Remove boring empty trailing lines from thumbnails

app/decorators/asciicast_decorator.rb

@@ -36,7 +36,7 @@ class AsciicastDecorator < ApplicationDecorator
 
   def thumbnail(width = THUMBNAIL_WIDTH, height = THUMBNAIL_HEIGHT)
     snapshot = Snapshot.build(model.snapshot || [])
-    thumbnail = snapshot.crop(width, height)
+    thumbnail = snapshot.rstrip.crop(width, height).expand(height)
     SnapshotPresenter.new(thumbnail).to_html
   end
 

app/models/snapshot.rb

@@ -21,6 +21,24 @@ class Snapshot
     min_height = [height, lines.size].min
     new_lines = lines.drop(lines.size - min_height).map { |line| line.crop(width) }
 
+    self.class.new(new_lines)
+  end
+
+  def rstrip
+    i = lines.size - 1
+
+    while i >= 0 && lines[i].empty?
+      i -= 1
+    end
+
+    new_lines = i > -1 ? lines[0..i] : []
+
+    self.class.new(new_lines)
+  end
+
+  def expand(height)
+    new_lines = lines
+
     while new_lines.size < height
       new_lines << []
     end

app/models/snapshot_fragment.rb

@@ -21,4 +21,8 @@ class SnapshotFragment # TODO: rename to Cell or SnapshotCell
     end
   end
 
+  def empty?
+    text.blank? && brush.default?
+  end
+
 end

app/models/snapshot_line.rb

@@ -37,6 +37,10 @@ class SnapshotLine
     self.class.new(new_fragments)
   end
 
+  def empty?
+    fragments.all?(&:empty?)
+  end
+
   protected
 
   attr_reader :fragments

spec/decorators/asciicast_decorator_spec.rb

@@ -135,14 +135,22 @@ describe AsciicastDecorator do
 
   describe '#thumbnail' do
     let(:json) { [:qux] }
-    let(:snapshot) { double('snapshot', :crop => thumbnail) }
+    let(:snapshot) { double('snapshot') }
-    let(:thumbnail) { double('thumbnail') }
     let(:snapshot_presenter) { double('snapshot_presenter', :to_html => '<pre></pre>') }
 
     before do
       allow(asciicast).to receive(:snapshot) { json }
       allow(Snapshot).to receive(:build).with(json) { snapshot }
-      allow(SnapshotPresenter).to receive(:new).with(thumbnail) { snapshot_presenter }
+      allow(snapshot).to receive(:rstrip) { snapshot }
+      allow(snapshot).to receive(:crop) { snapshot }
+      allow(snapshot).to receive(:expand) { snapshot }
+      allow(SnapshotPresenter).to receive(:new).with(snapshot) { snapshot_presenter }
+    end
+
+    it 'removes empty trailing lines from the snapshot' do
+      decorated.thumbnail(21, 13)
+
+      expect(snapshot).to have_received(:rstrip)
     end
 
     it 'crops the snapshot' do
@@ -151,6 +159,12 @@ describe AsciicastDecorator do
       expect(snapshot).to have_received(:crop).with(21, 13)
     end
 
+    it 'adds the missing lines to the end of the snapshot' do
+      decorated.thumbnail(21, 13)
+
+      expect(snapshot).to have_received(:expand).with(13)
+    end
+
     it 'returns html snapshot rendered by SnapshotPresenter#to_html' do
       expect(decorated.thumbnail).to eq('<pre></pre>')
     end

spec/models/snapshot_spec.rb

@@ -94,14 +94,5 @@ describe Snapshot do
                                             cropped_line_3]))
       end
     end
-
-    context "when height is greater than lines count" do
-      let(:height) { 4 }
-
-      it 'returns a new Snapshot with all lines cropped and missing lines added' do
-        expect(subject).to eq(Snapshot.new([cropped_line_1, cropped_line_2,
-                                            cropped_line_3, []]))
-      end
-    end
   end
 end