# Copyright 2018-2023 Descartes Labs.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from collections import UserList
from datetime import datetime, timezone
from typing import TYPE_CHECKING, Any, Callable, Iterable, Type, TypeVar, Union
from ..property_filtering import Property
from .sort import Sort
if TYPE_CHECKING:
from .document import Document
T = TypeVar("T")
[docs]class Attribute(Property):
"""An attribute defined on a Document."""
def __init__(
self,
type: Type[T] = None,
default: Union[T, Callable] = None,
doc: str = None,
filterable: bool = False,
mutable: bool = True,
readonly: bool = False,
sortable: bool = False,
sticky: bool = False,
):
"""Defines a document attribute.
Examples
--------
.. code::
class MyDocument(Document):
id: id = Attribute(readonly=True)
name: str = Attribute(str)
set_once: str = Attribute(str, mutable=False)
doc = MyDocument(name="test", set_once="can only be set once")
doc.set_once = "error"
Parameters
----------
default : Any, Callable, None
The default value for the attribute when no value is defined.
If a callable is provided, it will be called once when the attribute is first
fetched.
doc : str, None
Sets the doc string for the attribute.
filterable: bool, False
If set, the attribute can be used as a filter.
mutable : bool, True
If not set, the attribute will be immutable and can only be set once.
readonly : bool, False
If set, the attribute cannot be modified by the user.
This is designed for attributes set and managed exclusively by the server.
sortable : bool, False
If set, the attribute can be used to sort results.
sticky : bool, False
If set, the attribute exists on the client only.
This attribute will be ignored when set by the server.
"""
super().__init__(None)
if sticky and readonly:
raise ValueError("Using sticky and readonly together does not make sense.")
self.type = type
self.default = default
self.filterable = filterable
self.mutable = mutable
self.readonly = readonly
self.sortable = sortable
self.sticky = sticky
if doc is None and type:
doc = type.__doc__
doc_modifiers = []
if not self.mutable:
doc_modifiers.append(
"The attribute is `immutable` and cannot be modified once set."
)
if self.readonly:
doc_modifiers.append("The attribute is `readonly` and cannot be modified.")
doc = "{}: {}".format(self._doc_type, doc)
if doc_modifiers:
doc += "\n\n" + "\n\n".join(doc_modifiers)
self.__doc__ = doc
@property
def _doc_type(self) -> str:
return "{} or {}".format(self.type.__name__, self.default)
def __set_name__(self, owner: "Document", name: "str"):
"""Called when an attribute is defined on a document."""
if not hasattr(owner, "_attributes"):
setattr(owner, "_attributes", dict())
if not hasattr(owner, "_modified"):
setattr(owner, "_modified", set())
self.name = name
def __get__(self, instance: "Document", owner) -> T:
"""Called when an attribute value is accessed.
If no value is defined for the attribute, the default will be applied.
"""
# Instance will be None if accessed as a class property
# this occurs when generating documentation with Sphinx.
# In this case, return the attribute instance for documentation.
if instance is None:
return self
if self.name not in instance._attributes:
if callable(self.default):
default = self.default()
else:
default = self.default
instance._attributes[self.name] = self.deserialize(
default, instance=instance
)
return instance._attributes.get(self.name)
def __set__(self, instance: "Document", value, force: bool = False):
"""Called when attribute is set to a given value.
Values will be deserialized to the type defined in the attribute.
Additionally, the attribute will be marked as modified.
Parameters
----------
force : bool, False
When force is set, the value is assumed to be from the server.
In this case, `mutable` and `readonly` are ignored and `sticky` is respected.
