separated the asset id methods to a separate module, removed some dupliation with the various path methods, and moved the base asset tag methods to a base module so the asset id module can play nice with the path generation

6 files changed, 486 insertions, 413 deletions

diff --git a/actionpack/lib/action_view/helpers/asset_tag_helper.rb b/actionpack/lib/action_view/helpers/asset_tag_helper.rb
index 858fff2882..065df849a4 100644
--- a/actionpack/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionpack/lib/action_view/helpers/asset_tag_helper.rb
@@ -2,8 +2,10 @@ require 'thread'
 require 'cgi'
 require 'action_view/helpers/url_helper'
 require 'action_view/helpers/tag_helper'
+require 'action_view/helpers/asset_tag_helpers/base_asset_helpers'
 require 'action_view/helpers/asset_tag_helpers/javascript_tag_helpers'
 require 'action_view/helpers/asset_tag_helpers/stylesheet_tag_helpers'
+require 'action_view/helpers/asset_tag_helpers/asset_id_caching'
 require 'active_support/core_ext/file'
 require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/string/output_safety'
@@ -197,413 +199,10 @@ module ActionView
     #   RewriteEngine On
     #   RewriteRule ^/release-\d+/(images|javascripts|stylesheets)/(.*)$ /$1/$2 [L]
     module AssetTagHelper
+      include BaseAssetHelpers
       include JavascriptTagHelpers
       include StylesheetTagHelpers
-
-      # You can enable or disable the asset tag timestamps cache.
-      # With the cache enabled, the asset tag helper methods will make fewer
-      # expensive file system calls. However this prevents you from modifying
-      # any asset files while the server is running.
-      #
-      #   ActionView::Helpers::AssetTagHelper.cache_asset_timestamps = false
-      mattr_accessor :cache_asset_timestamps
-
-      # Returns a link tag that browsers and news readers can use to auto-detect
-      # an RSS or ATOM feed. The +type+ can either be <tt>:rss</tt> (default) or
-      # <tt>:atom</tt>. Control the link options in url_for format using the
-      # +url_options+. You can modify the LINK tag itself in +tag_options+.
-      #
-      # ==== Options
-      # * <tt>:rel</tt>  - Specify the relation of this link, defaults to "alternate"
-      # * <tt>:type</tt>  - Override the auto-generated mime type
-      # * <tt>:title</tt>  - Specify the title of the link, defaults to the +type+
-      #
-      # ==== Examples
-      #  auto_discovery_link_tag # =>
-      #     <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/action" />
-      #  auto_discovery_link_tag(:atom) # =>
-      #     <link rel="alternate" type="application/atom+xml" title="ATOM" href="http://www.currenthost.com/controller/action" />
-      #  auto_discovery_link_tag(:rss, {:action => "feed"}) # =>
-      #     <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/feed" />
-      #  auto_discovery_link_tag(:rss, {:action => "feed"}, {:title => "My RSS"}) # =>
-      #     <link rel="alternate" type="application/rss+xml" title="My RSS" href="http://www.currenthost.com/controller/feed" />
-      #  auto_discovery_link_tag(:rss, {:controller => "news", :action => "feed"}) # =>
-      #     <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/news/feed" />
-      #  auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", {:title => "Example RSS"}) # =>
-      #     <link rel="alternate" type="application/rss+xml" title="Example RSS" href="http://www.example.com/feed" />
-      def auto_discovery_link_tag(type = :rss, url_options = {}, tag_options = {})
-        tag(
-          "link",
-          "rel"   => tag_options[:rel] || "alternate",
-          "type"  => tag_options[:type] || Mime::Type.lookup_by_extension(type.to_s).to_s,
-          "title" => tag_options[:title] || type.to_s.upcase,
-          "href"  => url_options.is_a?(Hash) ? url_for(url_options.merge(:only_path => false)) : url_options
-        )
-      end
-
-      # Web browsers cache favicons. If you just throw a <tt>favicon.ico</tt> into the document
-      # root of your application and it changes later, clients that have it in their cache
-      # won't see the update. Using this helper prevents that because it appends an asset ID:
-      #
-      #   <%= favicon_link_tag %>
-      #
-      # generates
-      #
-      #   <link href="/favicon.ico?4649789979" rel="shortcut icon" type="image/vnd.microsoft.icon" />
-      #
-      # You may specify a different file in the first argument:
-      #
-      #   <%= favicon_link_tag 'favicon.ico' %>
-      #
-      # That's passed to +path_to_image+ as is, so it gives
-      #
-      #   <link href="/images/favicon.ico?4649789979" rel="shortcut icon" type="image/vnd.microsoft.icon" />
-      #
-      # The helper accepts an additional options hash where you can override "rel" and "type".
-      #
-      # For example, Mobile Safari looks for a different LINK tag, pointing to an image that
-      # will be used if you add the page to the home screen of an iPod Touch, iPhone, or iPad.
-      # The following call would generate such a tag:
-      #
-      #   <%= favicon_link_tag 'mb-icon.png', :rel => 'apple-touch-icon', :type => 'image/png' %>
-      #
-      def favicon_link_tag(source='/favicon.ico', options={})
-        tag('link', {
-          :rel  => 'shortcut icon',
-          :type => 'image/vnd.microsoft.icon',
-          :href => path_to_image(source)
-        }.merge(options.symbolize_keys))
-      end
-
-      # Computes the path to an image asset in the public images directory.
-      # Full paths from the document root will be passed through.
