"""
Token generation and validation utilities
"""

import secrets
import string
from datetime import datetime, timedelta
from typing import Optional


class TokenGenerator:
    """
    Secure token generator for authentication flows
    
    Generates various types of tokens:
    - Request tokens (for auth flow)
    - Session tokens
    - One-time tokens
    - Recovery codes
    """
    
    ALPHANUMERIC = string.ascii_letters + string.digits
    URLSAFE = string.ascii_letters + string.digits + "-_"
    
    @classmethod
    def generate_request_token(cls, length: int = 32) -> str:
        """Generate secure request token"""
        return f"req_{secrets.token_urlsafe(length)}"
    
    @classmethod
    def generate_session_token(cls, length: int = 32) -> str:
        """Generate secure session token"""
        return f"sess_{secrets.token_urlsafe(length)}"
    
    @classmethod
    def generate_refresh_token(cls, length: int = 48) -> str:
        """Generate secure refresh token"""
        return f"rt_{secrets.token_urlsafe(length)}"
    
    @classmethod
    def generate_nonce(cls, length: int = 32) -> str:
        """Generate cryptographic nonce"""
        return secrets.token_urlsafe(length)
    
    @classmethod
    def generate_pin(cls, length: int = 6) -> str:
        """Generate numeric PIN code"""
        return ''.join(secrets.choice(string.digits) for _ in range(length))
    
    @classmethod
    def generate_recovery_code(cls, segments: int = 4, segment_length: int = 4) -> str:
        """Generate human-readable recovery code"""
        segments_list = [
            ''.join(secrets.choice(cls.ALPHANUMERIC) for _ in range(segment_length))
            for _ in range(segments)
        ]
        return '-'.join(segments_list).upper()
    
    @classmethod
    def generate_api_key(cls, prefix: str = "qk", length: int = 32) -> str:
        """Generate API key with prefix"""
        return f"{prefix}_{secrets.token_urlsafe(length)}"
    
    @classmethod
    def generate_device_id(cls) -> str:
        """Generate unique device identifier"""
        return f"dev_{secrets.token_urlsafe(16)}"
    
    @classmethod
    def generate_qr_payload(
        cls,
        request_token: str,
        nonce: str,
        expires_at: datetime,
        base_url: str = "quixzoom://auth"
    ) -> str:
        """
        Generate QR code payload
        
        Format: quixzoom://auth?token=<token>&nonce=<nonce>&exp=<timestamp>
        """
        exp_timestamp = int(expires_at.timestamp())
        return f"{base_url}?token={request_token}&nonce={nonce}&exp={exp_timestamp}"
    
    @classmethod
    def parse_qr_payload(cls, payload: str) -> Optional[dict]:
        """
        Parse QR code payload
        
        Returns:
            dict with token, nonce, exp or None if invalid
        """
        try:
            # Remove scheme
            if '://' in payload:
                payload = payload.split('://', 1)[1]
            
            # Parse query parameters
            if '?' not in payload:
                return None
            
            query_string = payload.split('?', 1)[1]
            params = {}
            
            for param in query_string.split('&'):
                if '=' in param:
                    key, value = param.split('=', 1)
                    params[key] = value
            
            return {
                "token": params.get("token"),
                "nonce": params.get("nonce"),
                "exp": int(params.get("exp", 0)) if params.get("exp") else None
            }
        except Exception:
            return None
    
    @classmethod
    def is_token_format_valid(cls, token: str, prefix: Optional[str] = None) -> bool:
        """Check if token has valid format"""
        if not token or len(token) < 10:
            return False
        
        if prefix and not token.startswith(prefix):
            return False
        
        # Check for valid characters
        valid_chars = set(cls.URLSAFE + '_')
        return all(c in valid_chars for c in token.replace(prefix + '_', '') if prefix else token)


# Global token generator
token_generator = TokenGenerator()