"""
if force and self.sticky:
return
if not force:
self._raise_immutable("set", instance)
if self.type and value is not None:
value = self.deserialize(value, instance, force=force)
# Only update the value if it has changed
if (self.name not in instance._attributes and value is None) or (
instance._attributes.get(self.name) == value
):
return
# It is being set by the server, it is no longer modified
if force:
instance._modified.discard(self.name)
else:
instance._modified.add(self.name)
instance._attributes[self.name] = value
def __delete__(self, instance: "Document", force: bool = False):
"""Called when an attribute is deleted."""
if not force:
self._raise_immutable("delete", instance)
instance._attributes.pop(self.name, None)
def __neg__(self):
return self._to_sort(ascending=False)
def _to_sort(self, ascending: bool = True):
if not self.sortable:
raise ValueError(f"Cannot sort on property: {self.name}")
return Sort(self.name, ascending)
def _raise_immutable(self, operation: str, instance: "Document"):
"""Raises an error when an attribute cannot be modified."""
if self.readonly:
raise ValueError(
"Unable to {} readonly attribute '{}'".format(operation, self.name)
)
if not self.mutable and (
instance is None or instance._attributes.get(self.name, None)
):
raise ValueError(
"Unable to {} immutable attribute '{}'".format(operation, self.name)
)
def _set_modified(self, instance: "Document", changed: bool = True):
"""Marks the attribute as modified."""
if changed:
instance._modified.add(self.name)
def _serialize_to_filter(self, value: Any):
"""Serializes a value to a filter expression value."""
return self.serialize(value)
[docs] def deserialize(
self, value: Any, instance: "Document" = None, force: bool = False
) -> T:
"""Deserializes a value to the type in the attribute.
Parameters
----------
value : Any
The value to deserialize into a native Python type.
instance : Document, None
The document instance the value is being deserialized for.
When a value is set on a document, the instance will not be None.
"""
if value is None or isinstance(value, self.type):
return value
from .document import Document
try:
if issubclass(self.type, Document):
# Support nested documents
if isinstance(value, dict):
return self.type(**value, saved=force)
elif isinstance(value, Iterable):
return self.type(*value, saved=force)
else:
return self.type(value, saved=force)
else:
# Support single or native values
return self.type(value)
except (ValueError, TypeError) as e:
raise ValueError(f"Unable to assign {type(value)} to type {self.type}: {e}")
[docs] def serialize(self, value):
"""Serializes a value to a JSON encodable type."""
return value
def __repr__(self):
return (
"<Attribute name={} filterable={} mutable={} readonly={} sticky={}>".format(
repr(self.name),
self.filterable,
self.mutable,
self.readonly,
self.sticky,
)
)
[docs]class DatetimeAttribute(Attribute):
"""Represents a datetime attribute on a document."""
def __init__(
self,
timezone=None,
remote_timezone=timezone.utc,
default: Union[T, Callable] = None,
mutable: bool = True,
readonly: bool = False,
sticky: bool = False,
**extra,
):
"""Defines a datetime attribute.
Parameters
----------
timezone : timezone, None
The timezone the client would like dates to be in.
By default, this will used the timezone defined by the user's machine.
remote_timezone : timezone, timezone.utc
The timezone the server will return dates in.
By default, this is assumed to be UTC.
default : Any, Callable, None
The default value for the attribute when no value is defined.
If a callable is provided, it will be called once when the attribute is first
fetched.
mutable : bool, True
If not set, the attribute will be immutable and can only be set once.
readonly : bool, False
If set, the attribute cannot be modified by the user.
This is designed for attributes set and managed exclusively by the server.
sticky : bool, False
If set, the attribute exists on the client only.
This attribute will be ignored when set by the server.
"""
self.timezone = timezone
self.remote_timezone = remote_timezone
super().__init__(
type=datetime,
default=default,
mutable=mutable,
readonly=readonly,
sticky=sticky,
**extra,
)
[docs] def deserialize(
self, value: str, instance: "Document" = None, force: bool = False
) -> T:
"""Deserialize a server datetime."""
if value is None:
return None
if isinstance(value, (int, float)):
value = datetime.fromtimestamp(value, tz=timezone.utc)
elif isinstance(value, str):
if value.endswith("Z"):
value = value[:-1] + "+00:00"
value = datetime.fromisoformat(value)
if isinstance(value, datetime):
if not value.tzinfo:
value.replace(tzinfo=self.remote_timezone)
return value.astimezone(tz=self.timezone)
else:
raise ValueError("Expected datetime, iso formatted date or unix timestamp")
[docs] def serialize(self, value: datetime):
"""Serialize a datetime in local time to server time in iso format."""
