stripe_native_card_field/lib/card_details.dart

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import 'package:flutter/foundation.dart';
/// Class encapsulating the card's data
/// as well as validation of the data.
///
/// `CardDetails.validState == ValidState.ok`
/// when fields are filled and validated as correct.
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class CardDetails {
CardDetails({
required dynamic cardNumber,
required String? securityCode,
required this.expirationString,
required this.postalCode,
}) : _cardNumber = cardNumber {
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this.securityCode = int.tryParse(securityCode ?? '');
checkIsValid();
}
/// Sets every field to null, a default
/// `CardDetails` when nothing has been entered.
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factory CardDetails.blank() {
return CardDetails(cardNumber: null, securityCode: null, expirationString: null, postalCode: null);
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}
/// Returns the CardNumber as a `String` with the spaces removed.
String? get cardNumber => _cardNumber?.replaceAll(' ', '');
set cardNumber(String? num) => _cardNumber = num;
String? _cardNumber;
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int? securityCode;
String? postalCode;
String? expirationString;
DateTime? expirationDate;
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bool _complete = false;
ValidState _validState = ValidState.blank;
int _lastCheckHash = 0;
CardProvider? provider;
/// Checks the validity of the `CardDetails` and returns the result.
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ValidState get validState {
checkIsValid();
return _validState;
}
// TODO rename to be more clear
/// Returns true if `_cardNumber` is null, or
/// if the _cardNumber matches the detected `provider`'s
/// card lenght, defaulting to 16.
bool get cardNumberFilled =>
_cardNumber == null ? false : (provider?.cardLength ?? 16) == _cardNumber!.replaceAll(' ', '').length;
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/// Returns true if all details are complete and valid
/// otherwise, return false.
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bool get isComplete {
checkIsValid();
return _complete;
}
/// The maximum length of the INN (identifier)
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/// of a card provider.
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int get maxINNLength => 4;
/// Validates each field of the `CardDetails` object in entry order,
/// namely _cardNumber -> expirationString -> securityCode -> postalCode
///
/// If all fields are filled out and valid, `CardDetails.isComplete == true`
/// and `CardDetails.validState == ValidState.ok`.
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void checkIsValid() {
try {
int currentHash = hash;
if (currentHash == _lastCheckHash) {
return;
}
_lastCheckHash = currentHash;
if (_cardNumber == null && expirationString == null && securityCode == null && postalCode == null) {
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_complete = false;
_validState = ValidState.blank;
return;
}
final nums = _cardNumber!
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.replaceAll(' ', '')
.split('')
.map(
(i) => int.parse(i),
)
.toList();
if (!_luhnAlgorithmCheck(nums)) {
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_complete = false;
_validState = ValidState.invalidCard;
return;
}
if (_cardNumber == null || !cardNumberFilled) {
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_complete = false;
_validState = ValidState.missingCard;
return;
}
if (expirationString == null) {
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_complete = false;
_validState = ValidState.missingDate;
return;
}
final expSplits = expirationString!.split('/');
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if (expSplits.length != 2 || expSplits.last == '') {
_complete = false;
_validState = ValidState.missingDate;
return;
}
final month = int.parse(expSplits.first[0] == '0' ? expSplits.first[1] : expSplits.first);
if (month < 1 || month > 12) {
_complete = false;
_validState = ValidState.invalidMonth;
return;
}
final year = 2000 + int.parse(expSplits.last);
final date = DateTime(year, month);
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if (date.isBefore(DateTime.now())) {
_complete = false;
_validState = ValidState.dateTooEarly;
return;
} else if (date.isAfter(DateTime.now().add(const Duration(days: 365 * 50)))) {
_complete = false;
_validState = ValidState.dateTooLate;
return;
}
expirationDate = date;
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if (securityCode == null) {
_complete = false;
_validState = ValidState.missingCVC;
return;
}
if (postalCode == null) {
_complete = false;
_validState = ValidState.missingZip;
return;
}
if (!RegExp(r'^\d{5}(-\d{4})?$').hasMatch(postalCode!)) {
_complete = false;
_validState = ValidState.invalidZip;
return;
}
_complete = true;
_validState = ValidState.ok;
} catch (err, st) {
if (kDebugMode) {
print('Error while validating CardDetails: $err\n$st');
}
_complete = false;
_validState = ValidState.error;
}
}
/// Provides a hash of the CardDetails object
/// Hashes `_cardNumber`, `expirationString`,
/// `securityCode`, and `postalCode`.
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int get hash {
return Object.hash(_cardNumber, expirationString, securityCode, postalCode);
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}
/// Iterates over the list `_providers`, detecting which
/// provider the current `_cardNumber` falls under.
