software_patterns.handler

Complexity

Total Complexity

5

Size/Duplication

Total Lines	43
Duplicated Lines	0 %

Importance

Changes

0

4 Methods

Rating	Name	Duplication	Size	Complexity
A	AbstractHandler.handle()	0	6	2
A	Handler.handle()	0	3	1
A	Handler.set_next()	0	3	1
A	AbstractHandler.set_next()	0	6	1

from __future__ import annotations

from abc import ABC, abstractmethod
from typing import Any, Optional


class Handler(ABC):
    """
    The Handler interface declares a method for building the chain of handlers.
    It also declares a method for executing a request.
    """

    @abstractmethod
    def set_next(self, handler: Handler) -> Handler:
        pass

    @abstractmethod
    def handle(self, request) -> Optional[str]:
        pass


class AbstractHandler(Handler):
    """
    The default chaining behavior can be implemented inside a base handler
    class.
    """

    _next_handler: Optional[Handler] = None

    def set_next(self, handler: Handler) -> Handler:
        self._next_handler = handler
        # Returning a handler from here will let us link handlers in a
        # convenient way like this:
        # monkey.set_next(squirrel).set_next(dog)
        return handler

    @abstractmethod
    def handle(self, request: Any) -> Optional[str]:
        if self._next_handler:
            return self._next_handler.handle(request)

        return None