if value is None:
return value
# any value which is not a datetime must be coming from e.g. a filter expression
# so we need to convert it to a datetime.
if not isinstance(value, datetime):
value = self.deserialize(value)
if isinstance(value, datetime):
return value.astimezone(tz=self.remote_timezone).isoformat()
else:
raise ValueError("Expected datetime, iso formatted date or unix timestamp")
[docs]class ListAttribute(Attribute):
"""Represents a list attribute on a document."""
def __init__(
self,
type: Type[T] = None,
default: Union[T, Callable] = None,
mutable: bool = True,
readonly: bool = False,
sticky: bool = False,
**extra,
):
"""Defines a list attribute.
Parameters
----------
type : Type[T], None
The type of the items in the list.
default : Any, Callable, None
The default value for the attribute when no value is defined.
If a callable is provided, it will be called once when the attribute is first
fetched.
mutable : bool, True
If not set, the attribute will be immutable and can only be set once.
readonly : bool, False
If set, the attribute cannot be modified by the user.
This is designed for attributes set and managed exclusively by the server.
sticky : bool, False
If set, the attribute exists on the client only.
This attribute will be ignored when set by the server.
"""
super().__init__(
type=type,
default=default or [],
mutable=mutable,
readonly=readonly,
sticky=sticky,
**extra,
)
[docs] def deserialize(
self, value: Any, instance: "Document" = None, force: bool = False
) -> T:
"""Deserialize a list of values."""
if value is None:
return None
if not isinstance(value, Iterable):
raise ValueError("Expected a list of values")
if isinstance(self.type, Attribute):
return MutableList(
self, instance, [self.type.deserialize(v, instance) for v in value]
)
return MutableList(self, instance, [self.type(v) for v in value])
[docs] def serialize(self, value):
"""Serialize a list of values."""
if isinstance(self.type, Attribute):
return [v.serialize(v) for v in value]
if isinstance(value, MutableList):
return value.data
return value
def _serialize_to_filter(self, value: Any):
if isinstance(self.type, Attribute):
return self.type._serialize_to_filter(value)
return self.type(value)
class MutableList(UserList):
"""A mutable list that tracks changes and notifies the document."""
def __init__(self, attribute: Attribute, document: "Document", data: Iterable):
super().__init__(data)
self._attribute = attribute
self._document = document
def __delitem__(self, key):
self._attribute._raise_immutable("delete", self._document)
super().__delitem__(key)
self._attribute._set_modified(self._document)
def __iadd__(self, other: Iterable):
self._attribute._raise_immutable("add", self._document)
other = [self._attribute.type(o) for o in other]
result = super().__iadd__(other)
self._attribute._set_modified(self._document, changed=bool(other))
return result
def __setitem__(self, key, value):
self._attribute._raise_immutable("set", self._document)
value = self._attribute.type(value)
changed = self.__getitem__(key) != value
super().__setitem__(key, value)
self._attribute._set_modified(self._document, changed=changed)
def append(self, item):
self._attribute._raise_immutable("append", self._document)
item = self._attribute.type(item)
super().append(item)
self._attribute._set_modified(self._document)
def clear(self):
self._attribute._raise_immutable("clear", self._document)
super().clear()
self._attribute._set_modified(self._document)
def extend(self, other: Iterable):
self._attribute._raise_immutable("extend", self._document)
other = [self._attribute.type(o) for o in other]
result = super().extend(other)
self._attribute._set_modified(self._document, changed=bool(other))
return result
def insert(self, i, item):
self._attribute._raise_immutable("insert", self._document)
item = self._attribute.type(item)
super().insert(i, item)
self._attribute._set_modified(self._document)
def pop(self, i=-1):
self._attribute._raise_immutable("pop", self._document)
result = super().pop(i)
self._attribute._set_modified(self._document)
return result
def remove(self, item):
self._attribute._raise_immutable("remove", self._document)
super().remove(item)
self._attribute._set_modified(self._document)
def __repr__(self):
return repr(self.data)
