add only:species filter

app/models/item.rb

@@ -65,18 +65,22 @@ class Item < ActiveRecord::Base
     
     def narrow(scope)
       items = Table(:objects)
-      if @property == 'species'
+      if @property == 'species' || @property == 'only'
         species = Species.find_by_name(self)
         raise ArgumentError, "Species \"#{self.humanize}\" does not exist" unless species
         # TODO: add a many-to-many table to handle this relationship, if
         # performance becomes an issue
         ids = items[:species_support_ids]
+        if @property == 'species'
           condition = ids.eq('').or(ids.matches_any(
             species.id,
             "#{species.id},%",
             "%,#{species.id},%",
             "%,#{species.id}"
           ))
+        else
+          condition = items[:species_support_ids].eq(species.id.to_s)
+        end
       elsif @property == 'description' || @property.blank?
         column = @property == 'description' ? :description : :name
         condition = items[column].matches("%#{self}%")

spec/models/item_spec.rb

@@ -143,6 +143,16 @@ describe Item do
       Item.search('-species:aisha').count.should == 1
     end
     
+    specify "should search by only:species" do
+      Factory.create :item, :species_support_ids => [1], :name => 'a'
+      Factory.create :item, :species_support_ids => [1,2], :name => 'b'
+      Factory.create :item, :species_support_ids => [], :name => 'c'
+      Item.search('only:acara').map(&:name).should == ['a']
+      Item.search('only:aisha').count.should == 0
+      Item.search('-only:acara').map(&:name).should == ['b', 'c']
+      Item.search('-only:aisha').map(&:name).should == ['a', 'b', 'c']
+    end
+    
     specify "should be able to negate word in search" do
       query_should 'hat -blue',
         :return => [