Add isValid method to Multibase class

Starting point of #38,

generated by GitHub Copilot Workspace AI.

Author: vorburger

README.md

@@ -17,6 +17,7 @@ Simply clone this repo.
 byte[] data = ...
 String encoded = Multibase.encode(Multibase.Base.Base58BTC, data);
 byte[] decoded = Multibase.decode(encoded);
+boolean isValid = Multibase.isValid(encoded);
 ```
 
 ## Dependency

src/main/java/io/ipfs/multibase/Multibase.java

@@ -154,4 +154,13 @@ private static String safeSubstringFromIndexOne(String data) {
         int charIndex = data.offsetByCodePoints(0, 1);
         return data.substring(charIndex);
     }
+
+    public static boolean isValid(String data) {
+        try {
+            decode(data);
+            return true;
+        } catch (IllegalArgumentException | UnsupportedOperationException e) {
+            return false;
+        }
+    }
 }

src/test/java/io/ipfs/multibase/MultibaseTest.java

@@ -8,6 +8,8 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 
 public class MultibaseTest {
 
@@ -67,6 +69,29 @@ public void testDecode(Multibase.Base base, byte[] raw, String encoded) {
         assertArrayEquals(raw, output, String.format("Expected %s, but got %s", bytesToHex(raw), bytesToHex(output)));
     }
 
+    @MethodSource("data")
+    @ParameterizedTest(name = "{index}: {0}, {2}")
+    public void testIsValid(Multibase.Base base, byte[] raw, String encoded) {
+        assertTrue(Multibase.isValid(encoded));
+    }
+
+    public static Collection<String> invalidData() {
+        return Arrays.asList(
+                "f012", // Hex string of odd length, not allowed in Base16
+                "f0g", // 'g' char is not allowed in Base16
+                "zt1Zv2yaI", // 'I' char is not allowed in Base58
+                "2", // '2' is not a valid encoding marker
+                "", // Empty string is not a valid multibase
+                "🚀🫕" // This Emoji (Swiss Fondue) is not part of the Base256Emoji table
+        );
+    }
+
+    @MethodSource("invalidData")
+    @ParameterizedTest(name = "{index}: \"{0}\"")
+    public void testIsInvalid(String input) {
+        assertFalse(Multibase.isValid(input));
+    }
+
     //Copied from https://stackoverflow.com/a/140861
     private static byte[] hexToBytes(String s) {
         int len = s.length();