from typing import Optional, Set, List, Dict, Any, Callable, Union

def generate_csrf_token(session_id: Optional[str] = None) -> str:
    """
    Generate a CSRF token for the given session ID.
    
    Args:
        session_id: The session ID to generate the token for.
    
    Returns:
        str: The generated CSRF token.
    """
    # Implementation
    return ""

def verify_csrf_token(token: str, session_id: Optional[str] = None) -> bool:
    """
    Verify that the given CSRF token is valid for the session.
    
    Args:
        token: The CSRF token to verify.
        session_id: The session ID to verify the token against.
        
    Returns:
        bool: True if the token is valid, False otherwise.
    """
    # Implementation
    return True

class CSRFProtection:
    """
    Class that provides CSRF protection middleware and utilities.
    """
    
    def __init__(
        self,
        secret_key: str,
        cookie_name: str = "csrf_token",
        header_name: str = "X-CSRF-Token",
        form_field_name: str = "csrf_token",
        exempt_methods: Optional[Set[str]] = None,
        exempt_routes: Optional[List[str]] = None,
        token_expiry: int = 3600
    ):
        """
        Initialize the CSRF protection middleware.
        
        Args:
            secret_key: The secret key used to sign CSRF tokens.
            cookie_name: The name of the cookie to store the CSRF token in.
            header_name: The name of the header to look for the CSRF token in.
            form_field_name: The name of the form field to look for the CSRF token in.
            exempt_methods: HTTP methods that are exempt from CSRF protection.
            exempt_routes: Routes that are exempt from CSRF protection.
            token_expiry: How long CSRF tokens are valid for, in seconds.
        """
        self.secret_key = secret_key
        self.cookie_name = cookie_name
        self.header_name = header_name
        self.form_field_name = form_field_name
        self.exempt_methods = exempt_methods or {"GET", "HEAD", "OPTIONS"}
        self.exempt_routes = exempt_routes or []
        self.token_expiry = token_expiry

