🎯 feat: luhn

dart/luhn/.exercism/config.json

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+{
+  "authors": [
+    "amscotti"
+  ],
+  "contributors": [
+    "kytrinyx"
+  ],
+  "files": {
+    "solution": [
+      "lib/luhn.dart"
+    ],
+    "test": [
+      "test/luhn_test.dart"
+    ],
+    "example": [
+      ".meta/lib/example.dart"
+    ]
+  },
+  "blurb": "Given a number determine whether or not it is valid per the Luhn formula.",
+  "source": "The Luhn Algorithm on Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Luhn_algorithm"
+}

dart/luhn/.exercism/metadata.json

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+{"track":"dart","exercise":"luhn","id":"bf2ce773c30246a69f3805d717697f50","url":"https://exercism.org/tracks/dart/exercises/luhn","handle":"LuCCoelho","is_requester":true,"auto_approve":false}

dart/luhn/HELP.md

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+# Help
+
+## Running the tests
+
+To run the tests:
+
+```sh
+$ dart test
+```
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit lib/luhn.dart` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Dart track's documentation](https://exercism.org/docs/tracks/dart)
+- The [Dart track's programming category on the forum](https://forum.exercism.org/c/programming/dart)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+To get help if you're having trouble, you can use one of the following resources:
+
+- [Dart API Documentation](https://api.dart.dev/)
+- [Dart Gitter Chat](https://gitter.im/dart-lang/home)
+- [Community Information](https://www.dart.dev/community)
+- [/r/dartlang](https://www.reddit.com/r/dartlang) is the Dart subreddit.
+- [StackOverflow](https://stackoverflow.com/questions/tagged/dart) can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.

dart/luhn/README.md

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+# Luhn
+
+Welcome to Luhn on Exercism's Dart Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Given a number determine whether or not it is valid per the Luhn formula.
+
+The [Luhn algorithm][luhn] is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and Canadian Social Insurance Numbers.
+
+The task is to check if a given string is valid.
+
+## Validating a Number
+
+Strings of length 1 or less are not valid.
+Spaces are allowed in the input, but they should be stripped before checking.
+All other non-digit characters are disallowed.
+
+### Example 1: valid credit card number
+
+```text
+4539 3195 0343 6467
+```
+
+The first step of the Luhn algorithm is to double every second digit, starting from the right.
+We will be doubling
+
+```text
+4_3_ 3_9_ 0_4_ 6_6_
+```
+
+If doubling the number results in a number greater than 9 then subtract 9 from the product.
+The results of our doubling:
+
+```text
+8569 6195 0383 3437
+```
+
+Then sum all of the digits:
+
+```text
+8+5+6+9+6+1+9+5+0+3+8+3+3+4+3+7 = 80
+```
+
+If the sum is evenly divisible by 10, then the number is valid.
+This number is valid!
+
+### Example 2: invalid credit card number
+
+```text
+8273 1232 7352 0569
+```
+
+Double the second digits, starting from the right
+
+```text
+7253 2262 5312 0539
+```
+
+Sum the digits
+
+```text
+7+2+5+3+2+2+6+2+5+3+1+2+0+5+3+9 = 57
+```
+
+57 is not evenly divisible by 10, so this number is not valid.
+
+[luhn]: https://en.wikipedia.org/wiki/Luhn_algorithm
+
+## Source
+
+### Created by
+
+- @amscotti
+
+### Contributed to by
+
+- @kytrinyx
+
+### Based on
+
+The Luhn Algorithm on Wikipedia - https://en.wikipedia.org/wiki/Luhn_algorithm

dart/luhn/analysis_options.yaml

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+analyzer:
+  errors:
+    unused_element:        error
+    unused_import:         error
+    unused_local_variable: error
+    dead_code:             error
+
+linter:
+  rules:
+    # Error Rules
+    - avoid_relative_lib_imports
+    - avoid_types_as_parameter_names
+    - literal_only_boolean_expressions
+    - no_adjacent_strings_in_list
+    - valid_regexps

