Handle redirections properly

.gitignore

@@ -2,3 +2,8 @@ Session.vim
 coverage
 .rvmrc
 *.gem
+Gemfile.lock
+spec/fixtures/cassettes
+
+.DS_Store
+.ruby-version

gtfs.gemspec

@@ -21,7 +21,8 @@ Gem::Specification.new do |gem|
   gem.add_dependency 'rake'
   gem.add_dependency 'multi_json'
   gem.add_dependency 'rubyzip', ['~> 2.3']
-
+  gem.add_dependency 'csv'
+
   gem.add_development_dependency 'rspec', ['>= 2.0.0']
   gem.add_development_dependency 'simplecov'
   gem.add_development_dependency 'byebug'

lib/gtfs/url_source.rb

@@ -4,11 +4,26 @@
 module GTFS
   class URLSource < Source
 
+    MAXIMUM_REDIRECTS = 5
+
     def load_archive(source_url)
+      original_source_url = source_url.dup
       Dir.mktmpdir do |tmp|
+        n = 0
+        while n < MAXIMUM_REDIRECTS
+          uri = URI.parse(source_url)
+          response = Net::HTTP.get_response(uri)
+          if response.is_a?(Net::HTTPRedirection)
+            n += 1
+            source_url = response['location']
+          else
+            break
+          end
+        end
+        if n >= MAXIMUM_REDIRECTS
+          raise InvalidSourceException.new("Too many redirects for #{original_source_url}")
+        end
         file_name = File.join(tmp, "/gtfs_temp_#{Time.now.strftime('%Y%jT%H%M%S%z')}.zip")
-        uri = URI.parse(source_url)
-        response = Net::HTTP.get_response(uri)
         open(file_name, 'wb') do |file|
           file.write response.body
         end

spec/gtfs/url_source_spec.rb

@@ -10,6 +10,15 @@
     end
   end
 
+  context 'with a URI causing redirects' do
+    let(:source_path) {'https://api.gtfs-data.jp/v2/organizations/asatetu/feeds/asakaigantetsudo/files/feed.zip'} # 302 Found
+    it 'should create a new source successfully' do
+      VCR.use_cassette('redirect_gtfs_uri') do
+        lambda {GTFS::URLSource.new(source_path, {})}.should_not raise_error(GTFS::InvalidSourceException)
+      end
+    end
+  end
+
   context 'with a non-existent URI' do
     let(:source_path) {'https://example.org/gtfs.zip'}
     it 'should raise an exception' do