Refactor rebasing

lib/app.rb

@@ -1,6 +1,7 @@
 require_relative 'snapshot'
 require 'sinatra'
 require 'sinatra/jsonp'
+require 'yajl'
 
 helpers do
   def base
@@ -15,11 +16,13 @@ end
 get '/latest' do
   jsonp Snapshot
     .last
-    .to_base base
+    .with_base(base)
+    .to_hash
 end
 
 get '/:date' do |date|
   jsonp Snapshot
     .new(date)
-    .to_base base
+    .with_base(base)
+    .to_hash
 end

lib/snapshot.rb

@@ -1,22 +1,25 @@
 require_relative 'db'
 
 class Snapshot
+  DEFAULT_BASE = 'EUR'
+
   def self.last
     new Currency.last_date
   end
 
   def initialize(date)
     @date = date
+    @base = DEFAULT_BASE
   end
 
   # Ugly as fuck.
-  def to_base(base)
+  def to_hash
     rebased_rates = rates
 
-    unless base == 'EUR'
+    unless @base == DEFAULT_BASE
       base_rate = rebased_rates
         .update('EUR' => 1.0)
-        .delete base
+        .delete @base
 
       rebased_rates.each do |iso_code, rate|
         new_rate = rate / base_rate
@@ -33,12 +36,17 @@ class Snapshot
     end
 
     {
-      base:  base,
+      base:  @base,
       date:  @date,
       rates: rebased_rates
     }
   end
 
+  def with_base(base)
+    @base = base
+    self
+  end
+
   private
 
   def rates

spec/app_spec.rb

@@ -1,6 +1,7 @@
 require_relative 'helper'
 require 'rack/test'
 require 'app'
+require 'yajl'
 
 describe 'the application' do
   include Rack::Test::Methods

spec/rebasing_spec.rb

@@ -2,28 +2,30 @@ require_relative 'helper'
 require 'snapshot'
 
 describe 'when rebased to a new base' do
-  let(:base)     { 'USD' }
+  let(:new_base) { 'USD' }
   let(:snapshot) { Snapshot.new 'a date' }
-  let(:rates)    { { 'USD' => 1.2781 } }
-  let(:rebased) do
+  let(:rates)    { { new_base => 1.2781 } }
+  let(:rebased_hash) do
     snapshot.stub :rates, rates do
-      snapshot.to_base base
+      snapshot
+        .with_base(new_base)
+        .to_hash
     end
   end
 
   it 'resets base' do
-    rebased[:base].must_equal base
+    rebased_hash[:base].must_equal new_base
   end
 
   it 'adds former base to rates' do
-    rebased[:rates].keys.must_include 'EUR'
+    rebased_hash[:rates].keys.must_include Snapshot::DEFAULT_BASE
   end
 
   it 'removes new base from rates' do
-    rebased[:rates].keys.wont_include base
+    rebased_hash[:rates].keys.wont_include new_base
   end
 
   it 'rebases rates' do
-    rebased[:rates]['EUR'].must_equal 0.7824
+    rebased_hash[:rates][Snapshot::DEFAULT_BASE].must_equal 0.7824
   end
 end