Refactor snapshot

Gemfile

@@ -5,7 +5,8 @@ gem 'pg'
 gem 'sequel'
 gem 'sinatra-jsonp'
 gem 'unicorn'
-gem 'yajl-ruby', require: 'yajl'
+gem 'virtus'
+gem 'yajl-ruby'
 
 group :development do
   gem 'minitest'

Gemfile.lock

@@ -1,6 +1,7 @@
 GEM
   remote: http://rubygems.org/
   specs:
+    backports (2.6.5)
     fixer (0.5.0)
       nokogiri (~> 1.5)
     kgio (2.7.4)
@@ -29,6 +30,8 @@ GEM
       kgio (~> 2.6)
       rack
       raindrops (~> 0.7)
+    virtus (0.5.2)
+      backports (~> 2.6.1)
     yajl-ruby (1.1.0)
 
 PLATFORMS
@@ -43,4 +46,5 @@ DEPENDENCIES
   shotgun
   sinatra-jsonp
   unicorn
+  virtus
   yajl-ruby

lib/app.rb

@@ -6,8 +6,10 @@ require 'yajl'
 set :root, File.expand_path('..', File.dirname(__FILE__))
 
 helpers do
-  def base
-    params[:base] || Snapshot::DEFAULT_BASE
+  def snapshot
+    Snapshot
+      .new(params)
+      .quote
   end
 end
 
@@ -16,15 +18,13 @@ get '/' do
 end
 
 get '/latest' do
-  jsonp Snapshot
-    .last
-    .with_base(base)
-    .to_hash
+  jsonp snapshot
 end
 
 get '/:date' do
-  jsonp Snapshot
-    .new(params[:date])
-    .with_base(base)
-    .to_hash
+  jsonp snapshot
+end
+
+error do
+  "Something is rotten in the state of Denmark."
 end

lib/snapshot.rb

@@ -1,59 +1,49 @@
 require_relative 'db'
+require 'virtus'
 
 class Snapshot
-  DEFAULT_BASE = 'EUR'
+  include Virtus
 
-  def self.last
-    new Currency.last_date
-  end
+  attribute :base,  String, default: 'EUR'
+  attribute :date,  Date,   default: proc { Currency.last_date }
 
-  def initialize(date)
-    @date = date
-    @base = DEFAULT_BASE
-  end
-
-  # Ugly as fuck.
-  def to_hash
-    rebased_rates = rates
-
-    unless @base == DEFAULT_BASE
-      base_rate = rebased_rates
-        .update('EUR' => 1.0)
-        .delete @base
-
-      rebased_rates.each do |iso_code, rate|
-        new_rate = rate / base_rate
-        rebased_rates[iso_code] =
-          case new_rate
-          when new_rate > 100
-            new_rate.round 2
-          when new_rate > 10
-            new_rate.round 3
-          else
-            new_rate.round 4
-          end
-      end
-    end
-
-    {
-      base:  @base,
-      date:  @date,
-      rates: rebased_rates
-    }
-  end
-
-  def with_base(base)
-    @base = base
-    self
+  def quote
+    attributes.merge rates: rebase(rates)
   end
 
   private
 
   def rates
     Currency
-      .where(date: @date)
-      .reduce({}) { |hsh, currency|
-        hsh.update currency.to_hash
-      }
+      .where(date: date)
+      .reduce({}) do |rates, currency|
+        rates.update currency.to_hash
+      end
+  end
+
+  # Ugly as fuck.
+  def rebase(rates)
+    if base.upcase! != 'EUR'
+      denominator = rates
+        .update('EUR' => 1.0)
+        .delete base
+
+      rates.each do |iso_code, rate|
+        rates[iso_code] = round(rate / denominator)
+      end
+    end
+
+    rates
+  end
+
+  def round(rate)
+    case rate
+    when rate > 100
+      rate.round 2
+    when rate > 10
+      rate.round 3
+    else
+      rate.round 4
+    end
   end
 end

spec/app_spec.rb

@@ -7,6 +7,7 @@ describe 'the application' do
 
   let(:app)  { Sinatra::Application }
   let(:json) { Yajl::Parser.new.parse last_response.body }
+  let(:status) { last_response.status }
 
   it 'returns latest snapshot' do
     get '/latest'

spec/rebasing_spec.rb

@@ -1,31 +0,0 @@
-require_relative 'helper'
-require 'snapshot'
-
-describe 'when rebased to a new base' do
-  let(:new_base) { 'USD' }
-  let(:snapshot) { Snapshot.new 'a date' }
-  let(:rates)    { { new_base => 1.2781 } }
-  let(:rebased_hash) do
-    snapshot.stub :rates, rates do
-      snapshot
-        .with_base(new_base)
-        .to_hash
-    end
-  end
-
-  it 'resets base' do
-    rebased_hash[:base].must_equal new_base
-  end
-
-  it 'adds former base to rates' do
-    rebased_hash[:rates].keys.must_include Snapshot::DEFAULT_BASE
-  end
-
-  it 'removes new base from rates' do
-    rebased_hash[:rates].keys.wont_include new_base
-  end
-
-  it 'rebases rates' do
-    rebased_hash[:rates][Snapshot::DEFAULT_BASE].must_equal 0.7824
-  end
-end

spec/snapshot_spec.rb

@@ -0,0 +1,44 @@
+require_relative 'helper'
+require 'snapshot'
+
+describe Snapshot do
+  let(:snapshot) { Snapshot.new }
+
+  def stub_rates(rates = {})
+    snapshot.stub :rates, rates do
+      yield snapshot.quote[:rates]
+    end
+  end
+
+  describe 'by default' do
+    it 'quotes rates against the euro' do
+      stub_rates 'USD' => 1.25 do |quotes|
+        quotes['USD'].must_equal 1.25
+      end
+    end
+
+    it 'does not quote the euro' do
+      stub_rates do |quotes|
+        quotes.keys.wont_include 'EUR'
+      end
+    end
+  end
+
+  describe 'when base is set to a non-euro currency' do
+    before do
+      snapshot.base = 'USD'
+    end
+
+    it 'quotes rates against that currency' do
+      stub_rates 'USD' => 1.25 do |quotes|
+        quotes['EUR'].must_equal 0.8
+      end
+    end
+
+    it 'does not quote the base currency' do
+      stub_rates 'USD' => 1.25 do |quotes|
+        quotes.keys.wont_include 'USD'
+      end
+    end
+  end
+end