# Copyright (c) Huawei Technologies Co., Ltd. 2026-2026. All rights reserved.
# OpenOLC is licensed under Mulan PSL v2.
# You can use this software according to the terms and conditions of the Mulan PSL v2.
# You may obtain a copy of Mulan PSL v2 at:
#         `http://license.coscl.org.cn/MulanPSL2`
# THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
# EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
# MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
# See the Mulan PSL v2 for more details.

import os
import threading
from typing import Optional

from olc.encryptor.encryptor import Encryptor


class OlcEncryptorRegistry:
    """
    加密器注册表（单例模式）

    提供全局加密器管理机制，只存储一个解密器实例。
    允许在应用启动时通过编程方式注入自定义加密器。
    """

    _encryptor: Optional[Encryptor] = None
    _lock = threading.RLock()

    @classmethod
    def set(cls, encryptor: Encryptor) -> None:
        """
        设置加密器实例

        Args:
            encryptor: 加密器实例，必须实现 Encryptor 接口

        Raises:
            TypeError: 如果 encryptor 没有实现 Encryptor 接口

        Example:
            >>> encryptor = AesEncryptor("password")
            >>> OlcEncryptorRegistry.set(encryptor)
        """
        if not isinstance(encryptor, Encryptor):
            raise TypeError("Encryptor must implement the Encryptor interface")

        with cls._lock:
            cls._encryptor = encryptor

    @classmethod
    def get(cls) -> Optional[Encryptor]:
        """
        获取加密器实例

        Returns:
            Encryptor: 加密器实例，如果未设置返回 None

        Example:
            >>> encryptor = OlcEncryptorRegistry.get()
            >>> if encryptor:
            ...     encrypted = encryptor.encrypt("data")
        """
        with cls._lock:
            return cls._encryptor

    @classmethod
    def clear(cls) -> None:
        """
        清除加密器实例（主要用于测试）

        Example:
            >>> OlcEncryptorRegistry.clear()
        """
        with cls._lock:
            cls._encryptor = None

    @classmethod
    def is_set(cls) -> bool:
        """
        检查加密器是否已设置

        Returns:
            bool: 如果已设置返回 True，否则返回 False

        Example:
            >>> if OlcEncryptorRegistry.is_set():
            ...     print("加密器已设置")
        """
        with cls._lock:
            return cls._encryptor is not None

    @classmethod
    def create_aes(cls, password: str) -> Encryptor:
        """
        创建 AES 加密器并设置为全局加密器

        Args:
            password: 加密密码

        Returns:
            AesEncryptor: 创建的 AES 加密器实例

        Example:
            >>> encryptor = OlcEncryptorRegistry.create_aes("my_password")
        """
        from olc.encryptor.aes_encryptor import AesEncryptor
        encryptor = AesEncryptor(password)
        cls.set(encryptor)
        return encryptor

    @classmethod
    def create_aes_from_env(cls, env_var: str, default_password: str = None) -> Encryptor:
        """
        从环境变量创建 AES 加密器并设置为全局加密器

        从指定的环境变量读取密码，如果环境变量不存在则使用默认密码。
        如果都没有设置，会抛出 ValueError。

        Args:
            env_var: 环境变量名
            default_password: 默认密码（环境变量不存在时使用）

        Returns:
            AesEncryptor: 创建的 AES 加密器实例

        Raises:
            ValueError: 环境变量未设置且没有提供默认密码

        Example:
            >>> # 从环境变量读取密码
            >>> encryptor = OlcEncryptorRegistry.create_aes_from_env("OLC_ENCRYPTOR_PASSWORD")
            >>>
            >>> # 带默认值的环境变量
            >>> encryptor = OlcEncryptorRegistry.create_aes_from_env(
            ...     "OLC_ENCRYPTOR_PASSWORD",
            ...     default_password="fallback_password"
            ... )
        """
        password = os.environ.get(env_var, default_password)
        if not password:
            raise ValueError(
                f"Environment variable '{env_var}' is not set and no default password provided. "
                f"Please set the environment variable or provide a default password."
            )

        from olc.encryptor.aes_encryptor import AesEncryptor
        encryptor = AesEncryptor(password)
        cls.set(encryptor)
        return encryptor