Refactor ImagesController using interactor pattern

This demonstrates a demo of how the ImagesController could work using
the interactor gem.

There were some small changes I made here compared to the existing code:

1. We no longer preview on image creation. There isn't any point doing
   this as it won't succeed - as initial image is invalid
2. We round the number as part of cropping an image. This saves this
   frequently being off by 1 pixel, fixing this made tests easier.

app/controllers/images_controller.rb

@@ -7,28 +7,21 @@ def index
   end
 
   def create
-    Edition.find_and_lock_current(document: params[:document]) do |edition|
-      @issues = ::Requirements::ImageUploadChecker.new(params[:image]).issues
-
-      if @issues.any?
-        flash.now["alert_with_items"] = {
-          "title" => I18n.t!("images.index.flashes.upload_requirements"),
-          "items" => @issues.items,
-        }
-
-        render :index,
-               assigns: { edition: edition },
-               layout: rendering_context,
-               status: :unprocessable_entity
-        next
-      end
-
-      image_revision = ImageUploadService.new(params[:image], edition.revision).call(current_user)
-      updater = Versioning::RevisionUpdater.new(edition.revision, current_user)
-      updater.update_image(image_revision)
-      edition.assign_revision(updater.next_revision, current_user).save!
-      PreviewService.new(edition).try_create_preview
-      redirect_to crop_image_path(params[:document], image_revision.image_id, wizard: "upload")
+    result = Images::Create.call(params: params, user: current_user)
+    if result.failure?
+      flash.now["alert_with_items"] = {
+        "title" => I18n.t!("images.index.flashes.upload_requirements"),
+        "items" => result.issues.items,
+      }
+
+      render :index,
+             assigns: { edition: result.edition },
+             layout: rendering_context,
+             status: :unprocessable_entity
+    else
+      redirect_to crop_image_path(result.edition.document,
+                                  result.image_revision.image_id,
+                                  wizard: "upload")
     end
   end
 
@@ -39,21 +32,10 @@ def crop
   end
 
   def update_crop
-    Edition.find_and_lock_current(document: params[:document]) do |edition|
-      image_revision = edition.image_revisions.find_by!(image_id: params[:image_id])
-      image_updater = Versioning::ImageRevisionUpdater.new(image_revision, current_user)
-      image_updater.assign(update_crop_params)
-
-      if image_updater.changed?
-        updater = Versioning::RevisionUpdater.new(edition.revision, current_user)
-        updater.update_image(image_updater.next_revision)
-        edition.assign_revision(updater.next_revision, current_user).save!
-        TimelineEntry.create_for_revision(entry_type: :image_updated, edition: edition)
-        PreviewService.new(edition).try_create_preview
-      end
-
-      redirect_to edit_image_path(edition.document, image_revision.image_id, wizard: params[:wizard])
-    end
+    result = Images::UpdateCrop.call(params: params, user: current_user)
+    redirect_to edit_image_path(result.edition.document,
+                                result.image_revision.image_id,
+                                wizard: params[:wizard])
   end
 
