Added validateCreditMethod standalone method

README.md

@@ -24,7 +24,7 @@ This project provides a collection of useful template renderers.
 ## Encoding Renderers
 
 | Renderer                                                                                                                | Description                                             |
-|:--------------------------------------------------------------------------------------------------------------|:--------------------------------------------------------|
+|:------------------------------------------------------------------------------------------------------------------------|:--------------------------------------------------------|
 | [rife.render.EncodeBase64](https://github.com/rife2/rife2-template-renderers/wiki/rife.render.EncodeBase64)             | Encodes a template value to Base64                      |
 | [rife.render.EncodeHtml](https://github.com/rife2/rife2-template-renderers/wiki/rife.render.EncodeHtml)                 | Encodes a template value to HTML                        |
 | [rife.render.EncodeHtmlEntities](https://github.com/rife2/rife2-template-renderers/wiki/rife.render.EncodeHtmlEntities) | Encodes a template value to HTML decimal entities       |

lib/build.gradle.kts

@@ -13,7 +13,7 @@ plugins {
     id("com.github.ben-manes.versions") version "0.46.0"
 }
 
-val rifeVersion by rootProject.extra { "1.5.4" }
+val rifeVersion by rootProject.extra { "1.5.5" }
 
 group = "com.uwyn.rife2"
 version = "1.0.1-SNAPSHOT"

lib/src/main/java/rife/render/RenderUtils.java

@@ -192,39 +192,14 @@ public final class RenderUtils {
             return src;
         }
 
-        try {
         var cc = src.replaceAll("[^0-9]", "");
 
-            var len = cc.length();
+        if (validateCreditCard(cc)) {
-            if (len >= 4) {
+            return cc.substring(cc.length() - 4);
-                // Luhn algorithm
+        } else {
-                var sum = 0;
-                boolean isSecond = false;
-                int digit;
-                char c;
-                for (int i = len - 1; i >= 0; i--) {
-                    c = cc.charAt(i);
-                    if (c >= '0' && c <= '9') {
-                        digit = cc.charAt(i) - '0';
-                        if (isSecond) {
-                            digit = digit * 2;
-                        }
-                        sum += digit / 10;
-                        sum += digit % 10;
-                    }
-
-                    isSecond = !isSecond;
-                }
-                if (sum % 10 == 0) {
-                    return cc.substring(len - 4);
-                }
-            }
-        } catch (NumberFormatException ignore) {
-            // do nothing
-        }
-
             return "";
         }
+    }
 
     /**
      * Converts a text String to HTML decimal entities.
@@ -520,4 +495,42 @@ public final class RenderUtils {
 
         return sb.toString();
     }
+
+    /**
+     * Validates a credit card number using the Luhn algorithm.
+     *
+     * @param cc the credit card number
+     * @return {@code trude} if the credit card number is valid
+     */
+    public static boolean validateCreditCard(String cc) {
+        try {
+            var len = cc.length();
+            if (len >= 8 && len <= 19) {
+                // Luhn algorithm
+                var sum = 0;
+                boolean second = false;
+                int digit;
+                char c;
+                for (int i = len - 1; i >= 0; i--) {
+                    c = cc.charAt(i);
+                    if (c >= '0' && c <= '9') {
+                        digit = cc.charAt(i) - '0';
+                        if (second) {
+                            digit = digit * 2;
+                        }
+                        sum += digit / 10;
+                        sum += digit % 10;
+
+                        second = !second;
+                    }
+                }
+                if (sum % 10 == 0) {
+                    return true;
+                }
+            }
+        } catch (NumberFormatException ignore) {
+            // do nothing
+        }
+        return false;
+    }
 }

lib/src/test/java/rife/render/TestRenderUtils.java

@@ -83,4 +83,13 @@ class TestRenderUtils {
         assertThat(RenderUtils.uncapitalize("A")).isEqualTo("a");
         assertThat(RenderUtils.uncapitalize("")).as("empty").isEqualTo("");
     }
+
+    @Test
+    void testValidateCreditCard() {
+        assertThat(RenderUtils.validateCreditCard("4505 4672 3366 6430")).as("visa").isTrue();
+        assertThat(RenderUtils.validateCreditCard("5189-5923-3915-0425")).as("mastercard").isTrue();
+        assertThat(RenderUtils.validateCreditCard("3433634926643302")).as("amex").isTrue();
+        assertThat(RenderUtils.validateCreditCard("6011 1076-8252 0629")).as("discover").isTrue();
+        assertThat(RenderUtils.validateCreditCard("0123456789012345")).as("invalid").isFalse();
+    }
 }