from cryptography.fernet import Fernet
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC as PBKDF2
import base64
import os
from app.config import settings

class EncryptionManager:
    """Encrypt sensitive data at rest"""
    
    def __init__(self):
        self._cipher = None
        self._key = None
    
    def _get_key(self) -> bytes:
        """Derive encryption key from JWT secret"""
        if self._key is not None:
            return self._key
        
        # Use JWT secret as password
        password = settings.jwt_secret.encode()
        
        salt = os.urandom(16)
        
        # Derive key using PBKDF2
        kdf = PBKDF2(
            algorithm=hashes.SHA256(),
            length=32,
            salt=salt,
            iterations=600000,
        )
        
        key = base64.urlsafe_b64encode(kdf.derive(password))
        self._key = key
        return key
    
    def _get_cipher(self) -> Fernet:
        """Get Fernet cipher instance"""
        if not self._cipher:
            self._cipher = Fernet(self._get_key())
        return self._cipher
    
    def encrypt(self, data: str) -> str:
        """Encrypt string data"""
        if not data:
            return data
        
        cipher = self._get_cipher()
        encrypted = cipher.encrypt(data.encode())
        return base64.urlsafe_b64encode(encrypted).decode()
    
    def decrypt(self, encrypted_data: str) -> str:
        """Decrypt string data"""
        if not encrypted_data:
            return encrypted_data
        
        try:
            cipher = self._get_cipher()
            decoded = base64.urlsafe_b64decode(encrypted_data.encode())
            decrypted = cipher.decrypt(decoded)
            return decrypted.decode()
        except Exception as e:
            raise ValueError(f"Decryption failed: {e}")
    
    def encrypt_dict(self, data: dict, fields: list) -> dict:
        """Encrypt specific fields in a dictionary"""
        encrypted = data.copy()
        for field in fields:
            if field in encrypted and encrypted[field]:
                encrypted[field] = self.encrypt(str(encrypted[field]))
        return encrypted
    
    def decrypt_dict(self, data: dict, fields: list) -> dict:
        """Decrypt specific fields in a dictionary"""
        decrypted = data.copy()
        for field in fields:
            if field in decrypted and decrypted[field]:
                try:
                    decrypted[field] = self.decrypt(decrypted[field])
                except:
                    pass  # Field might not be encrypted
        return decrypted
    
    def hash_sensitive_data(self, data: str) -> str:
        """One-way hash for sensitive data (like API keys for comparison)"""
        import hashlib
        return hashlib.sha256(data.encode()).hexdigest()

encryption_manager = EncryptionManager()


class SecureStorage:
    """Secure storage for sensitive configuration"""
    
    def __init__(self):
        self.encryption = encryption_manager
    
    def store_hf_credentials(self, user_id: str, token: str, repo: str) -> dict:
        """Store HuggingFace credentials securely"""
        return {
            'user_id': user_id,
            'hf_token': self.encryption.encrypt(token) if token else None,
            'hf_repo': repo  # Repo name is not sensitive
        }
    
    def retrieve_hf_credentials(self, stored_data: dict) -> dict:
        """Retrieve and decrypt HuggingFace credentials"""
        return {
            'user_id': stored_data.get('user_id'),
            'hf_token': self.encryption.decrypt(stored_data['hf_token']) if stored_data.get('hf_token') else None,
            'hf_repo': stored_data.get('hf_repo')
        }
    
    def mask_sensitive_data(self, data: str, visible_chars: int = 4) -> str:
        """Mask sensitive data for display (e.g., API keys)"""
        if not data or len(data) <= visible_chars:
            return '*' * len(data) if data else ''
        
        return data[:visible_chars] + '*' * (len(data) - visible_chars)

secure_storage = SecureStorage()