require 'erb'

module Rake
  module Funnel
    module Support
      class TemplateEngine
        class << self
          def render(template, filename = nil, binding = nil)
            render = ERB.new(replace_at_markers(template), nil, '%<>')
            render.filename = filename
            render.result(binding || top_level_binding)
          end

          private
          def replace_at_markers(template)
            tags = /(@\w[\w\.]+\w@)/

            (template || '').gsub(tags) do |match|
              "<%= #{match[1...-1]} %>"
            end
          end

          def top_level_binding
            TOPLEVEL_BINDING.dup
          end
        end
      end
    end
  end
end