-      # Used internally by +image_tag+ to build the image path:
-      #
-      #   image_path("edit")                                         # => "/images/edit"
-      #   image_path("edit.png")                                     # => "/images/edit.png"
-      #   image_path("icons/edit.png")                               # => "/images/icons/edit.png"
-      #   image_path("/icons/edit.png")                              # => "/icons/edit.png"
-      #   image_path("http://www.railsapplication.com/img/edit.png") # => "http://www.railsapplication.com/img/edit.png"
-      #
-      # If you have images as application resources this method may conflict with their named routes.
-      # The alias +path_to_image+ is provided to avoid that. Rails uses the alias internally, and
-      # plugin authors are encouraged to do so.
-      def image_path(source)
-        compute_public_path(source, 'images')
-      end
-      alias_method :path_to_image, :image_path # aliased to avoid conflicts with an image_path named route
-
-      # Computes the path to a video asset in the public videos directory.
-      # Full paths from the document root will be passed through.
-      # Used internally by +video_tag+ to build the video path.
-      #
-      # ==== Examples
-      #   video_path("hd")                                            # => /videos/hd
-      #   video_path("hd.avi")                                        # => /videos/hd.avi
-      #   video_path("trailers/hd.avi")                               # => /videos/trailers/hd.avi
-      #   video_path("/trailers/hd.avi")                              # => /trailers/hd.avi
-      #   video_path("http://www.railsapplication.com/vid/hd.avi") # => http://www.railsapplication.com/vid/hd.avi
-      def video_path(source)
-        compute_public_path(source, 'videos')
-      end
-      alias_method :path_to_video, :video_path # aliased to avoid conflicts with a video_path named route
-
-      # Computes the path to an audio asset in the public audios directory.
-      # Full paths from the document root will be passed through.
-      # Used internally by +audio_tag+ to build the audio path.
-      #
-      # ==== Examples
-      #   audio_path("horse")                                            # => /audios/horse
-      #   audio_path("horse.wav")                                        # => /audios/horse.avi
-      #   audio_path("sounds/horse.wav")                                 # => /audios/sounds/horse.avi
-      #   audio_path("/sounds/horse.wav")                                # => /sounds/horse.avi
-      #   audio_path("http://www.railsapplication.com/sounds/horse.wav") # => http://www.railsapplication.com/sounds/horse.wav
-      def audio_path(source)
-        compute_public_path(source, 'audios')
-      end
-      alias_method :path_to_audio, :audio_path # aliased to avoid conflicts with an audio_path named route
-
-      # Returns an html image tag for the +source+. The +source+ can be a full
-      # path or a file that exists in your public images directory.
-      #
-      # ==== Options
-      # You can add HTML attributes using the +options+. The +options+ supports
-      # three additional keys for convenience and conformance:
-      #
-      # * <tt>:alt</tt>  - If no alt text is given, the file name part of the
-      #   +source+ is used (capitalized and without the extension)
-      # * <tt>:size</tt> - Supplied as "{Width}x{Height}", so "30x45" becomes
-      #   width="30" and height="45". <tt>:size</tt> will be ignored if the
-      #   value is not in the correct format.
-      # * <tt>:mouseover</tt> - Set an alternate image to be used when the onmouseover
-      #   event is fired, and sets the original image to be replaced onmouseout.
-      #   This can be used to implement an easy image toggle that fires on onmouseover.
-      #
-      # ==== Examples
-      #  image_tag("icon")  # =>
-      #    <img src="/images/icon" alt="Icon" />
-      #  image_tag("icon.png")  # =>
-      #    <img src="/images/icon.png" alt="Icon" />
-      #  image_tag("icon.png", :size => "16x10", :alt => "Edit Entry")  # =>
-      #    <img src="/images/icon.png" width="16" height="10" alt="Edit Entry" />
-      #  image_tag("/icons/icon.gif", :size => "16x16")  # =>
-      #    <img src="/icons/icon.gif" width="16" height="16" alt="Icon" />
-      #  image_tag("/icons/icon.gif", :height => '32', :width => '32') # =>
-      #    <img alt="Icon" height="32" src="/icons/icon.gif" width="32" />
-      #  image_tag("/icons/icon.gif", :class => "menu_icon") # =>
-      #    <img alt="Icon" class="menu_icon" src="/icons/icon.gif" />
-      #  image_tag("mouse.png", :mouseover => "/images/mouse_over.png") # =>
-      #    <img src="/images/mouse.png" onmouseover="this.src='/images/mouse_over.png'" onmouseout="this.src='/images/mouse.png'" alt="Mouse" />
-      #  image_tag("mouse.png", :mouseover => image_path("mouse_over.png")) # =>
-      #    <img src="/images/mouse.png" onmouseover="this.src='/images/mouse_over.png'" onmouseout="this.src='/images/mouse.png'" alt="Mouse" />
-      def image_tag(source, options = {})
-        options.symbolize_keys!
-
-        src = options[:src] = path_to_image(source)
-
-        unless src =~ /^cid:/
-          options[:alt] = options.fetch(:alt){ File.basename(src, '.*').capitalize }
-        end
-
-        if size = options.delete(:size)
-          options[:width], options[:height] = size.split("x") if size =~ %r{^\d+x\d+$}
-        end
-
-        if mouseover = options.delete(:mouseover)
-          options[:onmouseover] = "this.src='#{path_to_image(mouseover)}'"
-          options[:onmouseout]  = "this.src='#{src}'"
-        end
-
-        tag("img", options)
-      end
-
-      # Returns an html video tag for the +sources+. If +sources+ is a string,
-      # a single video tag will be returned. If +sources+ is an array, a video
-      # tag with nested source tags for each source will be returned. The
-      # +sources+ can be full paths or files that exists in your public videos
-      # directory.
