"""
Changes:
  * Custom field_property
  * Custom dataclass function to automatically annotate properties.
  * Modified _get_field to get default value for property.
  * No Changes to _process_class, included to use _get_field and _init_fn
"""

import sys
import types
import inspect
import functools
from typing import Callable, Any
from dataclasses import Field, _FIELD, MISSING, field, InitVar, _is_classvar, _FIELD_CLASSVAR, \
    _is_type, _is_initvar, _FIELD_INITVAR, _PARAMS, _DataclassParams, _FIELDS, _POST_INIT_NAME, _set_new_attribute, \
    _repr_fn, _tuple_str, _cmp_fn, _frozen_get_del_attr, _hash_action, _init_fn


__all__ = ['field_property', 'dataclass', '_get_field', '_process_class']


class field_property(property):

    def __init__(self,
                 fget: Callable[[Any], Any] = None,
                 fset: Callable[[Any, Any], None] = None,
                 fdel: Callable[[Any], None] = None,
                 doc: str = None,
                 default: Any = MISSING,
                 default_factory: Callable[[], Any] = MISSING):

        self.default_attr = default
        self.default_factory_attr = default_factory
        super().__init__(fget, fset, fdel, doc=doc)

    def getter(self, fget: Callable[[Any], Any]) -> 'field_property':
        return type(self)(fget, self.fset, self.fdel, self.__doc__,
                          default=self.default_attr, default_factory=self.default_factory_attr)

    def setter(self, fset: Callable[[Any, Any], None]) -> 'field_property':
        return type(self)(self.fget, fset, self.fdel, self.__doc__,
                          default=self.default_attr, default_factory=self.default_factory_attr)

    def deleter(self, fdel: Callable[[Any], None]) -> 'field_property':
        return type(self)(self.fget, self.fset, fdel, self.__doc__,
                          default=self.default_attr, default_factory=self.default_factory_attr)

    def default(self, default: Any) -> 'field_property':
        self.default_attr = default
        return self

    def default_factory(self, default_factory: Callable[[Any], None]) -> 'field_property':
        self.default_factory_attr = default_factory
        return self

    __call__ = getter


def dataclass(cls=None, /, *, init=True, repr=True, eq=True, order=False,
              unsafe_hash=False, frozen=False):
    """Returns the same class as was passed in, with dunder methods
    added based on the fields defined in the class.

    Examines PEP 526 __annotations__ to determine fields.

    If init is true, an __init__() method is added to the class. If
    repr is true, a __repr__() method is added. If order is true, rich
    comparison dunder methods are added. If unsafe_hash is true, a
    __hash__() method function is added. If frozen is true, fields may
    not be assigned to after instance creation.
    """
    def wrap(cls):
        # Annotate all properties
        if not hasattr(cls, '__annotations__'):
            cls.__annotations__ = {}
        for name, attr in cls.__dict__.items():
            if isinstance(attr, property) and name not in cls.__annotations__:
                return_type = inspect.signature(attr.fget).return_annotation
                if return_type != inspect.Signature.empty:
                    cls.__annotations__[name] = return_type

        return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)

    # See if we're being called as @dataclass or @dataclass().
    if cls is None:
        # We're called with parens.
        return wrap

    # We're called as @dataclass without parens.
    return wrap(cls)


def _get_field(cls, a_name, a_type):
    # Return a Field object for this field name and type.  ClassVars
    # and InitVars are also returned, but marked as such (see
    # f._field_type).

    # If the default value isn't derived from Field, then it's only a
    # normal default value.  Convert it to a Field().
    default = getattr(cls, a_name, MISSING)
    if isinstance(default, Field):
        f = default
    else:
        if isinstance(default, types.MemberDescriptorType):
            # This is a field in __slots__, so it has no default value.
            default = MISSING
        elif isinstance(default, property):
            default_factory_attr = getattr(default, 'default_factory_attr', MISSING)
            default_attr = getattr(default, 'default_attr', MISSING)

            if default_factory_attr != MISSING:
                if (isinstance(default_factory_attr, (staticmethod, classmethod)) or
                        len(inspect.signature(default_factory_attr).parameters) > 0):
                    default_factory_attr = default_factory_attr.__get__(cls, cls)
                f = field(default_factory=default_factory_attr)
            elif default_attr != MISSING:
                f = field(default=default_attr)
            else:
                return_type = inspect.signature(default.fget).return_annotation
                if return_type != inspect.Signature.empty:
                    default = return_type
                    f = field(default_factory=default)
                else:
                    default = MISSING
                    f = field(default=default)
        else:
            f = field(default=default)

    # Only at this point do we know the name and the type.  Set them.
    f.name = a_name
    f.type = a_type

    # Assume it's a normal field until proven otherwise.  We're next
    # going to decide if it's a ClassVar or InitVar, everything else
    # is just a normal field.
    f._field_type = _FIELD

    # In addition to checking for actual types here, also check for
    # string annotations.  get_type_hints() won't always work for us
    # (see https://github.com/python/typing/issues/508 for example),
    # plus it's expensive and would require an eval for every stirng
    # annotation.  So, make a best effort to see if this is a ClassVar
    # or InitVar using regex's and checking that the thing referenced
    # is actually of the correct type.

