Refactor construct_graph_row_presenter to return negative values for x-offset and extract percentage method

app/presenters/construct_graph_row_presenter.rb

@@ -25,19 +25,7 @@ class ConstructGraphRowPresenter
   end
 
   def bar_width
-    percentage = (@score - zone.low_benchmark) / (zone.high_benchmark - zone.low_benchmark)
+    unrounded_bar_width.round
-    case zone.type
-    when :ideal
-      (percentage * ideal_zone_params.width + approval_zone_params.width).round
-    when :approval
-      (percentage * approval_zone_params.width).round
-    when :growth
-      (percentage * growth_zone_params.width).round
-    when :watch
-      (percentage * watch_zone_params.width + growth_zone_params.width).round
-    else
-      (percentage * warning_zone_params.width + watch_zone_params.width + growth_zone_params.width).round
-    end
   end
 
   def x_offset
@@ -45,12 +33,31 @@ class ConstructGraphRowPresenter
     when :ideal, :approval
       0
     else
-      bar_width
+      -1 * bar_width
     end
   end
 
   private
 
+  def unrounded_bar_width
+    case zone.type
+    when :ideal
+      percentage * ideal_zone_params.width + approval_zone_params.width
+    when :approval
+      percentage * approval_zone_params.width
+    when :growth
+      percentage * growth_zone_params.width
+    when :watch
+      percentage * watch_zone_params.width + growth_zone_params.width
+    else
+      percentage * warning_zone_params.width + watch_zone_params.width + growth_zone_params.width
+    end
+  end
+
+  def percentage
+    (@score - zone.low_benchmark) / (zone.high_benchmark - zone.low_benchmark)
+  end
+
   def zone
     @construct.zone_for_score(@score)
   end

app/views/dashboard/index.html.erb

@@ -47,7 +47,7 @@
 
     <svg id="construct-row-bars" x="25%" y=<%= heading_gutter %>>
       <%= @construct_graph_row_presenters.each_with_index do |presenter, index| %>
-        <rect class="construct-row-bar" x=<%= graph_center - presenter.x_offset %> y=<%= index * construct_row_height + (construct_row_height - construct_row_bar_height) / 2 %> width="<%= presenter.bar_width %>" height=<%= construct_row_bar_height %> fill=<%= presenter.bar_color %> />
+        <rect class="construct-row-bar" x=<%= graph_center + presenter.x_offset %> y=<%= index * construct_row_height + (construct_row_height - construct_row_bar_height) / 2 %> width="<%= presenter.bar_width %>" height=<%= construct_row_bar_height %> fill=<%= presenter.bar_color %> />
       <% end %>
     </svg>
   </g>

spec/presenters/construct_graph_row_presenter_spec.rb

@@ -77,7 +77,7 @@ RSpec.describe "construct graph row presenter" do
     end
 
     it('returns an x-offset equal to the bar width') do
-      expect(presenter.x_offset).to eq 29
+      expect(presenter.x_offset).to eq -29
     end
   end
 
@@ -95,7 +95,7 @@ RSpec.describe "construct graph row presenter" do
     end
 
     it('returns an x-offset equal to the bar width') do
-      expect(presenter.x_offset).to be > 0
+      expect(presenter.x_offset).to eq -216
     end
   end
 
@@ -113,7 +113,7 @@ RSpec.describe "construct graph row presenter" do
     end
 
     it('returns an x-offset equal to the bar width') do
-      expect(presenter.x_offset).to eq 424
+      expect(presenter.x_offset).to eq -424
     end
   end
 end