-      #
-      # ==== Options
-      # You can add HTML attributes using the +options+. The +options+ supports
-      # two additional keys for convenience and conformance:
-      #
-      # * <tt>:poster</tt> - Set an image (like a screenshot) to be shown
-      #   before the video loads. The path is calculated like the +src+ of +image_tag+.
-      # * <tt>:size</tt> - Supplied as "{Width}x{Height}", so "30x45" becomes
-      #   width="30" and height="45". <tt>:size</tt> will be ignored if the
-      #   value is not in the correct format.
-      #
-      # ==== Examples
-      #  video_tag("trailer")  # =>
-      #    <video src="/videos/trailer" />
-      #  video_tag("trailer.ogg")  # =>
-      #    <video src="/videos/trailer.ogg" />
-      #  video_tag("trailer.ogg", :controls => true, :autobuffer => true)  # =>
-      #    <video autobuffer="autobuffer" controls="controls" src="/videos/trailer.ogg" />
-      #  video_tag("trailer.m4v", :size => "16x10", :poster => "screenshot.png")  # =>
-      #    <video src="/videos/trailer.m4v" width="16" height="10" poster="/images/screenshot.png" />
-      #  video_tag("/trailers/hd.avi", :size => "16x16")  # =>
-      #    <video src="/trailers/hd.avi" width="16" height="16" />
-      #  video_tag("/trailers/hd.avi", :height => '32', :width => '32') # =>
-      #    <video height="32" src="/trailers/hd.avi" width="32" />
-      #  video_tag(["trailer.ogg", "trailer.flv"]) # =>
-      #    <video><source src="trailer.ogg" /><source src="trailer.ogg" /><source src="trailer.flv" /></video>
-      #  video_tag(["trailer.ogg", "trailer.flv"] :size => "160x120") # =>
-      #    <video height="120" width="160"><source src="trailer.ogg" /><source src="trailer.flv" /></video>
-      def video_tag(sources, options = {})
-        options.symbolize_keys!
-
-        options[:poster] = path_to_image(options[:poster]) if options[:poster]
-
-        if size = options.delete(:size)
-          options[:width], options[:height] = size.split("x") if size =~ %r{^\d+x\d+$}
-        end
-
-        if sources.is_a?(Array)
-          content_tag("video", options) do
-            sources.map { |source| tag("source", :src => source) }.join.html_safe
-          end
-        else
-          options[:src] = path_to_video(sources)
-          tag("video", options)
-        end
-      end
-
-      # Returns an html audio tag for the +source+.
-      # The +source+ can be full path or file that exists in
-      # your public audios directory.
-      #
-      # ==== Examples
-      #  audio_tag("sound")  # =>
-      #    <audio src="/audios/sound" />
-      #  audio_tag("sound.wav")  # =>
-      #    <audio src="/audios/sound.wav" />
-      #  audio_tag("sound.wav", :autoplay => true, :controls => true)  # =>
-      #    <audio autoplay="autoplay" controls="controls" src="/audios/sound.wav" />
-      def audio_tag(source, options = {})
-        options.symbolize_keys!
-        options[:src] = path_to_audio(source)
-        tag("audio", options)
-      end
-
-      private
-
-        def rewrite_extension(source, dir, ext)
-          source_ext = File.extname(source)
-
-          if source_ext.empty?
-            "#{source}.#{ext}"
-          elsif ext != source_ext[1..-1]
-            with_ext = "#{source}.#{ext}"
-            with_ext if File.exist?(File.join(config.assets_dir, dir, with_ext))
-          end || source
-        end
-
-        def rewrite_host_and_protocol(source, has_request)
-          host = compute_asset_host(source)
-          if has_request && host && !is_uri?(host)
-            host = "#{controller.request.protocol}#{host}"
-          end
-          "#{host}#{source}"
-        end
-
-        def rewrite_relative_url_root(source, relative_url_root)
-          relative_url_root && !source.starts_with?("#{relative_url_root}/") ? "#{relative_url_root}#{source}" : source
-        end
-
-        # Add the the extension +ext+ if not present. Return full URLs otherwise untouched.
-        # Prefix with <tt>/dir/</tt> if lacking a leading +/+. Account for relative URL
-        # roots. Rewrite the asset path for cache-busting asset ids. Include
-        # asset host, if configured, with the correct request protocol.
-        def compute_public_path(source, dir, ext = nil, include_host = true)
-          return source if is_uri?(source)
-
-          source = rewrite_extension(source, dir, ext) if ext
-          source = "/#{dir}/#{source}" unless source[0] == ?/
-          if controller.respond_to?(:env) && controller.env["action_dispatch.asset_path"]
-            source = rewrite_asset_path(source, controller.env["action_dispatch.asset_path"])
-          end
-          source = rewrite_asset_path(source, config.asset_path)
-
-          has_request = controller.respond_to?(:request)
-          source = rewrite_relative_url_root(source, controller.config.relative_url_root) if has_request && include_host
-          source = rewrite_host_and_protocol(source, has_request) if include_host
-
-          source
-        end
-
-        def is_uri?(path)
-          path =~ %r{^[-a-z]+://|^cid:}
-        end
-
-        # Pick an asset host for this source. Returns +nil+ if no host is set,
-        # the host if no wildcard is set, the host interpolated with the
-        # numbers 0-3 if it contains <tt>%d</tt> (the number is the source hash mod 4),
-        # or the value returned from invoking the proc if it's a proc or the value from
-        # invoking call if it's an object responding to call.
