fix: introduce dedicated exception for signing failures

nostr-java-api/src/main/java/nostr/api/NostrIF.java

@@ -20,7 +20,7 @@ public interface NostrIF {
   List<String> sendRequest(@NonNull Filters filters, @NonNull String subscriptionId, Map<String, String> relays);
   List<String> sendRequest(@NonNull List<Filters> filtersList, @NonNull String subscriptionId);
   List<String> sendRequest(@NonNull List<Filters> filtersList, @NonNull String subscriptionId, Map<String, String> relays);
-  NostrIF sign(@NonNull Identity identity, @NonNull ISignable signable) throws Exception;
+  NostrIF sign(@NonNull Identity identity, @NonNull ISignable signable);
   boolean verify(@NonNull GenericEvent event);
   Identity getSender();
   Map<String, String> getRelays();

nostr-java-api/src/test/java/nostr/api/unit/NostrSpringWebSocketClientEventVerificationTest.java

@@ -5,6 +5,14 @@
 import nostr.config.Constants;
 import nostr.event.impl.GenericEvent;
 import nostr.id.Identity;
+import nostr.id.SigningException;
+import nostr.base.ISignable;
+import nostr.base.Signature;
+
+import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
 
@@ -41,4 +49,40 @@ void sendEventReturnsEmptyListWhenSigned() {
         List<String> responses = client.sendEvent(event);
         assertTrue(responses.isEmpty());
     }
+
+    @Test
+    // Verifies that SigningException bubbles up from the client when signing fails
+    void signPropagatesSigningException() {
+        String invalidPriv = "0000000000000000000000000000000000000000000000000000000000000000";
+        Identity identity = Identity.create(invalidPriv);
+
+        ISignable signable = new ISignable() {
+            private Signature signature;
+
+            @Override
+            public Signature getSignature() {
+                return signature;
+            }
+
+            @Override
+            public void setSignature(Signature signature) {
+                this.signature = signature;
+            }
+
+            @Override
+            public Consumer<Signature> getSignatureConsumer() {
+                return this::setSignature;
+            }
+
+            @Override
+            public Supplier<ByteBuffer> getByteArraySupplier() {
+                return () -> ByteBuffer.wrap("msg".getBytes(StandardCharsets.UTF_8));
+            }
+        };
+
+        NoteService service = Mockito.mock(NoteService.class);
+        NostrSpringWebSocketClient client = new NostrSpringWebSocketClient(service);
+
+        assertThrows(SigningException.class, () -> client.sign(identity, signable));
+    }
 }

nostr-java-id/src/main/java/nostr/id/Identity.java

@@ -88,15 +88,15 @@ public PublicKey getPublicKey() {
         return cachedPublicKey;
     }
 
-    //    TODO: exceptions refactor
     /**
      * Signs the supplied {@link ISignable} using this identity's private key.
      * The resulting {@link Signature} is returned and also provided to the
      * signable's signature consumer.
      *
      * @param signable the entity to sign
      * @return the generated signature
-     * @throws Exception if the signature cannot be created
+     * @throws IllegalStateException if the SHA-256 algorithm is unavailable
+     * @throws SigningException      if the signature cannot be created
      */
     public Signature sign(@NonNull ISignable signable) {
         try {
@@ -117,7 +117,7 @@ public Signature sign(@NonNull ISignable signable) {
             throw new IllegalStateException("SHA-256 algorithm not available", ex);
         } catch (Exception ex) {
             log.error("Signing failed", ex);
-            throw new IllegalArgumentException("Failed to sign with provided key", ex);
+            throw new SigningException("Failed to sign with provided key", ex);
         }
     }
 

nostr-java-id/src/main/java/nostr/id/SigningException.java

@@ -0,0 +1,10 @@
+package nostr.id;
+
+import lombok.experimental.StandardException;
+
+/**
+ * Exception thrown when signing an {@link nostr.base.ISignable} fails.
+ */
+@StandardException
+public class SigningException extends RuntimeException {
+}

nostr-java-id/src/test/java/nostr/id/IdentityTest.java

@@ -111,10 +111,11 @@ public void testGetPublicKeyFailure() {
         Assertions.assertThrows(IllegalStateException.class, identity::getPublicKey);
     }
 
-    @Test
-    public void testSignWithInvalidKeyFails() {
-        String invalidPriv = "0000000000000000000000000000000000000000000000000000000000000000";
-        Identity identity = Identity.create(invalidPriv);
+    @Test
+    // Ensures that signing with an invalid private key throws SigningException
+    public void testSignWithInvalidKeyFails() {
+        String invalidPriv = "0000000000000000000000000000000000000000000000000000000000000000";
+        Identity identity = Identity.create(invalidPriv);
 
         ISignable signable = new ISignable() {
             private Signature signature;
@@ -140,6 +141,6 @@ public Supplier<ByteBuffer> getByteArraySupplier() {
             }
         };
 
-        Assertions.assertThrows(IllegalArgumentException.class, () -> identity.sign(signable));
-    }
+        Assertions.assertThrows(SigningException.class, () -> identity.sign(signable));
+    }
 }