A lib/github/markup/markdown.rb

@@ -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

M lib/github/markups.rb → lib/github/markups.rb

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