Make interactors more step focused

Following a workshop with Ben we've been able to agree on an approach to
them that is quite focused on declarative steps.

This increases the readability of the call method, but does mean context
is set as a side effect of other methods. Hopefully that isn't too
confusing.

We've kept the delegates to context, they serve the purpose of reducing
context verbosity in the class and defining the available properties
that can be used when operating on the result.

We dropped the initialize with params and user. These were used as a
means to formalise the class interface but this is quite repetitive.

app/interactors/images/create_interactor.rb

@@ -9,35 +9,34 @@ class Images::CreateInteractor
            :issues,
            to: :context
 
-  def initialize(params:, user:)
-    super
-  end
-
   def call
     Edition.transaction do
-      context.edition = Edition.lock.find_current(document: params[:document])
-      check_for_issues(params[:image])
-
-      context.image_revision = upload_image(params[:image])
+      find_and_lock_edition
+      check_for_issues
+      create_image_revision
       update_edition
     end
   end
 
 private
 
-  def check_for_issues(image_params)
-    issues = Requirements::ImageUploadChecker.new(image_params).issues
+  def find_and_lock_edition
+    context.edition = Edition.lock.find_current(document: params[:document])
+  end
+
+  def check_for_issues
+    issues = Requirements::ImageUploadChecker.new(params[:image]).issues
     context.fail!(issues: issues) if issues.any?
   end
 
-  def upload_image(image_params)
-    ImageUploadService.new(image_params, edition.revision).call(user)
+  def create_image_revision
+    context.image_revision = ImageUploadService.new(params[:image], edition.revision)
+                                               .call(user)
   end
 
   def update_edition
-    Versioning::RevisionUpdater.new(edition.revision, user).tap do |updater|
-      updater.update_image(image_revision, false)
-      edition.assign_revision(updater.next_revision, user).save!
-    end
+    updater = Versioning::RevisionUpdater.new(edition.revision, user)
+    updater.update_image(image_revision, false)
+    edition.assign_revision(updater.next_revision, user).save!
   end
 end

app/interactors/images/destroy_interactor.rb

@@ -9,30 +9,29 @@ class Images::DestroyInteractor
            :removed_lead_image,
            to: :context
 
-  def initialize(params:, user:)
-    super
-  end
-
   def call
     Edition.transaction do
-      context.edition = Edition.lock.find_current(document: params[:document])
-      context.image_revision = edition.image_revisions.find_by!(image_id: params[:image_id])
-
-      updater = remove_image(image_revision)
+      find_and_lock_edition
+      find_and_remove_image
       create_timeline_entry
       update_preview
-
-      context.removed_lead_image = updater.removed_lead_image?
     end
   end
 
 private
 
-  def remove_image(image_revision)
-    Versioning::RevisionUpdater.new(edition.revision, user).tap do |updater|
-      updater.remove_image(image_revision)
-      edition.assign_revision(updater.next_revision, user).save!
-    end
+  def find_and_lock_edition
+    context.edition = Edition.lock.find_current(document: params[:document])
+  end
+
+  def find_and_remove_image
+    image_revision = edition.image_revisions.find_by!(image_id: params[:image_id])
+    updater = Versioning::RevisionUpdater.new(edition.revision, user)
+    updater.remove_image(image_revision)
+    edition.assign_revision(updater.next_revision, user).save!
+
+    context.image_revision = image_revision
+    context.removed_lead_image = updater.removed_lead_image?
   end
 
   def create_timeline_entry

app/interactors/images/update_crop_interactor.rb

@@ -6,31 +6,34 @@ class Images::UpdateCropInteractor
            :user,
            :edition,
            :image_revision,
+           :edition_updated,
            to: :context
 
-  def initialize(params:, user:)
-    super
-  end
-
   def call
     Edition.transaction do
-      context.edition = Edition.lock.find_current(document: params[:document])
+      find_and_lock_edition
+      find_and_update_image
 
-      updater = update_image(find_image_revision(params[:image_id]), crop_params)
+      update_edition
 
