Pagination Links

.gitignore

@@ -19,3 +19,4 @@ test/version_tmp
 tmp
 *.swp
 .ruby-version
+.ruby-gemset

CHANGELOG.md

@@ -9,4 +9,5 @@
   * adds cache support to attributes and associations [@joaomdmoura]
   * uses model name to determine the type [@lsylvester]
   * remove root key option and split JSON adapter [@joaomdmoura]
-  * adds FlattenJSON as default adapter [@joaomdmoura]
+  * adds FlattenJSON as default adapter [@joaomdmoura]
+  * adds support for `pagination links` at top level of JsonApi adapter [@bacarini]

README.md

@@ -118,7 +118,7 @@ If you wish to use a serializer other than the default, you can explicitly pass
 render json: @posts, each_serializer: PostPreviewSerializer
 
 # Or, you can explicitly provide the collection serializer as well
-render json: @posts, serializer: PaginatedSerializer, each_serializer: PostPreviewSerializer
+render json: @posts, serializer: CollectionSerializer, each_serializer: PostPreviewSerializer
 ```
 
 ### Meta
@@ -272,6 +272,11 @@ And you can change the JSON key that the serializer should use for a particular
 
 The `url` declaration describes which named routes to use while generating URLs
 for your JSON. Not every adapter will require URLs.
+## Pagination
+
+Pagination links will be included in your response automatically as long as the resource is paginated using [Kaminari](https://github.com/amatsuda/kaminari) or [WillPaginate](https://github.com/mislav/will_paginate) and if you are using a ```JSON-API``` adapter.
+
+Although the others adapters does not have this feature, it is possible to implement pagination links to `JSON` adapter. For more information about it, please see in our docs [How to add pagination links](https://github.com/rails-api/active_model_serializers/blob/master/docs/howto/add_pagination_links.md)
 
 ## Caching
 

active_model_serializers.gemspec

@@ -24,4 +24,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "bundler", "~> 1.6"
   spec.add_development_dependency "timecop", ">= 0.7"
   spec.add_development_dependency "rake"
+  spec.add_development_dependency "kaminari"
+  spec.add_development_dependency "will_paginate"
 end

docs/README.md

@@ -12,6 +12,7 @@ This is the documentation of AMS, it's focused on the **0.10.x version.**
 ## How to
 
 - [How to add root key](howto/add_root_key.md)
+- [How to add pagination links](howto/add_pagination_links.md)
 
 ## Getting Help
 

docs/howto/add_pagination_links.md

@@ -0,0 +1,98 @@
+# How to add pagination links
+
+### JSON-API adapter
+
+Pagination links will be included in your response automatically as long as the resource is paginated and if you are using a ```JSON-API``` adapter.
+
+If you want pagination links in your response, use [Kaminari](https://github.com/amatsuda/kaminari) or [WillPaginate](https://github.com/mislav/will_paginate).
+
+```ruby
+#kaminari example
+@posts = Kaminari.paginate_array(Post.all).page(3).per(1)
+render json: @posts
+
+#will_paginate example
+@posts = Post.all.paginate(page: 3, per_page: 1)
+render json: @posts
+```
+
+```ruby
+ActiveModel::Serializer.config.adapter = :json_api
+```
+
+ex:
+```json
+{
+  "data": [
+    {
+      "type": "articles",
+      "id": "3",
+      "attributes": {
+        "title": "JSON API paints my bikeshed!",
+        "body": "The shortest article. Ever.",
+        "created": "2015-05-22T14:56:29.000Z",
+        "updated": "2015-05-22T14:56:28.000Z"
+      }
+    }
+  ],
+  "links": {
+    "self": "http://example.com/articles?page[number]=3&page[size]=1",
+    "first": "http://example.com/articles?page[number]=1&page[size]=1",
+    "prev": "http://example.com/articles?page[number]=2&page[size]=1",
+    "next": "http://example.com/articles?page[number]=4&page[size]=1",
+    "last": "http://example.com/articles?page[number]=13&page[size]=1"
+  }
+}
+```
+
+AMS relies on either [Kaminari](https://github.com/amatsuda/kaminari) or [WillPaginate](https://github.com/mislav/will_paginate). Please install either dependency by adding one of those to your Gemfile.
+
+### JSON adapter
+
+If you are using `JSON` adapter, pagination links will not be included automatically, but it is possible to do so using `meta` key.
+
+In your action specify a custom serializer.
+```ruby
+render json: @posts, serializer: PaginatedSerializer, each_serializer: PostPreviewSerializer
+```
+
+And then, you could do something like the following class.
+```ruby
+class PaginatedSerializer < ActiveModel::Serializer::ArraySerializer
+  def initialize(object, options={})
+    meta_key = options[:meta_key] || :meta
+    options[meta_key] ||= {}
+    options[meta_key] = {
+      current_page: object.current_page,
+      next_page: object.next_page,
+      prev_page: object.prev_page,
+      total_pages: object.total_pages,
+      total_count: object.total_count
+    }
+    super(object, options)
+  end
+end
+```
+ex.
+```json
+{
+  "articles": [
+    {
+      "id": 2,
+      "title": "JSON API paints my bikeshed!",
+      "body": "The shortest article. Ever."
+    }
+  ],
+  "meta": {
+    "current_page": 3,
+    "next_page": 4,
+    "prev_page": 2,
+    "total_pages": 10,
+    "total_count": 10
+  }
+}
+```
+
+### FlattenJSON adapter
+
+This adapter does not allow us to use `meta` key, due to that it is not possible to add pagination links.

lib/action_controller/serialization.rb

@@ -47,6 +47,7 @@ def use_adapter?
 
     [:_render_option_json, :_render_with_renderer_json].each do |renderer_method|
       define_method renderer_method do |resource, options|
+        options.fetch(:context) { options[:context] = request }
         serializable_resource = get_serializer(resource, options)
         super(serializable_resource, options)
       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 @@ def serializable_hash(options = nil)
                 @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 @@ def add_resource_relationships(attrs, serializer, options = {})
             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