Basic structuring

planetmint/transactions/common/input.py

@@ -0,0 +1,117 @@
+# Copyright © 2020 Interplanetary Database Association e.V.,
+# Planetmint and IPDB software contributors.
+# SPDX-License-Identifier: (Apache-2.0 AND CC-BY-4.0)
+# Code is Apache-2.0 and docs are CC-BY-4.0
+
+class Input(object):
+    """A Input is used to spend assets locked by an Output.
+
+    Wraps around a Crypto-condition Fulfillment.
+
+        Attributes:
+            fulfillment (:class:`cryptoconditions.Fulfillment`): A Fulfillment
+                to be signed with a private key.
+            owners_before (:obj:`list` of :obj:`str`): A list of owners after a
+                Transaction was confirmed.
+            fulfills (:class:`~planetmint.common.transaction. TransactionLink`,
+                optional): A link representing the input of a `TRANSFER`
+                Transaction.
+    """
+
+    def __init__(self, fulfillment, owners_before, fulfills=None):
+        """Create an instance of an :class:`~.Input`.
+
+            Args:
+                fulfillment (:class:`cryptoconditions.Fulfillment`): A
+                    Fulfillment to be signed with a private key.
+                owners_before (:obj:`list` of :obj:`str`): A list of owners
+                    after a Transaction was confirmed.
+                fulfills (:class:`~planetmint.common.transaction.
+                    TransactionLink`, optional): A link representing the input
+                    of a `TRANSFER` Transaction.
+        """
+        if fulfills is not None and not isinstance(fulfills, TransactionLink):
+            raise TypeError('`fulfills` must be a TransactionLink instance')
+        if not isinstance(owners_before, list):
+            raise TypeError('`owners_before` must be a list instance')
+
+        self.fulfillment = fulfillment
+        self.fulfills = fulfills
+        self.owners_before = owners_before
+
+    def __eq__(self, other):
+        # TODO: If `other !== Fulfillment` return `False`
+        return self.to_dict() == other.to_dict()
+
+    # NOTE: This function is used to provide a unique key for a given
+    # Input to suppliment memoization
+    def __hash__(self):
+        return hash((self.fulfillment, self.fulfills))
+
+    def to_dict(self):
+        """Transforms the object to a Python dictionary.
+
+            Note:
+                If an Input hasn't been signed yet, this method returns a
+                dictionary representation.
+
+            Returns:
+                dict: The Input as an alternative serialization format.
+        """
+        try:
+            fulfillment = self.fulfillment.serialize_uri()
+        except (TypeError, AttributeError, ASN1EncodeError, ASN1DecodeError):
+            fulfillment = _fulfillment_to_details(self.fulfillment)
+
+        try:
+            # NOTE: `self.fulfills` can be `None` and that's fine
+            fulfills = self.fulfills.to_dict()
+        except AttributeError:
+            fulfills = None
+
+        input_ = {
+            'owners_before': self.owners_before,
+            'fulfills': fulfills,
+            'fulfillment': fulfillment,
+        }
+        return input_
+
+    @classmethod
+    def generate(cls, public_keys):
+        # TODO: write docstring
+        # The amount here does not really matter. It is only use on the
+        # output data model but here we only care about the fulfillment
+        output = Output.generate(public_keys, 1)
+        return cls(output.fulfillment, public_keys)
+
+    @classmethod
+    def from_dict(cls, data):
+        """Transforms a Python dictionary to an Input object.
+
+            Note:
+                Optionally, this method can also serialize a Cryptoconditions-
+                Fulfillment that is not yet signed.
+
+            Args:
+                data (dict): The Input to be transformed.
+
+            Returns:
+                :class:`~planetmint.common.transaction.Input`
+
+            Raises:
+                InvalidSignature: If an Input's URI couldn't be parsed.
+        """
+        fulfillment = data['fulfillment']
+        if not isinstance(fulfillment, (Fulfillment, type(None))):
+            try:
+                fulfillment = Fulfillment.from_uri(data['fulfillment'])
+            except ASN1DecodeError:
+                # TODO Remove as it is legacy code, and simply fall back on
+                # ASN1DecodeError
+                raise InvalidSignature("Fulfillment URI couldn't been parsed")
+            except TypeError:
+                # NOTE: See comment about this special case in
+                #       `Input.to_dict`
+                fulfillment = _fulfillment_from_details(data['fulfillment'])
+        fulfills = TransactionLink.from_dict(data['fulfills'])
+        return cls(fulfillment, data['owners_before'], fulfills)