import abc
from typing import Mapping

from bu4.evaluation.evaluable import Evaluable

try:
    from typing import TypeAlias
except ImportError:
    TypeAlias = type

envtype: TypeAlias = Mapping[bytes, 'AfterValue']


class AVTarget:
    def given(self, value: 'EValue') -> Evaluable:
        raise NotImplementedError


class AfterValue(Evaluable):
    def __init__(self, evaluable: Evaluable, target: AVTarget):
        self.evaluable = evaluable
        self.target = target

    def next(self) -> 'Evaluable':
        if isinstance(self.evaluable, EValue):
            if isinstance(self.target, AVAV):
                self.evaluable, self.target = self.target.target.given(self.evaluable), self.target.aftertarget
                return self
            return self.target.given(self.evaluable)
        if isinstance(self.evaluable, AfterValue):
            self.evaluable, self.target = self.evaluable.evaluable, AVAV(self.evaluable.target, self.target)
        self.evaluable = self.evaluable.next()
        return self


class AVAV(AVTarget):
    def __init__(self, target: AVTarget, aftertarget: AVTarget):
        self.target = target
        self.aftertarget = aftertarget

    def given(self, value: 'EValue') -> Evaluable:
        return AfterValue(self.target.given(value), self.aftertarget)


class EValue(Evaluable, abc.ABC):
    def next(self) -> 'EValue':
        return self

    def call(self, argument: Evaluable) -> Evaluable:
        raise NotImplementedError