    # For the complete discussion, see https://bugs.python.org/issue33453

    # If typing has not been imported, then it's impossible for any
    # annotation to be a ClassVar.  So, only look for ClassVar if
    # typing has been imported by any module (not necessarily cls's
    # module).
    typing = sys.modules.get('typing')
    if typing:
        if (_is_classvar(a_type, typing)
                or (isinstance(f.type, str)
                    and _is_type(f.type, cls, typing, typing.ClassVar,
                                 _is_classvar))):
            f._field_type = _FIELD_CLASSVAR

    # If the type is InitVar, or if it's a matching string annotation,
    # then it's an InitVar.
    if f._field_type is _FIELD:
        # The module we're checking against is the module we're
        # currently in (dataclasses.py).
        dataclasses = sys.modules[__name__]
        if (_is_initvar(a_type, dataclasses)
                or (isinstance(f.type, str)
                    and _is_type(f.type, cls, dataclasses, dataclasses.InitVar,
                                 _is_initvar))):
            f._field_type = _FIELD_INITVAR

    # Validations for individual fields.  This is delayed until now,
    # instead of in the Field() constructor, since only here do we
    # know the field name, which allows for better error reporting.

    # Special restrictions for ClassVar and InitVar.
    if f._field_type in (_FIELD_CLASSVAR, _FIELD_INITVAR):
        if f.default_factory is not MISSING:
            raise TypeError(f'field {f.name} cannot have a '
                            'default factory')
        # Should I check for other field settings? default_factory
        # seems the most serious to check for.  Maybe add others.  For
        # example, how about init=False (or really,
        # init=<not-the-default-init-value>)?  It makes no sense for
        # ClassVar and InitVar to specify init=<anything>.

    # For real fields, disallow mutable defaults for known types.
    if f._field_type is _FIELD and isinstance(f.default, (list, dict, set)):
        raise ValueError(f'mutable default {type(f.default)} for field '
                         f'{f.name} is not allowed: use default_factory')

    return f


def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
    # Now that dicts retain insertion order, there's no reason to use
    # an ordered dict.  I am leveraging that ordering here, because
    # derived class fields overwrite base class fields, but the order
    # is defined by the base class, which is found first.
    fields = {}

    if cls.__module__ in sys.modules:
        globals = sys.modules[cls.__module__].__dict__
    else:
        # Theoretically this can happen if someone writes
        # a custom string to cls.__module__.  In which case
        # such dataclass won't be fully introspectable
        # (w.r.t. typing.get_type_hints) but will still function
        # correctly.
        globals = {}

    setattr(cls, _PARAMS, _DataclassParams(init, repr, eq, order,
                                           unsafe_hash, frozen))

    # Find our base classes in reverse MRO order, and exclude
    # ourselves.  In reversed order so that more derived classes
    # override earlier field definitions in base classes.  As long as
    # we're iterating over them, see if any are frozen.
    any_frozen_base = False
    has_dataclass_bases = False
    for b in cls.__mro__[-1:0:-1]:
        # Only process classes that have been processed by our
        # decorator.  That is, they have a _FIELDS attribute.
        base_fields = getattr(b, _FIELDS, None)
        if base_fields:
            has_dataclass_bases = True
            for f in base_fields.values():
                fields[f.name] = f
            if getattr(b, _PARAMS).frozen:
                any_frozen_base = True

    # Annotations that are defined in this class (not in base
    # classes).  If __annotations__ isn't present, then this class
    # adds no new annotations.  We use this to compute fields that are
    # added by this class.
    #
    # Fields are found from cls_annotations, which is guaranteed to be
    # ordered.  Default values are from class attributes, if a field
    # has a default.  If the default value is a Field(), then it
    # contains additional info beyond (and possibly including) the
    # actual default value.  Pseudo-fields ClassVars and InitVars are
    # included, despite the fact that they're not real fields.  That's
    # dealt with later.
    cls_annotations = cls.__dict__.get('__annotations__', {})

    # Now find fields in our class.  While doing so, validate some
    # things, and set the default values (as class attributes) where
    # we can.
    cls_fields = [_get_field(cls, name, type)
                  for name, type in cls_annotations.items()]
    for f in cls_fields:
        fields[f.name] = f