-        def compute_asset_host(source)
-          if host = config.asset_host
-            if host.is_a?(Proc) || host.respond_to?(:call)
-              case host.is_a?(Proc) ? host.arity : host.method(:call).arity
-              when 2
-                request = controller.respond_to?(:request) && controller.request
-                host.call(source, request)
-              else
-                host.call(source)
-              end
-            else
-              (host =~ /%d/) ? host % (source.hash % 4) : host
-            end
-          end
-        end
-
-        @@asset_timestamps_cache = {}
-        @@asset_timestamps_cache_guard = Mutex.new
-
-        # Use the RAILS_ASSET_ID environment variable or the source's
-        # modification time as its cache-busting asset id.
-        def rails_asset_id(source)
-          if asset_id = ENV["RAILS_ASSET_ID"]
-            asset_id
-          else
-            if @@cache_asset_timestamps && (asset_id = @@asset_timestamps_cache[source])
-              asset_id
-            else
-              path = File.join(config.assets_dir, source)
-              asset_id = File.exist?(path) ? File.mtime(path).to_i.to_s : ''
-
-              if @@cache_asset_timestamps
-                @@asset_timestamps_cache_guard.synchronize do
-                  @@asset_timestamps_cache[source] = asset_id
-                end
-              end
-
-              asset_id
-            end
-          end
-        end
-
-        # Break out the asset path rewrite in case plugins wish to put the asset id
-        # someplace other than the query string.
-        def rewrite_asset_path(source, path = nil)
-          if path && path.respond_to?(:call)
-            return path.call(source)
-          elsif path && path.is_a?(String)
-            return path % [source]
-          end
-
-          asset_id = rails_asset_id(source)
-          if asset_id.empty?
-            source
-          else
-            "#{source}?#{asset_id}"
-          end
-        end
-
-        def determine_source(source, collection)
-          case source
-          when Symbol
-            collection[source] || raise(ArgumentError, "No expansion found for #{source.inspect}")
-          else
-            source
-          end
-        end
-
-        def join_asset_file_contents(paths)
-          paths.collect { |path| File.read(asset_file_path!(path, true)) }.join("\n\n")
-        end
-
-        def write_asset_file_contents(joined_asset_path, asset_paths)
-          FileUtils.mkdir_p(File.dirname(joined_asset_path))
-          File.atomic_write(joined_asset_path) { |cache| cache.write(join_asset_file_contents(asset_paths)) }
-
-          # Set mtime to the latest of the combined files to allow for
-          # consistent ETag without a shared filesystem.
-          mt = asset_paths.map { |p| File.mtime(asset_file_path(p)) }.max
-          File.utime(mt, mt, joined_asset_path)
-        end
-
-        def asset_file_path(path)
-          File.join(config.assets_dir, path.split('?').first)
-        end
-
-        def asset_file_path!(path, error_if_file_is_uri = false)
-          if is_uri?(path)
-            raise(Errno::ENOENT, "Asset file #{path} is uri and cannot be merged into single file") if error_if_file_is_uri
-          else
-            absolute_path = asset_file_path(path)
-            raise(Errno::ENOENT, "Asset file not found at '#{absolute_path}'" ) unless File.exist?(absolute_path)
-            return absolute_path
-          end
-        end
-
-        def collect_asset_files(*path)
-          dir = path.first
-
-          Dir[File.join(*path.compact)].collect do |file|
-            file[-(file.size - dir.size - 1)..-1].sub(/\.\w+$/, '')
-          end.sort
-        end
+      include AssetIdCaching
     end
   end
 end
diff --git a/actionpack/lib/action_view/helpers/asset_tag_helpers/asset_id_caching.rb b/actionpack/lib/action_view/helpers/asset_tag_helpers/asset_id_caching.rb
new file mode 100644
index 0000000000..36fe961a72
--- /dev/null
+++ b/actionpack/lib/action_view/helpers/asset_tag_helpers/asset_id_caching.rb
@@ -0,0 +1,67 @@
+require 'active_support/concern'
+
+module ActionView
+  module Helpers
+    module AssetTagHelper
+
+      module AssetIdCaching
+        extend ActiveSupport::Concern
+
+        included do
+          # You can enable or disable the asset tag timestamps cache.
+          # With the cache enabled, the asset tag helper methods will make fewer
+          # expensive file system calls. However this prevents you from modifying
+          # any asset files while the server is running.
+          #
+          #   ActionView::Helpers::AssetTagHelper.cache_asset_timestamps = false
+          mattr_accessor :cache_asset_timestamps
+
+          private
+          mattr_accessor :asset_timestamps_cache
+          self.asset_timestamps_cache = {}
+
+          mattr_accessor :asset_timestamps_cache_guard
+          self.asset_timestamps_cache_guard = Mutex.new
+        end
+
+        private
+
+          # Use the RAILS_ASSET_ID environment variable or the source's
+          # modification time as its cache-busting asset id.
+          def rails_asset_id(source)
+            if asset_id = ENV["RAILS_ASSET_ID"]
+              asset_id
+            else
+              if self.cache_asset_timestamps && (asset_id = self.asset_timestamps_cache[source])
+                asset_id
+              else
+                path = File.join(config.assets_dir, source)
+                asset_id = File.exist?(path) ? File.mtime(path).to_i.to_s : ''
+
+                if self.cache_asset_timestamps
+                  self.asset_timestamps_cache_guard.synchronize do
+                    self.asset_timestamps_cache[source] = asset_id
+                  end
+                end
+
+                asset_id
+              end
+            end
+          end
+
+          # Break out the asset path rewrite in case plugins wish to put the asset id
+          # someplace other than the query string.
