added preferred_language_from method

README.rdoc

@@ -4,18 +4,26 @@ A small effort in making a plugin which helps you detect the users prefered lang
 
 = Features
 
+* Splits the http-header into languages specified by the user
 * Returns empty array if header is illformed.
 * Corrects case to xx-XX
 * Sorted by priority given, as much as possible.
+* Gives you the most important language
 
 See also: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
 
 = Example
 
   class SomeController < ApplicationController
     def some_action
+
       request.user_preferred_language
       # => [ 'nl-NL', 'nl-BE', 'nl', 'en-US', 'en' ]
+
+      available = %w{en en-US nl-BE}
+      request.preferred_language_from(available)
+      # => 'nl-BE'
+
     end
   end
 

lib/http_accept_language.rb

@@ -14,4 +14,7 @@ def user_preferred_languages
   rescue
     []
   end
+  def preferred_language_from(array)
+    (user_preferred_languages & array).first
+  end
 end

test/http_accept_language_test.rb

@@ -28,6 +28,10 @@ def test_should_ignore_jambled_header
     assert_equal [], request.user_preferred_languages
   end
 
+  def test_should_find_first_available_language
+    assert_equal 'en-GB', request.preferred_language_from(%w{en en-GB})
+  end
+
   private
   def request
     @request ||= MockedCgiRequest.new