Updated model struct to include CSS density class

This information is provided via the TRMNL API which means we can now dynamically apply density for the model used.

Milestone: minor

Author: bkuhlmann

app/structs/model.rb

@@ -6,9 +6,10 @@ module Structs
     class Model < DB::Struct
       def css_classes
         size = css.dig "classes", "size"
+        density = css.dig "classes", "density"
 
         "screen screen--#{name} screen--#{bit_depth}bit screen--#{orientation} " \
-        "#{size} screen--1x".squeeze " "
+        "#{size} screen--1x #{density}".strip.squeeze " "
       end
 
       def orientation = rotation.zero? ? "landscape" : "portrait"

spec/app/structs/model_spec.rb

@@ -3,26 +3,39 @@
 require "hanami_helper"
 
 RSpec.describe Terminus::Structs::Model do
-  subject :model do
-    Factory.structs[
-      :model,
+  subject(:model) { Factory.structs[:model, **attributes] }
+
+  let :attributes do
+    {
       name: "test",
       label: "Test",
-      bit_depth: 2,
-      css: {"classes" => {"size" => "screen--lg"}}
-    ]
+      bit_depth: 4,
+      css: {"classes" => {"size" => "screen--lg", "density" => "screen--density-2x"}}
+    }
   end
 
   describe "#css_classes" do
     it "answers classes with full information" do
       expect(model.css_classes).to eq(
-        "screen screen--test screen--2bit screen--landscape screen--lg screen--1x"
+        "screen screen--test screen--4bit screen--landscape screen--lg " \
+        "screen--1x screen--density-2x"
       )
     end
 
-    it "answers classes with missing information" do
-      model = Factory.structs[:model, name: nil]
-      expect(model.css_classes).to eq("screen screen-- screen--bit screen--landscape screen--1x")
+    it "answers classes with missing values" do
+      attributes.merge! name: nil, bit_depth: nil
+
+      expect(model.css_classes).to eq(
+        "screen screen-- screen--bit screen--landscape screen--lg screen--1x screen--density-2x"
+      )
+    end
+
+    it "answers classes without model classes" do
+      attributes[:css].clear
+
+      expect(model.css_classes).to eq(
+        "screen screen--test screen--4bit screen--landscape screen--1x"
+      )
     end
   end