from abc import ABC, abstractmethod
import xml.etree.ElementTree as ET
from typing import Callable, List

class Entry(ABC):
    """
    Abstract base class for all entry types in the working memory.
    Provides observable pattern functionality.
    """
    
    def __init__(self, id: str):
        """
        Initialize a new entry with provided id and timestamp.
        
        Args:
            id: Unique identifier for this entry
        """
        self._id = id
        self._change_handlers: List[Callable[['Entry'], None]] = []

    @property
    def id(self) -> str:
        """Get entry's unique identifier."""
        return self._id

    def add_change_handler(self, handler: Callable[['Entry'], None]) -> None:
        """Add a callback for entry changes."""
        if handler not in self._change_handlers:
            self._change_handlers.append(handler)

    def notify_change(self) -> None:
        """Notify all handlers of entry state change."""
        for handler in self._change_handlers:
            handler(self)

    @abstractmethod
    def update(self) -> None:
        """
        Update the entry's state.
        Must be implemented by concrete classes.
        """
        pass
    
    @abstractmethod
    def generate_context(self) -> ET.Element:
        """
        Generate an XML Element representing this entry's context.
        Must be implemented by concrete classes.
        
        Returns:
            ET.Element: XML element containing the entry's data
        """
        pass

    def serialize(self) -> dict[str, str]:
        """
        Collect all public attributes of the entry into a dictionary.
        """
        pass

    def cleanup(self) -> None:
        """
        Clean up any resources used by this entry.
        Should be overridden by classes that need cleanup.
        Default implementation does nothing.
        """
        pass

    def reset(self) -> None:
        """
        Reset the entry as if update was never called.
        Default implementation does nothing.
        """
        pass