Mongoid criteria refactor

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2018-03-11 13:14:54 +0100 using RuboCop version 0.49.1.
+# on 2018-03-13 23:29:51 +0100 using RuboCop version 0.49.1.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -20,9 +20,9 @@ Metrics/AbcSize:
 # Offense count: 14
 # Configuration parameters: CountComments, ExcludedMethods.
 Metrics/BlockLength:
-  Max: 202
+  Max: 216
 
-# Offense count: 6
+# Offense count: 5
 Metrics/CyclomaticComplexity:
   Max: 11
 
@@ -37,7 +37,7 @@ Metrics/LineLength:
 Metrics/MethodLength:
   Max: 25
 
-# Offense count: 4
+# Offense count: 3
 Metrics/PerceivedComplexity:
   Max: 11
 
@@ -48,7 +48,7 @@ Style/Documentation:
     - 'test/**/*'
     - 'examples/mongoid_scroll_feed.rb'
     - 'lib/mongo/scrollable.rb'
-    - 'lib/mongoid/criterion/scrollable.rb'
+    - 'lib/mongoid/criteria/scrollable.rb'
     - 'lib/mongoid/scroll/cursor.rb'
     - 'lib/mongoid/scroll/errors/base.rb'
     - 'lib/mongoid/scroll/errors/invalid_cursor_error.rb'
@@ -64,11 +64,10 @@ Style/FileName:
   Exclude:
     - 'lib/mongoid-scroll.rb'
 
-# Offense count: 2
+# Offense count: 1
 # Configuration parameters: MinBodyLength.
 Style/GuardClause:
   Exclude:
-    - 'lib/mongoid/criterion/scrollable.rb'
     - 'lib/moped/scrollable.rb'
 
 # Offense count: 1

lib/mongoid-scroll.rb

@@ -9,4 +9,4 @@
 require 'mongoid/scroll/cursor'
 require 'moped/scrollable' if Object.const_defined?(:Moped)
 require 'mongo/scrollable' if Object.const_defined?(:Mongo)
-require 'mongoid/criterion/scrollable'
+require 'mongoid/criteria/scrollable'

lib/mongoid/criteria/scrollable.rb

@@ -0,0 +1,81 @@
+module Mongoid
+  class Criteria
+    module Scrollable
+      def scroll(cursor = nil, &_block)
+        raise_multiple_sort_fields_error if multiple_sort_fields?
+        criteria = dup
+        criteria.merge!(default_sort) if no_sort_option?
+        cursor_options = build_cursor_options(criteria)
+        cursor = cursor.is_a?(Mongoid::Scroll::Cursor) ? cursor : new_cursor(cursor, cursor_options)
+        cursor_criteria = build_cursor_criteria(criteria, cursor)
+        if block_given?
+          cursor_criteria.order_by(_id: scroll_direction(criteria)).each do |record|
+            yield record, cursor_from_record(record, cursor_options)
+          end
+        else
+          cursor_criteria
+        end
+      end
+
+      private
+
+      def raise_multiple_sort_fields_error
+        raise Mongoid::Scroll::Errors::MultipleSortFieldsError.new(sort: criteria.options.sort)
+      end
+
+      def multiple_sort_fields?
+        options.sort && options.sort.keys.size != 1
+      end
+
+      def no_sort_option?
+        options.sort.blank? || options.sort.empty?
+      end
+
+      def default_sort
+        asc(:_id)
+      end
+
+      def scroll_field(criteria)
+        criteria.options.sort.keys.first
+      end
+
+      def scroll_direction(criteria)
+        criteria.options.sort.values.first.to_i
+      end
+
+      def build_cursor_options(criteria)
+        {
+          field_type: scroll_field_type(criteria),
+          field_name: scroll_field(criteria),
+          direction: scroll_direction(criteria)
+        }
+      end
+
+      def new_cursor(cursor, cursor_options)
+        Mongoid::Scroll::Cursor.new(cursor, cursor_options)
+      end
+
+      def build_cursor_criteria(criteria, cursor)
+        cursor_criteria = criteria.dup
+        cursor_criteria.selector = { '$and' => [criteria.selector, cursor.criteria] }
+        cursor_criteria
+      end
+
+      def cursor_from_record(record, cursor_options)
+        Mongoid::Scroll::Cursor.from_record(record, cursor_options)
+      end
+
+      def scroll_field_type(criteria)
+        scroll_field = scroll_field(criteria)
+        field = criteria.klass.fields[scroll_field.to_s]
+        field.foreign_key? && field.object_id_field? ? bson_type : field.type
+      end
+
+      def bson_type
+        Mongoid::Compatibility::Version.mongoid3? ? Moped::BSON::ObjectId : BSON::ObjectId
+      end
+    end
+  end
+end
+
+Mongoid::Criteria.send(:include, Mongoid::Criteria::Scrollable)

spec/mongoid/criteria_spec.rb

@@ -43,6 +43,20 @@
         expect(records.size).to eq 10
         expect(records).to eq Feed::Item.all.to_a
       end
+      it 'does not change original criteria' do
+        criteria = Feed::Item.where(:a_time.gt => Time.new(2013, 7, 22, 1, 2, 3))
+        original_criteria = criteria.dup
+        criteria.limit(2).scroll
+        expect(criteria).to eq original_criteria
+        cursor = nil
+        criteria.limit(2).scroll(cursor) do |_record, next_cursor|
+          cursor = next_cursor
+        end
+        criteria.scroll(cursor) do |_record, next_cursor|
+          cursor = next_cursor
+        end
+        expect(criteria).to eq original_criteria
+      end
     end
 
     context 'with a foreign key' do