wilburx9 · March 4, 2021 22:12 · Jul 20, 2018 · Jul 20, 2018 · Jul 20, 2018
diff --git a/card_utils.dart b/card_utils.dart
@@ -64,15 +64,15 @@
     // The month has passed if:
     // 1. The year is in the past. In that case, we just assume that the month
     // has passed
-    // 2. Card's month (plus another month) is more than current month.
+    // 2. Card's month (plus another month) is less than current month.
     return hasYearPassed(year) ||
         convertYearTo4Digits(year) == now.year && (month < now.month + 1);
   }
 
   static bool hasYearPassed(int year) {
     int fourDigitsYear = convertYearTo4Digits(year);
     var now = DateTime.now();
-    // The year has passed if the year we are currently is more than card's
+    // The year has passed if the year we are currently, is greater than card's
     // year
     return fourDigitsYear < now.year;
   }
diff --git a/card_utils.dart b/card_utils.dart
@@ -26,7 +26,7 @@
 
     var fourDigitsYear = convertYearTo4Digits(year);
     if ((fourDigitsYear < 1) || (fourDigitsYear > 2099)) {
-      // We are assuming a valid should be between 1 and 2099.
+      // We are assuming a valid year should be between 1 and 2099.
       // Note that, it's valid doesn't mean that it has not expired.
       return 'Expiry year is invalid';
     }

diff --git a/card_utils.dart b/card_utils.dart
@@ -0,0 +1,78 @@
+  static String validateDate(String value) {
+    if (value.isEmpty) {
+      return Strings.fieldReq;
+    }
+
+    int year;
+    int month;
+    // The value contains a forward slash if the month and year has been
+    // entered.
+    if (value.contains(new RegExp(r'(\/)'))) {
+      var split = value.split(new RegExp(r'(\/)'));
+      // The value before the slash is the month while the value to right of
+      // it is the year.
+      month = int.parse(split[0]);
+      year = int.parse(split[1]);
+
+    } else { // Only the month was entered
+      month = int.parse(value.substring(0, (value.length)));
+      year = -1; // Lets use an invalid year intentionally
+    }
+
+    if ((month < 1) || (month > 12)) {
+      // A valid month is between 1 (January) and 12 (December)
+      return 'Expiry month is invalid';
+    }
+
+    var fourDigitsYear = convertYearTo4Digits(year);
+    if ((fourDigitsYear < 1) || (fourDigitsYear > 2099)) {
+      // We are assuming a valid should be between 1 and 2099.
+      // Note that, it's valid doesn't mean that it has not expired.
+      return 'Expiry year is invalid';
+    }
+
+    if (!hasDateExpired(month, year)) {
+      return "Card has expired";
+    }
+    return null;
+  }
+
+
+  /// Convert the two-digit year to four-digit year if necessary
+  static int convertYearTo4Digits(int year) {
+    if (year < 100 && year >= 0) {
+      var now = DateTime.now();
+      String currentYear = now.year.toString();
+      String prefix = currentYear.substring(0, currentYear.length - 2);
+      year = int.parse('$prefix${year.toString().padLeft(2, '0')}');
+    }
+    return year;
+  }
+
+
+  static bool hasDateExpired(int month, int year) {
+    return !(month == null || year == null) && isNotExpired(year, month);
+  }
+
+  static bool isNotExpired(int year, int month) {
+    // It has not expired if both the year and date has not passed
+    return !hasYearPassed(year) && !hasMonthPassed(year, month);
+  }
+
+ static bool hasMonthPassed(int year, int month) {
+    var now = DateTime.now();
+    // The month has passed if:
+    // 1. The year is in the past. In that case, we just assume that the month
+    // has passed
+    // 2. Card's month (plus another month) is more than current month.
+    return hasYearPassed(year) ||
+        convertYearTo4Digits(year) == now.year && (month < now.month + 1);
+  }
+
+  static bool hasYearPassed(int year) {
+    int fourDigitsYear = convertYearTo4Digits(year);
+    var now = DateTime.now();
+    // The year has passed if the year we are currently is more than card's
+    // year
+    return fourDigitsYear < now.year;
+  }
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