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