+          # This is the default implementation
+          def handle_asset_id(source)
+            asset_id = rails_asset_id(source)
+            if asset_id.empty?
+              source
+            else
+              "#{source}?#{asset_id}"
+            end
+          end
+      end
+
+    end
+  end
+end
\ No newline at end of file
diff --git a/actionpack/lib/action_view/helpers/asset_tag_helpers/base_asset_helpers.rb b/actionpack/lib/action_view/helpers/asset_tag_helpers/base_asset_helpers.rb
new file mode 100644
index 0000000000..7dbb0fa70f
--- /dev/null
+++ b/actionpack/lib/action_view/helpers/asset_tag_helpers/base_asset_helpers.rb
@@ -0,0 +1,330 @@
+require 'active_support/concern'
+require 'action_view/helpers/asset_tag_helpers/helper_methods'
+
+module ActionView
+  module Helpers
+    module AssetTagHelper
+
+      module BaseAssetHelpers
+        extend HelperMethods
+        # Returns a link tag that browsers and news readers can use to auto-detect
+        # an RSS or ATOM feed. The +type+ can either be <tt>:rss</tt> (default) or
+        # <tt>:atom</tt>. Control the link options in url_for format using the
+        # +url_options+. You can modify the LINK tag itself in +tag_options+.
+        #
+        # ==== Options
+        # * <tt>:rel</tt>  - Specify the relation of this link, defaults to "alternate"
+        # * <tt>:type</tt>  - Override the auto-generated mime type
+        # * <tt>:title</tt>  - Specify the title of the link, defaults to the +type+
+        #
+        # ==== Examples
+        #  auto_discovery_link_tag # =>
+        #     <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/action" />
+        #  auto_discovery_link_tag(:atom) # =>
+        #     <link rel="alternate" type="application/atom+xml" title="ATOM" href="http://www.currenthost.com/controller/action" />
+        #  auto_discovery_link_tag(:rss, {:action => "feed"}) # =>
+        #     <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/feed" />
+        #  auto_discovery_link_tag(:rss, {:action => "feed"}, {:title => "My RSS"}) # =>
+        #     <link rel="alternate" type="application/rss+xml" title="My RSS" href="http://www.currenthost.com/controller/feed" />
+        #  auto_discovery_link_tag(:rss, {:controller => "news", :action => "feed"}) # =>
+        #     <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/news/feed" />
+        #  auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", {:title => "Example RSS"}) # =>
+        #     <link rel="alternate" type="application/rss+xml" title="Example RSS" href="http://www.example.com/feed" />
+        def auto_discovery_link_tag(type = :rss, url_options = {}, tag_options = {})
+          tag(
+            "link",
+            "rel"   => tag_options[:rel] || "alternate",
+            "type"  => tag_options[:type] || Mime::Type.lookup_by_extension(type.to_s).to_s,
+            "title" => tag_options[:title] || type.to_s.upcase,
+            "href"  => url_options.is_a?(Hash) ? url_for(url_options.merge(:only_path => false)) : url_options
+          )
+        end
+
+        # Web browsers cache favicons. If you just throw a <tt>favicon.ico</tt> into the document
+        # root of your application and it changes later, clients that have it in their cache
+        # won't see the update. Using this helper prevents that because it appends an asset ID:
+        #
+        #   <%= favicon_link_tag %>
+        #
+        # generates
+        #
+        #   <link href="/favicon.ico?4649789979" rel="shortcut icon" type="image/vnd.microsoft.icon" />
+        #
+        # You may specify a different file in the first argument:
+        #
+        #   <%= favicon_link_tag 'favicon.ico' %>
+        #
+        # That's passed to +path_to_image+ as is, so it gives
+        #
+        #   <link href="/images/favicon.ico?4649789979" rel="shortcut icon" type="image/vnd.microsoft.icon" />
+        #
+        # The helper accepts an additional options hash where you can override "rel" and "type".
+        #
+        # For example, Mobile Safari looks for a different LINK tag, pointing to an image that
+        # will be used if you add the page to the home screen of an iPod Touch, iPhone, or iPad.
+        # The following call would generate such a tag:
+        #
+        #   <%= favicon_link_tag 'mb-icon.png', :rel => 'apple-touch-icon', :type => 'image/png' %>
+        #
+        def favicon_link_tag(source='/favicon.ico', options={})
+          tag('link', {
+            :rel  => 'shortcut icon',
+            :type => 'image/vnd.microsoft.icon',
+            :href => path_to_image(source)
+          }.merge(options.symbolize_keys))
+        end
+
+        # Computes the path to an image asset in the public images directory.
+        # Full paths from the document root will be passed through.
+        # Used internally by +image_tag+ to build the image path:
+        #
+        #   image_path("edit")                                         # => "/images/edit"
+        #   image_path("edit.png")                                     # => "/images/edit.png"
+        #   image_path("icons/edit.png")                               # => "/images/icons/edit.png"
+        #   image_path("/icons/edit.png")                              # => "/icons/edit.png"
+        #   image_path("http://www.railsapplication.com/img/edit.png") # => "http://www.railsapplication.com/img/edit.png"
+        #
+        # If you have images as application resources this method may conflict with their named routes.
+        # The alias +path_to_image+ is provided to avoid that. Rails uses the alias internally, and
+        # plugin authors are encouraged to do so.
+        asset_path :image
+
+        # Computes the path to a video asset in the public videos directory.
+        # Full paths from the document root will be passed through.
+        # Used internally by +video_tag+ to build the video path.
