module RubyNative::IAP::Decodable

def decode_and_verify_jws(jws)
  JWT.decode(jws, nil, true, algorithm: "ES256") { |header|
    verify_certificate_chain(header["x5c"])
  }.first
end

def parse_notification(signed_payload)
  payload = decode_and_verify_jws(signed_payload)
  transaction_info = decode_and_verify_jws(payload["data"]["signedTransactionInfo"])
  Notification.new(
    notification_type: payload["notificationType"],
    subtype: payload["subtype"],
    notification_uuid: payload["notificationUUID"],
    bundle_id: payload["data"]["bundleId"],
    app_account_token: transaction_info["appAccountToken"],
    product_id: transaction_info["productId"],
    original_transaction_id: transaction_info["originalTransactionId"],
    transaction_id: transaction_info["transactionId"],
    purchase_date: parse_timestamp(transaction_info["purchaseDate"]),
    expires_date: parse_timestamp(transaction_info["expiresDate"]),
    offer_type: transaction_info["offerType"],
    environment: payload["data"]["environment"]&.downcase
  )
end

def parse_timestamp(milliseconds)
  return nil if milliseconds.nil?
  Time.at(milliseconds / 1000.0).utc
end