Add Pagy Countless paginator

README.md

@@ -27,7 +27,7 @@ Or install it yourself as:
 
 ```ruby
 class UserQuery < Jsonapi::QueryBuilder::BaseQuery
-  ## pagination 
+  ## pagination
   paginator Jsonapi::QueryBuilder::Paginator::Pagy # default paginator
 
   ## sorting
@@ -62,9 +62,9 @@ pass the scoped collection to the `Jsonapi::QueryBuilder::BaseQuery` object.
 ### Pagination
 
 Pagination support is configurable using the `paginator` method to define the paginator. It defaults to the `Pagy`
-paginator, a lightweight and fast paginator. Other paginators currently supported are `Kaminari` and an implementation
-of keyset pagination. Before using these paginators we need to explicitly require the gems in our Gemfile and the
-paginator file in question. Additionally one can implement it's own paginator by inheriting
+paginator, a lightweight and fast paginator. Other paginators currently supported are `Kaminari`, `PagyCountless` and
+an implementation of keyset pagination. Before using these paginators we need to explicitly require the gems in our
+Gemfile and the paginator file in question. Additionally one can implement it's own paginator by inheriting
 from `Jsonapi::QueryBuilder::Paginator::BasePaginator`. The minimum required implementation is a `#paginate` method that
 receives page params and returns a page of the collection. It can return the pagination details as the second item of
 the returned array, that can be used in the serializer for pagination metadata.
@@ -85,6 +85,14 @@ require "jsonapi/query_builder/paginator/keyset"
 paginator Jsonapi::QueryBuilder::Paginator::Keyset
 ```
 
+#### Using the Pagy Countless Paginator
+
+```ruby
+require "jsonapi/query_builder/paginator/pagy_countless"
+
+paginator Jsonapi::QueryBuilder::Paginator::PagyCountless
+```
+
 ### Sorting
 
 #### Ensuring deterministic results

lib/jsonapi/query_builder/paginator/pagy_countless.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require "pagy"
+require "pagy/extras/items"
+require "pagy/extras/countless"
+
+module Jsonapi
+  module QueryBuilder
+    module Paginator
+      class PagyCountless < BasePaginator
+        include ::Pagy::Backend
+
+        def paginate(page_params)
+          @params = {page: page_params}
+
+          pagination_details, records = pagy_countless(collection, page: page_params[:number],
+            items: page_params[:size],
+            outset: page_params[:offset])
+
+          [records, pagination_details]
+        end
+
+        private
+
+        attr_reader :params
+      end
+    end
+  end
+end

spec/jsonapi/query_builder/paginator/pagy_countless_spec.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require "jsonapi/query_builder/paginator/pagy_countless"
+
+RSpec.describe Jsonapi::QueryBuilder::Paginator::PagyCountless do
+  describe "#paginate" do
+    subject(:paginate) { pagy_paginator.paginate(number: 2, size: 20, offset: 3) }
+
+    let(:pagy_paginator) { described_class.new(collection) }
+    let(:collection) { instance_double "collection" }
+    let(:paged_collection) { instance_double "paged-collection" }
+    let(:pagination_details) { instance_double Pagy, "pagination-details" }
+
+    before do
+      allow(pagy_paginator).to receive(:pagy_countless).and_return([pagination_details, paged_collection])
+    end
+
+    it { is_expected.to be_an Array }
+
+    it "returns the records and pagination details" do
+      expect(paginate).to eql [paged_collection, pagination_details]
+    end
+
+    it "passes the collection and pagination params to pagy_countless method" do
+      paginate
+
+      expect(pagy_paginator).to have_received(:pagy_countless).with(collection, page: 2, items: 20, outset: 3)
+    end
+
+    it "sets the private params attribute reader used internally by pagy backend" do
+      paginate
+
+      expect(pagy_paginator.send(:params)).to eql page: {number: 2, size: 20, offset: 3}
+    end
+  end
+end