From 49317e2c110736db802d5a5c513c3438d723f789 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alberto=20Miedes=20Garc=C3=A9s?= <albertomg994@gmail.com>
Date: Tue, 8 Nov 2016 22:19:16 +0100
Subject: [PATCH] Added support for associations (WITHOUT PAGINATION)

---
 app/graph/exposable_association.rb |  8 ++++++
 app/graph/exposable_model.rb       | 27 +++++++++++-------
 app/graph/type_builder.rb          | 46 +++++++++++++++++++++++++-----
 3 files changed, 63 insertions(+), 18 deletions(-)
 create mode 100644 app/graph/exposable_association.rb

diff --git a/app/graph/exposable_association.rb b/app/graph/exposable_association.rb
new file mode 100644
index 000000000..78e650b0a
--- /dev/null
+++ b/app/graph/exposable_association.rb
@@ -0,0 +1,8 @@
+class ExposableAssociation
+  attr_reader :name, :type
+
+  def initialize(association)
+    @name = association.name
+    @type = association.macro # :has_one, :belongs_to or :has_many
+  end
+end
diff --git a/app/graph/exposable_model.rb b/app/graph/exposable_model.rb
index 9e4b228ad..22976c63d 100644
--- a/app/graph/exposable_model.rb
+++ b/app/graph/exposable_model.rb
@@ -1,30 +1,35 @@
 class ExposableModel
-  attr_reader :exposed_fields, :name, :description
+  attr_reader :name, :description, :exposed_fields, :exposed_associations
 
   def initialize(model_class, options = {})
-    @model_class = model_class
-    @filter_list = options[:filter_list] || []
     @name = model_class.name
     @description = model_class.model_name.human
+    @field_filter_list = options[:field_filter_list] || []
+    @assoc_filter_list = options[:assoc_filter_list] || []
     @filter_strategy = options[:filter_strategy]
-    set_exposed_fields
+    set_exposed_items(model_class)
   end
 
   private
 
-  # determine which model fields are exposed to the API
-  def set_exposed_fields
+  # determine which model fields and associations are exposed to the API
+  def set_exposed_items(model_class)
+    @exposed_fields = check_against_safety_list(model_class.columns, @field_filter_list)
+    @exposed_associations = check_against_safety_list(model_class.reflect_on_all_associations, @assoc_filter_list)
+  end
+
+  def check_against_safety_list(all_items, safety_list)
     case @filter_strategy
     when :whitelist
-      @exposed_fields = @model_class.columns.select do |column|
-        @filter_list.include? column.name
+      exposed_items = all_items.select do |column|
+        safety_list.include? column.name.to_s  # works for both symbols and strings
       end
     when :blacklist
-      @exposed_fields = @model_class.columns.select do |column|
-        !(@filter_list.include? column.name)
+      exposed_items = all_items.select do |column|
+        !(safety_list.include? column.name.to_s)
       end
     else
-      @exposed_fields = []
+      exposed_items = []
     end
   end
 
diff --git a/app/graph/type_builder.rb b/app/graph/type_builder.rb
index 7de5bfd23..1277f8746 100644
--- a/app/graph/type_builder.rb
+++ b/app/graph/type_builder.rb
@@ -1,5 +1,6 @@
 class TypeBuilder
   attr_reader :filter_strategy, :graphql_models
+  attr_accessor :graphql_types  # contains all generated GraphQL types
 
   def initialize(graphql_models, options = {})
     @graphql_models = graphql_models
@@ -31,14 +32,30 @@ private
     type_builder = self
 
     graphql_type = GraphQL::ObjectType.define do
-      em = ExposableModel.new(model_class, filter_strategy: type_builder.filter_strategy, filter_list: type_builder.graphql_models[model_class])
+      em = ExposableModel.new(
+        model_class,
+        filter_strategy: type_builder.filter_strategy,
+        field_filter_list: type_builder.graphql_models[model_class][:fields],
+        assoc_filter_list: type_builder.graphql_models[model_class][:associations]
+      )
 
       name(em.name)
       description(em.description)
 
       em.exposed_fields.each do |column|
         ef = ExposableField.new(column)
-        field(ef.name, ef.graphql_type)
+        field(ef.name, ef.graphql_type) # returns a GraphQL::Field
+      end
+
+      em.exposed_associations.each do |association|
+        ea = ExposableAssociation.new(association)
+        if ea.type.in? [:has_one, :belongs_to]
+          field(ea.name, -> { type_builder.graphql_types[association.klass] })
+        elsif ea.type.in? [:has_many]
+          field(ea.name, -> {
+            types[type_builder.graphql_types[association.klass]]
+          })
+        end
       end
     end
 
@@ -48,10 +65,25 @@ end
 
 graphql_models = {}
 
-graphql_models.store(User, ['id', 'username'])
-graphql_models.store(Proposal, ['id', 'title', 'description', 'author_id', 'created_at'])
-graphql_models.store(Debate, ['id', 'title', 'description', 'author_id', 'created_at'])
-graphql_models.store(Comment, ['id', 'commentable_id', 'commentable_type', 'body'])
-graphql_models.store(Geozone, ['id', 'name', 'html_map_coordinates'])
+graphql_models.store(User, {
+  fields: ['id', 'username'],
+  associations: ['proposals', 'debates']
+})
+graphql_models.store(Proposal, {
+  fields: ['id', 'title', 'description', 'author_id', 'created_at'],
+  associations: ['author']
+})
+graphql_models.store(Debate, {
+  fields: ['id', 'title', 'description', 'author_id', 'created_at'],
+  associations: ['author']
+})
+graphql_models.store(Comment, {
+  fields: ['id', 'commentable_id', 'commentable_type', 'body'],
+  associations: ['author']
+})
+graphql_models.store(Geozone, {
+  fields: ['id', 'name', 'html_map_coordinates'],
+  associations: []
+})
 
 TYPE_BUILDER = TypeBuilder.new(graphql_models, filter_strategy: :whitelist)