Add local validation for card information.

2021-03-29 16:16:54 +04:00 · 2021-03-29 16:16:54 +04:00 · 0af6c4b0b6
parent e077163322
commit 0af6c4b0b6
23 changed files with 950 additions and 98 deletions
--- a/Telegram/CMakeLists.txt
+++ b/Telegram/CMakeLists.txt
@ -1029,8 +1029,6 @@ PRIVATE
    ui/search_field_controller.h
    ui/special_buttons.cpp
    ui/special_buttons.h
-    ui/special_fields.cpp
-    ui/special_fields.h
    ui/unread_badge.cpp
    ui/unread_badge.h
    window/main_window.cpp
--- a/Telegram/SourceFiles/boxes/change_phone_box.cpp
+++ b/Telegram/SourceFiles/boxes/change_phone_box.cpp
@ -151,7 +151,7 @@ void ChangePhoneBox::EnterPhone::prepare() {
 		this,
 		st::defaultInputField,
 		tr::lng_change_phone_new_title(),
-		ExtractPhonePrefix(_session->user()->phone()),
+		Ui::ExtractPhonePrefix(_session->user()->phone()),
 		phoneValue);

 	_phone->resize(st::boxWidth - 2 * st::boxPadding.left(), _phone->height());
--- a/Telegram/SourceFiles/boxes/confirm_phone_box.cpp
+++ b/Telegram/SourceFiles/boxes/confirm_phone_box.cpp
@ -71,14 +71,6 @@ void ShowPhoneBannedError(const QString &phone) {
 		[=] { SendToBannedHelp(phone); close(); }));
 }

-QString ExtractPhonePrefix(const QString &phone) {
-	const auto pattern = phoneNumberParse(phone);
-	if (!pattern.isEmpty()) {
-		return phone.mid(0, pattern[0]);
-	}
-	return QString();
-}
-
 SentCodeField::SentCodeField(
 	QWidget *parent,
 	const style::InputField &st,
--- a/Telegram/SourceFiles/boxes/confirm_phone_box.h
+++ b/Telegram/SourceFiles/boxes/confirm_phone_box.h
@ -22,7 +22,6 @@ class Session;
 } // namespace Main

 void ShowPhoneBannedError(const QString &phone);
-[[nodiscard]] QString ExtractPhonePrefix(const QString &phone);

 class SentCodeField : public Ui::InputField {
 public:
--- a/Telegram/SourceFiles/config.h
+++ b/Telegram/SourceFiles/config.h
@ -13,9 +13,6 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 enum {
 	MaxSelectedItems = 100,

-	MaxPhoneCodeLength = 4, // max length of country phone code
-	MaxPhoneTailLength = 32, // rest of the phone number, without country code (seen 12 at least), need more for service numbers
-
 	LocalEncryptIterCount = 4000, // key derivation iteration count
 	LocalEncryptNoPwdIterCount = 4, // key derivation iteration count without pwd (not secure anyway)
 	LocalEncryptSaltSize = 32, // 256 bit
--- a/Telegram/SourceFiles/passport/passport_panel_edit_contact.cpp
+++ b/Telegram/SourceFiles/passport/passport_panel_edit_contact.cpp
@ -278,7 +278,8 @@ void PanelEditContact::setupControls(
 			wrap.data(),
 			fieldStyle,
 			std::move(fieldPlaceholder),
-			ExtractPhonePrefix(_controller->bot()->session().user()->phone()),
+			Ui::ExtractPhonePrefix(
+				_controller->bot()->session().user()->phone()),
 			data);
 	} else {
 		_field = Ui::CreateChild<Ui::MaskedInputField>(
--- a/Telegram/SourceFiles/payments/payments_checkout_process.cpp
+++ b/Telegram/SourceFiles/payments/payments_checkout_process.cpp
@ -166,23 +166,36 @@ void CheckoutProcess::handleError(const Error &error) {
 			showForm();
 			return;
 		}
-		using Field = Ui::InformationField;
+		using InfoField = Ui::InformationField;
+		using CardField = Ui::CardField;
 		if (id == u"REQ_INFO_NAME_INVALID"_q) {
-			showInformationError(Field::Name);
+			showInformationError(InfoField::Name);
 		} else if (id == u"REQ_INFO_EMAIL_INVALID"_q) {
-			showInformationError(Field::Email);
+			showInformationError(InfoField::Email);
 		} else if (id == u"REQ_INFO_PHONE_INVALID"_q) {
-			showInformationError(Field::Phone);
+			showInformationError(InfoField::Phone);
 		} else if (id == u"ADDRESS_STREET_LINE1_INVALID"_q) {
-			showInformationError(Field::ShippingStreet);
+			showInformationError(InfoField::ShippingStreet);
 		} else if (id == u"ADDRESS_CITY_INVALID"_q) {
-			showInformationError(Field::ShippingCity);
+			showInformationError(InfoField::ShippingCity);
 		} else if (id == u"ADDRESS_STATE_INVALID"_q) {
-			showInformationError(Field::ShippingState);
+			showInformationError(InfoField::ShippingState);
 		} else if (id == u"ADDRESS_COUNTRY_INVALID"_q) {
-			showInformationError(Field::ShippingCountry);
+			showInformationError(InfoField::ShippingCountry);
 		} else if (id == u"ADDRESS_POSTCODE_INVALID"_q) {
-			showInformationError(Field::ShippingPostcode);
+			showInformationError(InfoField::ShippingPostcode);
+		} else if (id == u"LOCAL_CARD_NUMBER_INVALID"_q) {
+			showCardError(CardField::Number);
+		} else if (id == u"LOCAL_CARD_EXPIRE_DATE_INVALID"_q) {
+			showCardError(CardField::ExpireDate);
+		} else if (id == u"LOCAL_CARD_CVC_INVALID"_q) {
+			showCardError(CardField::Cvc);
+		} else if (id == u"LOCAL_CARD_HOLDER_NAME_INVALID"_q) {
+			showCardError(CardField::Name);
+		} else if (id == u"LOCAL_CARD_BILLING_COUNTRY_INVALID"_q) {
+			showCardError(CardField::AddressCountry);
+		} else if (id == u"LOCAL_CARD_BILLING_ZIP_INVALID"_q) {
+			showCardError(CardField::AddressZip);
 		} else if (id == u"SHIPPING_BOT_TIMEOUT"_q) {
 			showToast({ "Error: Bot Timeout!" }); // #TODO payments errors message
 		} else if (id == u"SHIPPING_NOT_AVAILABLE"_q) {
@ -196,11 +209,17 @@ void CheckoutProcess::handleError(const Error &error) {
 		if (id == u"InvalidNumber"_q || id == u"IncorrectNumber"_q) {
 			showCardError(Field::Number);
 		} else if (id == u"InvalidCVC"_q || id == u"IncorrectCVC"_q) {
-			showCardError(Field::CVC);
+			showCardError(Field::Cvc);
 		} else if (id == u"InvalidExpiryMonth"_q
 			|| id == u"InvalidExpiryYear"_q
 			|| id == u"ExpiredCard"_q) {
 			showCardError(Field::ExpireDate);
+		} else if (id == u"CardDeclined"_q) {
+			// #TODO payments errors message
+			showToast({ "Error: " + id });
+		} else if (id == u"ProcessingError"_q) {
+			// #TODO payments errors message
+			showToast({ "Error: " + id });
 		} else {
 			showToast({ "Error: " + id });
 		}
--- a/Telegram/SourceFiles/payments/payments_form.cpp
+++ b/Telegram/SourceFiles/payments/payments_form.cpp
@ -19,6 +19,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "stripe/stripe_api_client.h"
 #include "stripe/stripe_error.h"
 #include "stripe/stripe_token.h"
+#include "stripe/stripe_card_validator.h"
 #include "ui/image/image.h"
 #include "apiwrap.h"
 #include "styles/style_payments.h" // paymentsThumbnailSize.
@ -270,6 +271,7 @@ void Form::processDetails(const MTPDpayments_paymentForm &data) {
 void Form::processSavedInformation(const MTPDpaymentRequestedInfo &data) {
 	const auto address = data.vshipping_address();
 	_savedInformation = Ui::RequestedInformation{
+		.defaultPhone = defaultPhone(),
 		.defaultCountry = defaultCountry(),
 		.name = qs(data.vname().value_or_empty()),
 		.phone = qs(data.vphone().value_or_empty()),
@ -293,11 +295,16 @@ void Form::refreshPaymentMethodDetails() {
 	const auto &entered = _paymentMethod.newCredentials;
 	_paymentMethod.ui.title = entered ? entered.title : saved.title;
 	_paymentMethod.ui.ready = entered || saved;
+	_paymentMethod.ui.native.defaultPhone = defaultPhone();
 	_paymentMethod.ui.native.defaultCountry = defaultCountry();
 }