        # If the class attribute (which is the default value for this
        # field) exists and is of type 'Field', replace it with the
        # real default.  This is so that normal class introspection
        # sees a real default value, not a Field.
        if isinstance(getattr(cls, f.name, None), Field):
            if f.default is MISSING:
                # If there's no default, delete the class attribute.
                # This happens if we specify field(repr=False), for
                # example (that is, we specified a field object, but
                # no default value).  Also if we're using a default
                # factory.  The class attribute should not be set at
                # all in the post-processed class.
                delattr(cls, f.name)
            else:
                setattr(cls, f.name, f.default)

    # Do we have any Field members that don't also have annotations?
    for name, value in cls.__dict__.items():
        if isinstance(value, Field) and not name in cls_annotations:
            raise TypeError(f'{name!r} is a field but has no type annotation')

    # Check rules that apply if we are derived from any dataclasses.
    if has_dataclass_bases:
        # Raise an exception if any of our bases are frozen, but we're not.
        if any_frozen_base and not frozen:
            raise TypeError('cannot inherit non-frozen dataclass from a '
                            'frozen one')

        # Raise an exception if we're frozen, but none of our bases are.
        if not any_frozen_base and frozen:
            raise TypeError('cannot inherit frozen dataclass from a '
                            'non-frozen one')

    # Remember all of the fields on our class (including bases).  This
    # also marks this class as being a dataclass.
    setattr(cls, _FIELDS, fields)

    # Was this class defined with an explicit __hash__?  Note that if
    # __eq__ is defined in this class, then python will automatically
    # set __hash__ to None.  This is a heuristic, as it's possible
    # that such a __hash__ == None was not auto-generated, but it
    # close enough.
    class_hash = cls.__dict__.get('__hash__', MISSING)
    has_explicit_hash = not (class_hash is MISSING or
                             (class_hash is None and '__eq__' in cls.__dict__))

    # If we're generating ordering methods, we must be generating the
    # eq methods.
    if order and not eq:
        raise ValueError('eq must be true if order is true')

    if init:
        # Does this class have a post-init function?
        has_post_init = hasattr(cls, _POST_INIT_NAME)

        # Include InitVars and regular fields (so, not ClassVars).
        flds = [f for f in fields.values()
                if f._field_type in (_FIELD, _FIELD_INITVAR)]
        _set_new_attribute(cls, '__init__',
                           _init_fn(flds,
                                    frozen,
                                    has_post_init,
                                    # The name to use for the "self"
                                    # param in __init__.  Use "self"
                                    # if possible.
                                    '__dataclass_self__' if 'self' in fields
                                    else 'self',
                                    globals,
                                    ))

    # Get the fields as a list, and include only real fields.  This is
    # used in all of the following methods.
    field_list = [f for f in fields.values() if f._field_type is _FIELD]

    if repr:
        flds = [f for f in field_list if f.repr]
        _set_new_attribute(cls, '__repr__', _repr_fn(flds, globals))

    if eq:
        # Create _eq__ method.  There's no need for a __ne__ method,
        # since python will call __eq__ and negate it.
        flds = [f for f in field_list if f.compare]
        self_tuple = _tuple_str('self', flds)
        other_tuple = _tuple_str('other', flds)
        _set_new_attribute(cls, '__eq__',
                           _cmp_fn('__eq__', '==',
                                   self_tuple, other_tuple,
                                   globals=globals))

    if order:
        # Create and set the ordering methods.
        flds = [f for f in field_list if f.compare]
        self_tuple = _tuple_str('self', flds)
        other_tuple = _tuple_str('other', flds)
        for name, op in [('__lt__', '<'),
                         ('__le__', '<='),
                         ('__gt__', '>'),
                         ('__ge__', '>='),
                         ]:
            if _set_new_attribute(cls, name,
                                  _cmp_fn(name, op, self_tuple, other_tuple,
                                          globals=globals)):
                raise TypeError(f'Cannot overwrite attribute {name} '
                                f'in class {cls.__name__}. Consider using '
                                'functools.total_ordering')

    if frozen:
        for fn in _frozen_get_del_attr(cls, field_list, globals):
            if _set_new_attribute(cls, fn.__name__, fn):
                raise TypeError(f'Cannot overwrite attribute {fn.__name__} '
                                f'in class {cls.__name__}')

    # Decide if/how we're going to create a hash function.
    hash_action = _hash_action[bool(unsafe_hash),
                               bool(eq),
                               bool(frozen),
                               has_explicit_hash]
    if hash_action:
        # No need to call _set_new_attribute here, since by the time
        # we're here the overwriting is unconditional.
        cls.__hash__ = hash_action(cls, field_list, globals)

    if not getattr(cls, '__doc__'):
        # Create a class doc-string.
        cls.__doc__ = (cls.__name__ +
                       str(inspect.signature(cls)).replace(' -> None', ''))

    return cls
