feat: decode abi error payloads

src/main/java/org/arkecosystem/crypto/utils/AbiDecoder.java

@@ -33,15 +33,44 @@ public Map<String, Object> decodeFunctionData(String data) throws Exception {
         return result;
     }
 
+    public String decodeError(String data) throws Exception {
+        data = stripHexPrefix(data);
+
+        String errorSelector = data.substring(0, 8);
+
+        Map<String, Object> abiItem = findErrorBySelector(errorSelector);
+        if (abiItem == null) {
+            throw new Exception("Function selector not found in ABI: " + errorSelector);
+        }
+
+        return (String) abiItem.get("name");
+    }
+
     private Map<String, Object> findFunctionBySelector(String selector) {
         for (Map<String, Object> item : this.abi) {
-            if ("function".equals(item.get("type"))) {
-                String functionSignature = getFunctionSignature(item);
-                String functionSelector =
-                        stripHexPrefix(keccak256(functionSignature)).substring(0, 8);
-                if (functionSelector.equals(selector)) {
-                    return item;
-                }
+            if (!"function".equals(item.get("type"))) {
+                continue;
+            }
+
+            String functionSignature = getFunctionSignature(item);
+            String functionSelector = stripHexPrefix(keccak256(functionSignature)).substring(0, 8);
+            if (functionSelector.equals(selector)) {
+                return item;
+            }
+        }
+        return null;
+    }
+
+    private Map<String, Object> findErrorBySelector(String selector) {
+        for (Map<String, Object> item : this.abi) {
+            if (!"error".equals(item.get("type"))) {
+                continue;
+            }
+
+            String errorSignature = getFunctionSignature(item);
+            String errorSelector = stripHexPrefix(keccak256(errorSignature)).substring(0, 8);
+            if (errorSelector.equals(selector)) {
+                return item;
             }
         }
         return null;

src/test/java/org/arkecosystem/crypto/utils/AbiDecoderTest.java

@@ -191,4 +191,42 @@ void it_should_decode_vote_payload() throws Exception {
 
         assertEquals(expectedData, decodedData);
     }
+
+    @Test
+    void it_should_decode_error_payload() throws Exception {
+        assertEquals("CallerIsNotValidator", decoder.decodeError("cd03235e"));
+    }
+
+    @Test
+    void it_should_decode_error_payload_with_hex_prefix() throws Exception {
+        assertEquals("CallerIsNotValidator", decoder.decodeError("0xcd03235e"));
+    }
+
+    @Test
+    void it_should_decode_error_with_parameters() throws Exception {
+        String selector = stripSelector("InvalidRange(uint256,uint256)");
+
+        assertEquals("InvalidRange", decoder.decodeError(selector));
+    }
+
+    @Test
+    void it_should_throw_when_error_selector_is_not_found() {
+        Exception thrown = assertThrows(Exception.class, () -> decoder.decodeError("123456ab"));
+
+        assertEquals("Function selector not found in ABI: 123456ab", thrown.getMessage());
+    }
+
+    @Test
+    void it_should_not_decode_function_selectors_as_errors() {
+        String voteSelector = "6dd7d8ea";
+
+        Exception thrown = assertThrows(Exception.class, () -> decoder.decodeError(voteSelector));
+
+        assertEquals("Function selector not found in ABI: " + voteSelector, thrown.getMessage());
+    }
+
+    private String stripSelector(String signature) {
+        String hash = org.web3j.crypto.Hash.sha3String(signature);
+        return hash.startsWith("0x") ? hash.substring(2, 10) : hash.substring(0, 8);
+    }
 }