+QString Form::defaultPhone() const {
+	return _session->user()->phone();
+}
+
 QString Form::defaultCountry() const {
-	return Data::CountryISO2ByPhone(_session->user()->phone());
+	return Data::CountryISO2ByPhone(defaultPhone());
 }

 void Form::fillPaymentMethodInformation() {
@ -382,10 +389,16 @@ void Form::validateInformation(const Ui::RequestedInformation &information) {
 		_api.request(base::take(_validateRequestId)).cancel();
 	}
 	_validatedInformation = information;
-	if (const auto error = localInformationError(information)) {
-		_updates.fire_copy(error);
+	if (!validateInformationLocal(information)) {
 		return;
 	}
+
+	Assert(!_invoice.isShippingAddressRequested
+		|| information.shippingAddress);
+	Assert(!_invoice.isNameRequested || !information.name.isEmpty());
+	Assert(!_invoice.isEmailRequested || !information.email.isEmpty());
+	Assert(!_invoice.isPhoneRequested || !information.phone.isEmpty());
+
 	_validateRequestId = _api.request(MTPpayments_ValidateRequestedInfo(
 		MTP_flags(0), // #TODO payments save information
 		MTP_int(_msgId.msg),
@ -415,26 +428,43 @@ void Form::validateInformation(const Ui::RequestedInformation &information) {
 	}).send();
 }

-Error Form::localInformationError(
+bool Form::validateInformationLocal(
 		const Ui::RequestedInformation &information) const {
-	const auto error = [](const QString &id) {
-		return Error{ Error::Type::Validate, id };
+	if (const auto error = informationErrorLocal(information)) {
+		_updates.fire_copy(error);
+		return false;
+	}
+	return true;
+}
+
+Error Form::informationErrorLocal(
+		const Ui::RequestedInformation &information) const {
+	auto errors = QStringList();
+	const auto push = [&](const QString &id) {
+		errors.push_back(id);
 	};
-	if (_invoice.isShippingAddressRequested
-		&& !information.shippingAddress) {
-		return information.shippingAddress.address1.isEmpty()
-			? error(u"ADDRESS_STREET_LINE1_INVALID"_q)
-			: information.shippingAddress.city.isEmpty()
-			? error(u"ADDRESS_CITY_INVALID"_q)
-			: information.shippingAddress.countryIso2.isEmpty()
-			? error(u"ADDRESS_COUNTRY_INVALID"_q)
-			: (Unexpected("Shipping Address error."), Error());
-	} else if (_invoice.isNameRequested && information.name.isEmpty()) {
-		return error(u"REQ_INFO_NAME_INVALID"_q);
-	} else if (_invoice.isEmailRequested && information.email.isEmpty()) {
-		return error(u"REQ_INFO_EMAIL_INVALID"_q);
-	} else if (_invoice.isPhoneRequested && information.phone.isEmpty()) {
-		return error(u"REQ_INFO_PHONE_INVALID"_q);
+	if (_invoice.isShippingAddressRequested) {
+		if (information.shippingAddress.address1.isEmpty()) {
+			push(u"ADDRESS_STREET_LINE1_INVALID"_q);
+		}
+		if (information.shippingAddress.city.isEmpty()) {
+			push(u"ADDRESS_CITY_INVALID"_q);
+		}
+		if (information.shippingAddress.countryIso2.isEmpty()) {
+			push(u"ADDRESS_COUNTRY_INVALID"_q);
+		}
+	}
+	if (_invoice.isNameRequested && information.name.isEmpty()) {
+		push(u"REQ_INFO_NAME_INVALID"_q);
+	}
+	if (_invoice.isEmailRequested && information.email.isEmpty()) {
+		push(u"REQ_INFO_EMAIL_INVALID"_q);
+	}
+	if (_invoice.isPhoneRequested && information.phone.isEmpty()) {
+		push(u"REQ_INFO_PHONE_INVALID"_q);
+	}
+	if (!errors.isEmpty()) {
+		return Error{ Error::Type::Validate, errors.front() };
 	}
 	return Error();
 }
@ -442,6 +472,9 @@ Error Form::localInformationError(
 void Form::validateCard(const Ui::UncheckedCardDetails &details) {
 	Expects(!v::is_null(_paymentMethod.native.data));

+	if (!validateCardLocal(details)) {
+		return;
+	}
 	const auto &native = _paymentMethod.native.data;
 	if (const auto stripe = std::get_if<StripePaymentMethod>(&native)) {
 		validateCard(*stripe, details);
@ -450,6 +483,52 @@ void Form::validateCard(const Ui::UncheckedCardDetails &details) {
 	}
 }

+bool Form::validateCardLocal(const Ui::UncheckedCardDetails &details) const {
+	if (auto error = cardErrorLocal(details)) {
+		_updates.fire(std::move(error));
+		return false;
+	}
+	return true;
+}
+
+Error Form::cardErrorLocal(const Ui::UncheckedCardDetails &details) const {
+	using namespace Stripe;
+
+	auto errors = QStringList();
+	const auto push = [&](const QString &id) {
+		errors.push_back(id);
+	};
+	const auto kValid = ValidationState::Valid;
+	if (ValidateCard(details.number).state != kValid) {
+		push(u"LOCAL_CARD_NUMBER_INVALID"_q);
+	}
+	if (ValidateParsedExpireDate(
+		details.expireMonth,
+		details.expireYear
+	) != kValid) {
+		push(u"LOCAL_CARD_EXPIRE_DATE_INVALID"_q);
+	}
+	if (ValidateCvc(details.number, details.cvc).state != kValid) {
+		push(u"LOCAL_CARD_CVC_INVALID"_q);
+	}
+	if (_paymentMethod.ui.native.needCardholderName
+		&& details.cardholderName.isEmpty()) {
+		push(u"LOCAL_CARD_HOLDER_NAME_INVALID"_q);
+	}
+	if (_paymentMethod.ui.native.needCountry
+		&& details.addressCountry.isEmpty()) {
+		push(u"LOCAL_CARD_BILLING_COUNTRY_INVALID"_q);
+	}
+	if (_paymentMethod.ui.native.needZip
+		&& details.addressZip.isEmpty()) {
+		push(u"LOCAL_CARD_BILLING_ZIP_INVALID"_q);
+	}
+	if (!errors.isEmpty()) {
+		return Error{ Error::Type::Validate, errors.front() };
+	}
+	return Error();
+}
+
 void Form::validateCard(
 		const StripePaymentMethod &method,
 		const Ui::UncheckedCardDetails &details) {
--- a/Telegram/SourceFiles/payments/payments_form.h
+++ b/Telegram/SourceFiles/payments/payments_form.h
@ -196,14 +196,23 @@ private:
 	void fillPaymentMethodInformation();
 	void fillStripeNativeMethod();
 	void refreshPaymentMethodDetails();
+	[[nodiscard]] QString defaultPhone() const;
 	[[nodiscard]] QString defaultCountry() const;

 	void validateCard(
 		const StripePaymentMethod &method,
 		const Ui::UncheckedCardDetails &details);

