Item search can filter by fitting alt styles (but missing many details!)

A query like this works for finding items containing "hat" that fit
alt style #87296 (the Faerie Acara):

http://localhost:3000/items?q%5B0%5D%5Bkey%5D=name&q%5B0%5D%5Bvalue%5D=hat&q%5B1%5D%5Bkey%5D=fits&q%5B1%5D%5Bvalue%5D%5Bspecies_id%5D=1&q%5B1%5D%5Bvalue%5D%5Bcolor_id%5D=8&q%5B1%5D%5Bvalue%5D%5Balt_style_id%5D=87296

But there's two main missing pieces still:
1. You can't do a text-filter version of this—in fact, clicking Search
   immediately on the page this loads will return an error!
2. We haven't extended this to the `with_appearances_for` parameter,
   so we add a `NotImplementedError` to that bit for now too.

I'm also thinking that the text filter should ideally be like,
`fits:nostalgic-faerie-acara` if we can pull it off; and then fall back
to the plainer `fits:alt-style-87296` if e.g. we don't know the set
it's from yet.

app/controllers/items_controller.rb

@@ -123,6 +123,7 @@ class ItemsController < ApplicationController
   def load_appearances
     appearance_params = params[:with_appearances_for]
     return {} if appearance_params.blank?
+    raise NotImplementedError if appearance_params[:alt_style_id].present?
 
     pet_type = Item::Search::Query.load_pet_type_by_color_and_species(
       appearance_params[:color_id], appearance_params[:species_id])

app/models/item/search/query.rb

@@ -128,12 +128,18 @@ class Item
               Filter.restricts(value) :
               Filter.not_restricts(value))
           when 'fits'
-            raise NotImplementedError if value[:alt_style_id].present?
+            if value[:alt_style_id].present?
+              alt_style = load_alt_style_by_id(value[:alt_style_id])
+              filters << (is_positive ?
+                Filter.fits_alt_style(alt_style) :
+                Filter.fits_alt_style(alt_style))
+            else
               pet_type = load_pet_type_by_color_and_species(
                 value[:color_id], value[:species_id])
               filters << (is_positive ?
                 Filter.fits_pet_type(pet_type) :
                 Filter.not_fits_pet_type(pet_type))
+            end
           when 'user_closet_hanger_ownership'
             case value
             when 'true'
@@ -174,6 +180,16 @@ class Item
           raise Item::Search::Error, message
         end
       end
+
+      def self.load_alt_style_by_id(alt_style_id)
+        begin
+          AltStyle.find(alt_style_id)
+        rescue
+          message = I18n.translate('items.search.errors.not_found.alt_style',
+            filter_text: "alt-style-#{alt_style_id}")
+          raise Item::Search::Error, message
+        end
+      end
     end
 
     class Error < Exception
@@ -235,6 +251,16 @@ class Item
         self.new Item.not_fits(pet_type.body_id), "-fits:#{q value}"
       end
 
+      def self.fits_alt_style(alt_style)
+        value = alt_style_to_filter_text(alt_style)
+        self.new Item.fits(alt_style.body_id), "fits:#{q value}"
+      end
+
+      def self.not_fits_alt_style(alt_style)
+        value = alt_style_to_filter_text(alt_style)
+        self.new Item.not_fits(alt_style.body_id), "-fits:#{q value}"
+      end
+
       def self.fits_species(body_id, species_name)
         self.new Item.fits(body_id), "species:#{q species_name}"
       end
@@ -297,7 +323,11 @@ class Item
         species_name ||= pet_type.species.name
 
         # NOTE: Some color syntaxes are weird, like `fits:"polka dot-aisha"`!
-        value = "#{color_name}-#{species_name}".downcase
+        "#{color_name}-#{species_name}".downcase
+      end
+
+      def self.alt_style_to_filter_text(alt_style)
+        "alt-style-#{alt_style.id}"
       end
     end
   end

config/locales/en.yml

@@ -358,6 +358,8 @@ en:
             user:wants?
           pet_type: We have no record of the %{name1} %{name2}.
             It is spelled correctly?
+          alt_style: We have no record of the "%{filter_text}" alt style. Is it
+            spelled correctly?
           pet_type_id: We have no record of pet type %{id}. Weird.
         not_logged_in: The "user" filters are only available if you're logged in.
       flag_keywords: