From 845c96b9360f512edcc40db63de4e8ca71f2c423 Mon Sep 17 00:00:00 2001
From: Campbell Allen <campbell.allen@gmail.com>
Date: Thu, 12 Feb 2015 09:52:23 +0000
Subject: [PATCH] support polymorphic belongs_to associations

---
 lib/restpack_serializer/factory.rb            | 30 ++++++----
 lib/restpack_serializer/serializable.rb       | 26 ++++++++-
 .../serializable/paging.rb                    |  6 +-
 .../serializable/side_load_data_builder.rb    | 18 ++++--
 .../serializable/side_loading.rb              | 55 ++++++++++++++-----
 spec/factory/factory_spec.rb                  | 12 ++++
 spec/fixtures/db.rb                           | 28 ++++++++++
 spec/fixtures/serializers.rb                  | 15 ++++-
 spec/serializable/paging_spec.rb              | 22 ++++++++
 spec/serializable/serializer_spec.rb          | 17 ++++++
 .../side_loading/side_loading_spec.rb         | 14 +++++
 spec/support/factory.rb                       |  4 ++
 12 files changed, 214 insertions(+), 33 deletions(-)

diff --git a/lib/restpack_serializer/factory.rb b/lib/restpack_serializer/factory.rb
index dd8d0cf..fc73d8c 100644
--- a/lib/restpack_serializer/factory.rb
+++ b/lib/restpack_serializer/factory.rb
@@ -1,18 +1,24 @@
-class RestPack::Serializer::Factory
-  def self.create(*identifiers)
-    serializers = identifiers.map { |identifier| self.classify(identifier) }
-    serializers.count == 1 ? serializers.first : serializers
-  end
+module RestPack::Serializer
+
+  class UnknownSerializer < StandardError; end
 
-  private
+  class Factory
 
-  def self.classify(identifier)
-    normalised_identifier = identifier.to_s.underscore
-    [normalised_identifier, normalised_identifier.singularize].each do |format|
-      klass = RestPack::Serializer.class_map[format]
-      return klass.new if klass
+    def self.create(*identifiers)
+      serializers = identifiers.map { |identifier| self.classify(identifier) }
+      serializers.count == 1 ? serializers.first : serializers
     end
 
-    raise "Invalid RestPack::Serializer : #{identifier}"
+    private
+
+    def self.classify(identifier)
+      normalised_identifier = identifier.to_s.underscore
+      [normalised_identifier, normalised_identifier.singularize].each do |format|
+        klass = RestPack::Serializer.class_map[format]
+        return klass.new if klass
+      end
+
+      raise UnknownSerializer.new("Unknown serializer class: #{identifier}")
+    end
   end
 end
diff --git a/lib/restpack_serializer/serializable.rb b/lib/restpack_serializer/serializable.rb
index 770b66b..fb66775 100644
--- a/lib/restpack_serializer/serializable.rb
+++ b/lib/restpack_serializer/serializable.rb
@@ -56,6 +56,10 @@ def as_json(model, context = {})
     def custom_attributes
       {}
     end
+    
+    def url
+      self.class.url
+    end
 
     private
 
@@ -69,7 +73,22 @@ def add_links(model, data)
         data[:links] ||= {}
         links_value = case
         when association.macro == :belongs_to
-          model.send(association.foreign_key).try(:to_s)
+          if association.polymorphic?
+            linked_id = model.send(association.foreign_key)
+                        .try(:to_s)
+            linked_type = model.send(association.foreign_type)
+                          .try(:to_s)
+                          .demodulize
+                          .underscore
+                          .pluralize
+            {
+              href: "/#{linked_type}/#{linked_id}",
+              id: linked_id,
+              type: linked_type
+            }
+          else
+            model.send(association.foreign_key).try(:to_s)
+          end
         when association.macro.to_s.match(/has_/)
           if model.send(association.name).loaded?
             model.send(association.name).collect { |associated| associated.id.to_s }
@@ -126,6 +145,11 @@ def singular_key
       def plural_key
         self.key
       end
+
+      def url(path=nil)
+        return @url || plural_key unless path
+        @url = path
+      end
     end
   end
 end
diff --git a/lib/restpack_serializer/serializable/paging.rb b/lib/restpack_serializer/serializable/paging.rb
index 9ad2f46..031988e 100644
--- a/lib/restpack_serializer/serializable/paging.rb
+++ b/lib/restpack_serializer/serializable/paging.rb
@@ -16,7 +16,11 @@ def page_with_options(options)
 