-	[[nodiscard]] Error localInformationError(
+	bool validateInformationLocal(
 		const Ui::RequestedInformation &information) const;
+	[[nodiscard]] Error informationErrorLocal(
+		const Ui::RequestedInformation &information) const;
+
+	bool validateCardLocal(
+		const Ui::UncheckedCardDetails &details) const;
+	[[nodiscard]] Error cardErrorLocal(
+		const Ui::UncheckedCardDetails &details) const;
+

 	const not_null<Main::Session*> _session;
 	MTP::Sender _api;
--- a/Telegram/SourceFiles/payments/stripe/stripe_card.h
+++ b/Telegram/SourceFiles/payments/stripe/stripe_card.h
@ -20,6 +20,7 @@ enum class CardBrand {
 	Discover,
 	JCB,
 	DinersClub,
+	UnionPay,
 	Unknown,
 };

--- a/Telegram/SourceFiles/payments/stripe/stripe_card_validator.cpp
+++ b/Telegram/SourceFiles/payments/stripe/stripe_card_validator.cpp
@ -0,0 +1,279 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop application for the Telegram messaging service.
+
+For license and copyright information please follow this link:
+https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
+*/
+#include "stripe/stripe_card_validator.h"
+
+#include <QtCore/QDate>
+
+namespace Stripe {
+namespace {
+
+constexpr auto kMinCvcLength = 3;
+
+struct BinRange {
+	QString low;
+	QString high;
+	int length = 0;
+	CardBrand brand = CardBrand::Unknown;
+};
+
+[[nodiscard]] const std::vector<BinRange> &AllRanges() {
+	static auto kResult = std::vector<BinRange>{
+		// Unknown
+		{ "", "", 19, CardBrand::Unknown },
+		// American Express
+		{ "34", "34", 15, CardBrand::Amex },
+		{ "37", "37", 15, CardBrand::Amex },
+		// Diners Club
+		{ "30", "30", 16, CardBrand::DinersClub },
+		{ "36", "36", 14, CardBrand::DinersClub },
+		{ "38", "39", 16, CardBrand::DinersClub },
+		// Discover
+		{ "60", "60", 16, CardBrand::Discover },
+		{ "64", "65", 16, CardBrand::Discover },
+		// JCB
+		{ "35", "35", 16, CardBrand::JCB },
+		// Mastercard
+		{ "50", "59", 16, CardBrand::MasterCard },
+		{ "22", "27", 16, CardBrand::MasterCard },
+		{ "67", "67", 16, CardBrand::MasterCard }, // Maestro
+		// UnionPay
+		{ "62", "62", 16, CardBrand::UnionPay },
+		{ "81", "81", 16, CardBrand::UnionPay },
+		// Visa
+		{ "40", "49", 16, CardBrand::Visa },
+		{ "413600", "413600", 13, CardBrand::Visa },
+		{ "444509", "444509", 13, CardBrand::Visa },
+		{ "444509", "444509", 13, CardBrand::Visa },
+		{ "444550", "444550", 13, CardBrand::Visa },
+		{ "450603", "450603", 13, CardBrand::Visa },
+		{ "450617", "450617", 13, CardBrand::Visa },
+		{ "450628", "450629", 13, CardBrand::Visa },
+		{ "450636", "450636", 13, CardBrand::Visa },
+		{ "450640", "450641", 13, CardBrand::Visa },
+		{ "450662", "450662", 13, CardBrand::Visa },
+		{ "463100", "463100", 13, CardBrand::Visa },
+		{ "476142", "476142", 13, CardBrand::Visa },
+		{ "476143", "476143", 13, CardBrand::Visa },
+		{ "492901", "492902", 13, CardBrand::Visa },
+		{ "492920", "492920", 13, CardBrand::Visa },
+		{ "492923", "492923", 13, CardBrand::Visa },
+		{ "492928", "492930", 13, CardBrand::Visa },
+		{ "492937", "492937", 13, CardBrand::Visa },
+		{ "492939", "492939", 13, CardBrand::Visa },
+		{ "492960", "492960", 13, CardBrand::Visa },
+	};
+	return kResult;
+}
+
+[[nodiscard]] bool BinRangeMatchesNumber(
+		const BinRange &range,
+		const QString &sanitized) {
+	const auto minWithLow = std::min(sanitized.size(), range.low.size());
+	if (sanitized.midRef(0, minWithLow).toInt()
+		< range.low.midRef(0, minWithLow).toInt()) {
+		return false;
+	}
+	const auto minWithHigh = std::min(sanitized.size(), range.high.size());
+	if (sanitized.midRef(0, minWithHigh).toInt()
+		> range.high.midRef(0, minWithHigh).toInt()) {
+		return false;
+	}
+	return true;
+}
+
+[[nodiscard]] bool IsNumeric(const QString &value) {
+	return QRegularExpression("^[0-9]*$").match(value).hasMatch();
+}
+
+[[nodiscard]] QString RemoveWhitespaces(QString value) {
+	return value.replace(QRegularExpression("\\s"), QString());
+}
+
+[[nodiscard]] std::vector<BinRange> BinRangesForNumber(
+		const QString &sanitized) {
+	const auto &all = AllRanges();
+	auto result = std::vector<BinRange>();
+	result.reserve(all.size());
+	for (const auto &range : all) {
+		if (BinRangeMatchesNumber(range, sanitized)) {
+			result.push_back(range);
+		}
+	}
+	return result;
+}
+
+[[nodiscard]] BinRange MostSpecificBinRangeForNumber(
+		const QString &sanitized) {
+	auto possible = BinRangesForNumber(sanitized);
+	const auto compare = [&](const BinRange &a, const BinRange &b) {
+		if (sanitized.isEmpty()) {
+			const auto aUnknown = (a.brand == CardBrand::Unknown);
+			const auto bUnknown = (b.brand == CardBrand::Unknown);
+			if (aUnknown && !bUnknown) {
+				return true;
+			} else if (!aUnknown && bUnknown) {
+				return false;
+			}
+		}
+		return a.low.size() < b.low.size();
+	};
+	std::sort(begin(possible), end(possible), compare);
+	return possible.back();
+}
+
+[[nodiscard]] int MaxCvcLengthForBranch(CardBrand brand) {
+	switch (brand) {
+	case CardBrand::Amex:
+	case CardBrand::Unknown:
+		return 4;
+	default:
+		return 3;
+	}
+}
+
+[[nodiscard]] std::vector<CardBrand> PossibleBrandsForNumber(
+		const QString &sanitized) {
+	const auto ranges = BinRangesForNumber(sanitized);
+	auto result = std::vector<CardBrand>();
+	for (const auto &range : ranges) {
+		const auto brand = range.brand;
+		if (brand == CardBrand::Unknown
+			|| (std::find(begin(result), end(result), brand)
+				!= end(result))) {
+			continue;
+		}
+		result.push_back(brand);
+	}
+	return result;
+}
+
+[[nodiscard]] CardBrand BrandForNumber(const QString &number) {
+	const auto sanitized = RemoveWhitespaces(number);
+	if (!IsNumeric(sanitized)) {
+		return CardBrand::Unknown;
+	}
+	const auto possible = PossibleBrandsForNumber(sanitized);
+	return (possible.size() == 1) ? possible.front() : CardBrand::Unknown;
+}
+
+[[nodiscard]] bool IsValidLuhn(const QString &sanitized) {
+	auto odd = true;
+	auto sum = 0;
+	for (auto i = sanitized.end(); i != sanitized.begin();) {
+		--i;
+		auto digit = int(i->unicode() - '0');
+		odd = !odd;
+		if (odd) {
+			digit *= 2;
+		}
+		if (digit > 9) {
+			digit -= 9;
+		}
+		sum += digit;
+	}
+	return (sum % 10) == 0;
+}
+
+} // namespace
+
+CardValidationResult ValidateCard(const QString &number) {
+	const auto sanitized = RemoveWhitespaces(number);
+	if (!IsNumeric(sanitized)) {
+		return { .state = ValidationState::Invalid };
+	} else if (sanitized.isEmpty()) {
+		return { .state = ValidationState::Incomplete };
+	}
+	const auto range = MostSpecificBinRangeForNumber(sanitized);
+	const auto brand = range.brand;
+	if (sanitized.size() > range.length) {
+		return { .state = ValidationState::Invalid, .brand = brand };
+	} else if (sanitized.size() < range.length) {
+		return { .state = ValidationState::Incomplete, .brand = brand };
+	} else if (!IsValidLuhn(sanitized)) {
+		return { .state = ValidationState::Invalid, .brand = brand };
+	}
+	return {
+		.state = ValidationState::Valid,
+		.brand = brand,
+		.finished = true,
+	};
+}
+
+ExpireDateValidationResult ValidateExpireDate(const QString &date) {
+	const auto sanitized = RemoveWhitespaces(date).replace('/', QString());
+	if (!IsNumeric(sanitized)) {
+		return { ValidationState::Invalid };
+	} else if (sanitized.size() < 2) {
+		return { ValidationState::Incomplete };
+	}
+	const auto normalized = (sanitized[0] > '1' ? "0" : "") + sanitized;
+	const auto month = normalized.mid(0, 2).toInt();
+	if (month < 1 || month > 12) {
+		return { ValidationState::Invalid };
+	} else if (normalized.size() < 4) {
+		return { ValidationState::Incomplete };
+	} else if (normalized.size() > 4) {
+		return { ValidationState::Invalid };
+	}
+	const auto year = 2000 + normalized.mid(2).toInt();
+
+	const auto currentDate = QDate::currentDate();
+	const auto currentMonth = currentDate.month();
+	const auto currentYear = currentDate.year();
+	if (year < currentYear) {
+		return { ValidationState::Invalid };
+	} else if (year == currentYear && month < currentMonth) {
+		return { ValidationState::Invalid };
+	}
+	return { ValidationState::Valid, true };
+}
+
+ValidationState ValidateParsedExpireDate(
+		quint32 month,
+		quint32 year) {
+	if ((year / 100) != 20) {
+		return ValidationState::Invalid;
+	}
+	return ValidateExpireDate(
+		QString("%1%2"
+		).arg(month, 2, 10, QChar('0')
+		).arg(year % 100, 2, 10, QChar('0'))
+	).state;
+}
+
+CvcValidationResult ValidateCvc(
+		const QString &number,
+		const QString &cvc) {
+	if (!IsNumeric(cvc)) {
+		return { ValidationState::Invalid };
+	} else if (cvc.size() < kMinCvcLength) {
+		return { ValidationState::Incomplete };
+	}
+	const auto maxLength = MaxCvcLengthForBranch(BrandForNumber(number));
+	if (cvc.size() > maxLength) {
+		return { ValidationState::Invalid };
+	}
+	return { ValidationState::Valid, (cvc.size() == maxLength) };
+}
+
+std::vector<int> CardNumberFormat(const QString &number) {
+	static const auto kDefault = std::vector{ 4, 4, 4, 4 };
+	const auto sanitized = RemoveWhitespaces(number);
+	if (!IsNumeric(sanitized)) {
+		return kDefault;
+	}
+	const auto range = MostSpecificBinRangeForNumber(sanitized);
+	if (range.brand == CardBrand::DinersClub && range.length == 14) {
+		return { 4, 6, 4 };
+	} else if (range.brand == CardBrand::Amex) {
+		return { 4, 6, 5 };
+	}
+	return kDefault;
+}
+
+} // namespace Stripe
--- a/Telegram/SourceFiles/payments/stripe/stripe_card_validator.h
+++ b/Telegram/SourceFiles/payments/stripe/stripe_card_validator.h
@ -0,0 +1,51 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop application for the Telegram messaging service.
+
+For license and copyright information please follow this link:
+https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
+*/
+#pragma once
+
+#include "stripe/stripe_card.h"
+
+namespace Stripe {
+
+enum class ValidationState {
+	Invalid,
+	Incomplete,
+	Valid,
+};
+
+struct CardValidationResult {
+	ValidationState state = ValidationState::Invalid;
+	CardBrand brand = CardBrand::Unknown;
+	bool finished = false;
+};
+
+[[nodiscard]] CardValidationResult ValidateCard(const QString &number);
+
+struct ExpireDateValidationResult {
+	ValidationState state = ValidationState::Invalid;
+	bool finished = false;
+};
+
+[[nodiscard]] ExpireDateValidationResult ValidateExpireDate(
+	const QString &date);
+
+[[nodiscard]] ValidationState ValidateParsedExpireDate(
+	quint32 month,
+	quint32 year);
+
+struct CvcValidationResult {
+	ValidationState state = ValidationState::Invalid;
+	bool finished = false;
+};
+
+[[nodiscard]] CvcValidationResult ValidateCvc(
+	const QString &number,
+	const QString &cvc);
+
+[[nodiscard]] std::vector<int> CardNumberFormat(const QString &number);
+
+} // namespace Stripe
--- a/Telegram/SourceFiles/payments/ui/payments_edit_card.cpp
+++ b/Telegram/SourceFiles/payments/ui/payments_edit_card.cpp
@ -9,6 +9,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL

 #include "payments/ui/payments_panel_delegate.h"
 #include "payments/ui/payments_field.h"
+#include "stripe/stripe_card_validator.h"
 #include "ui/widgets/scroll_area.h"
 #include "ui/widgets/buttons.h"
 #include "ui/widgets/labels.h"
@ -18,10 +19,15 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "styles/style_payments.h"
 #include "styles/style_passport.h"

+#include <QtCore/QRegularExpression>
+
 namespace Payments::Ui {
 namespace {

-constexpr auto kMaxPostcodeSize = 10;
+struct SimpleFieldState {
+	QString value;
+	int position = 0;
+};

 [[nodiscard]] uint32 ExtractYear(const QString &value) {
 	return value.split('/').value(1).toInt() + 2000;
@ -31,6 +37,165 @@ constexpr auto kMaxPostcodeSize = 10;
 	return value.split('/').value(0).toInt();
 }

+[[nodiscard]] QString RemoveNonNumbers(QString value) {
+	return value.replace(QRegularExpression("[^0-9]"), QString());
+}
+
+[[nodiscard]] SimpleFieldState NumbersOnlyState(SimpleFieldState state) {
+	return {
+		.value = RemoveNonNumbers(state.value),
+		.position = RemoveNonNumbers(
+			state.value.mid(0, state.position)).size(),
+	};
+}
+
+[[nodiscard]] SimpleFieldState PostprocessCardValidateResult(
+		SimpleFieldState result) {
+	const auto groups = Stripe::CardNumberFormat(result.value);
+	auto position = 0;
+	for (const auto length : groups) {
+		position += length;
+		if (position >= result.value.size()) {
+			break;
+		}
+		result.value.insert(position, QChar(' '));
+		if (result.position >= position) {
+			++result.position;
+		}
+		++position;
+	}
+	return result;
+}
+
+[[nodiscard]] SimpleFieldState PostprocessExpireDateValidateResult(
+		SimpleFieldState result) {
+	if (result.value.isEmpty()) {
+		return result;
+	} else if (result.value[0] == '1' && result.value[1] > '2') {
+		result.value = result.value.mid(0, 2);
+		return result;
+	} else if (result.value[0] > '1') {
+		result.value = '0' + result.value;
+		++result.position;
+	}
+	if (result.value.size() > 1) {
+		if (result.value.size() > 4) {
+			result.value = result.value.mid(0, 4);
+		}
+		result.value.insert(2, '/');
+		if (result.position >= 2) {
+			++result.position;
+		}
+	}
+	return result;
+}
+
+[[nodiscard]] bool IsBackspace(const FieldValidateRequest &request) {
+	return (request.wasAnchor == request.wasPosition)
+		&& (request.wasPosition == request.nowPosition + 1)
+		&& (request.wasValue.midRef(0, request.wasPosition - 1)
+			== request.nowValue.midRef(0, request.nowPosition))
+		&& (request.wasValue.midRef(request.wasPosition)
+			== request.nowValue.midRef(request.nowPosition));
+}
+
+[[nodiscard]] bool IsDelete(const FieldValidateRequest &request) {
+	return (request.wasAnchor == request.wasPosition)
+		&& (request.wasPosition == request.nowPosition)
+		&& (request.wasValue.midRef(0, request.wasPosition)
+			== request.nowValue.midRef(0, request.nowPosition))
+		&& (request.wasValue.midRef(request.wasPosition + 1)
+			== request.nowValue.midRef(request.nowPosition));
+}
+
+template <
+	typename ValueValidator,
+	typename ValueValidateResult = decltype(
+		std::declval<ValueValidator>()(QString()))>
+[[nodiscard]] auto ComplexNumberValidator(
+		ValueValidator valueValidator,
+		Fn<SimpleFieldState(SimpleFieldState)> postprocess) {
+	using namespace Stripe;
+	return [=](FieldValidateRequest request) {
+		const auto realNowState = [&] {
+			const auto backspaced = IsBackspace(request);
+			const auto deleted = IsDelete(request);
+			if (!backspaced && !deleted) {
+				return NumbersOnlyState({
+					.value = request.nowValue,
+					.position = request.nowPosition,
+				});
+			}
+			const auto realWasState = NumbersOnlyState({
+				.value = request.wasValue,
+				.position = request.wasPosition,
+			});
+			const auto changedValue = deleted
+				? (realWasState.value.mid(0, realWasState.position)
+					+ realWasState.value.mid(realWasState.position + 1))
+				: (realWasState.position > 1)
+				? (realWasState.value.mid(0, realWasState.position - 1)
+					+ realWasState.value.mid(realWasState.position))
+				: realWasState.value.mid(realWasState.position);
+			return SimpleFieldState{
+				.value = changedValue,
+				.position = (deleted
+					? realWasState.position
+					: std::max(realWasState.position - 1, 0))
+			};
+		}();
+		const auto result = valueValidator(realNowState.value);
+		const auto postprocessed = postprocess(realNowState);
+		return FieldValidateResult{
+			.value = postprocessed.value,
+			.position = postprocessed.position,
+			.invalid = (result.state == ValidationState::Invalid),
+			.finished = result.finished,
+		};
+	};
+
+}
+
+[[nodiscard]] auto CardNumberValidator() {
+	return ComplexNumberValidator(
+		Stripe::ValidateCard,
+		PostprocessCardValidateResult);
+}
+
+[[nodiscard]] auto ExpireDateValidator() {
+	return ComplexNumberValidator(
+		Stripe::ValidateExpireDate,
+		PostprocessExpireDateValidateResult);
+}
+
+[[nodiscard]] auto CvcValidator(Fn<QString()> number) {
+	using namespace Stripe;
+	return [=](FieldValidateRequest request) {
+		const auto realNowState = NumbersOnlyState({
+			.value = request.nowValue,
+			.position = request.nowPosition,
+		});
+		const auto result = ValidateCvc(number(), realNowState.value);
+
+		return FieldValidateResult{
+			.value = realNowState.value,
+			.position = realNowState.position,
+			.invalid = (result.state == ValidationState::Invalid),
+			.finished = result.finished,
+		};
+	};
+}
+
+[[nodiscard]] auto CardHolderNameValidator() {
+	return [=](FieldValidateRequest request) {
+		return FieldValidateResult{
+			.value = request.nowValue.toUpper(),
+			.position = request.nowPosition,
+			.invalid = request.nowValue.isEmpty(),
+		};
+	};
+}
+
 } // namespace

 EditCard::EditCard(
@ -111,15 +276,8 @@ not_null<RpWidget*> EditCard::setupContent() {
 	_number = add({
 		.type = FieldType::CardNumber,
 		.placeholder = tr::lng_payments_card_number(),
-		.required = true,
+		.validator = CardNumberValidator(),
 	});
-	if (_native.needCardholderName) {
-		_name = add({
-			.type = FieldType::CardNumber,
-			.placeholder = tr::lng_payments_card_holder(),
-			.required = true,
-		});
-	}
 	auto container = inner->add(
 		object_ptr<FixedHeightWidget>(
 			inner,
@ -128,12 +286,12 @@ not_null<RpWidget*> EditCard::setupContent() {
 	_expire = std::make_unique<Field>(container, FieldConfig{
 		.type = FieldType::CardExpireDate,
 		.placeholder = rpl::single(u"MM / YY"_q),
-		.required = true,
+		.validator = ExpireDateValidator(),
 	});
 	_cvc = std::make_unique<Field>(container, FieldConfig{
 		.type = FieldType::CardCVC,
 		.placeholder = rpl::single(u"CVC"_q),
-		.required = true,
+		.validator = CvcValidator([=] { return _number->value(); }),
 	});
 	container->widthValue(
 	) | rpl::start_with_next([=](int width) {
@ -144,6 +302,24 @@ not_null<RpWidget*> EditCard::setupContent() {
 		_expire->widget()->moveToLeft(0, 0, width);
 		_cvc->widget()->moveToRight(0, 0, width);
 	}, container->lifetime());
+
+	if (_native.needCardholderName) {
+		_name = add({
+			.type = FieldType::CardNumber,
+			.placeholder = tr::lng_payments_card_holder(),
+			.validator = CardHolderNameValidator(),
+		});
+	}
+
+	_number->setNextField(_expire.get());
+	_expire->setPreviousField(_number.get());
+	_expire->setNextField(_cvc.get());
+	_cvc->setPreviousField(_expire.get());
+	if (_name) {
+		_cvc->setNextField(_name.get());
+		_name->setPreviousField(_cvc.get());
+	}
+
 	if (_native.needCountry || _native.needZip) {
 		inner->add(
 			object_ptr<Ui::FlatLabel>(
@ -156,18 +332,23 @@ not_null<RpWidget*> EditCard::setupContent() {
 		_country = add({
 			.type = FieldType::Country,
 			.placeholder = tr::lng_payments_billing_country(),
+			.validator = RequiredFinishedValidator(),
 			.showBox = showBox,
 			.defaultCountry = _native.defaultCountry,
-			.required = true,
 		});
 	}
 	if (_native.needZip) {
 		_zip = add({
 			.type = FieldType::Text,
 			.placeholder = tr::lng_payments_billing_zip_code(),
-			.maxLength = kMaxPostcodeSize,
-			.required = true,
+			.validator = RequiredValidator(),
 		});
+		if (_country) {
+			_country->finished(
+			) | rpl::start_with_next([=] {
+				_zip->setFocus();
+			}, lifetime());
+		}
 	}
 	return inner;
 }
@ -198,7 +379,7 @@ void EditCard::updateControlsGeometry() {
 auto EditCard::lookupField(CardField field) const -> Field* {
 	switch (field) {
 	case CardField::Number: return _number.get();
-	case CardField::CVC: return _cvc.get();
+	case CardField::Cvc: return _cvc.get();
 	case CardField::ExpireDate: return _expire.get();
 	case CardField::Name: return _name.get();
 	case CardField::AddressCountry: return _country.get();
--- a/Telegram/SourceFiles/payments/ui/payments_edit_information.cpp
+++ b/Telegram/SourceFiles/payments/ui/payments_edit_information.cpp
@ -26,6 +26,8 @@ constexpr auto kMaxPostcodeSize = 10;
 constexpr auto kMaxNameSize = 64;
 constexpr auto kMaxEmailSize = 128;
 constexpr auto kMaxPhoneSize = 16;
+constexpr auto kMinCitySize = 2;
+constexpr auto kMaxCitySize = 64;

 } // namespace

@ -112,18 +114,17 @@ not_null<RpWidget*> EditInformation::setupContent() {
 		_street1 = add({
 			.placeholder = tr::lng_payments_address_street1(),
 			.value = _information.shippingAddress.address1,
-			.maxLength = kMaxStreetSize,
-			.required = true,
+			.validator = RangeLengthValidator(1, kMaxStreetSize),
 		});
 		_street2 = add({
 			.placeholder = tr::lng_payments_address_street2(),
 			.value = _information.shippingAddress.address2,
-			.maxLength = kMaxStreetSize,
+			.validator = MaxLengthValidator(kMaxStreetSize),
 		});
 		_city = add({
 			.placeholder = tr::lng_payments_address_city(),
 			.value = _information.shippingAddress.city,
-			.required = true,
+			.validator = RangeLengthValidator(kMinCitySize, kMaxCitySize),
 		});
 		_state = add({
 			.placeholder = tr::lng_payments_address_state(),
@ -133,44 +134,38 @@ not_null<RpWidget*> EditInformation::setupContent() {
 			.type = FieldType::Country,
 			.placeholder = tr::lng_payments_address_country(),
 			.value = _information.shippingAddress.countryIso2,
+			.validator = RequiredFinishedValidator(),
 			.showBox = showBox,
 			.defaultCountry = _information.defaultCountry,
-			.required = true,
 		});
 		_postcode = add({
 			.placeholder = tr::lng_payments_address_postcode(),
 			.value = _information.shippingAddress.postcode,
-			.maxLength = kMaxPostcodeSize,
-			.required = true,
+			.validator = RangeLengthValidator(1, kMaxPostcodeSize),
 		});
-		//StreetValidate, // #TODO payments
-		//CityValidate,
-		//CountryValidate,
-		//CountryFormat,
-		//PostcodeValidate,
 	}
 	if (_invoice.isNameRequested) {
 		_name = add({
 			.placeholder = tr::lng_payments_info_name(),
 			.value = _information.name,
-			.maxLength = kMaxNameSize,
-			.required = true,
+			.validator = RangeLengthValidator(1, kMaxNameSize),
 		});
 	}
 	if (_invoice.isEmailRequested) {
 		_email = add({
+			.type = FieldType::Email,
 			.placeholder = tr::lng_payments_info_email(),
 			.value = _information.email,
-			.maxLength = kMaxEmailSize,
-			.required = true,
+			.validator = RangeLengthValidator(1, kMaxEmailSize),
 		});
 	}
 	if (_invoice.isPhoneRequested) {
 		_phone = add({
+			.type = FieldType::Phone,
 			.placeholder = tr::lng_payments_info_phone(),
 			.value = _information.phone,
-			.maxLength = kMaxPhoneSize,
-			.required = true,
+			.validator = RangeLengthValidator(1, kMaxPhoneSize),
+			.defaultPhone = _information.defaultPhone,
 		});
 	}
 	return inner;
@ -215,6 +210,8 @@ auto EditInformation::lookupField(InformationField field) const -> Field* {

 RequestedInformation EditInformation::collect() const {
 	return {
+		.defaultPhone = _information.defaultPhone,
+		.defaultCountry = _information.defaultCountry,
 		.name = _name ? _name->value() : QString(),
 		.phone = _phone ? _phone->value() : QString(),
 		.email = _email ? _email->value() : QString(),
--- a/Telegram/SourceFiles/payments/ui/payments_field.cpp
+++ b/Telegram/SourceFiles/payments/ui/payments_field.cpp
@ -9,8 +9,11 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL

 #include "ui/widgets/input_fields.h"
 #include "ui/boxes/country_select_box.h"
+#include "ui/ui_utility.h"
+#include "ui/special_fields.h"
 #include "data/data_countries.h"
 #include "base/platform/base_platform_info.h"
+#include "base/event_filter.h"
 #include "styles/style_payments.h"

 namespace Payments::Ui {
@ -91,12 +94,18 @@ namespace {
 	case FieldType::CardExpireDate:
 	case FieldType::CardCVC:
 	case FieldType::Country:
-	case FieldType::Phone:
 		return CreateChild<MaskedInputField>(
 			wrap.get(),
 			st::paymentsField,
 			std::move(config.placeholder),
 			Parse(config));
+	case FieldType::Phone:
+		return CreateChild<PhoneInput>(
+			wrap.get(),
+			st::paymentsField,
+			std::move(config.placeholder),
+			ExtractPhonePrefix(config.defaultPhone),
+			Parse(config));
 	}
 	Unexpected("FieldType in Payments::Ui::LookupMaskedField.");
 }
@ -115,6 +124,10 @@ Field::Field(QWidget *parent, FieldConfig &&config)
 	if (_config.type == FieldType::Country) {
 		setupCountry();
 	}
+	if (const auto &validator = config.validator) {
+		setupValidator(validator);
+	}
+	setupFrontBackspace();
 }

 RpWidget *Field::widget() const {
@ -132,6 +145,14 @@ QString Field::value() const {
 		_countryIso2);
 }

+rpl::producer<> Field::frontBackspace() const {
+	return _frontBackspace.events();
+}
+
+rpl::producer<> Field::finished() const {
+	return _finished.events();
+}
+
 void Field::setupMaskedGeometry() {
 	Expects(_masked != nullptr);

@ -168,13 +189,136 @@ void Field::setupCountry() {
 			_countryIso2 = iso2;
 			_masked->setText(Data::CountryNameByISO2(iso2));
 			_masked->hideError();
-			setFocus();
 			raw->closeBox();
 		}, _masked->lifetime());
+		raw->boxClosing() | rpl::start_with_next([=] {
+			setFocus();
+		}, _masked->lifetime());
 		_config.showBox(std::move(box));
 	});
 }

