class Sprockets::CharsetNormalizer

def evaluate(context, locals, &block)
  charset = nil
  # Find and strip out any `@charset` definitions
  filtered_data = data.gsub(/^@charset "([^"]+)";$/) {
    charset ||= $1; ""
  }
  if charset
    # If there was a charset, move it to the top
    "@charset \"#{charset}\";#{filtered_data}"
  else
    data
  end
end