import hashlib
import time
import random
import string
from typing import Dict, Any, Optional

class MFAService:
    """Multi-factor authentication service for identity verification"""
    
    def __init__(self, api_key: Optional[str] = None):
        """Initialize MFA service
        
        Args:
            api_key: Optional API key for an external MFA service
        """
        self.api_key = api_key
        # For demo purposes, we'll use a mock implementation
        self.connected = api_key is not None
        # Store active challenges (would be in a database in production)
        self.active_challenges = {}
    
    def generate_challenge(self, user_id: str) -> Dict[str, Any]:
        """Generate an MFA challenge for a user
        
        Args:
            user_id: User identifier
            
        Returns:
            Dictionary with challenge details
        """
        # Generate a random challenge code
        challenge_code = ''.join(random.choices(string.digits, k=6))
        
        # Create timestamp
        timestamp = time.time()
        
        # Store challenge (in production, this would be in a database)
        self.active_challenges[user_id] = {
            "code": challenge_code,
            "timestamp": timestamp,
            "verified": False
        }
        
        # In a real implementation, this would send an SMS, email, or push notification
        # to the user with the challenge code
        
        return {
            "challenge_id": hashlib.sha256(f"{user_id}-{timestamp}".encode()).hexdigest()[:12],
            "expires_at": timestamp + 300  # 5 minutes
        }
    
    def verify_challenge(self, user_id: str, response: str) -> bool:
        """Verify a user's response to an MFA challenge
        
        Args:
            user_id: User identifier
            response: User's response to the challenge
            
        Returns:
            True if verification successful
        """
        # Check if user has an active challenge
        if user_id not in self.active_challenges:
            return False
        
        challenge = self.active_challenges[user_id]
        
        # Check if challenge has expired (5 minutes)
        if time.time() - challenge["timestamp"] > 300:
            del self.active_challenges[user_id]
            return False
        
        # Verify the response
        if response == challenge["code"]:
            challenge["verified"] = True
            return True
        
        return False