taxon.rb in writefully-0.5.0

- old
+ new

@@ -1,7 +1,15 @@
 module Writefully
-  Taxon = Struct.new(:incoming, :existing, :type) do 
+  class Taxon
+    attr_reader :incoming, :existing, :type
+
+    def initialize(incoming, existing, type)
+      @incoming = incoming
+      @existing = existing
+      @type     = type
+    end
+
     def non_existing
       get_difference.map { |token| Tag.new(build_attributes(token)) }
     end
 
     def selector
@@ -21,8 +29,51 @@
         .merge({ name: token, slug: token.parameterize })
     end
 
     def parameterized items
       items.map { |t| t.parameterize }
+    end
+
+    class EagerLoader
+      attr_reader :tags, :taggings, :resource
+
+      def initialize(klass)
+        @tags      = Tag.arel_table
+        @taggings  = Tagging.arel_table
+        @resource  = klass.arel_table
+      end
+
+      def build *types
+        [resource[Arel.star]] << types.map { |type| array_of_taxonomy_hstores_for(type) }
+      end
+
+    private
+
+      def array_of_taxonomy_hstores_for type
+        Arel::Nodes::NamedFunction.new('ARRAY', [hstore_for_taxon(type)]).as("all_#{type}")
+      end
+
+      def hstore_for_taxon type
+        tags.project(Arel.sql('hstore(taxon)')).from(taxons_for_resource(type))
+      end
+
+      def taxons_for_resource type
+        Tag.joins(:taggings).arel.where(tags_by_type(type))
+                                 .where(taggings_by_resource).as('taxon')
+      end
+
+      def tags_by_type type
+        tags[:type].eq(calculate_type(type))
+      end
+
+      def taggings_by_resource
+        # we use post_id for now but we should 
+        # make it a polymorphic association later
+        taggings[:post_id].eq(resource[:id])
+      end
+
+      def calculate_type type
+        type == :tags ? nil : type.to_s.classify 
+      end
     end
   end
 end
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