feat: Implement roll_over_proofs() for NIP-60 state transitions

sixty_nuts/wallet.py

@@ -624,7 +624,43 @@ async def roll_over_proofs(
         unspent_proofs: list[Proof],
         deleted_event_ids: list[str],
     ) -> str:
-        return ""  # TODO: Implement roll over logic for wallet cleanup
+        """Roll over unspent proofs after a partial spend and return new token id.
+
+        This creates a new token event containing only the unspent proofs and marks
+        the old token event as superseded using the del field. Critical for proper
+        NIP-60 state transitions and preventing double-spending.
+
+        Args:
+            spent_proofs: List of proofs that were spent (not used in rollover)
+            unspent_proofs: List of proofs to roll over to new event
+            deleted_event_ids: List of old event IDs to mark as superseded
+
+        Returns:
+            New token event ID containing the rolled over proofs
+
+        Raises:
+            WalletError: If no unspent proofs provided or event publishing fails
+        """
+        if not unspent_proofs:
+            raise WalletError("No unspent proofs to roll over")
+
+        if not deleted_event_ids:
+            raise WalletError("No deleted event IDs provided for rollover")
+
+        try:
+            # Use EventManager to publish new token event with rollover
+            event_id = await self.event_manager.publish_token_event(
+                unspent_proofs,
+                deleted_token_ids=deleted_event_ids,
+            )
+
+            if not event_id:
+                raise WalletError("Failed to publish rollover token event")
+
+            return event_id
+
+        except Exception as e:
+            raise WalletError(f"Failed to roll over proofs: {e}") from e
 
     async def _consolidate_proofs(
         self, proofs: list[Proof], target_mint: str | None = None

tests/unit/test_wallet.py

@@ -417,3 +417,101 @@ def test_raise_if_insufficient_balance_insufficient(self) -> None:
 
         with pytest.raises(WalletError, match="Insufficient balance"):
             wallet.raise_if_insufficient_balance(0, 1)
+
+
+class TestWalletRolloverProofs:
+    """Test roll_over_proofs functionality."""
+
+    @pytest.mark.asyncio
+    async def test_roll_over_proofs_success(self) -> None:
+        """Test successful proof rollover."""
+        wallet = Wallet(
+            nsec=generate_privkey(),
+            mint_urls=["http://test.mint"],
+            relay_urls=["ws://test.relay"],
+        )
+
+        spent_proofs: list[Proof] = [
+            {
+                "id": "test1",
+                "amount": 10,
+                "secret": "secret1",
+                "C": "C1",
+                "mint": "http://test.mint",
+                "unit": "sat",
+            }
+        ]
+
+        unspent_proofs: list[Proof] = [
+            {
+                "id": "test2",
+                "amount": 20,
+                "secret": "secret2",
+                "C": "C2",
+                "mint": "http://test.mint",
+                "unit": "sat",
+            }
+        ]
+
+        deleted_event_ids = ["event1", "event2"]
+
+        with patch.object(wallet.event_manager, 'publish_token_event', new_callable=AsyncMock) as mock_publish:
+            mock_publish.return_value = "new_event_id"
+
+            result = await wallet.roll_over_proofs(
+                spent_proofs=spent_proofs,
+                unspent_proofs=unspent_proofs,
+                deleted_event_ids=deleted_event_ids,
+            )
+
+            assert result == "new_event_id"
+            mock_publish.assert_called_once_with(
+                unspent_proofs, deleted_token_ids=deleted_event_ids
+            )
+
+    @pytest.mark.asyncio
+    async def test_roll_over_proofs_no_unspent(self) -> None:
+        """Test rollover with no unspent proofs raises error."""
+        from sixty_nuts.types import WalletError
+
+        wallet = Wallet(
+            nsec=generate_privkey(),
+            mint_urls=["http://test.mint"],
+            relay_urls=["ws://test.relay"],
+        )
+
+        with pytest.raises(WalletError, match="No unspent proofs to roll over"):
+            await wallet.roll_over_proofs(
+                spent_proofs=[],
+                unspent_proofs=[],
+                deleted_event_ids=["event1"],
+            )
+
+    @pytest.mark.asyncio
+    async def test_roll_over_proofs_no_deleted_events(self) -> None:
+        """Test rollover with no deleted event IDs raises error."""
+        from sixty_nuts.types import WalletError
+
+        wallet = Wallet(
+            nsec=generate_privkey(),
+            mint_urls=["http://test.mint"],
+            relay_urls=["ws://test.relay"],
+        )
+
+        unspent_proofs: list[Proof] = [
+            {
+                "id": "test1",
+                "amount": 10,
+                "secret": "secret1",
+                "C": "C1",
+                "mint": "http://test.mint",
+                "unit": "sat",
+            }
+        ]
+
+        with pytest.raises(WalletError, match="No deleted event IDs provided for rollover"):
+            await wallet.roll_over_proofs(
+                spent_proofs=[],
+                unspent_proofs=unspent_proofs,
+                deleted_event_ids=[],
+            )