+void Field::setupValidator(Fn<ValidateResult(ValidateRequest)> validator) {
+	Expects(validator != nullptr);
+
+	const auto state = [=]() -> State {
+		if (_masked) {
+			const auto position = _masked->cursorPosition();
+			const auto selectionStart = _masked->selectionStart();
+			const auto selectionEnd = _masked->selectionEnd();
+			return {
+				.value = value(),
+				.position = position,
+				.anchor = (selectionStart == selectionEnd
+					? position
+					: (selectionStart == position)
+					? selectionEnd
+					: selectionStart),
+			};
+		}
+		const auto cursor = _input->textCursor();
+		return {
+			.value = value(),
+			.position = cursor.position(),
+			.anchor = cursor.anchor(),
+		};
+	};
+	const auto save = [=] {
+		_was = state();
+	};
+	const auto setText = [=](const QString &text) {
+		if (_masked) {
+			_masked->setText(text);
+		} else {
+			_input->setText(text);
+		}
+	};
+	const auto setPosition = [=](int position) {
+		if (_masked) {
+			_masked->setCursorPosition(position);
+		} else {
+			auto cursor = _input->textCursor();
+			cursor.setPosition(position);
+			_input->setTextCursor(cursor);
+		}
+	};
+	const auto validate = [=] {
+		if (_validating) {
+			return;
+		}
+		_validating = true;
+		const auto guard = gsl::finally([&] {
+			_validating = false;
+			save();
+		});
+
+		const auto now = state();
+		const auto result = validator(ValidateRequest{
+			.wasValue = _was.value,
+			.wasPosition = _was.position,
+			.wasAnchor = _was.anchor,
+			.nowValue = now.value,
+			.nowPosition = now.position,
+		});
+		const auto changed = (result.value != now.value);
+		if (changed) {
+			setText(result.value);
+		}
+		if (changed || result.position != now.position) {
+			setPosition(result.position);
+		}
+		if (result.finished) {
+			_finished.fire({});
+		} else if (result.invalid) {
+			Ui::PostponeCall(
+				_masked ? (QWidget*)_masked : _input,
+				[=] { showErrorNoFocus(); });
+		}
+	};
+	if (_masked) {
+		QObject::connect(_masked, &QLineEdit::cursorPositionChanged, save);
+		QObject::connect(_masked, &MaskedInputField::changed, validate);
+	} else {
+		const auto raw = _input->rawTextEdit();
+		QObject::connect(raw, &QTextEdit::cursorPositionChanged, save);
+		QObject::connect(_input, &InputField::changed, validate);
+	}
+}
+
+void Field::setupFrontBackspace() {
+	const auto filter = [=](not_null<QEvent*> e) {
+		const auto frontBackspace = (e->type() == QEvent::KeyPress)
+			&& (static_cast<QKeyEvent*>(e.get())->key() == Qt::Key_Backspace)
+			&& (_masked
+				? (_masked->cursorPosition() == 0
+					&& _masked->selectionLength() == 0)
+				: (_input->textCursor().position() == 0
+					&& _input->textCursor().anchor() == 0));
+		if (frontBackspace) {
+			_frontBackspace.fire({});
+		}
+		return base::EventFilterResult::Continue;
+	};
+	if (_masked) {
+		base::install_event_filter(_masked, filter);
+	} else {
+		base::install_event_filter(_input->rawTextEdit(), filter);
+	}
+}
+
+void Field::setNextField(not_null<Field*> field) {
+	finished() | rpl::start_with_next([=] {
+		field->setFocus();
+	}, _masked ? _masked->lifetime() : _input->lifetime());
+}
+
+void Field::setPreviousField(not_null<Field*> field) {
+	frontBackspace(
+	) | rpl::start_with_next([=] {
+		field->setFocus();
+	}, _masked ? _masked->lifetime() : _input->lifetime());
+}
+
 void Field::setFocus() {
 	if (_config.type == FieldType::Country) {
 		_wrap->setFocus();
@ -206,4 +350,12 @@ void Field::showError() {
 	}
 }

+void Field::showErrorNoFocus() {
+	if (_input) {
+		_input->showErrorNoFocus();
+	} else {
+		_masked->showErrorNoFocus();
+	}
+}
+
 } // namespace Payments::Ui
--- a/Telegram/SourceFiles/payments/ui/payments_field.h
+++ b/Telegram/SourceFiles/payments/ui/payments_field.h
@ -31,14 +31,59 @@ enum class FieldType {
 	Email,
 };

+struct FieldValidateRequest {
+	QString wasValue;
+	int wasPosition = 0;
+	int wasAnchor = 0;
+	QString nowValue;
+	int nowPosition = 0;
+};
+
+struct FieldValidateResult {
+	QString value;
+	int position = 0;
+	bool invalid = false;
+	bool finished = false;
+};
+
+[[nodiscard]] auto RangeLengthValidator(int minLength, int maxLength) {
+	return [=](FieldValidateRequest request) {
+		return FieldValidateResult{
+			.value = request.nowValue,
+			.position = request.nowPosition,
+			.invalid = (request.nowValue.size() < minLength
+				|| request.nowValue.size() > maxLength),
+		};
+	};
+}
+
+[[nodiscard]] auto MaxLengthValidator(int maxLength) {
+	return RangeLengthValidator(0, maxLength);
+}
+
+[[nodiscard]] auto RequiredValidator() {
+	return RangeLengthValidator(1, std::numeric_limits<int>::max());
+}
+
+[[nodiscard]] auto RequiredFinishedValidator() {
+	return [=](FieldValidateRequest request) {
+		return FieldValidateResult{
+			.value = request.nowValue,
+			.position = request.nowPosition,
+			.invalid = request.nowValue.isEmpty(),
+			.finished = !request.nowValue.isEmpty(),
+		};
+	};
+}
+
 struct FieldConfig {
 	FieldType type = FieldType::Text;
 	rpl::producer<QString> placeholder;
 	QString value;
+	Fn<FieldValidateResult(FieldValidateRequest)> validator;
 	Fn<void(object_ptr<BoxContent>)> showBox;
+	QString defaultPhone;
 	QString defaultCountry;
-	int maxLength = 0;
-	bool required = false;
 };

 class Field final {
@ -49,20 +94,40 @@ public:
 	[[nodiscard]] object_ptr<RpWidget> ownedWidget() const;

 	[[nodiscard]] QString value() const;
+	[[nodiscard]] rpl::producer<> frontBackspace() const;
+	[[nodiscard]] rpl::producer<> finished() const;

 	void setFocus();
 	void setFocusFast();
 	void showError();
+	void showErrorNoFocus();
+
+	void setNextField(not_null<Field*> field);
+	void setPreviousField(not_null<Field*> field);

 private:
+	struct State {
+		QString value;
+		int position = 0;
+		int anchor = 0;
+	};
+	using ValidateRequest = FieldValidateRequest;
+	using ValidateResult = FieldValidateResult;
+
 	void setupMaskedGeometry();
 	void setupCountry();
+	void setupValidator(Fn<ValidateResult(ValidateRequest)> validator);
+	void setupFrontBackspace();

 	const FieldConfig _config;
 	const base::unique_qptr<RpWidget> _wrap;
+	rpl::event_stream<> _frontBackspace;
+	rpl::event_stream<> _finished;
 	InputField *_input = nullptr;
 	MaskedInputField *_masked = nullptr;
 	QString _countryIso2;
+	State _was;
+	bool _validating = false;

