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. class CardDetails { CardDetails({ required String? cardNumber, required this.securityCode, required this.expirationString, required this.postalCode, }) : _cardNumber = cardNumber { checkIsValid(); } /// Sets every field to null, a default /// `CardDetails` when nothing has been entered. factory CardDetails.blank() { return CardDetails( cardNumber: null, securityCode: null, expirationString: null, postalCode: null); } /// Returns the CardNumber as a `String` with the spaces removed. String? get cardNumber => _cardNumber?.replaceAll(' ', ''); set cardNumber(String? num) => _cardNumber = num; String? _cardNumber; String? securityCode; String? postalCode; String? expirationString; DateTime? expirationDate; bool _complete = false; CardDetailsValidState _validState = CardDetailsValidState.blank; int _lastCheckHash = 0; CardProvider? provider; set overrideValidState(CardDetailsValidState state) => _validState = state; /// Checks the validity of the `CardDetails` and returns the result. CardDetailsValidState get validState { checkIsValid(); return _validState; } String get expMonth => isComplete ? expirationString!.split('/').first : ''; String get expYear => isComplete ? expirationString!.split('/').last : ''; // 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; /// Returns true if all details are complete and valid /// otherwise, return false. bool get isComplete { checkIsValid(); return _complete; } /// The maximum length of the INN (identifier) /// of a card provider. 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`. void checkIsValid() { try { int currentHash = hash; if (currentHash == _lastCheckHash) { return; } _lastCheckHash = currentHash; if (_cardNumber == null && expirationString == null && securityCode == null && postalCode == null) { _complete = false; _validState = CardDetailsValidState.blank; return; } final nums = _cardNumber! .replaceAll(' ', '') .split('') .map( (i) => int.parse(i), ) .toList(); if (!_luhnAlgorithmCheck(nums)) { _complete = false; _validState = CardDetailsValidState.invalidCard; return; } if (_cardNumber == null || !cardNumberFilled) { _complete = false; _validState = CardDetailsValidState.missingCard; return; } if (expirationString == null) { _complete = false; _validState = CardDetailsValidState.missingDate; return; } final expSplits = expirationString!.split('/'); if (expSplits.length != 2 || expSplits.last == '') { _complete = false; _validState = CardDetailsValidState.missingDate; return; } final month = int.parse( expSplits.first[0] == '0' ? expSplits.first[1] : expSplits.first); if (month < 1 || month > 12) { _complete = false; _validState = CardDetailsValidState.invalidMonth; return; } final year = 2000 + int.parse(expSplits.last); final date = DateTime(year, month); if (date.isBefore(DateTime.now())) { _complete = false; _validState = CardDetailsValidState.dateTooEarly; return; } else if (date .isAfter(DateTime.now().add(const Duration(days: 365 * 50)))) { _complete = false; _validState = CardDetailsValidState.dateTooLate; return; } expirationDate = date; if (securityCode == null) { _complete = false; _validState = CardDetailsValidState.missingCVC; return; } if (provider != null && securityCode!.length != provider!.cvcLength) { _complete = false; _validState = CardDetailsValidState.invalidCVC; return; } if (postalCode == null) { _complete = false; _validState = CardDetailsValidState.missingZip; return; } if (!RegExp(r'^\d{5}(-\d{4})?$').hasMatch(postalCode!)) { _complete = false; _validState = CardDetailsValidState.invalidZip; return; } _complete = true; _validState = CardDetailsValidState.ok; } catch (err, st) { if (kDebugMode) { print('Error while validating CardDetails: $err\n$st'); } _complete = false; _validState = CardDetailsValidState.error; } } /// Provides a hash of the CardDetails object /// Hashes `_cardNumber`, `expirationString`, /// `securityCode`, and `postalCode`. int get hash { return Object.hash(_cardNumber, expirationString, securityCode, postalCode); } /// Iterates over the list `_providers`, detecting which /// provider the current `_cardNumber` falls under. void detectCardProvider() { bool found = false; if (_cardNumber == null) { return; } for (var cardPvd in _providers) { if (cardPvd.innValidNums != null) { // trim card number to correct length String trimmedNum = _cardNumber!; String innNumStr = '${cardPvd.innValidNums!.first}'; if (trimmedNum.length > innNumStr.length) { trimmedNum = trimmedNum.substring(0, innNumStr.length); } final num = int.tryParse(trimmedNum); if (num == null) continue; if (cardPvd.innValidNums!.contains(num)) { provider = cardPvd; found = true; break; } } if (cardPvd.innValidRanges != null) { // trim card number to correct length String trimmedNum = _cardNumber!; String innNumStr = '${cardPvd.innValidRanges!.first.low}'; 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))) { 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 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; } } /// Enum of validation states a `CardDetails` object can have. enum CardDetailsValidState { ok, error, blank, missingCard, invalidCard, missingDate, invalidMonth, dateTooEarly, dateTooLate, missingCVC, invalidCVC, missingZip, invalidZip, } /// Enum of supported Card Providers enum CardProviderID { americanExpress, dinersClub, discoverCard, mastercard, jcb, visa, } /// Encapsulates criteria for Card Providers in the U.S. /// Used by `CardDetails.detectCardProvider()` to determine /// a card's Provider. class CardProvider { CardProviderID id; List? innValidNums; List? innValidRanges; int cardLength; int cvcLength; CardProvider( {required this.id, required this.cardLength, required this.cvcLength, this.innValidNums, this.innValidRanges}) { // Must provide one or the other assert(innValidNums != null || innValidRanges != null); // Do not provide empty list of valid nums assert(innValidNums == null || innValidNums!.isNotEmpty); } @override String toString() { return id.toString(); } } /// Object for `CardProvider` to determine valid number ranges. /// A loose wrapper on a tuple, that provides assertion of /// valid inputs and the `isWithin()` helper function. class Range { int high; int low; Range({required this.low, required this.high}) { 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. bool isWithin(int val) { return low <= val && val <= high; } } /// List of CardProviders for US-based Credit / Debit Cards. List _providers = [ CardProvider( id: CardProviderID.americanExpress, cardLength: 15, cvcLength: 4, innValidNums: [34, 37], ), CardProvider( id: CardProviderID.dinersClub, cardLength: 16, cvcLength: 3, innValidNums: [30, 36, 38, 39], ), CardProvider( id: CardProviderID.discoverCard, cardLength: 16, cvcLength: 3, innValidNums: [60, 65], innValidRanges: [Range(low: 644, high: 649)], ), CardProvider( id: CardProviderID.jcb, cardLength: 16, cvcLength: 3, innValidNums: [35], ), CardProvider( id: CardProviderID.mastercard, cardLength: 16, cvcLength: 3, innValidRanges: [Range(low: 22, high: 27), Range(low: 51, high: 55)], ), CardProvider( id: CardProviderID.visa, cardLength: 16, cvcLength: 3, innValidNums: [4], ) ];