Add protection type image details to specialist document model

This is to get the images when the document type is
"protected_food_drink_name".

It might be worth separating this into a separate model and presenter.

app/models/specialist_document.rb

@@ -12,6 +12,12 @@ def initialize(content_store_response)
     @headers = headers_list(content_store_hash.dig("details", "headers"))
   end
 
+  def protection_type_image
+    return if protection_type.blank?
+
+    all_protection_type_images[protection_type]
+  end
+
 private
 
   def headers_list(headers)
@@ -31,4 +37,8 @@ def headers_list(headers)
       h
     end
   end
+
+  def all_protection_type_images
+    @all_protection_type_images ||= YAML.load_file(Rails.root.join("lib/data/specialist_documents/protected_food_drink_name/images.yaml"))
+  end
 end

lib/data/specialist_documents/protected_food_drink_name/images.yaml

@@ -0,0 +1,9 @@
+protected-designation-of-origin-pdo:
+  file_name: protected-designation-of-origin-pdo.png
+  alt_text_tag: pdo_alt_text
+protected-geographical-indication-pgi:
+  file_name: protected-geographical-indication-pgi.png
+  alt_text_tag: pgi_alt_text
+traditional-speciality-guaranteed-tsg:
+  file_name: traditional-speciality-guaranteed-tsg.png
+  alt_text_tag: tsg_alt_text

spec/models/specialist_document_spec.rb

@@ -66,4 +66,36 @@
       end
     end
   end
+
+  describe "protection type images" do
+    let(:content_store_response) { GovukSchemas::Example.find("specialist_document", example_name: "protected-food-drink-names") }
+
+    context "when a protection type exists and is known" do
+      it "gets the image details" do
+        content_store_response["details"]["metadata"]["protection_type"] = "protected-designation-of-origin-pdo"
+        expected = {
+          "file_name" => "protected-designation-of-origin-pdo.png",
+          "alt_text_tag" => "pdo_alt_text",
+        }
+
+        expect(described_class.new(content_store_response).protection_type_image).to eq(expected)
+      end
+    end
+
+    context "when a protection type exists but is not recognised" do
+      it "returns nil" do
+        content_store_response["details"]["metadata"]["protection_type"] = "fake-type"
+
+        expect(described_class.new(content_store_response).protection_type_image).to be_nil
+      end
+    end
+
+    context "when a protection type does not exist" do
+      it "returns nil" do
+        content_store_response["details"]["metadata"]["protection_type"] = nil
+
+        expect(described_class.new(content_store_response).protection_type_image).to be_nil
+      end
+    end
+  end
 end