   def edit
@@ -63,80 +45,49 @@ def edit
   end
 
   def update
-    Edition.find_and_lock_current(document: params[:document]) do |edition| # rubocop:disable Metrics/BlockLength
-      image_revision = edition.image_revisions.find_by!(image_id: params[:image_id])
-      image_updater = Versioning::ImageRevisionUpdater.new(image_revision, current_user)
-
-      image_updater.assign(update_params)
-      next_image_revision = image_updater.next_revision
-
-      issues = Requirements::ImageRevisionChecker.new(next_image_revision)
-                                                 .pre_preview_metadata_issues
-
-      if issues.any?
-        flash.now["alert_with_items"] = {
-          "title" => I18n.t!("images.edit.flashes.requirements"),
-          "items" => issues.items,
-        }
-
-        render :edit,
-               assigns: { edition: edition, image_revision: next_image_revision, issues: issues },
-               layout: rendering_context,
-               status: :unprocessable_entity
-        next
-      end
-
-      updater = Versioning::RevisionUpdater.new(edition.revision, current_user)
-      updater.update_image(next_image_revision, params[:lead_image] == "on")
-
-      if updater.changed?
-        timeline_entry_type = if updater.selected_lead_image?
-                                :lead_image_selected
-                              elsif updater.removed_lead_image?
-                                :lead_image_removed
-                              else
-                                :image_updated
-                              end
-
-        TimelineEntry.create_for_revision(entry_type: timeline_entry_type, edition: edition)
-        edition.assign_revision(updater.next_revision, current_user).save!
-        PreviewService.new(edition).try_create_preview
-      end
-
-      if updater.selected_lead_image?
-        redirect_to document_path(edition.document),
+    result = Images::Update.call(params: params, user: current_user)
+
+    if result.failure?
+      flash.now["alert_with_items"] = {
+        "title" => I18n.t!("images.edit.flashes.requirements"),
+        "items" => result.issues.items,
+      }
+
+      render :edit,
+             assigns: { edition: result.edition,
+                        image_revision: result.image_revision,
+                        issues: result.issues },
+             layout: rendering_context,
+             status: :unprocessable_entity
+    else
+      document = result.edition.document
+
+      if result.updater.selected_lead_image?
+        redirect_to document_path(document),
                     notice: t("documents.show.flashes.lead_image.selected",
-                              file: image_revision.filename)
-      elsif updater.removed_lead_image?
-        redirect_to images_path(edition.document),
+                              file: result.image_revision.filename)
+      elsif result.updater.removed_lead_image?
+        redirect_to images_path(document),
                     notice: t("images.index.flashes.lead_image.removed",
-                              file: image_revision.filename)
+                              file: result.image_revision.filename)
       else
-        redirect_to images_path(edition.document)
+        redirect_to images_path(document)
       end
     end
   end
 
   def destroy
-    Edition.find_and_lock_current(document: params[:document]) do |edition|
-      image_revision = edition.image_revisions.find_by!(image_id: params[:image_id])
-      updater = Versioning::RevisionUpdater.new(edition.revision, current_user)
-
-      updater.remove_image(image_revision)
-      edition.assign_revision(updater.next_revision, current_user).save!
-
-      TimelineEntry.create_for_revision(entry_type: :image_deleted, edition: edition)
-      PreviewService.new(edition).try_create_preview
-
-      if updater.removed_lead_image?
-        redirect_to images_path(edition.document),
-                    notice: t("images.index.flashes.lead_image.deleted",
-                              file: image_revision.filename)
-      else
-        redirect_to images_path(edition.document),
-                    notice: t("images.index.flashes.deleted",
-                              file: image_revision.filename)
-      end
+    result = Images::Destroy.call(params: params, user: current_user)
+    document = result.edition.document
+
+    if result.updater.removed_lead_image?
+      redirect_to images_path(document),
+                  notice: t("images.index.flashes.lead_image.deleted",
+                            file: result.image_revision.filename)
+    else
+      redirect_to images_path(document),
+                  notice: t("images.index.flashes.deleted",
+                            file: result.image_revision.filename)
     end
   end
 
@@ -151,19 +102,4 @@ def download
       type: image_revision.content_type,
     )
   end
-
-private
-
-  def update_params
-    params.require(:image_revision).permit(:caption, :alt_text, :credit)
-  end
-
-  def update_crop_params
-    image_aspect_ratio = Image::HEIGHT.to_f / Image::WIDTH
-
-    params
-      .require(:image_revision)
-      .permit(:crop_x, :crop_y, :crop_width, :crop_width)
-      .tap { |p| p[:crop_height] = (p[:crop_width].to_i * image_aspect_ratio).round }
-  end
 end

