Implements the EntryPoint command pattern in Python

entry_point_action_authorizer_pattern.py

from typing import Any, List, Optional, TypeVar, Generic, Protocol, ClassVar, Sequence, Union, Iterable
from polls.models import Question


class BaseAuthorizer:
    """BaseAuthorizer defines how child classes should behavior
    when called by EntryPoints"""

    def __init__(self, entry_point: "BaseEntryPoint") -> None:
        self.entry_point = entry_point

    def check(self) -> None:
        raise NotImplementedError


class ActionBase:
    """ActionBase class defines how action classes behave"""

    def __call__(self):
        raise NotImplementedError


class AuthorizerError(Exception):
    ...


TAuthorizer = TypeVar("TAuthorizer", bound=BaseAuthorizer)
# TAuthorizer = TypeVar("TAuthorizer", covariant=True)


class UserAuthorizer(BaseAuthorizer):
    def check(self):
        """Check if the user/employee/person has permission to perform
        this action"""

        if self.entry_point.user["name"] == "Joffily":
            return None

        raise AuthorizerError("User not authorized")


class PollAction(ActionBase):
    def __init__(self, user: dict) -> None:
        self.user = user

    def __call__(self):
        print(f"PollAction.call, user: {self.user}")


class BaseEntryPoint:
    """Base class that defines how authorizers and actions are called.

    Every unit that use entry point pattern should inherent from here."""

    authorizers: Iterable[BaseAuthorizer] = []
    action: Optional[ActionBase] = None

    def execute(self):
        self.run_authorizers()

        if hasattr(self, "action"):
            self.action()

        if hasattr(self, "form"):
            ...

    def run_authorizers(self):
        for authorizer in self.authorizers:
            print(f"Executing authorizer <{authorizer.__name__}>")
            authorizer(self).check()


def entry_point(cls):
    """Decorates entry points classes"""

    class Base(cls, BaseEntryPoint):
        ...

    return Base


class EntryPoint(BaseEntryPoint):
    authorizers = [UserAuthorizer]

    def __init__(self, name):
        self.name = name
        self.action = PollAction(user=self.user)

    @property
    def user(self):
        return {"name": self.name}