-      if updater.changed?
-        create_timeline_entry
-        update_preview
-      end
-
-      context.image_revision = updater.next_revision
+      create_timeline_entry
+      update_preview
     end
   end
 
 private
 
-  def find_image_revision(image_id)
-    edition.image_revisions.find_by!(image_id: image_id)
+  def find_and_lock_edition
+    context.edition = Edition.lock.find_current(document: params[:document])
+  end
+
+  def find_and_update_image
+    image_revision = edition.image_revisions.find_by!(image_id: params[:image_id])
+
+    updater = Versioning::ImageRevisionUpdater.new(image_revision, user)
+    updater.assign(crop_params)
+
+    context.image_revision = updater.next_revision
   end
 
   def crop_params
@@ -42,24 +45,24 @@ def crop_params
       .tap { |p| p[:crop_height] = (p[:crop_width].to_i * image_aspect_ratio).round }
   end
 
-  def update_image(image_revision, params)
-    Versioning::ImageRevisionUpdater.new(image_revision, user).tap do |updater|
-      updater.assign(params)
-      update_edition(updater.next_revision) if updater.changed?
-    end
-  end
-
-  def update_edition(image_revision)
+  def update_edition
     updater = Versioning::RevisionUpdater.new(edition.revision, user)
+
     updater.update_image(image_revision, false)
-    edition.assign_revision(updater.next_revision, user).save!
+    edition.assign_revision(updater.next_revision, user).save! if updater.changed?
+
+    context.edition_updated = updater.changed?
   end
 
   def create_timeline_entry
+    return unless edition_updated
+
     TimelineEntry.create_for_revision(entry_type: :image_updated, edition: edition)
   end
 
   def update_preview
+    return unless edition_updated
+
     PreviewService.new(edition).try_create_preview
   end
 end

app/interactors/images/update_interactor.rb

@@ -7,65 +7,62 @@ class Images::UpdateInteractor
            :edition,
            :image_revision,
            :issues,
+           :edition_updated,
            :selected_lead_image,
            :removed_lead_image,
            to: :context
 
-  def initialize(params:, user:)
-    super
-  end
-
   def call
     Edition.transaction do
-      context.edition = Edition.lock.find_current(document: params[:document])
-      context.image_revision = update_image_revision(image_params)
+      find_and_lock_edition
+      find_and_update_image
 
       check_for_issues
+      update_edition
 
-      updater = update_image(params[:lead_image] == "on")
-
-      context.selected_lead_image = updater.selected_lead_image?
-      context.removed_lead_image = updater.removed_lead_image?
-
-      if updater.changed?
-        create_timeline_entry
-        update_preview
-      end
+      create_timeline_entry
+      update_preview
     end
   end
 
 private
 
-  def update_image_revision(update_params)
+  def find_and_lock_edition
+    context.edition = Edition.lock.find_current(document: params[:document])
+  end
+
+  def find_and_update_image
     image_revision = edition.image_revisions.find_by!(image_id: params[:image_id])
+    image_params = params.require(:image_revision).permit(:caption, :alt_text, :credit)
+
     updater = Versioning::ImageRevisionUpdater.new(image_revision, user)
-    updater.assign(update_params)
-    updater.next_revision
-  end
+    updater.assign(image_params)
 
-  def image_params
-    params.require(:image_revision).permit(:caption, :alt_text, :credit)
+    context.image_revision = updater.next_revision
   end
 
   def check_for_issues
     checker = Requirements::ImageRevisionChecker.new(image_revision)
     issues = checker.pre_preview_metadata_issues
+
     context.fail!(issues: issues) if issues.any?
   end
 
-  def update_image(lead_image)
-    Versioning::RevisionUpdater.new(edition.revision, user).tap do |updater|
-      updater.update_image(image_revision, lead_image)
-      edition.assign_revision(updater.next_revision, user).save! if updater.changed?
-    end
-  end
+  def update_edition
+    is_lead_image = params[:lead_image] == "on"
+    updater = Versioning::RevisionUpdater.new(edition.revision, user)
 
-  def upload_image(image_params)
-    upload_service = ImageUploadService.new(image_params, context.edition.revision)
-    context.image_revision = upload_service.call(context.user)
+    updater.update_image(image_revision, is_lead_image)
+    edition.assign_revision(updater.next_revision, user).save! if updater.changed?
+
+    context.edition_updated = updater.changed?
+    context.selected_lead_image = updater.selected_lead_image?
+    context.removed_lead_image = updater.removed_lead_image?
   end
 
   def create_timeline_entry
+    return unless edition_updated
+
     timeline_entry_type = if selected_lead_image
                             :lead_image_selected
                           elsif removed_lead_image
@@ -78,6 +75,8 @@ def create_timeline_entry
   end
 
   def update_preview
+    return unless edition_updated
+
     PreviewService.new(edition).try_create_preview
   end
 end