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void detectCardProvider() {
bool found = false;
if (_cardNumber == null) {
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return;
}
for (var cardPvd in _providers) {
if (cardPvd.innValidNums != null) {
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// trim card number to correct length
String trimmedNum = _cardNumber!;
String innNumStr = '${cardPvd.innValidNums!.first}';
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if (trimmedNum.length > innNumStr.length) {
trimmedNum = trimmedNum.substring(0, innNumStr.length);
}
final num = int.tryParse(trimmedNum);
if (num == null) continue;
if (cardPvd.innValidNums!.contains(num)) {
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provider = cardPvd;
found = true;
break;
}
}
if (cardPvd.innValidRanges != null) {
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// trim card number to correct length
String trimmedNum = _cardNumber!;
String innNumStr = '${cardPvd.innValidRanges!.first.low}';
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if (trimmedNum.length > innNumStr.length) {
trimmedNum = trimmedNum.substring(0, innNumStr.length);
}
final num = int.tryParse(trimmedNum);
if (num == null) continue;
if (cardPvd.innValidRanges!.any((range) => range.isWithin(num))) {
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provider = cardPvd;
found = true;
break;
}
}
}
if (!found) provider = null;
}
@override
String toString() {
return 'Number: "$_cardNumber" - Exp: "$expirationString" CVC: $securityCode Zip: "$postalCode"';
}
/// https://en.wikipedia.org/wiki/Luhn_algorithm
/// The Luhn algorithm is used in industry to check
/// for valid credit / debit card numbers
///
/// The algorithm adds together all the numbers, every
/// other number is doubled, then the sum is checked to
/// see if it is a multiple of 10.
/// https://en.wikipedia.org/wiki/Luhn_algorithm
bool _luhnAlgorithmCheck(List<int> digits) {
int sum = 0;
bool isSecond = false;
for (int i = digits.length - 1; i >= 0; i--) {
int d = digits[i];
if (isSecond) {
d *= 2;
if (d > 9) {
d -= 9;
}
}
sum += d;
isSecond = !isSecond;
}
return (sum % 10) == 0;
}
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}
/// Enum of validation states a `CardDetails` object can have.
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enum ValidState {
ok,
error,
blank,
missingCard,
invalidCard,
missingDate,
invalidMonth,
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dateTooEarly,
dateTooLate,
missingCVC,
invalidCVC,
missingZip,
invalidZip,
}
/// Enum of supported U.S. Card Providers
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enum CardProviderID {
americanExpress,
dinersClub,
discoverCard,
mastercard,
jcb,
visa,
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}
/// Encapsulates criteria for Card Providers in the U.S.
/// Used by `CardDetails.detectCardProvider()` to determine
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/// a card's Provider.
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class CardProvider {
CardProviderID id;
List<int>? innValidNums;
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List<Range>? innValidRanges;
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int cardLength;
int cvcLength;
CardProvider(
{required this.id, required this.cardLength, required this.cvcLength, this.innValidNums, this.innValidRanges}) {
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// Must provide one or the other
assert(innValidNums != null || innValidRanges != null);
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// Do not provide empty list of valid nums
assert(innValidNums == null || innValidNums!.isNotEmpty);
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}
@override
String toString() {
return id.toString();
}
}
/// Object for `CardProvider` to determine valid number ranges.
/// A loose wrapper on a tuple, that provides assertion of
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/// valid inputs and the `isWithin()` helper function.
class Range {
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int high;
int low;
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Range({required this.low, required this.high}) {
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assert(low <= high);
}
/// Returns bool whether or not `val` is between `low` and `high`.
/// The range includes the `val`, so
/// ```dart
/// Range(low: 1, high: 3).isWithin(3);
/// ```
/// would return true.
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bool isWithin(int val) {
return low <= val && val <= high;
}
}
/// List of CardProviders for US-based Credit / Debit Cards.
List<CardProvider> _providers = [
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CardProvider(
id: CardProviderID.americanExpress,
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cardLength: 15,
cvcLength: 4,
innValidNums: [34, 37],
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),
CardProvider(
id: CardProviderID.dinersClub,
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cardLength: 16,
cvcLength: 3,
innValidNums: [30, 36, 38, 39],
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),
CardProvider(
id: CardProviderID.discoverCard,
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cardLength: 16,
cvcLength: 3,
innValidNums: [60, 65],
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innValidRanges: [Range(low: 644, high: 649)],
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),
CardProvider(
id: CardProviderID.jcb,
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cardLength: 16,
cvcLength: 3,
innValidNums: [35],
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),
CardProvider(
id: CardProviderID.mastercard,
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cardLength: 16,
cvcLength: 3,
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innValidRanges: [Range(low: 22, high: 27), Range(low: 51, high: 55)],
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),
CardProvider(
id: CardProviderID.visa,
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cardLength: 16,
cvcLength: 3,
innValidNums: [4],
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)
];