Support zone restriction in new item preview

Adapted from wardrobe-2020's `getVisibleLayers`! Thanks past-Matchu for
all the comments lol!

app/controllers/items_controller.rb

@@ -187,7 +187,7 @@ class ItemsController < ApplicationController
         appearance_params[:color_id], appearance_params[:species_id])
     end
 
-    target.appearances_for(@items.map(&:id), swf_asset_includes: [:zone]).
+    target.appearances_for(@items, swf_asset_includes: [:zone]).
       tap do |appearances|
         # Preload the manifests for these SWF assets concurrently, rather than
         # loading them in sequence when we generate the JSON.
@@ -223,7 +223,7 @@ class ItemsController < ApplicationController
   def validate_preview
     if @selected_preview_pet_type.new_record?
       :pet_type_does_not_exist
-    elsif @preview_outfit.item_appearances.values.any?(&:empty?)
+    elsif @preview_outfit.item_appearances.any?(&:empty?)
       :no_item_data
     end
   end

app/models/alt_style.rb

@@ -49,9 +49,9 @@ class AltStyle < ApplicationRecord
     swf_asset.image_url
   end
 
-  # Given a list of item IDs, return how they look on this alt style.
-  def appearances_for(item_ids, ...)
-    Item.appearances_for(item_ids, self, ...)
+  # Given a list of items, return how they look on this alt style.
+  def appearances_for(items, ...)
+    Item.appearances_for(items, self, ...)
   end
 
   def biology=(biology)

app/models/item.rb

@@ -555,17 +555,23 @@ class Item < ApplicationRecord
   # instead of like a hash, so you can target its children with things like
   # the `include` option. This feels clunky though, I wish I had something a
   # bit more suited to it!
-  Appearance = Struct.new(:body, :swf_assets) do
+  Appearance = Struct.new(:item, :body, :swf_assets) do
     include ActiveModel::Serializers::JSON
     delegate :present?, :empty?, to: :swf_assets
+
     def attributes
-      {body: body, swf_assets: swf_assets}
+      {item:, body:, swf_assets:}
+    end
+
+    def restricted_zone_ids
+      return [] if empty?
+      ([item] + swf_assets).map(&:restricted_zone_ids).flatten.uniq.sort
     end
   end
   Appearance::Body = Struct.new(:id, :species) do
     include ActiveModel::Serializers::JSON
     def attributes
-      {id: id, species: species}
+      {id:, species:}
     end
   end
 
@@ -582,7 +588,7 @@ class Item < ApplicationRecord
     # If there are no body-specific assets, return one appearance for them all.
     if swf_assets_by_body_id.empty?
       body = Appearance::Body.new(0, nil)
-      return [Appearance.new(body, swf_assets_for_all_bodies)]
+      return [Appearance.new(self, body, swf_assets_for_all_bodies)]
     end
 
     # Otherwise, create an appearance for each real (nonzero) body ID. We don't
@@ -592,22 +598,22 @@ class Item < ApplicationRecord
       swf_assets_for_body = body_specific_assets + swf_assets_for_all_bodies
       species = Species.with_body_id(body_id).first!
       body = Appearance::Body.new(body_id, species)
-      Appearance.new(body, swf_assets_for_body)
+      Appearance.new(self, body, swf_assets_for_body)
     end
   end
 
   def appearance_for(target, ...)
-    Item.appearances_for([id], target, ...)[id]
+    Item.appearances_for([self], target, ...)[id]
   end
 
-  # Given a list of item IDs, return how they look on the given target (either
-  # a pet type or an alt style).
-  def self.appearances_for(item_ids, target, swf_asset_includes: [])
+  # Given a list of items, return how they look on the given target (either a
+  # pet type or an alt style).
+  def self.appearances_for(items, target, swf_asset_includes: [])
     # First, load all the relationships for these items that also fit this
     # body.
     relationships = ParentSwfAssetRelationship.
       includes(swf_asset: swf_asset_includes).
-      where(parent_type: "Item", parent_id: item_ids).
+      where(parent_type: "Item", parent_id: items.map(&:id)).
       where(swf_asset: {body_id: [target.body_id, 0]})
 
     pet_type_body = Appearance::Body.new(target.body_id, target.species)
@@ -618,13 +624,13 @@ class Item < ApplicationRecord
       transform_values { |rels| rels.map(&:swf_asset) }
 
     # Finally, for each item, return an appearance—even if it's empty!
-    item_ids.to_h do |item_id|
-      assets = assets_by_item_id.fetch(item_id, [])
+    items.to_h do |item|
+      assets = assets_by_item_id.fetch(item.id, [])
 
       fits_all_pets = assets.present? && assets.all? { |a| a.body_id == 0 }
       body = fits_all_pets ? all_pets_body : pet_type_body
 
