Add HasOne Association

.rubocop.yml

@@ -11,10 +11,21 @@ Style/ClassAndModuleChildren:
 
 Metrics/LineLength:
   Max: 100
+  Exclude:
+    - spec/**/*.rb
+    - examples/**/*.rb
 
 Metrics/MethodLength:
   Max: 25
 
 Metrics/AbcSize:
   Max: 25
 
+Metrics/BlockLength:
+  Max: 100
+  Exclude:
+    - spec/pdc/**/*.rb
+    - examples/**/*.rb
+
+Naming/PredicateName:
+  Enabled: false

lib/pdc/base.rb

@@ -7,6 +7,7 @@ class Base
     include PDC::Resource::Attributes
     include PDC::Resource::Scopes
     include PDC::Resource::RestApi
+    include PDC::Resource::Associations
 
     scope :page, ->(value) { where(page: value) }
     scope :page_size, ->(value) { where(page_size: value) }

lib/pdc/resource.rb

@@ -10,3 +10,4 @@
 require 'pdc/resource/relation'
 require 'pdc/resource/rest_api'
 require 'pdc/resource/wip'
+require 'pdc/resource/associations'

lib/pdc/resource/associations.rb

@@ -0,0 +1,44 @@
+require 'pdc/resource/associations/has_many'
+require 'pdc/resource/associations/association'
+require 'pdc/resource/associations/builder'
+require 'pdc/resource/associations/has_one'
+
+module PDC::Resource
+  module Associations
+    extend ActiveSupport::Concern
+
+    included do
+      class_attribute :associations
+      self.associations = {}.freeze
+    end
+
+    module ClassMethods
+      def has_many(name, options = {})
+        create_association(name, HasMany, options)
+
+        define_method "#{name.to_s.singularize}_ids=" do |ids|
+          attributes[name] = []
+          ids.reject(&:blank?).each { |id| association(name).build(id: id) }
+        end
+
+        define_method "#{name.to_s.singularize}_ids" do
+          association(name).map(&:id)
+        end
+      end
+
+      def has_one(name, options = {})
+        create_association(name, HasOne, options)
+
+        define_method "build_#{name}" do |attributes = nil|
+          association(name).build(attributes)
+        end
+      end
+
+      private
+
+      def create_association(name, type, options)
+        self.associations = associations.merge(name => Builder.new(self, name, type, options))
+      end
+    end
+  end
+end

lib/pdc/resource/associations/association.rb

@@ -0,0 +1,25 @@
+require 'pdc/resource/relation'
+
+module PDC::Resource
+  module Associations
+    class Association < Relation
+      attr_reader :parent, :name
+
+      def initialize(klass, parent, name, options = {})
+        super(klass, options)
+        @parent = parent
+        @name = name
+      end
+
+      def load
+        find_one! # Override for plural associations that return an association object
+      end
+
+      private
+
+      def foreign_key
+        (@options[:foreign_key] || "#{parent.class.model_name.element}_id").to_sym
+      end
+    end
+  end
+end

lib/pdc/resource/associations/builder.rb

@@ -0,0 +1,44 @@
+require 'active_support/dependencies'
+
+module PDC::Resource
+  module Associations
+    class Builder
+      def initialize(parent_class, name, type, options = {})
+        @parent_class = parent_class
+        @name = name
+        @type = type
+        @options = options
+      end
+
+      def build(parent)
+        @type.new(klass, parent, @name, @options)
+      end
+
+      def klass
+        @klass ||= custom_class || compute_class(@name)
+      end
+
+      private
+
+      def custom_class
+        @options[:class_name].constantize if @options[:class_name]
+      end
+
+      # https://github.com/rails/rails/blob/70ac072976c8cc6f013f0df3777e54ccae3f4f8c/activerecord/lib/active_record/inheritance.rb#L132-L150
+      def compute_class(type_name)
+        parent_name = @parent_class.to_s
+        type_name = type_name.to_s.classify
+
+        candidates = []
+        parent_name.scan(/::|$/) { candidates.unshift "#{$`}::#{type_name}" }
+        candidates << type_name
+
+        candidates.each do |candidate|
+          constant = ActiveSupport::Dependencies.safe_constantize(candidate)
+          return constant if candidate == constant.to_s
+        end
+        raise NameError.new("uninitialized constant #{candidates.first}", candidates.first)
+      end
+    end
+  end
+end

lib/pdc/resource/associations/has_many.rb

@@ -0,0 +1,23 @@
+require 'pdc/resource/associations/association'
+
+module PDC::Resource
+  module Associations
+    class HasMany < Association
+      def initialize(*args)
+        super
+        @options.reverse_merge!(uri: "#{parent_path}/:#{foreign_key}/#{@name}/(:#{primary_key})")
+        @params[foreign_key] = parent.id
+      end
+
+      def load
+        self
+      end
+
+      private
+
+      def parent_path
+        parent.class.model_name.element.pluralize
+      end
+    end
+  end
+end

lib/pdc/resource/associations/has_one.rb

@@ -0,0 +1,29 @@
+module PDC::Resource
+  module Associations
+    class HasOne < Association
+      def initialize(*args)
+        super
+        @options.reverse_merge!(uri: "#{parent.class.model_name.plural}/:#{foreign_key}/#{@name}")
+        collect_params
+      end
+
+      def collect_params
+        p_mapping = parent.class.mapping
+        s_foreign_key = foreign_key.to_s
+        if s_foreign_key.include? '/'
+          s_foreign_key.split('/').each do |fk|
+            p_mapping_value = p_mapping[fk.to_sym]
+            @params[fk] =
+              if p_mapping && p_mapping_value
+                parent.attributes[p_mapping_value.to_sym]
+              else
+                parent.attributes[fk]
+              end
+          end
+        else
+          @params[foreign_key] = parent.id
+        end
+      end
+    end
+  end
+end

lib/pdc/resource/attributes.rb

@@ -90,15 +90,24 @@ def use_setters(attributes)
     end
 
     def method_missing(name, *args, &block)
-      if attribute?(name) then attribute(name)
+      if association?(name) then association(name).load
+      elsif attribute?(name) then attribute(name)
       elsif predicate?(name)   then predicate(name)
       elsif setter?(name)      then set_attribute(name, args.first)
       else super
       end
     end
 
     def respond_to_missing?(name, include_private = false)
-      attribute?(name) || predicate?(name) || setter?(name) || super
+      association?(name) || attribute?(name) || predicate?(name) || setter?(name) || super
+    end
+
+    def association?(name)
+      associations.key?(name)
+    end
+
+    def association(name)
+      associations[name].build(self)
     end
 
     def attribute?(name)

lib/pdc/resource/identity.rb

@@ -24,6 +24,14 @@ def resource_path
         @resource_path ||= model_name.collection.sub(%r{^pdc\/}, '').tr('_', '-')
       end
 
+      def mapping
+        @mapping || {}
+      end
+
+      def mapping=(mapping = {})
+        @mapping = mapping
+      end
+
       private
 
       def default_uri

lib/pdc/resource/relation.rb

@@ -12,6 +12,7 @@ class Relation
 
     attr_reader :klass
     attr_writer :params
+    delegate :to_ary, :[], :any?, :empty?, :last, :size, :metadata, to: :contents!
 
     alias all to_a