download.rb

def download_file(url)
  uri = URI(url)

  Rails.logger.info("Downloading evidence #{id} from filepicker.io")

  Net::HTTP.start(uri.host, uri.port, :use_ssl => uri.scheme == 'https') do |http|
    request = Net::HTTP::Get.new(uri.path)

    http.request(request) do |response|
      file = File.new('evidence')
      file.binmode
      response.read_body do |chunk|
        file.write chunk
      end
      file.close
    end
  end
end