Merge pull request #3 from Applicat/caching

Caching of http requests

README.rdoc

@@ -18,6 +18,9 @@
     # Use them like ActiveRecord models
     @empire_tracks = @kasabian.release_groups[8].releases.first.tracks
 
+    # Setting a cache path enables caching of requests
+    MusicBrainz.cache_path = File.join(File.dirname(__FILE__), '../../tmp/test/musicbrainz')
+    
 === Api
 
 MusicBrainz::Artist

lib/models/music_brainz.rb

@@ -1,6 +1,7 @@
 module MusicBrainz
   @@last_query_time = 0
   @@query_interval = 1.5 # Min: 1.0 Safe: 1.5
+  @@cache_path = nil
   
   WEB_SERVICE_URL = 'http://musicbrainz.org/ws/2/'
   USER_AGENT = "gem musicbrainz (https://github.com/magnolia-fan/musicbrainz) @ " + Socket.gethostname
@@ -9,30 +10,69 @@ module MusicBrainz
     @@query_interval = sec.to_f
   end
   
+  def self.cache_path= path
+    @@cache_path = path
+  end
+  
   def self.load resourse, params = {}
     url = WEB_SERVICE_URL + resourse.to_s.gsub('_', '-') + '/' + (params[:id].to_s || '')
     params.delete(:id) unless params[:id].nil?
     url << '?' + params.map{ |k, v|
       k.to_s.gsub('_', '-') + '=' + (v.is_a?(Array) ? v.map{ |_| _.to_s.gsub('_', '-') }.join('+') : v.to_s)
     }.join('&') unless params.empty?
-    self.get_contents url
+    self.cache_contents(url) do 
+      self.get_contents url
+    end
+  end
+  
+  def self.clear_cache
+    FileUtils.rm_r(@@cache_path) if @@cache_path && File.exist?(@@cache_path)
   end
   
 private
 
-  def self.get_contents url
-    time_passed = Time.now.to_f - @@last_query_time
-    sleep @@query_interval - time_passed if time_passed < @@query_interval
+  def self.cache_contents url
     response = nil
+    url_parts = url.split('/')
+    file_name = url_parts.pop
+    directory = url_parts.pop
+    file_path = @@cache_path ? "#{@@cache_path}/#{directory}/#{file_name}" : nil
+        
+    if file_path && File.exist?(file_path)
+      response = File.open(file_path).gets
+    else
+      response = yield
+        
+      unless response.nil? || file_path.nil?
+        FileUtils.mkdir_p file_path.split('/')[0..-2].join('/')
+        file = File.new(file_path, 'w')
+        file.puts(response.gets.force_encoding('UTF-8'))
+        file.chmod(0755)
+        file.close
+        response.rewind
+      end
+    end
+    
+    response
+  end
+
+  def self.get_contents url
+    response = nil
+    
     5.times do
+      time_passed = Time.now.to_f - @@last_query_time
+      sleep @@query_interval - time_passed if time_passed < @@query_interval
+      
       begin
         response = open(url, "User-Agent" => USER_AGENT)
         @@last_query_time = Time.now.to_f
       rescue => e
-        return nil if e.io.status[0].to_i == 404
+        response = nil if e.io.status[0].to_i == 404
       end
-      break unless response.nil?
+      
+      break unless response.nil? 
     end
+    
     response
   end
-end
+end

spec/models/music_brainz_spec.rb

@@ -0,0 +1,51 @@
+require 'spec_helper'
+
+describe MusicBrainz do
+  
+  describe '.cache_contents', :vcr do
+    let(:cache_path) { File.join(File.dirname(__FILE__), '../../tmp/rspec_test/musicbrainz') }
+    let(:response) { ::StringIO.new('<?xml version="1.0" encoding="UTF-8"?><metadata xmlns="http://musicbrainz.org/ns/mmd-2.0#"><artist type="Group" id="69b39eab-6577-46a4-a9f5-817839092033"><name>Kasabian</name><sort-name>Kasabian</sort-name><country>GB</country><life-span><begin>1999</begin></life-span><relation-list target-type="url"><relation type="allmusic"><target>http://allmusic.com/artist/p678134</target></relation><relation type="wikipedia"><target>http://en.wikipedia.org/wiki/Kasabian</target></relation><relation type="microblog"><target>http://twitter.com/kasabianhq</target></relation><relation type="BBC Music page"><target>http://www.bbc.co.uk/music/artists/69b39eab-6577-46a4-a9f5-817839092033</target></relation><relation type="discogs"><target>http://www.discogs.com/artist/Kasabian</target></relation><relation type="social network"><target>http://www.facebook.com/kasabian</target></relation><relation type="IMDb"><target>http://www.imdb.com/name/nm1868442/</target></relation><relation type="official homepage"><target>http://www.kasabian.co.uk/</target></relation><relation type="myspace"><target>http://www.myspace.com/kasabian</target></relation><relation type="youtube"><target>http://www.youtube.com/kasabianvevo</target></relation><relation type="youtube"><target>http://www.youtube.com/user/KasabianTour</target></relation></relation-list></artist></metadata>') }
+    
+    before(:each) do
+      MusicBrainz.clear_cache
+    end
+    
+    after(:each) do
+      MusicBrainz.clear_cache
+    end
+    
+    context 'with cache enabled' do
+      it 'calls get contents only once when requesting the resource twice' do
+        MusicBrainz.cache_path = cache_path
+        MusicBrainz.stub(:get_contents).and_return(response)
+        MusicBrainz.should_receive(:get_contents).once
+        mbid = '69b39eab-6577-46a4-a9f5-817839092033'
+        File.exist?("#{cache_path}/artist/#{mbid}?inc=url-rels").should be_false
+        artist = MusicBrainz::Artist.find(mbid)
+        artist.should be_a_kind_of(MusicBrainz::Artist)
+        
+        File.exist?("#{cache_path}/artist/#{mbid}?inc=url-rels").should be_true
+        artist = MusicBrainz::Artist.find(mbid)
+        artist.should be_a_kind_of(MusicBrainz::Artist)
+      end
+    end
+    
+    context 'with cache disabled' do
+      it 'calls get contents twice when requesting the resource twice' do
+        MusicBrainz.cache_path = nil
+        MusicBrainz.stub(:get_contents).and_return(response)
+        MusicBrainz.should_receive(:get_contents).twice
+        mbid = '69b39eab-6577-46a4-a9f5-817839092033'
+        File.exist?("#{cache_path}/artist/#{mbid}?inc=url-rels").should be_false
+        artist = MusicBrainz::Artist.find(mbid)
+        artist.should be_a_kind_of(MusicBrainz::Artist)
+        
+        File.exist?("#{cache_path}/artist/#{mbid}?inc=url-rels").should be_false
+        response.rewind
+        MusicBrainz.stub(:get_contents).and_return(response)
+        artist = MusicBrainz::Artist.find(mbid)
+        artist.should be_a_kind_of(MusicBrainz::Artist)
+      end
+    end
+  end
+end

test/helper.rb

@@ -24,5 +24,7 @@ $LOAD_PATH.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))
 $LOAD_PATH.unshift(File.dirname(__FILE__))
 require 'musicbrainz'
 
+MusicBrainz.cache_path = File.join(File.dirname(__FILE__), '../tmp/test/musicbrainz')
+
 class Test::Unit::TestCase
 end