Better CSS extraction

- Move all methods in the subclassed Premailer to a separate module responsible
for loading CSS files.
- No longer force a specific adapter.

lib/premailer-rails3.rb

@@ -1,5 +1,5 @@
 require 'premailer'
-require 'hpricot'
+require 'premailer-rails3/css_helper'
 require 'premailer-rails3/premailer'
 require 'premailer-rails3/hook'
 

lib/premailer-rails3/css_helper.rb

@@ -0,0 +1,52 @@
+module PremailerRails
+  module CSSHelper
+    extend self
+
+    @@css_cache = {}
+
+    def css_for_doc(doc)
+      css = doc.search('link[@type="text/css"]').map { |link|
+              url = link.attributes['href']
+              load_css_at_path(url) unless url.blank?
+            }.reject(&:blank?).join("\n")
+      css = load_css_at_path(:default) if css.blank?
+      css
+    end
+
+    private
+
+    def load_css_at_path(path)
+      if path.is_a? String
+        # Remove everything after ? including ?
+        path = path[0..(path.index('?') - 1)] if path.include? '?'
+        # Remove the host
+        path = path.gsub(/^https?\:\/\/[^\/]*/, '') if path.index('http') == 0
+      end
+
+      # Don't cache in development.
+      if Rails.env.development? or not @@css_cache.include? path
+        @@css_cache[path] =
+          if defined? Hassle and Rails.configuration.middleware.include? Hassle
+            file = path == :default ? 'stylesheets/email.css' : path
+            File.read("#{Rails.root}/tmp/hassle/#{file}")
+          elsif Rails.configuration.try(:assets).try(:enabled)
+            file = if path == :default
+                     'email.css'
+                   else
+                     path.sub("#{Rails.configuration.assets.prefix}/", '')
+                   end
+            Rails.application.assets.find_asset(file).body
+          else
+            file = path == :default ? 'stylesheets/email.css' : path
+            File.read("#{Rails.root}/public/#{file}")
+          end
+      end
+
+      @@css_cache[path]
+    rescue => ex
+      # Print an error and store empty string as the CSS.
+      puts ex.message
+      @@css_cache[path] = ''
+    end
+  end
+end

lib/premailer-rails3/premailer.rb

@@ -1,64 +1,21 @@
 module PremailerRails
   class Premailer < ::Premailer
-    @@_css_cache = {}
-
     def initialize(html)
-      load_html(html)
-      options = {
-        :with_html_string => true,
-        :adapter          => :hpricot
-      }.merge css_options
-      super(html, options)
-    end
-
-    def load_html(string)
-      # @doc is also used by ::Premailer
-      @doc ||= Hpricot(string)
-    end
-
-    protected
+      # In order to pass the CSS as string to super it is necessary to access
+      # the parsed HTML beforehand. To do so, the adapter needs to be
+      # initialized. The ::Premailer::Adaptor handles the discovery of a
+      # suitable adaptor (Nokogiri or Hpricot). To make load_html work, an
+      # adaptor needs to be included and @options[:with_html_string] needs to be
+      # set. For further information, refer to ::Premailer#initialize.
+      @options = { :with_html_string => true }
+      ::Premailer.send(:include, Adapter.find(Adapter.use))
+      doc = load_html(html)
 
-    def css_options
       options = {
-        :css => linked_css_files
+        :with_html_string => true,
+        :css_string       => CSSHelper.css_for_doc(doc)
       }
-
-      if linked_css_files.empty?
-        options[:css_string] = default_css_file
-      end
-
-      options
-    end
-
-    def default_css_file
-      # Don't cache in development.
-      if Rails.env.development? or not @@_css_cache.include? :default
-        @@_css_cache[:default] =
-          if defined? Hassle and Rails.configuration.middleware.include? Hassle
-            File.read("#{Rails.root}/tmp/hassle/stylesheets/email.css")
-          elsif Rails.configuration.try(:assets).try(:enabled)
-            Rails.application.assets.find_asset('email.css').body
-          else
-            File.read("#{Rails.root}/public/stylesheets/email.css")
-          end
-      end
-      @@_css_cache[:default]
-    rescue => ex
-      puts ex.message
-      @@_css_cache[:default] = nil
-    end
-
-    # Scan the HTML mailer template for CSS files, specifically link tags with
-    # types of text/css (other ways of including CSS are not supported).
-    def linked_css_files
-      @_linked_css_files ||= @doc.search('link[@type="text/css"]').collect do |l|
-        href = l.attributes['href']
-        if href.include? '?'
-          href[0..(href.index('?') - 1)]
-        else
-          href
-        end
-      end
+      super(html, options)
     end
   end
 end

premailer-rails3.gemspec

@@ -23,5 +23,4 @@ Gem::Specification.new do |s|
   s.require_paths = ["lib"]
 
   s.add_dependency("premailer", ["~> 1.7"])
-  s.add_dependency("hpricot", ["~> 0.8"])
 end