+        #
+        # ==== Examples
+        #   video_path("hd")                                            # => /videos/hd
+        #   video_path("hd.avi")                                        # => /videos/hd.avi
+        #   video_path("trailers/hd.avi")                               # => /videos/trailers/hd.avi
+        #   video_path("/trailers/hd.avi")                              # => /trailers/hd.avi
+        #   video_path("http://www.railsapplication.com/vid/hd.avi") # => http://www.railsapplication.com/vid/hd.avi
+        asset_path :video
+
+        # Computes the path to an audio asset in the public audios directory.
+        # Full paths from the document root will be passed through.
+        # Used internally by +audio_tag+ to build the audio path.
+        #
+        # ==== Examples
+        #   audio_path("horse")                                            # => /audios/horse
+        #   audio_path("horse.wav")                                        # => /audios/horse.wav
+        #   audio_path("sounds/horse.wav")                                 # => /audios/sounds/horse.wav
+        #   audio_path("/sounds/horse.wav")                                # => /sounds/horse.wav
+        #   audio_path("http://www.railsapplication.com/sounds/horse.wav") # => http://www.railsapplication.com/sounds/horse.wav
+        asset_path :audio
+
+        # Returns an html image tag for the +source+. The +source+ can be a full
+        # path or a file that exists in your public images directory.
+        #
+        # ==== Options
+        # You can add HTML attributes using the +options+. The +options+ supports
+        # three additional keys for convenience and conformance:
+        #
+        # * <tt>:alt</tt>  - If no alt text is given, the file name part of the
+        #   +source+ is used (capitalized and without the extension)
+        # * <tt>:size</tt> - Supplied as "{Width}x{Height}", so "30x45" becomes
+        #   width="30" and height="45". <tt>:size</tt> will be ignored if the
+        #   value is not in the correct format.
+        # * <tt>:mouseover</tt> - Set an alternate image to be used when the onmouseover
+        #   event is fired, and sets the original image to be replaced onmouseout.
+        #   This can be used to implement an easy image toggle that fires on onmouseover.
+        #
+        # ==== Examples
+        #  image_tag("icon")  # =>
+        #    <img src="/images/icon" alt="Icon" />
+        #  image_tag("icon.png")  # =>
+        #    <img src="/images/icon.png" alt="Icon" />
+        #  image_tag("icon.png", :size => "16x10", :alt => "Edit Entry")  # =>
+        #    <img src="/images/icon.png" width="16" height="10" alt="Edit Entry" />
+        #  image_tag("/icons/icon.gif", :size => "16x16")  # =>
+        #    <img src="/icons/icon.gif" width="16" height="16" alt="Icon" />
+        #  image_tag("/icons/icon.gif", :height => '32', :width => '32') # =>
+        #    <img alt="Icon" height="32" src="/icons/icon.gif" width="32" />
+        #  image_tag("/icons/icon.gif", :class => "menu_icon") # =>
+        #    <img alt="Icon" class="menu_icon" src="/icons/icon.gif" />
+        #  image_tag("mouse.png", :mouseover => "/images/mouse_over.png") # =>
+        #    <img src="/images/mouse.png" onmouseover="this.src='/images/mouse_over.png'" onmouseout="this.src='/images/mouse.png'" alt="Mouse" />
+        #  image_tag("mouse.png", :mouseover => image_path("mouse_over.png")) # =>
+        #    <img src="/images/mouse.png" onmouseover="this.src='/images/mouse_over.png'" onmouseout="this.src='/images/mouse.png'" alt="Mouse" />
+        def image_tag(source, options = {})
+          options.symbolize_keys!
+
+          src = options[:src] = path_to_image(source)
+
+          unless src =~ /^cid:/
+            options[:alt] = options.fetch(:alt){ File.basename(src, '.*').capitalize }
+          end
+
+          if size = options.delete(:size)
+            options[:width], options[:height] = size.split("x") if size =~ %r{^\d+x\d+$}
+          end
+
+          if mouseover = options.delete(:mouseover)
+            options[:onmouseover] = "this.src='#{path_to_image(mouseover)}'"
+            options[:onmouseout]  = "this.src='#{src}'"
+          end
+
+          tag("img", options)
+        end
+
+        # Returns an html video tag for the +sources+. If +sources+ is a string,
+        # a single video tag will be returned. If +sources+ is an array, a video
+        # tag with nested source tags for each source will be returned. The
+        # +sources+ can be full paths or files that exists in your public videos
+        # directory.
+        #
+        # ==== Options
+        # You can add HTML attributes using the +options+. The +options+ supports
+        # two additional keys for convenience and conformance:
+        #
+        # * <tt>:poster</tt> - Set an image (like a screenshot) to be shown
+        #   before the video loads. The path is calculated like the +src+ of +image_tag+.
+        # * <tt>:size</tt> - Supplied as "{Width}x{Height}", so "30x45" becomes
+        #   width="30" and height="45". <tt>:size</tt> will be ignored if the
+        #   value is not in the correct format.
+        #
+        # ==== Examples
+        #  video_tag("trailer")  # =>
+        #    <video src="/videos/trailer" />
+        #  video_tag("trailer.ogg")  # =>
+        #    <video src="/videos/trailer.ogg" />
+        #  video_tag("trailer.ogg", :controls => true, :autobuffer => true)  # =>
+        #    <video autobuffer="autobuffer" controls="controls" src="/videos/trailer.ogg" />
+        #  video_tag("trailer.m4v", :size => "16x10", :poster => "screenshot.png")  # =>
+        #    <video src="/videos/trailer.m4v" width="16" height="10" poster="/images/screenshot.png" />
+        #  video_tag("/trailers/hd.avi", :size => "16x16")  # =>
+        #    <video src="/trailers/hd.avi" width="16" height="16" />
+        #  video_tag("/trailers/hd.avi", :height => '32', :width => '32') # =>
+        #    <video height="32" src="/trailers/hd.avi" width="32" />
+        #  video_tag(["trailer.ogg", "trailer.flv"]) # =>
+        #    <video><source src="trailer.ogg" /><source src="trailer.ogg" /><source src="trailer.flv" /></video>
+        #  video_tag(["trailer.ogg", "trailer.flv"] :size => "160x120") # =>
+        #    <video height="120" width="160"><source src="trailer.ogg" /><source src="trailer.flv" /></video>
+        def video_tag(sources, options = {})
+          options.symbolize_keys!
