Extract cover cache duration

lib/music_library_web/controllers/cover_controller.ex

@@ -4,6 +4,8 @@ defmodule MusicLibraryWeb.CoverController do
   alias MusicLibrary.Records
   alias MusicLibrary.Records.Cover
 
+  @cache_duration 60 * 60 * 24
+
   def show(conn, %{"record_id" => record_id, "size" => size}) do
     case Records.get_cover(record_id) do
       nil ->
@@ -12,7 +14,7 @@ defmodule MusicLibraryWeb.CoverController do
       %{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()
+        hash = Cover.hash(thumb_data)
 
         case get_req_header(conn, "if-none-match") do
           [^hash] -> extend_cache(conn)
@@ -43,7 +45,7 @@ defmodule MusicLibraryWeb.CoverController do
   # 24 hours
   defp extend_cache(conn) do
     conn
-    |> put_resp_header("cache-control", "public, max-age=86400")
+    |> put_resp_header("cache-control", "public, max-age=#{@cache_duration}")
     |> send_resp(304, "")
   end
 
@@ -51,7 +53,7 @@ defmodule MusicLibraryWeb.CoverController do
   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("cache-control", "public, max-age=#{@cache_duration}")
     |> put_resp_header("etag", etag)
     |> send_resp(200, cover_data)
   end