Track preferred color/species for new item page previews

Also adapted from the Impress 2020 logic!

Note that I refactored `compatible_pet_type` to a series of scopes on
`PetType`. I think this is a simpler, clearer, and more flexible API!

app/controllers/items_controller.rb

@@ -202,7 +202,12 @@ class ItemsController < ApplicationController
 
     return load_default_preview_pet_type if color_id.nil? || species_id.nil?
 
-    PetType.find_or_initialize_by(color_id:, species_id:)
+    PetType.find_or_initialize_by(color_id:, species_id:).tap do |pet_type|
+      if pet_type.persisted?
+        cookies["preferred-preview-color-id"] = color_id
+        cookies["preferred-preview-species-id"] = species_id
+      end
+    end
   end
 
   def load_preview_pet_type
@@ -214,7 +219,10 @@ class ItemsController < ApplicationController
   end
 
   def load_default_preview_pet_type
-    @item.compatible_pet_type
+    @item.compatible_pet_types.
+      preferring_species(cookies["preferred-preview-species-id"] || "<ignore>").
+      preferring_color(cookies["preferred-preview-color-id"] || "<ignore>").
+      preferring_simple.first
   end
 
   def validate_preview

app/models/item.rb

@@ -498,15 +498,6 @@ class Item < ApplicationRecord
     PetType.where(body_id: compatible_body_ids)
   end
 
-  # Return a pet type that can wear this item, preferring simple colors and
-  # early-alphabetically species.
-  def compatible_pet_type
-    compatible_pet_types.joins(:color, :species).order(:species_id).
-      merge(Color.order(basic: :desc, standard: :desc, name: :asc)).
-      merge(Species.order(name: :asc)).
-      first
-  end
-
   def handle_assets!
     if @parent_swf_asset_relationships_to_update && @current_body_id
       new_swf_asset_ids = @parent_swf_asset_relationships_to_update.map(&:swf_asset_id)

app/models/pet_type.rb

@@ -16,6 +16,17 @@ class PetType < ApplicationRecord
     species = Species.find_by_name!(species_name)
     where(color_id: color.id, species_id: species.id)
   }
+  scope :preferring_species, ->(species_id) {
+    joins(:species).order([Arel.sql("species_id = ? DESC"), species_id])
+  }
+  scope :preferring_color, ->(color_id) {
+    joins(:color).order([Arel.sql("color_id = ? DESC"), color_id])
+  }
+  scope :preferring_simple, -> {
+    joins(:species, :color).
+      merge(Species.order(name: :asc)).
+      merge(Color.order(basic: :desc, standard: :desc, name: :asc))
+  }
 
   def self.special_color_or_basic(special_color)
     color_ids = special_color ? [special_color.id] : Color.basic.select([:id]).map(&:id)