+
+          options[:poster] = path_to_image(options[:poster]) if options[:poster]
+
+          if size = options.delete(:size)
+            options[:width], options[:height] = size.split("x") if size =~ %r{^\d+x\d+$}
+          end
+
+          if sources.is_a?(Array)
+            content_tag("video", options) do
+              sources.map { |source| tag("source", :src => source) }.join.html_safe
+            end
+          else
+            options[:src] = path_to_video(sources)
+            tag("video", options)
+          end
+        end
+
+        # Returns an html audio tag for the +source+.
+        # The +source+ can be full path or file that exists in
+        # your public audios directory.
+        #
+        # ==== Examples
+        #  audio_tag("sound")  # =>
+        #    <audio src="/audios/sound" />
+        #  audio_tag("sound.wav")  # =>
+        #    <audio src="/audios/sound.wav" />
+        #  audio_tag("sound.wav", :autoplay => true, :controls => true)  # =>
+        #    <audio autoplay="autoplay" controls="controls" src="/audios/sound.wav" />
+        def audio_tag(source, options = {})
+          options.symbolize_keys!
+          options[:src] = path_to_audio(source)
+          tag("audio", options)
+        end
+
+        private
+
+          def rewrite_extension(source, dir, ext)
+            source_ext = File.extname(source)
+
+            if source_ext.empty?
+              "#{source}.#{ext}"
+            elsif ext != source_ext[1..-1]
+              with_ext = "#{source}.#{ext}"
+              with_ext if File.exist?(File.join(config.assets_dir, dir, with_ext))
+            end || source
+          end
+
+          def rewrite_host_and_protocol(source, has_request)
+            host = compute_asset_host(source)
+            if has_request && host && !is_uri?(host)
+              host = "#{controller.request.protocol}#{host}"
+            end
+            "#{host}#{source}"
+          end
+
+          def rewrite_relative_url_root(source, relative_url_root)
+            relative_url_root && !source.starts_with?("#{relative_url_root}/") ? "#{relative_url_root}#{source}" : source
+          end
+
+          # Add the the extension +ext+ if not present. Return full URLs otherwise untouched.
+          # Prefix with <tt>/dir/</tt> if lacking a leading +/+. Account for relative URL
+          # roots. Rewrite the asset path for cache-busting asset ids. Include
+          # asset host, if configured, with the correct request protocol.
+          def compute_public_path(source, dir, ext = nil, include_host = true)
+            return source if is_uri?(source)
+
+            source = rewrite_extension(source, dir, ext) if ext
+            source = "/#{dir}/#{source}" unless source[0] == ?/
+            if controller.respond_to?(:env) && controller.env["action_dispatch.asset_path"]
+              source = rewrite_asset_path(source, controller.env["action_dispatch.asset_path"])
+            end
+            source = rewrite_asset_path(source, config.asset_path)
+
+            has_request = controller.respond_to?(:request)
+            source = rewrite_relative_url_root(source, controller.config.relative_url_root) if has_request && include_host
+            source = rewrite_host_and_protocol(source, has_request) if include_host
+
+            source
+          end
+
+          def is_uri?(path)
+            path =~ %r{^[-a-z]+://|^cid:}
+          end
+
+          # Pick an asset host for this source. Returns +nil+ if no host is set,
+          # the host if no wildcard is set, the host interpolated with the
+          # numbers 0-3 if it contains <tt>%d</tt> (the number is the source hash mod 4),
+          # or the value returned from invoking the proc if it's a proc or the value from
+          # invoking call if it's an object responding to call.
+          def compute_asset_host(source)
+            if host = config.asset_host
+              if host.is_a?(Proc) || host.respond_to?(:call)
+                case host.is_a?(Proc) ? host.arity : host.method(:call).arity
+                when 2
+                  request = controller.respond_to?(:request) && controller.request
+                  host.call(source, request)
+                else
+                  host.call(source)
+                end
+              else
+                (host =~ /%d/) ? host % (source.hash % 4) : host
+              end
+            end
+          end
+
+          # Break out the asset path rewrite in case plugins wish to put the asset id
+          # someplace other than the query string.
