first draft of relative URL rewriting

index.html

@@ -250,7 +250,7 @@ <h2 id="configuration">Configuration</h2>
           The URL at which packaged assets are cached and made available.
           Defaults to <b>assets</b>, but if you already have an existing
           AssetsController with a different purpose, you could change it to, say,
-          <b>packages</b>.
+          <b>packages</b>. <i>(Single directory names only, please.)</i>
         </td>
       </tr>
     </table>

lib/jammit.rb

@@ -4,11 +4,13 @@
 # to all of the configuration options.
 module Jammit
 
-  VERSION = "0.2.7"
+  VERSION               = "0.2.7"
 
-  ROOT = File.expand_path(File.dirname(__FILE__) + '/..')
+  ROOT                  = File.expand_path(File.dirname(__FILE__) + '/..')
 
-  ASSET_ROOT            = defined?(RAILS_ROOT) ? RAILS_ROOT : "."
+  ASSET_ROOT            = File.expand_path(defined?(RAILS_ROOT) ? RAILS_ROOT : ".")
+
+  PUBLIC_ROOT           = "#{ASSET_ROOT}/public"
 
   DEFAULT_CONFIG_PATH   = "#{ASSET_ROOT}/config/assets.yml"
 

lib/jammit/compressor.rb

@@ -17,8 +17,9 @@ class Compressor
       '.tiff' => 'image/tiff'
     }
 
-    # Detect all image URLs that are inside of an "embed" folder.
-    IMAGE_DETECTOR  = /url\(['"]?([^\s)]*embed\/[^\s)]+\.(png|jpg|jpeg|gif|tif|tiff))['"]?\)/
+
+    IMAGE_DETECTOR  = /url\(['"]?([^\s)]+\.(png|jpg|jpeg|gif|tif|tiff))['"]?\)/
+    IMAGE_EMBED     = /[\A\/]embed\//
     IMAGE_REPLACER  = /url\(__EMBED__([^\s)]+)\)/
 
     # MHTML file constants.
@@ -57,11 +58,13 @@ def compress_js(paths)
     # :datauri or :mhtml variant, post-processes the result to embed
     # referenced images.
     def compress_css(paths, variant=nil, asset_url=nil)
-      return @css_compressor.compress(concatenate(paths)) if variant.nil?
-      compressed_css = @css_compressor.compress(concatenate_and_tag_images(paths))
-      return with_data_uris(compressed_css) if variant == :datauri
-      return with_mhtml(compressed_css, asset_url) if variant == :mhtml
-      raise PackageNotFound, "\"#{variant}\" is not a valid stylesheet variant"
+      compressed_css = @css_compressor.compress(concatenate_and_tag_images(paths, variant))
+      case variant
+      when nil      then return compressed_css
+      when :datauri then return with_data_uris(compressed_css)
+      when :mhtml   then return with_mhtml(compressed_css, asset_url)
+      else raise PackageNotFound, "\"#{variant}\" is not a valid stylesheet variant"
+      end
     end
 
     # Compiles a single JST file by writing out a javascript that adds
@@ -86,11 +89,11 @@ def compile_jst(paths)
     # expand the paths before contatenating the CSS together and losing the
     # location of the original stylesheet path. Validate the images while we're
     # at it.
-    def concatenate_and_tag_images(paths)
+    def concatenate_and_tag_images(paths, variant=nil)
       stylesheets = [paths].flatten.map do |css_path|
         File.read(css_path).gsub(IMAGE_DETECTOR) do |url|
-          image_path = public_path($1, css_path)
-          valid_image(image_path) ? "url(__EMBED__#{image_path})" : url
+          new_path = rewrite_image_path(Pathname.new($1), Pathname.new(File.expand_path(css_path)), !!variant)
+          "url(#{new_path})"
         end
       end
       stylesheets.join("\n")
@@ -120,18 +123,35 @@ def with_mhtml(css, asset_url)
       [MHTML_START, mhtml, MHTML_END, css].flatten.join('')
     end
 
+    # Return a rewritten image URL for a new stylesheet -- the image should
+    # be tagged for embedding if embeddable, and referenced at the correct level
+    # if relative.
+    def rewrite_image_path(image_path, css_path, embed=false)
+      public_path = absolute_path(image_path, css_path)
+      return "__EMBED__#{public_path}" if embed && embeddable?(public_path)
+      image_path.relative? ? relative_path(public_path) : image_path.to_s
+    end
+
     # Get the site-absolute public path for an image file path that may or may
     # not be relative, given the path of the stylesheet that contains it.
-    def public_path(image_path, css_path)
-      image_path, css_path = Pathname.new(image_path), Pathname.new(css_path)
-      (image_path.absolute? ? Pathname.new("#{ASSET_ROOT}/public#{image_path}") : css_path.dirname + image_path).cleanpath
+    def absolute_path(image_pathname, css_pathname)
+      (image_pathname.absolute? ?
+        Pathname.new(File.join(PUBLIC_ROOT, image_pathname)) :
+        css_pathname.dirname + image_pathname).cleanpath
+    end
+
+    # CSS images that are referenced by relative paths, and are *not* being
+    # embedded, must be rewritten relative to the newly-merged stylesheet path.
+    def relative_path(absolute_path)
+      File.join('../', absolute_path.sub(PUBLIC_ROOT, ''))
     end
 
-    # An image is valid if it exists, and is less than 32K.
+    # An image is valid for embedding if it exists, is less than 32K, and is
+    # stored somewhere inside of a folder named "embed".
     # IE does not support Data-URIs larger than 32K, and you probably shouldn't
     # be embedding images that large in any case.
-    def valid_image(image_path)
-      image_path.exist? && image_path.size < 32.kilobytes
+    def embeddable?(image_path)
+      image_path.to_s.match(IMAGE_EMBED) && image_path.exist? && image_path.size < 32.kilobytes
     end
 
     # Return the Base64-encoded contents of an image on a single line.

lib/jammit/controller.rb

@@ -9,7 +9,7 @@ class Controller < ActionController::Base
 
     SUFFIX_STRIPPER = /-(datauri|mhtml)\Z/
 
-    NOT_FOUND_PATH  = "#{ASSET_ROOT}/public/404.html"
+    NOT_FOUND_PATH  = "#{PUBLIC_ROOT}/404.html"
 
     after_filter :cache_package if perform_caching
 
@@ -82,6 +82,7 @@ def package_not_found
 
 end
 
+# Make the Jammit::Controller available to Rails as a top-level controller.
 ::JammitController = Jammit::Controller
 
 if RAILS_ENV == 'development'

lib/jammit/packager.rb

@@ -37,7 +37,7 @@ def initialize
     # Unless forced, will only rebuild assets whose source files have been
     # changed since their last package build.
     def precache_all(output_dir=nil, base_url=nil)
-      output_dir ||= "#{ASSET_ROOT}/public/#{Jammit.package_path}"
+      output_dir ||= File.join(PUBLIC_ROOT, Jammit.package_path)
       cacheable(:js, output_dir).each  {|p| cache(p, 'js',  pack_javascripts(p), output_dir) }
       cacheable(:jst, output_dir).each {|p| cache(p, 'jst', pack_templates(p),  output_dir) }
       cacheable(:css, output_dir).each do |p|