Added task to resolve relative URLs in CSS files with Rails asset_pat…

…h helper.

lib/tasks/bower.rake

@@ -30,7 +30,7 @@ namespace :bower do
     perform false do
       sh 'bower list'
     end
-  end  
+  end
 
   namespace :update do
     desc "Update existing components and uninstalls extraneous components"
@@ -40,6 +40,13 @@ namespace :bower do
       end
     end
   end
+
+  desc "Resolve assets paths in bower components"
+  task :resolve do
+    perform false do
+      resolve_asset_paths
+    end
+  end
 end
 
 def perform remove_components = true, &block
@@ -133,3 +140,31 @@ def perform_command remove_components = true, &block
     end if data && !data["dependencies"].empty?
   end
 end
+
+def resolve_asset_paths
+  # Resolve relative paths in CSS
+  Dir['bower_components/**/*.css'].each do |filename|
+    contents = File.read(filename)
+    # http://www.w3.org/TR/CSS2/syndata.html#uri
+    url_regex = /url\(\s*['"]?(?![a-z]+:)([^'"\)]*)['"]?\s*\)/
+
+    # Resolve paths in CSS file if it contains a url
+    if contents =~ url_regex
+      directory_path = Pathname.new(File.dirname(filename))
+        .relative_path_from(Pathname.new('bower_components'))
+
+      # Replace relative paths in URLs with Rails asset_path helper
+      new_contents = contents.gsub(url_regex) do |match|
+        relative_path = $1
+        image_path = directory_path.join(relative_path).cleanpath
+        puts "#{match} => #{image_path}"
+
+        "url(<%= asset_path '#{image_path}' %>)"
+      end
+
+      # Replace CSS with ERB CSS file with resolved asset paths
+      FileUtils.rm(filename)
+      File.write(filename + '.erb', new_contents)
+    end
+  end
+end