8b724..a81d67cc5 100644
--- a/lib/asciinema_web/controllers/recording_html.ex
+++ b/lib/asciinema_web/controllers/recording_html.ex
@@ -221,6 +221,9 @@ defmodule AsciinemaWeb.RecordingHTML do
     asciicast.views_count
   end
 
+  def svg_cache_key(asciicast),
+    do: Timex.to_unix(asciicast.updated_at) - Timex.to_unix(asciicast.inserted_at)
+
   def head("show.html", assigns), do: head_for_show(assigns)
   def head(_, _), do: nil
 end