module Idempo::RequestFingerprint
  def self.call(idempotency_key, rack_request)
    d = Digest::SHA256.new
    d << idempotency_key << "\n"
    d << rack_request.url << "\n"
    d << rack_request.request_method << "\n"
    d << rack_request.get_header("HTTP_AUTHORIZATION").to_s << "\n"
    while (chunk = rack_request.env["rack.input"].read(1024 * 65))
      d << chunk
    end
    Base64.strict_encode64(d.digest)
  ensure
    rack_request.env["rack.input"].rewind
  end
end