-      [item_id, Appearance.new(body, assets)]
+      [item.id, Appearance.new(item, body, assets)]
     end
   end
 

app/models/outfit.rb

@@ -160,13 +160,73 @@ class Outfit < ApplicationRecord
   end
 
   def item_appearances(...)
-    Item.appearances_for(worn_item_ids, pet_type, ...)
+    Item.appearances_for(worn_items, pet_type, ...).values
   end
 
   def visible_layers
-    pet_layers = pet_state.swf_assets.includes(:zone)
-    item_layers = item_appearances(swf_asset_includes: [:zone]).values.
-      map(&:swf_assets).flatten
+    item_appearances = item_appearances(swf_asset_includes: [:zone])
+
+    pet_layers = pet_state.swf_assets.includes(:zone).to_a
+    item_layers = item_appearances.map(&:swf_assets).flatten
+
+    pet_restricted_zone_ids = pet_layers.map(&:restricted_zone_ids).
+      flatten.to_set
+    item_restricted_zone_ids = item_appearances.
+      map(&:restricted_zone_ids).flatten.to_set
+
+    # When an item restricts a zone, it hides pet layers of the same zone.
+    # We use this to e.g. make a hat hide a hair ruff.
+    #
+    # NOTE: Items' restricted layers also affect what items you can wear at
+    #       the same time. We don't enforce anything about that here, and
+    #       instead assume that the input by this point is valid!
+    pet_layers.reject! { |sa| item_restricted_zone_ids.include?(sa.zone_id) }
+
+    # When a pet appearance restricts a zone, or when the pet is Unconverted,
+    # it makes body-specific items incompatible. We use this to disallow UCs
+    # from wearing certain body-specific Biology Effects, Statics, etc, while
+    # still allowing non-body-specific items in those zones! (I think this
+    # happens for some Invisible pet stuff, too?)
+    #
+    # TODO: We shouldn't be *hiding* these zones, like we do with items; we
+    #       should be doing this way earlier, to prevent the item from even
+    #       showing up even in search results!
+    #
+    # NOTE: This can result in both pet layers and items occupying the same
+    #       zone, like Static, so long as the item isn't body-specific! That's
+    #       correct, and the item layer should be on top! (Here, we implement
+    #       it by placing item layers second in the list, and rely on JS sort
+    #       stability, and *then* rely on the UI to respect that ordering when
+    #       rendering them by depth. Not great! 😅)
+    #
+    # NOTE: We used to also include the pet appearance's *occupied* zones in
+    #       this condition, not just the restricted zones, as a sensible
+    #       defensive default, even though we weren't aware of any relevant
+    #       items. But now we know that actually the "Bruce Brucey B Mouth"
+    #       occupies the real Mouth zone, and still should be visible and
+    #       above pet layers! So, we now only check *restricted* zones.
+    #
+    # NOTE: UCs used to implement their restrictions by listing specific
+    #       zones, but it seems that the logic has changed to just be about
+    #       UC-ness and body-specific-ness, and not necessarily involve the
+    #       set of restricted zones at all. (This matters because e.g. UCs
+    #       shouldn't show _any_ part of the Rainy Day Umbrella, but most UCs
+    #       don't restrict Right-Hand Item (Zone 49).) Still, I'm keeping the
+    #       zone restriction case running too, because I don't think it
+    #       _hurts_ anything, and I'm not confident enough in this conclusion.
+    #
+    # TODO: Do Invisibles follow this new rule like UCs, too? Or do they still
+    #       use zone restrictions?
+    if pet_state.pose === "UNCONVERTED"
+      item_layers.reject! { |sa| sa.body_specific? }
+    else
+      item_layers.reject! { |sa| sa.body_specific? &&
+        pet_restricted_zone_ids.include?(sa.zone_id) }
+    end
+
+    # A pet appearance can also restrict its own zones. The Wraith Uni is an
+    # interesting example: it has a horn, but its zone restrictions hide it!
+    pet_layers.reject! { |sa| pet_restricted_zone_ids.include?(sa.zone_id) }
 
     (pet_layers + item_layers).sort_by(&:depth)
   end

app/models/pet_type.rb

@@ -124,9 +124,9 @@ class PetType < ApplicationRecord
     }.first
   end
 
-  # Given a list of item IDs, return how they look on this pet type.
-  def appearances_for(item_ids, ...)
-    Item.appearances_for(item_ids, self, ...)
+  # Given a list of items, return how they look on this pet type.
+  def appearances_for(item, ...)
+    Item.appearances_for(item, self, ...)
   end
 
   def self.all_by_ids_or_children(ids, pet_states)