# --------------------------------------------------------------------------------------
# Copyright (c) 2013-2021, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file LICENSE, distributed with this software.
# --------------------------------------------------------------------------------------
from .catom import DefaultValue, Member, Validate
from .typing_utils import extract_types, is_optional


class Typed(Member):
    """A value which allows objects of a given type or types.

    Values will be tested using the `PyObject_TypeCheck` C API call.
    This call is equivalent to `type(obj) in cls.mro()`. It is less
    flexible but can be faster than Instance. Use Instance when allowing
    you need a tuple of types or (abstract) types relying on custom
    __isinstancecheck__ and Typed when the value type is explicit.

    If optional is True, the value of a Typed may be set to None,
    otherwise None is not considered as a valid value.

    """

    __slots__ = ()

    def __init__(self, kind, args=None, kwargs=None, *, factory=None, optional=None):
        """Initialize an Typed.

        Parameters
        ----------
        kind : type
            The allowed type for the value.

        args : tuple, optional
            If 'factory' is None, then 'kind' is a callable type and
            these arguments will be passed to the constructor to create
            the default value.

        kwargs : dict, optional
            If 'factory' is None, then 'kind' is a callable type and
            these keywords will be passed to the constructor to create
            the default value.

        factory : callable, optional
            An optional factory to use for creating the default value.
            If this is not provided and 'args' and 'kwargs' is None,
            then the default value will be None, which will raised if
            accessed when optional is False.

        optional : bool | None, optional
            Boolean indicating if None is a valid value for the member.
            By default, the value is inferred to be True if no args or factory
            is provided.

        """
        opt, (kind,) = is_optional(extract_types(kind))
        if opt and optional is False:
            raise ValueError(
                "The type passed to Typed is declared optional but optional was "
                "explicitly set to False"
            )
        # If opt is False we preserve optional as None for backward compatibility.
        optional = optional if optional is not None else (opt or None)

        if factory is not None:
            self.set_default_value_mode(DefaultValue.CallObject, factory)
        elif args is not None or kwargs is not None:
            args = args or ()
            kwargs = kwargs or {}
            factory = lambda: kind(*args, **kwargs)
            self.set_default_value_mode(DefaultValue.CallObject, factory)
        elif optional is False:
            self.set_default_value_mode(DefaultValue.NonOptional, None)

        optional = (
            optional
            if optional is not None
            else factory is None and args is None and kwargs is None
        )
        if optional:
            self.set_validate_mode(Validate.OptionalTyped, kind)
        else:
            self.set_validate_mode(Validate.Typed, kind)


class ForwardTyped(Typed):
    """A Typed which delays resolving the type definition.

    The first time the value is accessed or modified, the type will
    be resolved and the forward typed will behave identically to a
    normal typed.

    """

    __slots__ = ("resolve", "args", "kwargs", "optional")

    def __init__(self, resolve, args=None, kwargs=None, *, factory=None, optional=None):
        """Initialize a ForwardTyped.

        resolve : callable
            A callable which takes no arguments and returns the type to
            use for validating the values. This type can be a generic but
            must resolve to a single type. list[int] is valid but Optional[int]
            is not.

        args : tuple, optional
            If 'factory' is None, then 'resolve' will return a callable
            type and these arguments will be passed to the constructor
            to create the default value.

        kwargs : dict, optional
            If 'factory' is None, then 'resolve' will return a callable
            type and these keywords will be passed to the constructor to
            create the default value.

        factory : callable, optional
            An optional factory to use for creating the default value.
            If this is not provided and 'args' and 'kwargs' is None,
            then the default value will be None, which will raised if
            accessed when optional is False.

        optional : bool | None, optional
            Boolean indicating if None is a valid value for the member.
            By default, the value is inferred to be True if no args or factory
            is provided.

        """
        self.resolve = resolve
        self.args = args
        self.kwargs = kwargs
        if factory is not None:
            self.set_default_value_mode(DefaultValue.CallObject, factory)
        elif args is not None or kwargs is not None:
            mode = DefaultValue.MemberMethod_Object
            self.set_default_value_mode(mode, "default")
        elif optional is False:
            self.set_default_value_mode(DefaultValue.NonOptional, None)

        self.optional = (
            optional
            if optional is not None
            else factory is None and args is None and kwargs is None
        )

        self.set_validate_mode(Validate.MemberMethod_ObjectOldNew, "validate")

    def default(self, owner):
        """Called to retrieve the default value.

        This is called the first time the default value is retrieved
        for the member. It resolves the type and updates the internal
        default handler to behave like a normal Typed member.

        """
        (kind,) = extract_types(self.resolve())
        args = self.args or ()
        kwargs = self.kwargs or {}
        factory = lambda: kind(*args, **kwargs)
        self.set_default_value_mode(DefaultValue.CallObject, factory)
        return kind(*args, **kwargs)

    def validate(self, owner, old, new):
        """Called to validate the value.

        This is called the first time a value is validated for the
        member. It resolves the type and updates the internal validate
        handler to behave like a normal Typed member.

        """
        (kind,) = extract_types(self.resolve())
        if self.optional:
            self.set_validate_mode(Validate.OptionalTyped, kind)
        else:
            self.set_validate_mode(Validate.Typed, kind)
        return self.do_validate(owner, old, new)

    def clone(self):
        """Create a clone of the ForwardTyped instance."""
        clone = super(ForwardTyped, self).clone()
        clone.resolve = self.resolve
        clone.args = self.args
        clone.kwargs = self.kwargs
        clone.optional = self.optional
        return clone
