exchange pagination class to inside json_api scope

README.md

@@ -283,7 +283,7 @@ If you want pagination links in your response, specify it in the `render`
 
 AMS relies on either Kaminari or WillPaginate. Please install either dependency by adding one of those to your Gemfile.
 
-Pagination links will only be included in your response if you are using an Adapter that supports `root`, as JsonAPI and Json adapters, the default adapter (FlattenJson) doesn't have `root`.
+Pagination links will only be included in your response if you are using a JsonAPI adapter, the others adapters doesn't have this feature.
 
 ## Caching
 

lib/active_model/serializer/adapter.rb

@@ -94,21 +94,6 @@ module ActiveModel
         json[meta_key] = meta if meta
         json
       end
-
-      def include_pagination_links(json)
-        return unless page_links
-
-        links?(json) ? json.merge!(page_links) : json['links'] = page_links
-        json
-      end
-
-      def page_links
-        @links ||= serializer.page_links
-      end
-
-      def links?(json)
-        !json['links'].nil?
-      end
     end
   end
 end

lib/active_model/serializer/adapter/json_api.rb

@@ -1,4 +1,5 @@
 require 'active_model/serializer/adapter/json_api/fragment_cache'
+require 'active_model/serializer/adapter/json_api/pagination_links'
 
 module ActiveModel
   class Serializer
@@ -27,6 +28,8 @@ module ActiveModel
                 @hash[:included] |= result[:included]
               end
             end
+
+            include_pagination_links if serializer.pagination
           else
             @hash[:data] = attributes_for_serializer(serializer, options)
             add_resource_relationships(@hash[:data], serializer)
@@ -157,6 +160,20 @@ module ActiveModel
             end
           end
         end
+
+        def include_pagination_links
+          return if page_links.empty?
+
+          links? ? @hash[:links].merge!(page_links) : @hash[:links] = page_links
+        end
+
+        def page_links
+          @links ||= JsonApi::PaginationLinks.new(serializer.resource).page_links
+        end
+
+        def links?
+          !@hash[:links].nil?
+        end
       end
     end
   end

lib/active_model/serializer/adapter/json_api/pagination_links.rb

@@ -0,0 +1,52 @@
+module ActiveModel
+  class Serializer
+    class Adapter
+      class JsonApi < Adapter
+        class PaginationLinks
+          FIRST_PAGE = 1
+
+          attr_reader :collection
+
+          def initialize(collection)
+            raise_unless_any_gem_installed
+            @collection = collection
+          end
+
+          def page_links
+            build_links
+          end
+
+          private
+
+          def build_links
+            pages_from.each_with_object({}) do |(key, value), hash|
+              hash[key] = "?page=#{value}&per_page=#{collection.size}"
+            end
+          end
+
+          def pages_from
+            return {} if collection.total_pages == FIRST_PAGE
+
+            {}.tap do |pages|
+              unless collection.current_page == FIRST_PAGE
+                pages[:first] = FIRST_PAGE
+                pages[:prev]  = collection.current_page - FIRST_PAGE
+              end
+
+              unless collection.current_page == collection.total_pages
+                pages[:next] = collection.current_page + FIRST_PAGE
+                pages[:last] = collection.total_pages
+              end
+            end
+          end
+
+          def raise_unless_any_gem_installed
+            return if defined?(WillPaginate) || defined?(Kaminari)
+            raise "AMS relies on either Kaminari or WillPaginate." +
+              "Please install either dependency by adding one of those to your Gemfile"
+          end
+        end
+      end
+    end
+  end
+end

lib/active_model/serializer/array_serializer.rb

@@ -4,9 +4,8 @@ module ActiveModel
       NoSerializerError = Class.new(StandardError)
       include Enumerable
       delegate :each, to: :@objects
-      delegate :page_links, to: :pagination
 
-      attr_reader :root, :meta, :meta_key, :pagination
+      attr_reader :root, :meta, :meta_key, :pagination, :resource
 
       def initialize(objects, options = {})
         @root = options[:root]
@@ -25,7 +24,7 @@ module ActiveModel
         end
         @meta     = options[:meta]
         @meta_key = options[:meta_key]
-        @pagination = ActiveModel::Serializer::Pagination.new(objects) if options[:pagination]
+        @pagination = options[:pagination]
       end
 
       def json_key

lib/active_model/serializer/pagination.rb

@@ -1,62 +0,0 @@
-module ActiveModel
-  class Serializer
-    class Pagination
-      attr_reader :collection
-
-      def initialize(collection)
-        @collection = collection
-      end
-
-      def page_links
-        send(default_adapter)
-      end
-
-      private
-
-      def kaminari
-        build_links collection.size
-      end
-
-      def will_paginate
-        setup_will_paginate
-        build_links collection.per_page
-      end
-
-      def build_links(per_page)
-        pages_from.each_with_object({}) do |(key, value), hash|
-          hash[key] = "?page=#{value}&per_page=#{per_page}"
-        end
-      end
-
-      def pages_from
-        return {} if collection.total_pages == 1
-
-        {}.tap do |pages|
-          unless collection.first_page?
-            pages[:first] = 1
-            pages[:prev]  = collection.current_page - 1
-          end
-
-          unless collection.last_page?
-            pages[:next] = collection.current_page + 1
-            pages[:last] = collection.total_pages
-          end
-        end
-      end
-
-      def default_adapter
-        return :kaminari if defined?(Kaminari)
-        return :will_paginate if defined?(WillPaginate::CollectionMethods)
-        raise "AMS relies on either Kaminari or WillPaginate." +
-          "Please install either dependency by adding one of those to your Gemfile"
-      end
-
-      def setup_will_paginate
-        WillPaginate::CollectionMethods.module_eval do
-          def first_page?() !previous_page end
-          def last_page?() !next_page end
-        end
-      end
-    end
-  end
-end

lib/active_model_serializers.rb

@@ -2,7 +2,6 @@ require 'active_model'
 require 'active_model/serializer/version'
 require 'active_model/serializer'
 require 'active_model/serializer/fieldset'
-require 'active_model/serializer/pagination'
 require 'active_model/serializable_resource'
 
 begin

test/array_serializer_test.rb

@@ -92,6 +92,15 @@ module ActiveModel
         serializer = ArraySerializer.new(build_named_collection, root: 'custom_root')
         assert_equal serializer.json_key, 'custom_roots'
       end
+
+      def test_pagination_attr_readers
+        serializer = ArraySerializer.new(@resource, pagination: true)
+        assert_equal serializer.pagination, true
+      end
+
+      def test_resource
+        assert_equal @serializer.resource, @resource
+      end
     end
   end
 end