       if options.include_links
         result.links = self.links
-        Array(RestPack::Serializer::Factory.create(*options.include)).each do |serializer|
+        linkable_types = result.links.values.map { |link| link[:type].to_s }
+        includes = options.include.select do |include|
+          linkable_types.include?(include)
+        end
+        Array(RestPack::Serializer::Factory.create(*includes)).each do |serializer|
           result.links.merge! serializer.class.links
         end
       end
diff --git a/lib/restpack_serializer/serializable/side_load_data_builder.rb b/lib/restpack_serializer/serializable/side_load_data_builder.rb
index 495cfad..b24bc98 100644
--- a/lib/restpack_serializer/serializable/side_load_data_builder.rb
+++ b/lib/restpack_serializer/serializable/side_load_data_builder.rb
@@ -2,16 +2,17 @@ module RestPack
   module Serializer
     class SideLoadDataBuilder
 
-      def initialize(association, models, serializer)
+      def initialize(association, models)
         @association = association
         @models = models
-        @serializer = serializer
       end
 
       def side_load_belongs_to
         foreign_keys = @models.map { |model| model.send(@association.foreign_key) }.uniq.compact
         side_load = foreign_keys.any? ? @association.klass.find(foreign_keys) : []
-        json_model_data = side_load.map { |model| @serializer.as_json(model) }
+        json_model_data = side_load.map do |model|
+          model_serializer(model).as_json(model)
+        end
         { @association.plural_name.to_sym => json_model_data, meta: { } }
       end
 
@@ -43,9 +44,18 @@ def model_ids
         @models.map(&:id)
       end
 
+      def model_serializer(model)
+        serializer_type = if @association.polymorphic?
+          model.class.name
+        else
+          @association.class_name
+        end
+        RestPack::Serializer::Factory.create(serializer_type)
+      end
+
       def has_association_relation
         return {} if @models.empty?
-        serializer_class = @serializer.class
+        serializer_class = RestPack::Serializer::Factory.create(@association.class_name).class
         options = RestPack::Serializer::Options.new(serializer_class)
         yield options
         options.include_links = false
diff --git a/lib/restpack_serializer/serializable/side_loading.rb b/lib/restpack_serializer/serializable/side_loading.rb
index e5a1b12..c6b352b 100644
--- a/lib/restpack_serializer/serializable/side_loading.rb
+++ b/lib/restpack_serializer/serializable/side_loading.rb
@@ -19,24 +19,25 @@ def can_includes
     end
 
     def can_include(*includes)
+      @can_include_options = {}
+      @can_include_options = includes.last if includes.last.is_a?(Hash)
       @can_includes ||= []
-      @can_includes += includes
+      @can_includes += includes.flat_map do
+        |include| include.try(:keys)|| include
+      end
     end
 
     def links
       {}.tap do |links|
-        associations.each do |association|
-          if association.macro == :belongs_to
-            link_key = "#{self.key}.#{association.name}"
-            href = "/#{association.plural_name}/{#{link_key}}"
+        non_polymorphic_associations.each do |association|
+          link_key = if association.macro == :belongs_to
+            "#{key}.#{association.name}"
           elsif association.macro.to_s.match(/has_/)
-            singular_key = self.key.to_s.singularize
-            link_key = "#{self.key}.#{association.plural_name}"
-            href = "/#{association.plural_name}?#{singular_key}_id={#{key}.id}"
+            "#{key}.#{association.plural_name}"
           end
 
           links.merge!(link_key => {
-            :href => href_prefix + href,
+            :href => href_prefix + url_for_association(association),
             :type => association.plural_name.to_sym
             }
           )
@@ -53,13 +54,16 @@ def associations
 
     private
 
+    def non_polymorphic_associations
+      associations.select do |association|
+        !association.polymorphic?
+      end
+    end
+
     def side_load(include, models, options)
       association = association_from_include(include)
       return {} unless supported_association?(association.macro)
-      serializer = RestPack::Serializer::Factory.create(association.class_name)
-      builder = RestPack::Serializer::SideLoadDataBuilder.new(association,
-                                                              models,
-                                                              serializer)
+      builder = RestPack::Serializer::SideLoadDataBuilder.new(association,models)
       builder.send("side_load_#{association.macro}")
     end
 