 };

--- a/Telegram/SourceFiles/payments/ui/payments_form_summary.cpp
+++ b/Telegram/SourceFiles/payments/ui/payments_form_summary.cpp
@ -15,6 +15,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "ui/wrap/vertical_layout.h"
 #include "ui/wrap/fade_wrap.h"
 #include "ui/text/format_values.h"
+#include "data/data_countries.h"
 #include "lang/lang_keys.h"
 #include "styles/style_payments.h"
 #include "styles/style_passport.h"
@ -267,7 +268,8 @@ void FormSummary::setupSections(not_null<VerticalLayout*> layout) {
 		push(_information.shippingAddress.address2);
 		push(_information.shippingAddress.city);
 		push(_information.shippingAddress.state);
-		push(_information.shippingAddress.countryIso2);
+		push(Data::CountryNameByISO2(
+			_information.shippingAddress.countryIso2));
 		push(_information.shippingAddress.postcode);
 		add(
 			tr::lng_payments_shipping_address(),
--- a/Telegram/SourceFiles/payments/ui/payments_panel_data.h
+++ b/Telegram/SourceFiles/payments/ui/payments_panel_data.h
@ -87,6 +87,7 @@ struct Address {
 };

 struct RequestedInformation {
+	QString defaultPhone;
 	QString defaultCountry;

 	QString name;
@ -144,7 +145,7 @@ struct PaymentMethodDetails {

 enum class CardField {
 	Number,
-	CVC,
+	Cvc,
 	ExpireDate,
 	Name,
 	AddressCountry,
--- a/Telegram/SourceFiles/ui/boxes/country_select_box.cpp
+++ b/Telegram/SourceFiles/ui/boxes/country_select_box.cpp
@ -28,7 +28,7 @@ QString LastValidISO;

 class CountrySelectBox::Inner : public TWidget {
 public:
-	Inner(QWidget *parent, Type type);
+	Inner(QWidget *parent, const QString &iso, Type type);
 	~Inner();

 	void updateFilter(QString filter = QString());
@ -93,10 +93,7 @@ CountrySelectBox::CountrySelectBox(QWidget*)
 CountrySelectBox::CountrySelectBox(QWidget*, const QString &iso, Type type)
 : _type(type)
 , _select(this, st::defaultMultiSelect, tr::lng_country_ph())
-, _ownedInner(this, type) {
-	if (Data::CountriesByISO2().contains(iso)) {
-		LastValidISO = iso;
-	}
+, _ownedInner(this, iso, type) {
 }

 rpl::producer<QString> CountrySelectBox::countryChosen() const {
@ -169,7 +166,10 @@ void CountrySelectBox::setInnerFocus() {
 	_select->setInnerFocus();
 }

-CountrySelectBox::Inner::Inner(QWidget *parent, Type type)
+CountrySelectBox::Inner::Inner(
+	QWidget *parent,
+	const QString &iso,
+	Type type)
 : TWidget(parent)
 , _type(type)
 , _rowHeight(st::countryRowHeight) {
@ -177,6 +177,10 @@ CountrySelectBox::Inner::Inner(QWidget *parent, Type type)

 	const auto &byISO2 = Data::CountriesByISO2();

+	if (byISO2.contains(iso)) {
+		LastValidISO = iso;
+	}
+
 	_list.reserve(byISO2.size());
 	_namesList.reserve(byISO2.size());

--- a/Telegram/SourceFiles/ui/special_fields.cpp
+++ b/Telegram/SourceFiles/ui/special_fields.cpp
@ -7,16 +7,24 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 */
 #include "ui/special_fields.h"

-#include "core/application.h"
 #include "lang/lang_keys.h"
 #include "data/data_countries.h" // Data::ValidPhoneCode
 #include "numbers.h"

+#include <QtCore/QRegularExpression>
+
 namespace Ui {
 namespace {

 constexpr auto kMaxUsernameLength = 32;

+// Rest of the phone number, without country code (seen 12 at least),
+// need more for service numbers.
+constexpr auto kMaxPhoneTailLength = 32;
+
+// Max length of country phone code.
+constexpr auto kMaxPhoneCodeLength = 4;
+
 } // namespace

 CountryCodeInput::CountryCodeInput(
@ -130,7 +138,9 @@ void PhonePartInput::correctValue(
 			++digitCount;
 		}
 	}
-	if (digitCount > MaxPhoneTailLength) digitCount = MaxPhoneTailLength;
+	if (digitCount > kMaxPhoneTailLength) {
+		digitCount = kMaxPhoneTailLength;
+	}

 	bool inPart = !_pattern.isEmpty();
 	int curPart = -1, leftInPart = 0;
@ -273,6 +283,14 @@ void UsernameInput::correctValue(
 	setCorrectedText(now, nowCursor, now.mid(from, len), newPos);
 }

+QString ExtractPhonePrefix(const QString &phone) {
+	const auto pattern = phoneNumberParse(phone);
+	if (!pattern.isEmpty()) {
+		return phone.mid(0, pattern[0]);
+	}
+	return QString();
+}
+
 PhoneInput::PhoneInput(
 	QWidget *parent,
 	const style::InputField &st,
@ -324,7 +342,7 @@ void PhoneInput::correctValue(
 		QString &now,
 		int &nowCursor) {
 	auto digits = now;
-	digits.replace(QRegularExpression(qsl("[^\\d]")), QString());
+	digits.replace(QRegularExpression("[^\\d]"), QString());
 	_pattern = phoneNumberParse(digits);

 	QString newPlaceholder;
@ -350,7 +368,7 @@ void PhoneInput::correctValue(
 	}

 	QString newText;
-	int oldPos(nowCursor), newPos(-1), oldLen(now.length()), digitCount = qMin(digits.size(), MaxPhoneCodeLength + MaxPhoneTailLength);
+	int oldPos(nowCursor), newPos(-1), oldLen(now.length()), digitCount = qMin(digits.size(), kMaxPhoneCodeLength + kMaxPhoneTailLength);

 	bool inPart = !_pattern.isEmpty(), plusFound = false;
 	int curPart = 0, leftInPart = inPart ? _pattern.at(curPart) : 0;
--- a/Telegram/SourceFiles/ui/special_fields.h
+++ b/Telegram/SourceFiles/ui/special_fields.h
@ -90,6 +90,8 @@ private:

 };

+[[nodiscard]] QString ExtractPhonePrefix(const QString &phone);
+
 class PhoneInput : public MaskedInputField {
 public:
 	PhoneInput(
--- a/Telegram/cmake/lib_stripe.cmake
+++ b/Telegram/cmake/lib_stripe.cmake
@ -21,6 +21,8 @@ PRIVATE
    stripe/stripe_card.h
    stripe/stripe_card_params.cpp
    stripe/stripe_card_params.h
+    stripe/stripe_card_validator.cpp
+    stripe/stripe_card_validator.h
    stripe/stripe_decode.cpp
    stripe/stripe_decode.h
    stripe/stripe_error.cpp
--- a/Telegram/cmake/td_ui.cmake
+++ b/Telegram/cmake/td_ui.cmake
@ -146,7 +146,9 @@ PRIVATE
    ui/cached_round_corners.h
    ui/grouped_layout.cpp
    ui/grouped_layout.h
-    
+    ui/special_fields.cpp
+    ui/special_fields.h
+
    ui/ui_pch.h
 )

@ -163,4 +165,5 @@ PUBLIC
 PRIVATE
    desktop-app::lib_ffmpeg
    desktop-app::lib_webview
+    desktop-app::lib_stripe
 )