Merge pull request #1041 from bacarini/master

Adding pagination links

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
+
+            add_links(options)
           else
             @hash[:data] = attributes_for_serializer(serializer, options)
             add_resource_relationships(@hash[:data], serializer)
@@ -157,6 +160,23 @@ module ActiveModel
             end
           end
         end
+
+        def add_links(options)
+          links = @hash.fetch(:links) { {} }
+          resources = serializer.instance_variable_get(:@resource)
+          @hash[:links] = add_pagination_links(links, resources, options) if is_paginated?(resources)
+        end
+
+        def add_pagination_links(links, resources, options)
+          pagination_links = JsonApi::PaginationLinks.new(resources, options[:context]).serializable_hash(options)
+          links.update(pagination_links)
+        end
+
+        def is_paginated?(resource)
+          resource.respond_to?(:current_page) &&
+            resource.respond_to?(:total_pages) &&
+            resource.respond_to?(:size)
+        end
       end
     end
   end

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

@@ -0,0 +1,58 @@
+module ActiveModel
+  class Serializer
+    class Adapter
+      class JsonApi < Adapter
+        class PaginationLinks
+          FIRST_PAGE = 1
+
+          attr_reader :collection, :context
+
+          def initialize(collection, context)
+            @collection = collection
+            @context = context
+          end
+
+          def serializable_hash(options = {})
+            pages_from.each_with_object({}) do |(key, value), hash|
+              params = query_parameters.merge(page: { number: value, size: collection.size }).to_query
+
+              hash[key] = "#{url(options)}?#{params}"
+            end
+          end
+
+          private
+
+          def pages_from
+            return {} if collection.total_pages == FIRST_PAGE
+
+            {}.tap do |pages|
+              pages[:self] = collection.current_page
+
+              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 url(options)
+            @url ||= options.fetch(:links, {}).fetch(:self, nil) || original_url
+          end
+
+          def original_url
+            @original_url ||= context.original_url[/\A[^?]+/]
+          end
+
+          def query_parameters
+            @query_parameters ||= context.query_parameters
+          end
+        end
+      end
+    end
+  end
+end