Convert Snapshot into value object

lib/api.rb

@@ -2,7 +2,7 @@ require 'sinatra'
 require 'sinatra/cross_origin'
 require 'sinatra/jsonp'
 require 'yajl'
-require 'snapshot'
+require 'quote'
 
 configure do
   enable :cross_origin
@@ -17,8 +17,8 @@ configure :production do
 end
 
 helpers do
-  def snapshot
-    quotes = Snapshot.new(params).quote
+  def quote
+    quotes = Quote.new(params).to_h
 
     symbols = params.delete('symbols') || params.delete('currencies')
     if symbols
@@ -45,12 +45,12 @@ get '/' do
 end
 
 get '/latest' do
-  jsonp snapshot
+  jsonp quote
 end
 
 get(/(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/) do
   process_date
-  jsonp snapshot
+  jsonp quote
 end
 
 not_found do

lib/quote.rb

@@ -1,26 +1,29 @@
 require 'virtus'
 require 'currency'
 
-# Quotes exchange rates on a specific date
-class Snapshot
-  include Virtus.model
+class Quote
+  include Virtus.value_object
 
-  attribute :base, String, default: 'EUR'
+  DEFAULT_BASE = 'EUR'
+
+  values do
+    attribute :base, String, default: DEFAULT_BASE
     attribute :date, Date, default: Currency.current_date
-
-  def quote
-    self.date =
-      if date
-        last_date = Currency.current_date_before(date)
-        fail ArgumentError, 'Date too old' unless last_date
-        last_date
   end
 
+  def to_h
     attributes.merge(rates: rebase(rates))
   end
 
   private
 
+  def date=(date)
+    current_date = Currency.current_date_before(date)
+    fail ArgumentError, 'Date too old' unless current_date
+
+    super current_date
+  end
+
   def rates
     Currency.where(date: date).reduce({}) do |rates, currency|
       rates.update(currency.to_hash)
@@ -28,8 +31,8 @@ class Snapshot
   end
 
   def rebase(rates)
-    if base.upcase! != 'EUR'
-      denominator = rates.update('EUR' => 1.0).delete(base)
+    if base.upcase! != DEFAULT_BASE
+      denominator = rates.update(DEFAULT_BASE => 1.0).delete(base)
       fail ArgumentError, 'Invalid base' unless denominator
       rates.each do |iso_code, rate|
         rates[iso_code] = round(rate / denominator)

spec/api_spec.rb

@@ -14,7 +14,7 @@ describe 'the API' do
     last_response.must_be :ok?
   end
 
-  it 'returns latest snapshot' do
+  it 'returns latest quotes' do
     get '/latest'
     last_response.must_be :ok?
   end
@@ -29,7 +29,7 @@ describe 'the API' do
     json['rates'].keys.must_equal %w(USD)
   end
 
-  it 'returns historical data' do
+  it 'returns historical quotes' do
     get '/2012-11-20'
     json['rates'].wont_be :empty?
     json['date'].must_equal '2012-11-20'

spec/quote_spec.rb

@@ -1,16 +1,16 @@
 require_relative 'helper'
-require 'snapshot'
-
-describe Snapshot do
-  let(:snapshot) { Snapshot.new }
+require 'quote'
 
+describe Quote do
   def stub_rates(rates = {})
-    snapshot.stub :rates, rates do
-      yield snapshot.quote[:rates]
+    quote.stub :rates, rates do
+      yield quote.to_h[:rates]
     end
   end
 
   describe 'by default' do
+    let(:quote) { Quote.new }
+
     it 'quotes rates against the euro' do
       stub_rates 'USD' => 1.25 do |quotes|
         quotes['USD'].must_equal 1.25
@@ -25,9 +25,7 @@ describe Snapshot do
   end
 
   describe 'when base is set to a non-euro currency' do
-    before do
-      snapshot.base = 'USD'
-    end
+    let(:quote) { Quote.new(base: 'USD') }
 
     it 'quotes rates against that currency' do
       stub_rates 'USD' => 1.25 do |quotes|