dart/luhn/lib/luhn.dart

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+class Luhn {
+  bool valid(String number) {
+    List<String> validCharacters = [
+      '0',
+      '1',
+      '2',
+      '3',
+      '4',
+      '5',
+      '6',
+      '7',
+      '8',
+      '9'
+    ];
+
+    number = number.replaceAll(' ', '');
+    int result = 0;
+    List<String> numberDigits = number.split('');
+
+    if (numberDigits.length < 2) {
+      return false;
+    }
+
+    for (int i = (numberDigits.length - 2); i > -1; i -= 2) {
+      if (validCharacters.contains(numberDigits[i])) {
+        int digit = int.parse(numberDigits[i]);
+        int digitDouble = digit * 2;
+        if (digitDouble > 9) {
+          digitDouble -= 9;
+        }
+        numberDigits[i] = digitDouble.toString();
+      } else {
+        return false;
+      }
+    }
+
+    for (int i = 0; i < numberDigits.length; i++) {
+      if (validCharacters.contains(numberDigits[i])) {
+        result += int.parse(numberDigits[i]);
+      } else {
+        return false;
+      }
+    }
+
+    return result % 10 == 0;
+  }
+}

dart/luhn/pubspec.yaml

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+name: 'luhn'
+environment:
+  sdk: '>=2.18.0 <3.0.0'
+dev_dependencies:
+  test: '<2.0.0'

dart/luhn/test/luhn_test.dart

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+import 'package:luhn/luhn.dart';
+import 'package:test/test.dart';
+
+void main() {
+  final luhn = Luhn();
+
+  group('Luhn', () {
+    test('single digit strings can not be valid', () {
+      final result = luhn.valid('1');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('a single zero is invalid', () {
+      final result = luhn.valid('0');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('a simple valid SIN that remains valid if reversed', () {
+      final result = luhn.valid('059');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('a simple valid SIN that becomes invalid if reversed', () {
+      final result = luhn.valid('59');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('a valid Canadian SIN', () {
+      final result = luhn.valid('055 444 285');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('invalid Canadian SIN', () {
+      final result = luhn.valid('055 444 286');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('invalid credit card', () {
+      final result = luhn.valid('8273 1232 7352 0569');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('invalid long number with an even remainder', () {
+      final result = luhn.valid('1 2345 6789 1234 5678 9012');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('invalid long number with a remainder divisible by 5', () {
+      final result = luhn.valid('1 2345 6789 1234 5678 9013');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('valid number with an even number of digits', () {
+      final result = luhn.valid('095 245 88');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('valid number with an odd number of spaces', () {
+      final result = luhn.valid('234 567 891 234');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('valid strings with a non-digit added at the end become invalid', () {
+      final result = luhn.valid('059a');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('valid strings with punctuation included become invalid', () {
+      final result = luhn.valid('055-444-285');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('valid strings with symbols included become invalid', () {
+      final result = luhn.valid('055# 444\$ 285');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('single zero with space is invalid', () {
+      final result = luhn.valid(' 0');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('more than a single zero is valid', () {
+      final result = luhn.valid('0000 0');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('input digit 9 is correctly converted to output digit 9', () {
+      final result = luhn.valid('091');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('very long input is valid', () {
+      final result = luhn.valid('9999999999 9999999999 9999999999 9999999999');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('valid luhn with an odd number of digits and non zero first digit', () {
+      final result = luhn.valid('109');
+      expect(result, equals(true));
+    }, skip: false);
+
+    test('using ascii value for non-doubled non-digit isn\'t allowed', () {
+      final result = luhn.valid('055b 444 285');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('using ascii value for doubled non-digit isn\'t allowed', () {
+      final result = luhn.valid(':9');
+      expect(result, equals(false));
+    }, skip: false);
+
+    test('non-numeric, non-space char in the middle with a sum that\'s divisible by 10 isn\'t allowed', () {
+      final result = luhn.valid('59%59');
+      expect(result, equals(false));
+    }, skip: false);
+  });
+}