refactor(gallery): extract representation_url_for method

app/components/attachment/gallery_item_component/gallery_item_component.html.haml

@@ -2,7 +2,7 @@
   - if displayable_pdf?(blob)
     = link_to blob.url, id: blob.id, data: { iframe: true, src: blob.url }, class: 'gallery-link', type: blob.content_type, title: title do
       .thumbnail
-        = image_tag(preview_url_for(attachment), loading: :lazy)
+        = image_tag(representation_url_for(attachment), loading: :lazy)
         .fr-btn.fr-btn--tertiary.fr-btn--icon-left.fr-icon-eye{ role: :button }
           Visualiser
     .champ-libelle
@@ -12,13 +12,12 @@
   - elsif displayable_image?(blob)
     = link_to image_url(blob_url(attachment)), title: title, data: { src: blob.url }, class: 'gallery-link' do
       .thumbnail
-        = image_tag(variant_url_for(attachment), loading: :lazy)
+        = image_tag(representation_url_for(attachment), loading: :lazy)
         .fr-btn.fr-btn--tertiary.fr-btn--icon-left.fr-icon-eye{ role: :button }
           Visualiser
     .champ-libelle
       = libelle.truncate(25)
     = render Attachment::ShowComponent.new(attachment: attachment, truncate: true)
-
   - else
     .thumbnail
       = image_tag('apercu-indisponible.png')

app/helpers/gallery_helper.rb

@@ -9,6 +9,12 @@ module GalleryHelper
     blob.variable? && blob.content_type.in?(AUTHORIZED_IMAGE_TYPES)
   end
 
+  def representation_url_for(attachment)
+    return variant_url_for(attachment) if displayable_image?(attachment.blob)
+
+    preview_url_for(attachment) if displayable_pdf?(attachment.blob)
+  end
+
   def preview_url_for(attachment)
     preview = attachment.preview(resize_to_limit: [400, 400])
     preview.image.attached? ? preview.processed.url : 'pdf-placeholder.png'

spec/helpers/gallery_helper_spec.rb

@@ -74,4 +74,20 @@ RSpec.describe GalleryHelper, type: :helper do
       it { is_expected.to eq("pdf-placeholder.png") }
     end
   end
+
+  describe ".representation_url_for" do
+    subject { representation_url_for(attachment) }
+
+    context "when attachment is an image with no variant" do
+      let(:file) { fixture_file_upload('spec/fixtures/files/logo_test_procedure.png', 'image/png') }
+
+      it { is_expected.to eq("apercu-indisponible.png") }
+    end
+
+    context "when attachment is a pdf with no preview" do
+      let(:file) { fixture_file_upload('spec/fixtures/files/RIB.pdf', 'application/pdf') }
+
+      it { is_expected.to eq("pdf-placeholder.png") }
+    end
+  end
 end