Tidying up methods

README

@@ -1,13 +1,41 @@
 AssetFingerprint
 ================
+Ruby on Rails plugin to fingerprint asset files using md5 checksum in filenames
+to improve cacheability compared to default Rails asset caching strategy.
 
-Introduction goes here.
+Originally developed to improve the performance of MissedConnections.com.
 
+Plugin can also be configured to use the default Rails asset caching strategy of 
+putting file timestamps in the query string.
 
-Example
-=======
+Based on guidelines recommended by Google Page Speed here:
+http://code.google.com/speed/page-speed/docs/caching.html
 
-Example goes here.
+Rails Versions
+==============
+Tested with Rails 2.2.3 though there's a good chance it'll work with earlier
+and newer versions with little or no modification.
 
+HOWTO
+=====
+Install the plugin at vendor/plugins/asset_fingerprint in your app.
+
+Create a config/initializers/asset_fingerprint.rb file and add these lines:
+
+# config/initializers/asset_fingerprint.rb start
+require 'asset_fingerprint/asset_tag_helper'
+
+ActionView::Helpers::AssetTagHelper.asset_fingerprint_strategy = 
+  { :fingerprint => :timestamp, :path => :query_string }
+
+# config/initializers/asset_fingerprint.rb end
+
+Change the asset_fingerprint_strategy in this initializer file to suit
+your needs. Set :fingerprint to :timestamp and :path to :query_string if
+you want the same behaviour that ships with Rails, however, recommended strategy
+is { :fingerprint => :md5, :path => :file_name } for maximum cacheability. 
+
+Copyright (c) 2010 Eliot Sykes, released under the MIT license
+
+More projects at http://blog.eliotsykes.com/my-projects/
 
-Copyright (c) 2010 [name of plugin creator], released under the MIT license

lib/asset_fingerprint/asset_tag_helper.rb

@@ -48,15 +48,27 @@ def rails_asset_fingerprint(source)
         end
       end
 
+      def fingerprint_in_query_string(source, asset_fingerprint)
+        source + "?#{asset_fingerprint}"
+      end
+
+      def fingerprint_in_file_name(source, asset_fingerprint)
+        # Insert the fingerprinted string as part of the filename
+        # The -1 value causes the fingerprint to be appended, happens
+        # if there is no period in source.
+        # Example result if source = 'images/logo.png' the result would
+        # be "images/logo-fp-#{asset_fingerprint}.png"
+        fingerprint_index = source.rindex('.') || -1
+        String.new(source).insert(fingerprint_index, "-fp-#{asset_fingerprint}")
+      end
+
       # Replaces the Rails method of the same name in AssetTagHelper.
       def rewrite_asset_path(source)
         asset_fingerprint = rails_asset_fingerprint(source)
         if :query_string == @@asset_fingerprint_strategy[:path]
-          result = source + "?#{asset_fingerprint}"
+          result = fingerprint_in_query_string(source, asset_fingerprint)
         elsif :file_name == @@asset_fingerprint_strategy[:path]
-          # Replace the file extension with -asset_fingerprint
-          #result = source.replace
-          result = source
+          result = fingerprint_in_file_name(source, asset_fingerprint)
         else
           raise RuntimeError.new "Unknown :path strategy '#{@@asset_fingerprint_strategy[:path]}'"
         end