Use less spans for thumbnail rendering

app/decorators/snapshot_decorator.rb

@@ -9,7 +9,9 @@ class SnapshotDecorator < ApplicationDecorator
   private
 
   def line(line_no)
-    (0...width).map { |column_no| model.cell(column_no, line_no) }
+    line = (0...width).map { |column_no| model.cell(column_no, line_no) }
+
+    LineOptimizer.new(line).optimize
   end
 
 end

app/services/line_optimizer.rb

@@ -0,0 +1,33 @@
+class LineOptimizer
+
+  def initialize(line)
+    @line = line
+  end
+
+  def optimize
+    return [] if line.empty?
+
+    text = [line[0].text]
+    brush = line[0].brush
+
+    cells = []
+
+    line[1..-1].each do |cell|
+      if cell.brush == brush
+        text << cell.text
+      else
+        cells << Cell.new(text.join, brush)
+        text, brush = [cell.text], cell.brush
+      end
+    end
+
+    cells << Cell.new(text.join, brush)
+
+    cells
+  end
+
+  private
+
+  attr_reader :line
+
+end

spec/decorators/snapshot_decorator_spec.rb

@@ -14,9 +14,17 @@ describe SnapshotDecorator do
 
     before do
       allow(snapshot).to receive(:cell) { |x, y| cells[y][x] }
+
+      allow(LineOptimizer).to receive(:new).with([:a, :b]) {
+        double('optimizer', :optimize => [:ab])
+      }
+
+      allow(LineOptimizer).to receive(:new).with([:c, :d]) {
+        double('optimizer', :optimize => [:c, :d])
+      }
     end
 
-    it { should eq(cells) }
+    it { should eq([ [:ab], [:c, :d] ]) }
   end
 
 end

spec/services/line_optimizer_spec.rb

@@ -0,0 +1,29 @@
+require 'spec_helper'
+
+describe LineOptimizer do
+
+  let(:line_optimizer) { described_class.new(line) }
+
+  def brush(attrs)
+    Brush.new(attrs)
+  end
+
+  describe '#optimize' do
+    let(:line) { [
+      Cell.new('a', brush(fg: 1)),
+      Cell.new('b', brush(fg: 1)),
+      Cell.new('c', brush(fg: 2)),
+      Cell.new('d', brush(fg: 3)),
+      Cell.new('e', brush(fg: 3))
+    ] }
+
+    subject { line_optimizer.optimize }
+
+    it { should eq([
+      Cell.new('ab', brush(fg: 1)),
+      Cell.new('c',  brush(fg: 2)),
+      Cell.new('de', brush(fg: 3))
+    ]) }
+  end
+
+end