patch for #issue/21, add #export_rate and #import_rates

lib/money/bank/variable_exchange.rb

@@ -1,7 +1,12 @@
 require 'money/bank/base'
+require 'json'
+require 'yaml'
 
 class Money
   module Bank
+    # Thrown by VariableExchange#export_rates and VariableExchange#import_rates
+    # when an unknown rate format is requested.
+    class UnknownRateFormat < StandardError; end
 
     # Class for aiding in exchanging money between different currencies.
     # By default, the Money class uses an object of this class (accessible through
@@ -22,6 +27,8 @@ module Bank
     #
     class VariableExchange < Base
 
+      RATE_FORMATS = [:json, :ruby, :yaml]
+
       def setup
         @rates = {}
         @mutex = Mutex.new
@@ -71,12 +78,60 @@ def get_rate(from, to)
         @mutex.synchronize { @rates[rate_key_for(from, to)] }
       end
 
+      # Return the known rates as a string in the format specified. If +file+
+      # is given will also write the string out to the file specified.
+      # Available formats are +:json+, +:ruby+ and +:yaml+.
+      #
+      # Raises +Money::Bank::UnknownRateFormat+ if format is unknown.
+      def export_rates(format, file=nil)
+        raise Money::Bank::UnknownRateFormat unless
+          RATE_FORMATS.include? format
+
+        s = ""
+        @mutex.synchronize {
+          s = case format
+              when :json
+                @rates.to_json
+              when :ruby
+                Marshal.dump(@rates)
+              when :yaml
+                @rates.to_yaml
+              end
+
+          unless file.nil?
+            File.open(file, "w").write(s)
+          end
+        }
+        s
+      end
+
+      # Loads rates provided in +s+ given the specified format. Available
+      # formats are +:json+, +:ruby+ and +:yaml+.
+      #
+      # Raises +Money::Bank::UnknownRateFormat+ if format is unknown.
+      def import_rates(format, s)
+        raise Money::Bank::UnknownRateFormat unless
+          RATE_FORMATS.include? format
+
+        @mutex.synchronize {
+          @rates = case format
+                   when :json
+                     JSON.load(s)
+                   when :ruby
+                     Marshal.load(s)
+                   when :yaml
+                     YAML.load(s)
+                   end
+        }
+        self
+      end
+
       private
 
-        # Return the rate hashkey for the given currencies.
-        def rate_key_for(from, to)
-          "#{Currency.wrap(from).iso_code}_TO_#{Currency.wrap(to).iso_code}".upcase
-        end
+      # Return the rate hashkey for the given currencies.
+      def rate_key_for(from, to)
+        "#{Currency.wrap(from).iso_code}_TO_#{Currency.wrap(to).iso_code}".upcase
+      end
 
     end
 

spec/bank/variable_exchange_spec.rb

@@ -1,4 +1,6 @@
 require "spec_helper"
+require "json"
+require "yaml"
 
 describe Money::Bank::VariableExchange do
 
@@ -165,6 +167,85 @@
       end
     end
 
+    describe '#export_rates' do
+      before :each do
+        @bank.set_rate('USD', 'EUR', 1.25)
+        @bank.set_rate('USD', 'JPY', 2.55)
+      end
+
+      describe 'with format == :json' do
+        it 'should return rates formatted as json' do
+          rates_as_json = '{"USD_TO_EUR":1.25,"USD_TO_JPY":2.55}'
+          @bank.export_rates(:json).should == rates_as_json
+        end
+      end
+
+      describe 'with format == :ruby' do
+        it 'should return rates formatted as ruby objects' do
+          rates = {"USD_TO_EUR"=>1.25,"USD_TO_JPY"=>2.55}
+          @bank.export_rates(:ruby).should == Marshal.dump(rates)
+        end
+      end
+
+      describe 'with format == :yaml' do
+        it 'should return rates formatted as yaml' do
+          rates_as_yaml = "--- \nUSD_TO_EUR: 1.25\nUSD_TO_JPY: 2.55\n"
+          @bank.export_rates(:yaml).should == rates_as_yaml
+        end
+      end
+
+      describe 'with unknown format' do
+        it 'should raise `UnknownRateFormat`' do
+          lambda{@bank.export_rates(:foo)}.should raise_error Money::Bank::UnknownRateFormat
+        end
+      end
+
+      describe 'with :file provided' do
+        it 'should write rates to file' do
+          f = mock('IO')
+          File.should_receive(:open).with('null', 'w').and_return(f)
+          f.should_receive(:write).with('{"USD_TO_EUR":1.25,"USD_TO_JPY":2.55}')
+
+          @bank.export_rates(:json, 'null')
+        end
+      end
+    end
+
+    describe '#import_rates' do
+      describe 'with format == :json' do
+        it 'should load the rates provided' do
+          s = '{"USD_TO_EUR":1.25,"USD_TO_JPY":2.55}'
+          @bank.import_rates(:json, s)
+          @bank.get_rate('USD', 'EUR').should == 1.25
+          @bank.get_rate('USD', 'JPY').should == 2.55
+        end
+      end
+
+      describe 'with format == :ruby' do
+        it 'should load the rates provided' do
+          s = Marshal.dump({"USD_TO_EUR"=>1.25,"USD_TO_JPY"=>2.55})
+          @bank.import_rates(:ruby, s)
+          @bank.get_rate('USD', 'EUR').should == 1.25
+          @bank.get_rate('USD', 'JPY').should == 2.55
+        end
+      end
+
+      describe 'with format == :yaml' do
+        it 'should load the rates provided' do
+          s = "--- \nUSD_TO_EUR: 1.25\nUSD_TO_JPY: 2.55\n"
+          @bank.import_rates(:yaml, s)
+          @bank.get_rate('USD', 'EUR').should == 1.25
+          @bank.get_rate('USD', 'JPY').should == 2.55
+        end
+      end
+
+      describe 'with unknown format' do
+        it 'should raise `UnknownRateFormat`' do
+          lambda{@bank.import_rates(:foo, "")}.should raise_error Money::Bank::UnknownRateFormat
+        end
+      end
+    end
+
     describe '#rate_key_for' do
       it 'should accept str/str' do
         lambda{@bank.send(:rate_key_for, 'USD', 'EUR')}.should_not raise_exception