Added File.metadata to define metadata properties

This writes the properties to ./fcr:metadata relative to the files URI
Fixes #499

lib/active_fedora.rb

@@ -105,6 +105,7 @@ class Rollback < RuntimeError; end # :nodoc:
     autoload :Predicates
     autoload :Validations
     autoload :Versionable
+    autoload :WithMetadata
   end
 
   module AttributeMethods

lib/active_fedora/with_metadata.rb

@@ -0,0 +1,99 @@
+module ActiveFedora
+  module WithMetadata
+    extend ActiveSupport::Concern
+
+    def metadata_node
+      @metadata_node ||= self.class.metadata_schema.new(self)
+    end
+
+    def save(*)
+      if super
+        metadata_node.metadata_uri = described_by # TODO only necessary if the URI was < > before
+        metadata_node.save # TODO if changed?
+      end
+    end
+
+    module ClassMethods
+      def metadata(&block)
+        metadata_schema.exec_block(&block)
+      end
+
+      def metadata_schema
+        @metadata_schema ||= MetadataNode(self)
+      end
+
+      def MetadataNode(parent_klass)
+        klass = self.const_set(:GeneratedMetadataSchema, Class.new(MetadataNode))
+        klass.parent_class = parent_klass
+        klass
+      end
+    end
+
+    class MetadataNode < ActiveTriples::Resource
+      include ActiveModel::Dirty
+      attr_reader :file
+
+      def initialize(file)
+        @file = file
+        super(file.uri, ldp_source.graph)
+      end
+
+      def metadata_uri= uri
+        @metadata_uri = uri
+      end
+
+      def metadata_uri
+        @metadata_uri ||= if file.new_record?
+          RDF::URI.new nil
+        else
+          raise "#{file} must respond_to described_by" unless file.respond_to? :described_by
+          file.described_by
+        end
+      end
+
+      def set_value(*args)
+        super
+        attribute_will_change! args.first
+      end
+
+      def self.parent_class= parent
+        @parent_class = parent
+      end
+
+      def self.parent_class
+        @parent_class
+      end
+
+      def self.property(name, options)
+        parent_class.delegate name, :"#{name}=", :"#{name}_changed?", to: :metadata_node
+        super
+      end
+
+      def self.create_delegating_setter(name)
+        file.class.delegate(name, to: :metadata_node)
+      end
+
+      def ldp_source
+        @ldp_source ||= LdpResource.new(ldp_connection, metadata_uri)
+      end
+
+      def ldp_connection
+        ActiveFedora.fedora.connection
+      end
+
+      def save
+        raise "Save the file first" if file.new_record?
+        change_set = ChangeSet.new(self, self, changed_attributes.keys)
+        SparqlInsert.new(change_set.changes, RDF::URI.new(file.uri)).execute(metadata_uri)
+        @ldp_source = nil
+        true
+      end
+
+      def self.exec_block(&block)
+        class_eval &block
+      end
+
+    end
+
+  end
+end

spec/integration/with_metadata_spec.rb

@@ -0,0 +1,52 @@
+require 'spec_helper'
+
+describe ActiveFedora::WithMetadata do
+  before do
+    class Sample < ActiveFedora::Base
+      contains :file, class_name: 'SampleFile'
+    end
+
+    class SampleFile < ActiveFedora::File
+      include ActiveFedora::WithMetadata
+
+      metadata do
+        property :title, predicate: RDF::DC.title
+      end
+    end
+  end
+
+  after do
+    Object.send(:remove_const, :SampleFile)
+    Object.send(:remove_const, :Sample)
+  end
+
+  let(:base) { Sample.new }
+  let(:file) { base.file }
+
+  describe "properties" do
+    before do
+      file.title = ['one', 'two']
+    end
+    it "should set and retrieve properties" do
+      expect(file.title).to eq ['one', 'two']
+    end
+
+    it "should track changes" do
+      expect(file.title_changed?).to be true
+    end
+  end
+
+  describe "#save" do
+    before do
+      file.content = "Hey"
+      file.title = ["foo"]
+      base.save
+      base.reload
+    end
+
+    it "should save the metadata too" do
+      expect(base.file.title).to eq ['foo']
+    end
+  end
+
+end