♻️ Extract Action Logic for improved composibility (#6644)

Prior to this commit, there was a precarity regarding the extensibility
of the create action for valkyrie objects.

The create method had several interacting objects, which made downstream
composibility harder to implement (without completely overriding the
action's behavior).  Downstream could:

1. Provide a different container for transactions
2. Inject additional steps into the transaction container, and those
   steps could require step args.
3. Remove/replace one of the transactions that has a step arg (which
   would then raise an error).

In all of these cases, the size of the original method makes for harder
downstream extensibility.

With this commit, I'm extracting an action object, putting forward a
minimum amount of work so we can discuss the approach.

This should be considered a noop change as I'm moving where the logic
happens.

If we deem that this is a good approach, I'd envision extracting some of
the work controller behavior specs into the given action.  I would also
anticipate extracting the update and delete actions.

Co-authored-by: Daniel Pierce <[email protected]>

app/controllers/concerns/hyrax/works_controller_behavior.rb

@@ -18,9 +18,12 @@ module WorksControllerBehavior
 
       class_attribute :_curation_concern_type, :show_presenter, :work_form_service, :search_builder_class
       class_attribute :iiif_manifest_builder, instance_accessor: false
+      class_attribute :create_valkyrie_work_action
+
       self.show_presenter = Hyrax::WorkShowPresenter
       self.work_form_service = Hyrax::WorkFormService
       self.search_builder_class = WorkSearchBuilder
+      self.create_valkyrie_work_action = Hyrax::Action::CreateValkyrieWork
       self.iiif_manifest_builder = nil
       attr_accessor :curation_concern
       helper_method :curation_concern, :contextual_path
@@ -187,20 +190,16 @@ def actor
     # rubocop:disable Metrics/MethodLength
     def create_valkyrie_work
       form = build_form
-      # fallback to an empty hash to avoid: # NoMethodError: undefined method `has_key?` for nil:NilClass
-      original_input_params_for_form = params[hash_key_for_curation_concern] ? params[hash_key_for_curation_concern] : {}
-      return after_create_error(form_err_msg(form), original_input_params_for_form) unless form.validate(original_input_params_for_form)
+      action = create_valkyrie_work_action.new(form: form,
+                                               transactions: transactions,
+                                               user: current_user,
+                                               params: params,
+                                               work_attributes_key: hash_key_for_curation_concern)
+
+      return after_create_error(form_err_msg(action.form), action.work_attributes) unless action.validate
+
+      result = action.perform
 
-      result =
-        transactions['change_set.create_work']
-        .with_step_args(
-          'work_resource.add_to_parent' => { parent_id: params[:parent_id], user: current_user },
-          'work_resource.add_file_sets' => { uploaded_files: uploaded_files, file_set_params: original_input_params_for_form[:file_set] },
-          'change_set.set_user_as_depositor' => { user: current_user },
-          'work_resource.change_depositor' => { user: ::User.find_by_user_key(form.on_behalf_of) },
-          'work_resource.save_acl' => { permissions_params: form.input_params["permissions"] }
-        )
-        .call(form)
       @curation_concern = result.value_or { return after_create_error(transaction_err_msg(result)) }
       after_create_response
     end

app/services/hyrax/action/create_valkyrie_work.rb

@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+module Hyrax
+  module Action
+    ##
+    # @since 5.0.0
+    # @api public
+    #
+    # Encapsulating the logic of several interacting objects.  Namely the idea of using a form to
+    # {#validate} given parameters then to {#perform} the action by leveraging the {#transactions}'s
+    # {#transaction_name} configured with appropriate {#step_args} and ultimately providing the
+    # {#form} to then perform that work.
+    class CreateValkyrieWork
+      ##
+      # @!group Class Attributes
+      #
+      # @!attribute transaction_name
+      #   @return [String] the name of the transaction that we call for the CreateValkyrieWorkAction.
+      class_attribute :transaction_name, default: 'change_set.create_work'
+      # @!endgroup Class Attributes
+      ##
+
+      ##
+      # @param form [Object] the form that we'll use for validation and performing the action.
+      # @param transactions [Hyrax::Transactions::Container] the transactions
+      # @param user [User] the person performing the action
+      # @param params [Hash] the contextual parameters for the action; ApplicationController#params
+      #        if you will.
+      # @param work_attribute_key [String] the name of the key within the params that contains
+      #        the work's attributes
+      def initialize(form:, transactions:, user:, params:, work_attributes_key:)
+        @form = form
+        @transactions = transactions
+        @user = user
+        @params = params
+        @work_attributes_key = work_attributes_key
+        @work_attributes = @params.fetch(work_attributes_key, {})
+      end
+
+      attr_reader :form, :transactions, :user, :parent_id, :work_attributes, :uploaded_files, :params, :work_attributes_key
+
+      ##
+      # @api public
+      # @return [TrueClass] when the object is valid.
+      # @return [FalseClass] when the object is valid.
+      def validate
+        form.validate(work_attributes)
+      end
+
+      ##
+      # @api public
+      # @return [#value_or] the resulting created work, when successful.  When not successful, the
+      #         returned value call the given block.
+      def perform
+        transactions[transaction_name].with_step_args(**step_args).call(form)
+      end
+
+      ##
+      # @api public
+      #
+      # @return [Hash<String,Hash>] the step args to use for the given {#transactions}'s
+      #         {.transaction_name}
+      def step_args
+        {
+          'work_resource.add_to_parent' => { parent_id: params[:parent_id], user: user },
+          'work_resource.add_file_sets' => { uploaded_files: uploaded_files, file_set_params: work_attributes[:file_set] },
+          'change_set.set_user_as_depositor' => { user: user },
+          'work_resource.change_depositor' => { user: ::User.find_by_user_key(form.on_behalf_of) },
+          'work_resource.save_acl' => { permissions_params: form.input_params["permissions"] }
+        }
+      end
+
+      # rubocop:disable Lint/DuplicateMethods
+      def uploaded_files
+        UploadedFile.find(params.fetch(:uploaded_files, []))
+      end
+      # rubocop:enable Lint/DuplicateMethods
+    end
+  end
+end