class Middleman::Extensions::Gzip

def gzip_file(path)
  input_file = File.open(path, 'rb').read
  output_filename = options.overwrite ? path : path + '.gz'
  input_file_time = File.mtime(path)
  # Check if the right file's already there
  if !options.overwrite && File.exist?(output_filename) && File.mtime(output_filename) == input_file_time
    return [nil, nil, nil]
  end
  File.open(output_filename, 'wb') do |f|
    gz = Zlib::GzipWriter.new(f, Zlib::BEST_COMPRESSION)
    gz.mtime = input_file_time.to_i
    gz.write input_file
    gz.close
  end
  # Make the file times match, both for Nginx's gzip_static extension
  # and so we can ID existing files. Also, so even if the GZ files are
  # wiped out by build --clean and recreated, we won't rsync them over
  # again because they'll end up with the same mtime.
  File.utime(File.atime(output_filename), input_file_time, output_filename)
  old_size = File.size(path)
  new_size = File.size(output_filename)
  [output_filename, old_size, new_size]
end