Validate output value is non-negative

Author: cffls

pycardano/transaction.py

@@ -11,7 +11,7 @@
 from typeguard import typechecked
 
 from pycardano.address import Address
-from pycardano.exception import InvalidOperationException
+from pycardano.exception import InvalidDataException, InvalidOperationException
 from pycardano.hash import (
     TRANSACTION_HASH_SIZE,
     AuxiliaryDataHash,
@@ -182,6 +182,24 @@ def filter(
 
         return new_multi_asset
 
+    def count(self, criteria=Callable[[ScriptHash, AssetName, int], bool]) -> int:
+        """Count number of distinct assets that satisfy a certain criteria.
+
+        Args:
+            criteria: A function that takes in three input arguments (policy_id, asset_name, amount) and returns a
+                bool.
+
+        Returns:
+            int: Total number of distinct assets that satisfy the criteria.
+        """
+        count = 0
+        for p in self:
+            for n in self[p]:
+                if criteria(p, n, self[p][n]):
+                    count += 1
+
+        return count
+
 
 @typechecked
 @dataclass(repr=False)
@@ -236,6 +254,21 @@ class TransactionOutput(ArrayCBORSerializable):
 
     datum_hash: DatumHash = field(default=None, metadata={"optional": True})
 
+    def validate(self):
+        if isinstance(self.amount, int) and self.amount < 0:
+            raise InvalidDataException(
+                f"Transaction output cannot have negative amount of ADA or "
+                f"native asset: \n {self.amount}"
+            )
+        if isinstance(self.amount, Value) and (
+            self.amount.coin < 0
+            or self.amount.multi_asset.count(lambda p, n, v: v < 0) > 0
+        ):
+            raise InvalidDataException(
+                f"Transaction output cannot have negative amount of ADA or "
+                f"native asset: \n {self.amount}"
+            )
+
     @property
     def lovelace(self) -> int:
         if isinstance(self.amount, int):

test/pycardano/test_transaction.py

@@ -3,7 +3,7 @@
 import pytest
 
 from pycardano.address import Address
-from pycardano.exception import InvalidOperationException
+from pycardano.exception import InvalidDataException, InvalidOperationException
 from pycardano.hash import SCRIPT_HASH_SIZE, ScriptHash, TransactionId
 from pycardano.key import PaymentKeyPair, PaymentSigningKey, VerificationKey
 from pycardano.transaction import (
@@ -42,6 +42,28 @@ def test_transaction_output():
     check_two_way_cbor(output)
 
 
+def test_invalid_transaction_output():
+    addr = Address.decode(
+        "addr_test1vrm9x2zsux7va6w892g38tvchnzahvcd9tykqf3ygnmwtaqyfg52x"
+    )
+    output = TransactionOutput(addr, -100000000000)
+    with pytest.raises(InvalidDataException):
+        output.to_cbor()
+
+    value = Value.from_primitive(
+        [
+            100,
+            {
+                b"1"
+                * SCRIPT_HASH_SIZE: {b"TestToken1": -10000000, b"TestToken2": 20000000}
+            },
+        ]
+    )
+    output = TransactionOutput(addr, value)
+    with pytest.raises(InvalidDataException):
+        output.to_cbor()
+
+
 def make_transaction_body():
     tx_id_hex = "732bfd67e66be8e8288349fcaaa2294973ef6271cc189a239bb431275401b8e5"
     tx_in = TransactionInput(TransactionId(bytes.fromhex(tx_id_hex)), 0)