Set the Content-Disposition header to trigger download with the file …

…name

.rubocop.yml

@@ -14,3 +14,6 @@ AllCops:
 
 Metrics/LineLength:
   Max: 120
+
+Metrics/AbcSize:
+  Max: 15.1

app/controllers/iiif_controller.rb

@@ -23,6 +23,8 @@ def show
     authorize! :read, @image
     expires_in 10.minutes, public: anonymous_ability.can?(:read, @image)
 
+    set_image_response_headers
+
     self.content_type = Mime::Type.lookup_by_extension(params[:format]).to_s
     self.response_body = @image.response
   end
@@ -64,6 +66,14 @@ def cache_headers
     }
   end
 
+  def set_image_response_headers
+    set_attachment_content_disposition_header if params[:download]
+  end
+
+  def set_attachment_content_disposition_header
+    response.headers['Content-Disposition'] = "attachment;filename=#{params[:identifier]}.#{params[:format]}"
+  end
+
   def load_image
     @image ||= StacksImage.new(image_params)
   end

spec/controllers/iiif_controller_spec.rb

@@ -7,13 +7,19 @@
   end
 
   describe '#show' do
+    let(:iiif_params) do
+      {
+        identifier: 'nr349ct7889%2Fnr349ct7889_00_0001',
+        region: '0,640,2552,2552',
+        size: '100,100',
+        rotation: '0',
+        quality: 'default',
+        format: 'jpg'
+      }
+    end
+
     subject do
-      get :show, identifier: 'nr349ct7889%2Fnr349ct7889_00_0001',
-                 region: '0,640,2552,2552',
-                 size: '100,100',
-                 rotation: '0',
-                 quality: 'default',
-                 format: 'jpg'
+      get :show, iiif_params
     end
 
     it 'loads the image' do
@@ -63,6 +69,18 @@
         end
       end
     end
+
+    context 'with the download flag set' do
+      subject { get :show, iiif_params.merge(download: true) }
+
+      it 'sets the content-disposition header to attachment' do
+        expect(subject.headers['Content-Disposition']).to start_with 'attachment'
+      end
+
+      it 'sets the preferred filename' do
+        expect(subject.headers['Content-Disposition']).to include 'filename=nr349ct7889%2Fnr349ct7889_00_0001.jpg'
+      end
+    end
   end
 
   describe '#metadata' do