app/interactors/images/create.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+class Images::Create
+  include Interactor
+  delegate :params, :user, to: :context
+
+  def initialize(params:, user:)
+    super
+  end
+
+  def call
+    Edition.find_and_lock_current(document: params[:document]) do |edition|
+      check_issues(edition, params[:image])
+      image_revision = upload_image(edition, params[:image])
+      update_edition(edition, image_revision)
+      update_context(edition: edition, image_revision: image_revision)
+    end
+  end
+
+private
+
+  def check_issues(edition, image_params)
+    issues = Requirements::ImageUploadChecker.new(image_params).issues
+    context.fail!(edition: edition, issues: issues) if issues.any?
+  end
+
+  def upload_image(edition, image_params)
+    ImageUploadService.new(image_params, edition.revision).call(user)
+  end
+
+  def update_edition(edition, image_revision)
+    updater = Versioning::RevisionUpdater.new(edition.revision, user)
+    updater.update_image(image_revision, false)
+    edition.assign_revision(updater.next_revision, user).save!
+  end
+
+  def update_context(attributes)
+    attributes.each { |k, v| context[k.to_sym] = v }
+  end
+end

app/interactors/images/destroy.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+class Images::Destroy
+  include Interactor
+  delegate :params, :user, to: :context
+
+  def initialize(params:, user:)
+    super
+  end
+
+  def call
+    Edition.find_and_lock_current(document: params[:document]) do |edition|
+      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!
+
+      TimelineEntry.create_for_revision(entry_type: :image_deleted,
+                                        edition: edition)
+      PreviewService.new(edition).try_create_preview
+
+      update_context(edition: edition,
+                     image_revision: image_revision,
+                     updater: updater)
+    end
+  end
+
+private
+
+  def update_context(attributes)
+    attributes.each { |k, v| context[k.to_sym] = v }
+  end
+end

app/interactors/images/update.rb

@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+class Images::Update
+  include Interactor
+  delegate :params, :user, to: :context
+
+  def initialize(params:, user:)
+    super
+  end
+
+  def call
+    Edition.find_and_lock_current(document: params[:document]) do |edition|
+      image_revision = update_image_revision(edition, image_params)
+      check_issues(edition, image_revision)
+
+      updater = Versioning::RevisionUpdater.new(edition.revision, user)
+      updater.update_image(image_revision, params[:lead_image] == "on")
+
+      if updater.changed?
+        create_timeline_entry(edition, updater)
+        edition.assign_revision(updater.next_revision, user).save!
+        PreviewService.new(edition).try_create_preview
+      end
+
+      update_context(edition: edition,
+                     image_revision: image_revision,
+                     updater: updater)
+    end
+  end
+
+private
+
+  def update_image_revision(edition, update_params)
+    image_revision = edition.image_revisions.find_by!(image_id: params[:image_id])
+    updater = Versioning::ImageRevisionUpdater.new(image_revision, user)
+    updater.assign(update_params)
+    updater.next_revision
+  end
+
+  def image_params
+    params.require(:image_revision).permit(:caption, :alt_text, :credit)
+  end
+
+  def check_issues(edition, image_revision)
+    checker = Requirements::ImageRevisionChecker.new(image_revision)
+    issues = checker.pre_preview_metadata_issues
+    if issues.any?
+      context.fail!(edition: edition,
+                    image_revision: image_revision,
+                    issues: issues)
+    end
+  end
+
+  def upload_image(image_params)
+    upload_service = ImageUploadService.new(image_params, context.edition.revision)
+    context.image_revision = upload_service.call(context.user)
+  end
+
+  def update_edition
+    updater = Versioning::RevisionUpdater.new(context.edition.revision,
+                                              context.user)
+
+    updater.update_image(context.image_revision, false)
+    context.edition.assign_revision(updater.next_revision, context.user).save!
+  end
+
+  def create_timeline_entry(edition, updater)
+    timeline_entry_type = if updater.selected_lead_image?
+                            :lead_image_selected
+                          elsif updater.removed_lead_image?
+                            :lead_image_removed
+                          else
+                            :image_updated
+                          end
+
+    TimelineEntry.create_for_revision(entry_type: timeline_entry_type, edition: edition)
+  end
+
+  def update_context(attributes)
+    attributes.each { |k, v| context[k.to_sym] = v }
+  end
+end