Create chain_of_responsability.py

Author: ma1onso

behavioral _patterns/chain_of_responsability.py

@@ -0,0 +1,80 @@
+from __future__ import annotations
+from abc import ABC, abstractmethod
+from typing import Any, Optional
+
+
+class Handler(ABC):
+    @abstractmethod
+    def set_next(self, handler: Handler) -> Handler:
+        pass
+
+    @abstractmethod
+    def handle(self, request) -> Optional[str]:
+        pass
+
+
+class AbstractHandler(Handler):
+    _next_handler: Handler = None
+
+    def set_next(self, handler: Handler) -> Handler:
+        self._next_handler = handler
+
+        return handler
+    
+    @abstractmethod
+    def handle(self, request) -> str | None:
+        if self._next_handler:
+            return self._next_handler.handle(request)
+
+        return super().handle(request)
+
+
+# Concrete handlers
+class MonkeyHandler(AbstractHandler):
+    def handle(self, request) -> str | None:
+        if request == "Banana":
+            return f"Monkey: I'll eat the {request}"
+        else:
+            return super().handle(request)
+
+
+class SquirrelHandler(AbstractHandler):
+    def handle(self, request) -> str | None:
+        if request == "Nut":
+            return f"Squirrel: I'll eat the {request}"
+        else:
+            return super().handle(request)
+
+
+class DogHandler(AbstractHandler):
+    def handle(self, request) -> str | None:
+        if request == "MeatBall":
+            return f"Dog: I'll eat the {request}"
+        else:
+            return super().handle(request)
+        
+
+def client_code(handler: Handler) -> None:
+    for food in ["Nut", "Banana", "Cup of coffe"]:
+        print(f"\nClient: Who wants a {food}?")
+        result = handler.handle(food)
+
+        if result:
+            print(f"{result}", end="")
+        else:
+            print(f"{food} was left untouched.", end="")
+
+
+if __name__ == "__main__":
+    monkey = MonkeyHandler()
+    squirrel = SquirrelHandler()
+    dog = DogHandler()
+
+    monkey.set_next(squirrel).set_next(dog)
+
+    print("Chain: Monkey > Squirrel > Dog")
+    client_code(monkey)
+    print("\n")
+
+    print("Subchain: Squirrel > Dog")
+    client_code(squirrel)