@@ -92,5 +96,30 @@ def raise_invalid_include(include)
       raise RestPack::Serializer::InvalidInclude.new,
         ":#{include} is not a valid include for #{self.model_class}"
     end
+
+    def url_from_association(association)
+      serializer_from_association_class(association).url
+    end
+
+    def url_for_association(association)
+      identifier = if association.macro == :belongs_to
+        "/{#{key}.#{association.name}}"
+      else association.macro.to_s.match(/has_/)
+        param = can_include_options(association)[:param] || "#{singular_key}_id"
+        value = can_include_options(association)[:value] || "id"
+
+        "?#{param}={#{key}.#{value}}"
+      end
+
+      "/#{url_from_association(association)}#{identifier}"
+    end
+
+    def can_include_options(association)
+      @can_include_options.fetch(association.name.to_sym, {})
+    end
+
+    def serializer_from_association_class(association)
+      RestPack::Serializer::Factory.create(association.class_name)
+    end
   end
 end
diff --git a/spec/factory/factory_spec.rb b/spec/factory/factory_spec.rb
index c481200..0244e72 100644
--- a/spec/factory/factory_spec.rb
+++ b/spec/factory/factory_spec.rb
@@ -32,6 +32,7 @@
     it "creates multi-word string" do
       factory.create("AlbumReview").should be_an_instance_of(MyApp::AlbumReviewSerializer)
     end
+
     it "creates multi-word lowercase string" do
       factory.create("album_review").should be_an_instance_of(MyApp::AlbumReviewSerializer)
     end
@@ -46,4 +47,15 @@
     end
   end
 
+  describe "unknown serializer word" do
+
+    it "raises a custom exception" do
+      unknown_serializer_class = "UnknownModelType"
+      message = "Unknown serializer class: #{unknown_serializer_class}"
+      expect do
+        factory.create(unknown_serializer_class)
+      end.to raise_error(RestPack::Serializer::UnknownSerializer, message)
+    end
+  end
+
 end
diff --git a/spec/fixtures/db.rb b/spec/fixtures/db.rb
index be89b82..b73bf09 100644
--- a/spec/fixtures/db.rb
+++ b/spec/fixtures/db.rb
@@ -19,6 +19,7 @@
     t.string   "title"
     t.integer  "year"
     t.integer  "artist_id"
+    t.string "producer"
     t.datetime "created_at"
     t.datetime "updated_at"
   end
@@ -62,6 +63,17 @@
     t.integer :artist_id
     t.integer :stalker_id
   end
+
+  create_table "producers", force: true do |t|
+    t.string :name
+    t.string :album
+  end
+  
+  create_table "generic_metadata", force: true do |t|
+    t.integer :linked_id
+    t.string :linked_type
+    t.string :some_stuff_about_the_link
+  end
 end
 
 module MyApp
@@ -72,6 +84,8 @@ class Artist < ActiveRecord::Base
     has_many :songs
     has_many :payments
     has_many :fans, :through => :payments
+    has_many :generic_metadata, as: :linked
+    
     has_and_belongs_to_many :stalkers
   end
 
@@ -82,6 +96,8 @@ class Album < ActiveRecord::Base
     belongs_to :artist
     has_many :songs
     has_many :album_reviews
+    has_many :producers, foreign_key: :album
+    has_many :generic_metadata, as: :linked
   end
 
   class AlbumReview < ActiveRecord::Base
@@ -94,6 +110,7 @@ class Song < ActiveRecord::Base
 
     attr_accessible :title, :artist, :album
 
+    has_many :generic_metadata, as: :linked
     belongs_to :artist
     belongs_to :album
   end
@@ -108,6 +125,7 @@ class Payment < ActiveRecord::Base
   class Fan < ActiveRecord::Base
     attr_accessible :name
     has_many :payments
+    has_many :generic_metadata, as: :linked
     has_many :artists, :through => :albums
   end
 
@@ -115,4 +133,14 @@ class Stalker < ActiveRecord::Base
     attr_accessible :name
     has_and_belongs_to_many :artists
   end
+
+  class Producer < ActiveRecord::Base
+    attr_accessible :name
+    belongs_to :album, foreign_key: :album
+  end
+  
+  class GenericMetadatum < ActiveRecord::Base
+    attr_accessible :some_stuff_about_the_link
+    belongs_to :linked, polymorphic: true
+  end
 end
diff --git a/spec/fixtures/serializers.rb b/spec/fixtures/serializers.rb
index ff7e88a..828f0d5 100644
--- a/spec/fixtures/serializers.rb
+++ b/spec/fixtures/serializers.rb
@@ -2,7 +2,7 @@ module MyApp
   class SongSerializer
     include RestPack::Serializer
     attributes :id, :title, :album_id
-    can_include :albums, :artists
+    can_include :artists, :albums
     can_filter_by :title
     can_sort_by :id, :title
 
@@ -14,7 +14,7 @@ def title
   class AlbumSerializer
     include RestPack::Serializer
     attributes :id, :title, :year, :artist_id
-    can_include :artists, :songs
+    can_include :artists, :songs, producers: { param: "album", value: "title" }
     can_filter_by :year
   end
 