+          def rewrite_asset_path(source, path = nil)
+            if path && path.respond_to?(:call)
+              return path.call(source)
+            elsif path && path.is_a?(String)
+              return path % [source]
+            else
+              handle_asset_id(source)
+            end
+          end
+
+          # This is the default implementation
+          def handle_asset_id(source)
+            source
+          end
+      end
+
+    end
+  end
+end
\ No newline at end of file
diff --git a/actionpack/lib/action_view/helpers/asset_tag_helpers/helper_methods.rb b/actionpack/lib/action_view/helpers/asset_tag_helpers/helper_methods.rb
new file mode 100644
index 0000000000..348e33d535
--- /dev/null
+++ b/actionpack/lib/action_view/helpers/asset_tag_helpers/helper_methods.rb
@@ -0,0 +1,67 @@
+require 'active_support/concern'
+require 'active_support/inflector'
+
+module ActionView
+  module Helpers
+    module AssetTagHelper
+
+      module HelperMethods
+        private
+        def asset_path(asset_type, extension = nil)
+          define_method("#{asset_type}_path") do |source|
+            compute_public_path(source, asset_type.to_s.pluralize, extension)
+          end
+          alias_method :"path_to_#{asset_type}", :"#{asset_type}_path" # aliased to avoid conflicts with a *_path named route
+        end
+      end
+
+      module SharedHelpers
+        def determine_source(source, collection)
+          case source
+          when Symbol
+            collection[source] || raise(ArgumentError, "No expansion found for #{source.inspect}")
+          else
+            source
+          end
+        end
+
+        def join_asset_file_contents(paths)
+          paths.collect { |path| File.read(asset_file_path!(path, true)) }.join("\n\n")
+        end
+
+        def write_asset_file_contents(joined_asset_path, asset_paths)
+          FileUtils.mkdir_p(File.dirname(joined_asset_path))
+          File.atomic_write(joined_asset_path) { |cache| cache.write(join_asset_file_contents(asset_paths)) }
+
+          # Set mtime to the latest of the combined files to allow for
+          # consistent ETag without a shared filesystem.
+          mt = asset_paths.map { |p| File.mtime(asset_file_path(p)) }.max
+          File.utime(mt, mt, joined_asset_path)
+        end
+
+        def asset_file_path(path)
+          File.join(config.assets_dir, path.split('?').first)
+        end
+
+        def asset_file_path!(path, error_if_file_is_uri = false)
+          if is_uri?(path)
+            raise(Errno::ENOENT, "Asset file #{path} is uri and cannot be merged into single file") if error_if_file_is_uri
+          else
+            absolute_path = asset_file_path(path)
+            raise(Errno::ENOENT, "Asset file not found at '#{absolute_path}'" ) unless File.exist?(absolute_path)
+            return absolute_path
+          end
+        end
+
+        def collect_asset_files(*path)
+          dir = path.first
+
+          Dir[File.join(*path.compact)].collect do |file|
+            file[-(file.size - dir.size - 1)..-1].sub(/\.\w+$/, '')
+          end.sort
+        end
+      end
+
+    end
+  end
+end
\ No newline at end of file
diff --git a/actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb b/actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb
index ea8ac3f9a1..668a6136bc 100644
--- a/actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb
+++ b/actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb
@@ -1,8 +1,14 @@
+require 'active_support/concern'
+require 'action_view/helpers/asset_tag_helpers/helper_methods'
+
 module ActionView
   module Helpers
     module AssetTagHelper
+
       module JavascriptTagHelpers
         extend ActiveSupport::Concern
+        extend HelperMethods
+        include SharedHelpers
 
         included do
           mattr_accessor :javascript_expansions
@@ -37,10 +43,7 @@ module ActionView
         #   javascript_path "/dir/xmlhr" # => /dir/xmlhr.js
         #   javascript_path "http://www.railsapplication.com/js/xmlhr" # => http://www.railsapplication.com/js/xmlhr
         #   javascript_path "http://www.railsapplication.com/js/xmlhr.js" # => http://www.railsapplication.com/js/xmlhr.js
-        def javascript_path(source)
-          compute_public_path(source, 'javascripts', 'js')
-        end
-        alias_method :path_to_javascript, :javascript_path # aliased to avoid conflicts with a javascript_path named route
+        asset_path :javascript, 'js'
 
         # Returns an HTML script tag for each of the +sources+ provided. You
         # can pass in the filename (.js extension is optional) of JavaScript files
@@ -174,7 +177,9 @@ module ActionView
             end
             return sources
           end
+
       end
+
     end
   end
 end
\ No newline at end of file
diff --git a/actionpack/lib/action_view/helpers/asset_tag_helpers/stylesheet_tag_helpers.rb b/actionpack/lib/action_view/helpers/asset_tag_helpers/stylesheet_tag_helpers.rb
index 6ae4792b70..1f18e9dfce 100644
--- a/actionpack/lib/action_view/helpers/asset_tag_helpers/stylesheet_tag_helpers.rb
+++ b/actionpack/lib/action_view/helpers/asset_tag_helpers/stylesheet_tag_helpers.rb
@@ -1,8 +1,14 @@
+require 'active_support/concern'
+require 'action_view/helpers/asset_tag_helpers/helper_methods'
+
 module ActionView
   module Helpers
     module AssetTagHelper
+
       module StylesheetTagHelpers
         extend ActiveSupport::Concern
+        extend HelperMethods
+        include SharedHelpers
 
         included do
           mattr_accessor :stylesheet_expansions
@@ -37,10 +43,8 @@ module ActionView
         #   stylesheet_path "/dir/style.css" # => /dir/style.css
         #   stylesheet_path "http://www.railsapplication.com/css/style" # => http://www.railsapplication.com/css/style
         #   stylesheet_path "http://www.railsapplication.com/css/style.css" # => http://www.railsapplication.com/css/style.css
-        def stylesheet_path(source)
-          compute_public_path(source, 'stylesheets', 'css')
-        end
-        alias_method :path_to_stylesheet, :stylesheet_path # aliased to avoid conflicts with a stylesheet_path named route
+        asset_path :stylesheet, 'css'
+
 
         # Returns a stylesheet link tag for the sources specified as arguments. If
         # you don't specify an extension, <tt>.css</tt> will be appended automatically.
@@ -159,6 +163,7 @@ module ActionView
           end
 
       end
+
     end
   end
 end
\ No newline at end of file