High-level caching for closet lists

Okay, so I still don't know why rendering is just so slow (though
migrating away from item translations did help!), but I can at least
cache entire closet lists as a basic measure.

That way, the first user to see the latest version of a closet list
will still need just as much time to load it… but *only* the ones that
have changed since last time (rather than always the full page), and
then subsequent users get to reuse it too!

Should help a lot for high-traffic lists, which incidentally are likely
to be the big ones belonging to highly active traders!

One big change we needed to make was to extract the `user-owns` and
`user-wants` classes (which we use for trade matches for *the user
viewing the list right now*) out of the cached HTML, and apply them
after with Javascript instead. I always dislike moving stuff to JS, but
the wins here seem. truly very very good, all things considered!

app/assets/javascripts/closet_hangers/index.js

@@ -7,7 +7,11 @@
 
   function hangersInit() {
     for (var i = 0; i < hangersInitCallbacks.length; i++) {
+      try {
         hangersInitCallbacks[i]();
+      } catch (error) {
+        console.error(error);
+      }
     }
   }
 
@@ -58,6 +62,36 @@
     hangersEl.toggleClass("comparing");
   });
 
+  // Read the item IDs of trade matches from the meta tags.
+  const ownedIds =
+    document
+      .querySelector("meta[name=trade-matches-owns]")
+      ?.getAttribute("value")
+      ?.split(",") ?? [];
+  const wantedIds =
+    document
+      .querySelector("meta[name=trade-matches-wants]")
+      ?.getAttribute("value")
+      ?.split(",") ?? [];
+
+  // Apply the `user-owns` and `user-wants` classes to the relevant entries.
+  // This both provides immediate visual feedback, and sets up "Compare with
+  // Your Items" to toggle to just them!
+  //
+  // NOTE: The motivation here is caching: this allows us to share a cache of
+  // the closet list contents across all users, without `user-owns` or
+  // `user-wants` classes for one specific user getting cached and reused.
+  const hangerEls = document.querySelectorAll("#closet-hangers .object");
+  for (const hangerEl of hangerEls) {
+    const itemId = hangerEl.getAttribute("data-item-id");
+    if (ownedIds.includes(itemId)) {
+      hangerEl.classList.add("user-owns");
+    }
+    if (wantedIds.includes(itemId)) {
+      hangerEl.classList.add("user-wants");
+    }
+  }
+
   /*
 
     Hanger forms

app/controllers/closet_hangers_controller.rb

@@ -45,24 +45,24 @@ class ClosetHangersController < ApplicationController
     visible_groups = @user.closet_hangers_groups_visible_to(@perspective_user)
     @unlisted_closet_hangers_by_owned = find_unlisted_closet_hangers_by_owned(visible_groups)
 
-    items = []
+    @items = []
 
     @closet_lists_by_owned.each do |owned, lists|
       lists.each do |list|
         list.hangers.each do |hanger|
-          items << hanger.item
+          @items << hanger.item
         end
       end
     end
 
     @unlisted_closet_hangers_by_owned.each do |owned, hangers|
       hangers.each do |hanger|
-        items << hanger.item
+        @items << hanger.item
       end
     end
 
     if @public_perspective && user_signed_in?
-      current_user.assign_closeted_to_items!(items)
+      current_user.assign_closeted_to_items!(@items)
     end
 
     @campaign = Fundraising::Campaign.current

app/helpers/closet_hangers_helper.rb

@@ -1,17 +1,11 @@
 require 'cgi'
+require 'digest'
 
 module ClosetHangersHelper
   def closet_hangers_help_class(user)
     'hidden' unless user.closet_hangers.empty?
   end
 
-  def closet_hanger_partial_class(hanger)
-    'object'.tap do |class_name|
-      class_name << ' user-owns' if hanger.item.owned?
-      class_name << ' user-wants' if hanger.item.wanted?
-    end
-  end
-
   def send_neomail_url(neopets_username)
     "https://www.neopets.com/neomessages.phtml?type=send&recipient=#{CGI.escape neopets_username}"
   end
@@ -124,8 +118,8 @@ module ClosetHangersHelper
 
   def render_closet_lists(lists)
     if lists
-      render :partial => 'closet_lists/closet_list', :collection => lists,
-        :locals => {:show_controls => !public_perspective?}
+      render partial: 'closet_lists/closet_list', collection: lists,
+        locals: {show_controls: !public_perspective?}
     end
   end
 
