generate css from less using lessc

_plugins/less.rb

@@ -0,0 +1,61 @@
+require 'digest/md5'
+
+module Jekyll
+
+  class LessCSSFile < StaticFile
+    def write(dest)
+      # do nothing
+    end
+  end
+
+  class LessCSS < Liquid::Tag
+    def initialize(tag_name, file, tokens)
+      super
+      @file = file.strip
+    end
+
+    def render(context)
+      site = context.registers[:site]
+
+      less_dir = File.join(site.source, '_less')
+
+      if File.symlink?(less_dir)
+        return "LessCSS directory '#{less_dir}' cannot be a symlink"
+      end
+
+      if @file !~ /^[a-zA-Z0-9_\/\.-]+$/ || @file =~ /\.\// || @file =~ /\/\./
+        return "LessCSS file '#{@file}' contains invalid characters or sequences"
+      end
+
+      Dir.chdir(less_dir) do
+        choices = Dir['**/*'].reject { |x| File.symlink?(x) }
+        if choices.include?(@file)
+          source = File.read(@file)
+          f = IO.popen("lessc", "w+")
+          f.write(source)
+          f.close_write()
+
+          css = f.readlines().join()
+
+          digest = Digest::MD5.hexdigest(css)
+
+          css_file = digest + ".css"
+          css_path = File.join(site.dest, css_file)
+
+          File.open(css_path, "w") do |f|
+            f.write(css)
+          end
+
+          site.static_files << LessCSSFile.new(site, site.source, '', css_file)
+        
+          '<link rel="stylesheet" type="text/css" href="/' + css_file + '" />'
+        else
+          return "LessCSS file '#{@file}' not found in '#{less_dir}'"
+        end
+      end
+    end
+  end
+
+end
+
+Liquid::Template.register_tag('lesscss', Jekyll::LessCSS)