@@ -1,59 +1,41 @@
-begin
-  require 'open3_detach'
-rescue LoadError
-  require 'open3'
-end
+require "github/markup/command_implementation"
+require "github/markup/gem_implementation"
 
 module GitHub
   module Markup
     extend self
-    @@markups = {}
+    @@markups = []
+
+    def markups
+      @@markups
+    end
+
+    def preload!
+      markups.each do |markup|
+        markup.load
+      end
+    end
 
     def render(filename, content = nil)
       content ||= File.read(filename)
 
-      if proc = renderer(filename)
-        proc[content]
+      if impl = renderer(filename)
+        impl.render(content)
       else
         content
       end
     end
 
-    def markup(file, pattern, &block)
-      require file.to_s
-      add_markup(pattern, &block)
-      true
-    rescue LoadError
-      false
+    def markup(file, pattern, opts = {}, &block)
+      markups << GemImplementation.new(pattern, file, &block)
     end
 
     def command(command, regexp, &block)
-      command = command.to_s
-
       if File.exists?(file = File.dirname(__FILE__) + "/commands/#{command}")
         command = file
       end
 
-      add_markup(regexp) do |content|
-        rendered = execute(command, content)
-        rendered = rendered.to_s.empty? ? content : rendered
-
-        if block && block.arity == 2
-          # If the block takes two arguments, pass new content and old
-          # content.
-          block.call(rendered, content)
-        elsif block
-          # One argument is just the new content.
-          block.call(rendered)
-        else
-          # No block? No problem!
-          rendered
-        end
-      end
-    end
-
-    def add_markup(regexp, &block)
-      @@markups[regexp] = block
+      markups << CommandImplementation.new(regexp, command, &block)
     end
 
     def can_render?(filename)
@@ -61,38 +43,13 @@ !!renderer(filename)
     end
 
     def renderer(filename)
-      @@markups.each do |key, value|
-        if Regexp.compile("\\.(#{key})$") =~ filename
-          return value
-        end
-      end
-      nil
-    end
-
-    def renderer_name(filename)
-      @@markups.each do |key, value|
-        if Regexp.compile("\\.(#{key})$") =~ filename
-          return key
-        end
-      end
-      nil
-    end
-
-    def execute(command, target)
-      out = ''
-      Open3.popen3(command) do |stdin, stdout, _|
-        stdin.puts target
-        stdin.close
-        out = stdout.read
-      end
-      out.gsub("\r", '')
-    rescue Errno::EPIPE
-      ""
-    rescue Errno::ENOENT
-      ""
+      markups.find { |impl|
+        impl.match?(filename)
+      }
     end
 
     # Define markups
-    instance_eval File.read(File.dirname(__FILE__) + '/markups.rb')
+    markups_rb = File.dirname(__FILE__) + '/markups.rb'
+    instance_eval File.read(markups_rb), markups_rb
   end
 end

@@ -0,0 +1,52 @@
+begin
+  require "open3_detach"
+rescue LoadError
+  require "open3"
+end
+
+require "github/markup/implementation"
+
+module GitHub
+  module Markup
+    class CommandImplementation < Implementation
+      attr_reader :command, :block
+
+      def initialize(regexp, command, &block)
+        super regexp
+        @command = command.to_s
+        @block = block
+      end
+
+      def render(content)
+        rendered = execute(command, content)
+        rendered = rendered.to_s.empty? ? content : rendered
+        call_block(rendered, content)
+      end
+
+    private
+      def call_block(rendered, content)
+        if block && block.arity == 2
+          block.call(rendered, content)
+        elsif block
+          block.call(rendered)
+        else
+          rendered
+        end
+      end
+
+      def execute(command, target)
+        out = ''
+        Open3.popen3(command) do |stdin, stdout, _|
+          stdin.puts target
+          stdin.close
+          out = stdout.read
+        end
+        out.gsub("\r", '')
+      rescue Errno::EPIPE
+        ""
+      rescue Errno::ENOENT
+        ""
+      end
+    end
+  end
+end

@@ -0,0 +1,26 @@
+require "github/markup/implementation"
+
+module GitHub
+  module Markup
+    class GemImplementation < Implementation
+      attr_reader :gem_name, :renderer
+
+      def initialize(regexp, gem_name, &renderer)
+        super regexp
+        @gem_name = gem_name.to_s
+        @renderer = renderer
+      end
+
+      def load
+        return if @loaded
+        require gem_name
+        @loaded = true
+      end
+
+      def render(content)
+        load
+        renderer.call(content)
+      end
+    end
+  end
+end

@@ -0,0 +1,28 @@
+module GitHub
+  module Markup
+    class Implementation
+      attr_reader :regexp
+
+      def initialize(regexp)
+        @regexp = regexp
+      end
+
+      def load
+        # no-op by default
+      end
+
+      def render(content)
+        raise NotImplementedError, "subclasses of GitHub::Markup::Implementation must define #render"
+      end
+
+      def match?(filename)
+        file_ext_regexp =~ filename
+      end
+
+    private
+      def file_ext_regexp
+        @file_ext_regexp ||= /\.(#{regexp})\z/
+      end
+    end
+  end
+end

@@ -0,0 +1,56 @@
+require "github/markup/implementation"
+
+module GitHub
+  module Markup
+    class Markdown < Implementation
+      MARKDOWN_GEMS = {
+        "github/markdown" => proc { |content|
+          GitHub::Markdown.render(content)
+        },
+        "redcarpet" => proc { |content|
+          RedcarpetCompat.new(content).to_html
+        },
+        "rdiscount" => proc { |content|
+          RDiscount.new(content).to_html
+        },
+        "maruku" => proc { |content|
+          Maruku.new(content).to_html
+        },
+        "kramdown" => proc { |content|
+          Kramdown::Document.new(content).to_html
+        },
+        "bluecloth" => proc { |content|
+          BlueCloth.new(content).to_html
+        },
+      }
+
+      def initialize
+        super(/md|mkdn?|mdwn|mdown|markdown|litcoffee/)
+      end
+
+      def load
+        return if @renderer
+        MARKDOWN_GEMS.each do |gem_name, renderer|
+          if try_require(gem_name)
+            @renderer = renderer
+            return
+          end
+        end
+        raise LoadError, "no suitable markdown gem found"
+      end
+
+      def render(content)
+        load
+        @renderer.call(content)
+      end
+
+    private
+      def try_require(file)
+        require file
+        true
+      rescue LoadError
+        false
+      end
+    end
+  end
+end

@@ -1,24 +1,6 @@
-MD_FILES = /md|mkdn?|mdwn|mdown|markdown|litcoffee/
+require "github/markup/markdown"
 
-if markup('github/markdown', MD_FILES) do |content|
-    GitHub::Markdown.render(content)
-  end
-elsif markup(:redcarpet, MD_FILES) do |content|
-    RedcarpetCompat.new(content).to_html
-  end
-elsif markup(:rdiscount, MD_FILES) do |content|
-    RDiscount.new(content).to_html
-  end
-elsif markup(:maruku, MD_FILES) do |content|
-    Maruku.new(content).to_html
-  end
-elsif markup(:kramdown, MD_FILES) do |content|
-    Kramdown::Document.new(content).to_html
-  end
-elsif markup(:bluecloth, MD_FILES) do |content|
-    BlueCloth.new(content).to_html
-  end
-end
+markups << GitHub::Markup::Markdown.new
 
 markup(:redcloth, /textile/) do |content|
   RedCloth.new(content).to_html