@@ -140,6 +134,20 @@ module ClosetHangersHelper
     hangers ? hangers.size : 0
   end
 
+  def unlisted_hangers_cache_key(owned)
+    # It'd be nice if this was a closet list like any other, instead of being a
+    # weird separate thing! Then we could use the same closet list cache key,
+    # in which adding/removing stuff in the list touches the simple updated_at.
+    # Instead, we encode the hashed list of hanger IDs and last updated_at into
+    # the key! (The digest is to prevent the cache key from getting obscenely
+    # large for long lists!)
+    hangers = @unlisted_closet_hangers_by_owned[owned] || []
+    ids = hangers.map(&:id).join(",")
+    last_updated_at = hangers.map(&:updated_at).max
+
+    ["owned=#{owned}", Digest::MD5.hexdigest(ids), last_updated_at.to_i]
+  end
+  
   def closet_lists_group_name(subject, owned)
     ownership_key = owned ? 'owned_by' : 'wanted_by'
     if subject == :you

app/models/closet_hanger.rb

@@ -1,6 +1,6 @@
 class ClosetHanger < ApplicationRecord
   belongs_to :item
-  belongs_to :list, class_name: 'ClosetList', optional: true
+  belongs_to :list, class_name: 'ClosetList', optional: true, touch: true
   belongs_to :user
 
   delegate :name, to: :item, prefix: true

app/views/closet_hangers/_closet_hanger.html.haml

@@ -1,4 +1,5 @@
-%div{'class' => closet_hanger_partial_class(closet_hanger), 'data-item-id' => closet_hanger.item_id, 'data-quantity' => closet_hanger.quantity, 'data-id' => closet_hanger.id}
+-# NOTE: Changing this requires bumping the cache at `_closet_list.html.haml`!
+.object{'data-item-id' => closet_hanger.item_id, 'data-quantity' => closet_hanger.quantity, 'data-id' => closet_hanger.id}
   = render_item_link(closet_hanger.item)
   .quantity{:class => "quantity-#{closet_hanger.quantity}"}
     %span= closet_hanger.quantity

app/views/closet_hangers/index.html.haml

@@ -108,13 +108,13 @@
                 %h4= t '.unlisted.header'
             - if !@public_perspective
               = render partial: 'closet_lists/trading_neomail_warning', locals: {list: @user.null_closet_list(owned), user: @user}
+            - cache unlisted_hangers_cache_key(owned) do
               .closet-list-content
                 .closet-list-hangers
                   = render_unlisted_closet_hangers(owned)
                   %span.empty-list= t '.unlisted.empty'
 
 - if user_signed_in?
-  - localized_cache action_suffix: 'tmpls' do
   %script#autocomplete-item-tmpl{type: 'text/x-jquery-tmpl'}
     %a
       = t '.autocomplete.add_item_html', item_name: '${item_name}'
@@ -154,3 +154,14 @@
   = include_javascript_libraries :jquery, :jquery_tmpl
   = javascript_include_tag 'ajax_auth', 'lib/jquery.ui', 'lib/jquery.jgrowl',
     'closet_hangers/index'
+
+- if public_perspective? && user_signed_in?
+  - content_for :meta do
+    %meta{
+      name: "trade-matches-owns",
+      value: @items.select(&:owned?).map(&:id).join(",")
+    }
+    %meta{
+      name: "trade-matches-wants",
+      value: @items.select(&:wanted?).map(&:id).join(",")
+    }

app/views/closet_lists/_closet_list.html.haml

@@ -18,6 +18,8 @@
   - if show_controls
     = render partial: 'closet_lists/trading_neomail_warning', locals: {list: closet_list, user: @user}
 
+  -# Cachebuster comment: Updated downstream content at Feb 20 2024, 6:15pm
+  - cache closet_list do
     .closet-list-content
       - if closet_list.description?
         = closet_list_description_format closet_list

app/views/items/_item_link.html.haml

@@ -1,4 +1,6 @@
+-# NOTE: Changing this requires bumping the cache at `_closet_list.html.haml`!
 = link_to item_path(item) do
-  = image_tag item.thumbnail_url, :alt => item.description, :title => item.description
+  = image_tag item.thumbnail_url, alt: "Thumbnail for #{item.name}",
+    title: item.description, loading: "lazy"
   %span.name= item.name
   = nc_icon_for(item)