add layouts to renderer

The renderer is now able to render templates in the context of their
layouts.

lib/renderer.rb

@@ -3,6 +3,25 @@ class Renderer
   DEFAULT_TYPE = :default_type
 
   def self.call(session)
+    template = do_checks(session)
+    return nil unless template
+    type = get_type(session, template)
+    session.response.body = render(template, type, session.options)
+    session.response.content_type = type_map[type]
+    nil
+  end
+
+  def self.render(template, type, object)
+    layout = templates['layout']
+    if layout && layout.has_key?(type)
+      return layout[type].render(object) do
+        template[type].render(object)
+      end
+    end
+    template[type].render(object)
+  end
+
+  def self.do_checks(session)
     unless session.options.has_key? :render
       session.response.body = ':render not set!'
       return nil
@@ -12,31 +31,27 @@ class Renderer
       session.response.body = 'Template does not exist!'
       return nil
     end
-    template = templates[to_render]
-    type = get_preferred_type(session, template)
-    type = template.first[0] if type == DEFAULT_TYPE
-    session.response.body = Tilt.new(template[type]).render(session.options)
-    session.response.content_type = type_map[type]
-    nil
+    return templates[to_render]
   end
 
   # initialize the template cache
   def self.find_templates(path)
-    @@templates = {}
+    templates = {}
     Dir[path + '/**/*'].each do |file|
-      next unless File.file?(file)
       parts = file.gsub(path, '').match(COMPONENT_MATCHER)
-      @@templates[parts[:template]] ||= {}
-      @@templates[parts[:template]].merge!({parts[:type].to_sym => file})
+      next unless File.file?(file) && parts
+      templates[parts[:template]] ||= {}
+      templates[parts[:template]].merge!({parts[:type].to_sym => Tilt.new(file)})
     end
+    templates
   end
 
   def self.templates
-    find_templates 'templates' unless @@templates
-    @@templates
+    @@templates ||= find_templates 'templates'
   end
 
   def self.set_types(types)
+    @@type_map = types.invert
     @@types = types
   end
 
@@ -50,11 +65,17 @@ class Renderer
   end
 
   def self.type_map
-    @type_map ||= types.invert
+    @@type_map ||= types.invert
   end
 
-  def self.get_preferred_type(session, template)
-    session.request.accept.types.each do |type|
+  def self.get_type(session, template)
+    type = get_preferred_type(session.request, template)
+    return template.first[0] if type == DEFAULT_TYPE
+    type
+  end
+
+  def self.get_preferred_type(request, template)
+    request.accept.types.each do |type|
       next unless types.has_key? type
       return types[type] if template.has_key? types[type]
       return DEFAULT_TYPE if types[type] == DEFAULT_TYPE