🎁 Add Bulkrax.persistence_adapter

At present we have not incorporated using the
`Bulkrax.persistence_adapter` into the application.  It is instead put
forward for discussion and review.

lib/bulkrax.rb

@@ -35,6 +35,36 @@ class Configuration
                   :reserved_properties,
                   :server_name
 
+    attr_writer :persistence_adapter
+
+    ##
+    # Configure the persistence adapter used for persisting imported data.
+    #
+    # @return [Bulkrax::PersistenceLayer::AbstractAdapter]
+    # @see Bulkrax::PersistenceLayer
+    def persistence_adapter
+      @persistence_adapter || derived_persistence_adapter
+    end
+
+    def derived_persistence_adapter
+      if defined?(Hyrax)
+        # There's probably some configuration of Hyrax we could use to better refine this; but it's
+        # likely a reasonable guess.  The main goal is to not break existing implementations and
+        # maintain an upgrade path.
+        if Gem::Version.new(Hyrax::VERSION) >= Gem::Version.new('6.0.0')
+          Bulkrax::PersistenceLayer::ValkyrieAdapter
+        else
+          Bulkrax::PersistenceLayer::ActiveFedoraAdapter
+        end
+      elsif defined?(ActiveFedora)
+        Bulkrax::PersistenceLayer::ActiveFedoraAdapter
+      elsif defined?(Valkyrie)
+        Bulkrax::PersistenceLayer::ValkyrieAdapter
+      else
+        raise "Unable to derive a persistence adapter"
+      end
+    end
+
     attr_writer :use_locking
 
     def use_locking
@@ -81,6 +111,8 @@ def config
                  :object_factory=,
                  :parsers,
                  :parsers=,
+                 :persistence_adapter,
+                 :persistence_adapter=,
                  :qa_controlled_properties,
                  :qa_controlled_properties=,
                  :related_children_field_mapping,

lib/bulkrax/engine.rb

@@ -13,6 +13,12 @@ class Engine < ::Rails::Engine
       end
     end
 
+    initializer 'requires' do
+      require 'bulkrax/persistence_layer'
+      require 'bulkrax/persistence_layer/active_fedora_adapter' if defined?(ActiveFedora)
+      require 'bulkrax/persistence_layer/valkyrie_adapter' if defined?(Valkyrie)
+    end
+
     config.generators do |g|
       g.test_framework :rspec
       begin

lib/bulkrax/persistence_layer.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Bulkrax
+  ##
+  # The target data layer where we write and read our imported {Bulkrax::Entry} objects.
+  module PersistenceLayer
+    # We're inheriting from an ActiveRecord exception as that is something we know will be here; and
+    # something that the main_app will be expect to be able to handle.
+    class ObjectNotFoundError < ActiveRecord::RecordNotFound
+    end
+
+    # We're inheriting from an ActiveRecord exception as that is something we know will be here; and
+    # something that the main_app will be expect to be able to handle.
+    class RecordInvalid < ActiveRecord::RecordInvalid
+    end
+
+    class AbstractAdapter
+      # @see ActiveFedora::Base.find
+      def self.find(id)
+        raise NotImplementedError, "#{self}.#{__method__}"
+      end
+
+      def self.solr_name(field_name)
+        raise NotImplementedError, "#{self}.#{__method__}"
+      end
+
+      # @yield when Rails application is running in test environment.
+      def self.clean!
+        return true unless Rails.env.test?
+        yield
+      end
+
+      def self.query(q, **kwargs)
+        raise NotImplementedError, "#{self}.#{__method__}"
+      end
+    end
+  end
+end

lib/bulkrax/persistence_layer/active_fedora_adapter.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Bulkrax
+  module PersistenceLayer
+    class ActiveFedoraAdapter < AbstractAdapter
+      def self.find(id)
+        ActiveFedora::Base.find(id)
+      rescue ActiveFedora::ObjectNotFoundError => e
+        raise PersistenceLayer::RecordNotFound, e.message
+      end
+
+      def self.query(q, **kwargs)
+        ActiveFedora::SolrService.query(q, **kwargs)
+      end
+
+      def self.clean!
+        super do
+          ActiveFedora::Cleaner.clean!
+        end
+      end
+
+      def self.solr_name(field_name)
+        ActiveFedora.index_field_mapper.solr_name(field_name)
+      end
+    end
+  end
+end

lib/bulkrax/persistence_layer/valkyrie_adapter.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Bulkrax
+  module PersistenceLayer
+    class ValkyrieAdapter < AbstractAdapter
+    end
+  end
+end

spec/lib/bulkrax_spec.rb

@@ -197,4 +197,13 @@
       expect(returned_value).to eq("file")
     end
   end
+
+  context '.persistence_adapter' do
+    subject { described_class.persistence_adapter }
+    it { is_expected.to respond_to(:find) }
+    it { is_expected.to respond_to(:query) }
+    it { is_expected.to respond_to(:solr_name) }
+    it { is_expected.to respond_to(:clean!) }
+  end
+
 end