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from __future__ import annotations
from collections import defaultdict
from typing import Any, Dict, Optional, Tuple
from .fields import Field, ModelField
from .validation import Validation
class ModelBase:
__slots__ = ()
def __init__(self):
pass
@classmethod
def get_xmltag(cls) -> str:
xmltag = getattr(cls, "__xmltag__", None)
if xmltag is None:
xmltag = cls.__name__
xmlns = getattr(cls, "__xmlns__", None)
if xmlns:
return "{" + xmlns + "}" + xmltag
else:
return xmltag
def get_xmlattrs(self) -> Dict[str, str]:
return {}
class ModelMetaclass(type):
def __new__(cls, name, bases, dct):
_meta = {}
# Add fields from subclasses
for b in bases:
if not issubclass(b, ModelBase):
continue
b_meta = getattr(b, "_meta", None)
if b_meta is None:
continue
_meta.update(b_meta)
# Add fields from the class itself
slots = []
for field_name, val in list(dct.items()):
if isinstance(val, Field):
# Store its description in the Model _meta
_meta[field_name] = val
val.set_name(field_name)
elif isinstance(val, type) and issubclass(val, ModelBase):
# Store its description in the Model _meta
val = ModelField(val)
_meta[field_name] = val
val.set_name(field_name)
else:
# Leave untouched
continue
# Remove field_name from class variables
del dct[field_name]
# Add it as a slot in the instance
slots.append(field_name)
dct["__slots__"] = slots
res = super().__new__(cls, name, bases, dct)
res._meta = _meta
return res
class Model(ModelBase, metaclass=ModelMetaclass):
"""
Declarative description of a data structure that can be validated and
serialized to XML.
"""
__slots__ = ()
def __init__(self, *args, **kw):
super().__init__()
for name, value in zip(self._meta.keys(), args):
kw[name] = value
for name, field in self._meta.items():
value = kw.pop(name, None)
if value is None:
value = field.get_construct_default()
else:
value = field.clean_value(value)
setattr(self, name, value)
def update(self, *args, **kw):
"""
Set multiple values in the model.
Arguments are treated in the same way as in the constructor. Any field
not mentioned is left untouched.
"""
for name, value in zip(self._meta.keys(), args):
setattr(self, name, value)
for name, value in kw.items():
setattr(self, name, value)
def has_value(self):
for name, field in self._meta.items():
if field.has_value(getattr(self, name)):
return True
return False
@classmethod
def clean_value(cls, value: Any) -> Optional["Model"]:
"""
Create a model from the given value.
Always make a copy even if value is already of the right class, to
prevent mutability issues.
"""
if value is None:
return None
if isinstance(value, dict):
return cls(**value)
elif isinstance(value, ModelBase):
kw = {}
for name, field in cls._meta.items():
kw[name] = getattr(value, name, None)
return cls(**kw)
else:
raise TypeError(f"{cls.__name__}: {value!r} is {type(value).__name__}"
" instead of a Model or dict instance")
def validate_fields(self, validation: Validation):
for name, field in self._meta.items():
field.validate(validation, getattr(self, name))
def validate_model(self, validation: Validation):
pass
def validate(self, validation: Validation):
self.validate_fields(validation)
self.validate_model(validation)
def to_jsonable(self):
res = {}
for name, field in self._meta.items():
value = field.to_jsonable(getattr(self, name))
if value is not None:
res[name] = value
return res
def to_python(self, **kw) -> str:
args = []
for name, field in self._meta.items():
value = getattr(self, name)
if not field.has_value(value):
continue
args.append(name + "=" + field.to_python(value, **kw))
namespace = kw.get("namespace")
if namespace is None:
constructor = self.__class__.__module__ + "." + self.__class__.__qualname__
elif namespace is False:
constructor = self.__class__.__qualname__
else:
constructor = namespace + "." + self.__class__.__qualname__
return "{}({})".format(constructor, ", ".join(args))
def to_xml(self, builder):
with builder.element(self.get_xmltag(), **self.get_xmlattrs()) as b:
for name, field in self._meta.items():
field.to_xml(b, getattr(self, name))
def __setattr__(self, key: str, value: any):
field = self._meta.get(key, None)
if field is not None:
value = field.clean_value(value)
super().__setattr__(key, value)
def _to_tuple(self) -> Tuple[Any]:
return tuple(getattr(self, name) for name in self._meta.keys())
def __eq__(self, other):
other = self.clean_value(other)
has_self = self.has_value()
has_other = other is not None and other.has_value()
if not has_self and not has_other:
return True
if has_self != has_other:
return False
return self._to_tuple() == other._to_tuple()
def __ne__(self, other):
other = self.clean_value(other)
has_self = self.has_value()
has_other = other is not None and other.has_value()
if not has_self and not has_other:
return False
if has_self != has_other:
return True
return self._to_tuple() != other._to_tuple()
def __lt__(self, other):
other = self.clean_value(other)
has_self = self.has_value()
has_other = other is not None and other.has_value()
if not has_self and not has_other:
return False
if has_self and not has_other:
return False
if not has_self and has_other:
return True
return self._to_tuple() < other._to_tuple()
def __gt__(self, other):
other = self.clean_value(other)
has_self = self.has_value()
has_other = other is not None and other.has_value()
if not has_self and not has_other:
return False
if has_self and not has_other:
return True
if not has_self and has_other:
return False
return self._to_tuple() > other._to_tuple()
def __le__(self, other):
other = self.clean_value(other)
has_self = self.has_value()
has_other = other is not None and other.has_value()
if not has_self and not has_other:
return True
if has_self and not has_other:
return False
if not has_self and has_other:
return True
return self._to_tuple() <= other._to_tuple()
def __ge__(self, other):
other = self.clean_value(other)
has_self = self.has_value()
has_other = other is not None and other.has_value()
if not has_self and not has_other:
return True
if has_self and not has_other:
return True
if not has_self and has_other:
return False
return self._to_tuple() >= other._to_tuple()
def __str__(self):
vals = []
for name, field in self._meta.items():
vals.append(name + "=" + field.to_str(getattr(self, name)))
return "{}({})".format(self.__class__.__name__, ", ".join(vals))
def __repr__(self):
vals = []
for name, field in self._meta.items():
vals.append(name + "=" + field.to_str(getattr(self, name)))
return "{}({})".format(self.__class__.__name__, ", ".join(vals))
def from_etree(self, el):
if el.tag != self.get_xmltag():
raise RuntimeError("element is {} instead of {}".format(el.tag, self.get_xmltag()))
tag_map = {field.get_xmltag(): (name, field) for name, field in self._meta.items()}
# Group values by tag
by_name = defaultdict(list)
for child in el:
try:
name, field = tag_map[child.tag]
except KeyError:
raise RuntimeError("found unexpected element {} in {}".format(child.tag, el.tag))
by_name[name].append(child)
for name, elements in by_name.items():
field = self._meta[name]
if field.multivalue:
setattr(self, name, field.from_etree(elements))
elif len(elements) != 1:
raise RuntimeError(
"found {} {} elements in {} instead of just 1".format(
len(elements), child.tag, el.tag))
else:
setattr(self, name, field.from_etree(elements[0]))
def diff(self, diff, other):
has_self = self.has_value()
has_other = other.has_value()
if not has_self and not has_other:
return
if has_self != has_other:
diff.add(None, self, other)
return
for name, field in self._meta.items():
first = getattr(self, name)
second = getattr(other, name)
field.diff(diff, first, second)
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