[STORE] Added the Serialize module

The repository uses two symmetric methods: `serialize` and `deserialize`
to convert documents when:

1. passing them to the storage,
2. initializing Ruby objects when retrieving documents from storage

Every repository can easily customize (overload) these methods,
to provide (de)serialization for complex use-cases, such as storing
PDF files or images in the storage.

See:

* https://www.braintreepayments.com/braintrust/untangle-domain-and-persistence-logic-with-curator
* https://github.com/braintree/curator/blob/master/lib/curator/repository.rb

Author: karmi

Diff for: elasticsearch-persistence/lib/elasticsearch/persistence.rb

@@ -6,6 +6,7 @@
 
 require 'elasticsearch/persistence/client'
 require 'elasticsearch/persistence/repository/naming'
+require 'elasticsearch/persistence/repository/serialize'
 require 'elasticsearch/persistence/repository'
 
 require 'elasticsearch/persistence/repository/class'

Diff for: elasticsearch-persistence/lib/elasticsearch/persistence/repository.rb

@@ -4,6 +4,7 @@ module Persistence
     module Repository
       include Elasticsearch::Persistence::Client
       include Elasticsearch::Persistence::Repository::Naming
+      include Elasticsearch::Persistence::Repository::Serialize
 
       def new(options={}, &block)
         Elasticsearch::Persistence::Repository::Class.new options, &block

Diff for: elasticsearch-persistence/lib/elasticsearch/persistence/repository/serialize.rb

@@ -0,0 +1,18 @@
+module Elasticsearch
+  module Persistence
+    module Repository
+
+      module Serialize
+        def serialize(document)
+          document.to_hash
+        end
+
+        def deserialize(document)
+          _klass = klass || __get_klass_from_type(document['_type'])
+          _klass.new document['_source']
+        end
+      end
+
+    end
+  end
+end

Diff for: elasticsearch-persistence/test/unit/repository_serialize_test.rb

@@ -0,0 +1,57 @@
+require 'test_helper'
+
+class Elasticsearch::Persistence::RepositorySerializeTest < Test::Unit::TestCase
+  context "The repository serialization" do
+    class DummyDocument
+      def to_hash
+        { foo: 'bar' }
+      end
+    end
+
+    class MyDocument; end
+
+    setup do
+      @shoulda_subject = Class.new() { include Elasticsearch::Persistence::Repository::Serialize }.new
+    end
+
+    context "serialize" do
+      should "call #to_hash on passed object" do
+        document = DummyDocument.new
+        assert_equal( { foo: 'bar' }, subject.serialize(document))
+      end
+    end
+
+    context "deserialize" do
+      should "get the class name from #klass" do
+        subject.expects(:klass)
+               .returns(MyDocument)
+
+        MyDocument.expects(:new)
+
+        subject.deserialize( {} )
+      end
+
+      should "get the class name from Elasticsearch _type" do
+        subject.expects(:klass)
+               .returns(nil)
+
+        subject.expects(:__get_klass_from_type)
+               .returns(MyDocument)
+
+        MyDocument.expects(:new)
+
+        subject.deserialize( {} )
+      end
+
+      should "create the class instance with _source attributes" do
+        subject.expects(:klass).returns(nil)
+
+        subject.expects(:__get_klass_from_type).returns(MyDocument)
+
+        MyDocument.expects(:new).with({ 'foo' => 'bar' })
+
+        subject.deserialize( {'_source' => { 'foo' => 'bar' } } )
+      end
+    end
+  end
+end