@@ -39,4 +39,15 @@ class StalkerSerializer
     include RestPack::Serializer
     attributes :id, :name
   end
+
+  class ProducerSerializer 
+    include RestPack::Serializer
+    attributes :id, :name
+  end
+  
+  class GenericMetadatumSerializer
+    include RestPack::Serializer
+    attributes :id, :some_stuff_about_the_link
+    can_include :linked
+  end
 end
diff --git a/spec/serializable/paging_spec.rb b/spec/serializable/paging_spec.rb
index 2eba6a2..108b1ec 100644
--- a/spec/serializable/paging_spec.rb
+++ b/spec/serializable/paging_spec.rb
@@ -175,6 +175,17 @@
           page[:links]['artists.albums'].should_not == nil
         end
       end
+
+      context "with an unknown include link" do
+        let(:params) { { include: "unknown_link" } }
+
+        it "raises an exception" do
+          message = ":unknown_link is not a valid include for MyApp::Song"
+          expect do
+            page[:links]
+          end.to raise_error(RestPack::Serializer::InvalidInclude, message)
+        end
+      end
     end
 
     context "when filtering" do
@@ -256,6 +267,17 @@
         page[:meta][:songs][:page_count].should == 6
       end
     end
+
+    context "with an unknown include link" do
+      let(:params) { { include: "unknown_link" } }
+
+      it "raises an exception" do
+        message = ":unknown_link is not a valid include for MyApp::Song"
+        expect do
+          page[:links]
+        end.to raise_error(RestPack::Serializer::InvalidInclude, message)
+      end
+    end
   end
 
   context "paging with paged side-load" do
diff --git a/spec/serializable/serializer_spec.rb b/spec/serializable/serializer_spec.rb
index aaa3e3a..8f956db 100644
--- a/spec/serializable/serializer_spec.rb
+++ b/spec/serializable/serializer_spec.rb
@@ -152,6 +152,23 @@ def custom_attributes
         end
       end
 
+      context "'belongs to polymorphic' associations" do
+        let(:serializer) { MyApp::GenericMetadatumSerializer.new }
+
+        it "includes a hash describe its polymorphic relationship" do
+          linked = FactoryGirl.create(:album)
+          datum = FactoryGirl.create(:generic_metadatum, linked: linked)
+          json = serializer.as_json(datum)
+          json[:links].should == {
+            linked: {
+              href: "/albums/#{linked.id}",
+              id: linked.id.to_s,
+              type: "albums"
+            }
+          }
+        end
+      end
+
       context "with a serializer with has_* associations" do
         let(:artist_factory) { FactoryGirl.create :artist_with_fans }
         let(:artist_serializer) { MyApp::ArtistSerializer.new }
diff --git a/spec/serializable/side_loading/side_loading_spec.rb b/spec/serializable/side_loading/side_loading_spec.rb
index ec890b5..26e8b4c 100644
--- a/spec/serializable/side_loading/side_loading_spec.rb
+++ b/spec/serializable/side_loading/side_loading_spec.rb
@@ -58,6 +58,10 @@ class CustomSerializer
       "albums.songs" => {
         :href => "/songs?album_id={albums.id}",
         :type => :songs
+      },
+      "albums.producers" => {
+        :href => "/producers?album={albums.title}",
+        :type => :producers
       }
     }
 
@@ -74,6 +78,16 @@ class CustomSerializer
       MyApp::AlbumSerializer.links["albums.artist"][:href].should == "/api/v2/artists/{albums.artist}"
       MyApp::AlbumSerializer.href_prefix = original
     end
+
+    it "applies a custom url to links" do
+      MyApp::ProducerSerializer.url("prods")
+      MyApp::AlbumSerializer.links["albums.producers"][:href].should == "/prods?album={albums.title}"
+      MyApp::ProducerSerializer.url("producers")
+    end
+    
+    it "should not include polymorphic belongs to" do
+      MyApp::GenericMetadatumSerializer.links.should == {}
+    end
   end
 
   describe "#filterable_by" do
diff --git a/spec/support/factory.rb b/spec/support/factory.rb
index 40d0f5e..90ac118 100644
--- a/spec/support/factory.rb
+++ b/spec/support/factory.rb
@@ -69,4 +69,8 @@
   factory :stalker, :class => MyApp::Stalker do
     sequence(:name) {|n| "Stalker ##{n}"}
   end
+
+  factory :generic_metadatum, :class => MyApp::GenericMetadatum do
+    some_stuff_about_the_link "Somethinge!"
+  end
 end