middleman-premailer-config.rb

require 'premailer'

###
# Helpers
###

# Integrated Premailer from https://github.com/RyanParsley/OMP-Generator/blob/master/config.rb
# Premailer API: http://premailer.dialect.ca/api
module PreMailer
  class << self
    def registered(app)
      require 'premailer'
      app.after_build do |builder|
        prefix = build_dir + File::SEPARATOR
        Dir.chdir(build_dir) do
          Dir.glob('**/*.html') do |file|
            premailer = Premailer.new(file, :warn_level => Premailer::Warnings::SAFE, :adapter => :nokogiri, :preserve_styles => false, :remove_comments => false, :remove_ids => true, :'query-string' => '')
            fileout = File.open(file, 'w')
            fileout.puts premailer.to_inline_css
            fileout.close
            premailer.warnings.each do |w|
              builder.say_status :premailer, "#{w[:message]} (#{w[:level]}) may not render properly in #{w[:clients]}"
            end
            builder.say_status :premailer, prefix+file
          end
        end
      end
    end
    alias :included :registered
  end
end

::Middleman::Extensions.register(:inline_premailer, PreMailer)

activate :inline_premailer