import copy
import threading
from typing import Any, Union, Dict, Optional

from sqlalchemy.orm import Session

from app.db.base import DbOper
from app.db.models.userconfig import UserConfig
from app.schemas.types import UserConfigKey
from app.foundation.singleton import Singleton


class UserConfigOper(DbOper, metaclass=Singleton):
    """
    用户配置管理
    """
    def __init__(self):
        """初始化空快照，数据库加载由启动组合根显式执行。"""
        super().__init__()
        self.__USERCONF = {}
        self._snapshot_lock = threading.RLock()
        self._write_lock = threading.RLock()
        self._loaded = False

    def load_snapshot(self, db: Optional[Session] = None) -> None:
        """从显式会话或 Oper 事务边界加载用户配置并发布内存快照。"""
        with self._write_lock:
            snapshot: dict[str, dict[str, Any]] = {}
            items = UserConfig.list(db) if db is not None else self._execute_sync_query(
                UserConfig.list
            )
            for item in items:
                if item.username and item.key:
                    snapshot.setdefault(item.username, {})[item.key] = copy.deepcopy(
                        item.value
                    )
            with self._snapshot_lock:
                self.__USERCONF = snapshot
                self._loaded = True

    def _require_loaded(self) -> None:
        """阻止消费者读取尚未完成启动加载的半成品快照。"""
        if not self._loaded:
            raise RuntimeError("用户配置快照尚未加载")

    def set(self, username: str, key: Union[str, UserConfigKey], value: Any):
        """
        设置用户配置
        """
        if isinstance(key, UserConfigKey):
            key = key.value
        self._require_loaded()
        with self._write_lock:

            def write(db):
                """在当前事务中按用户配置的假值规则写入记录。"""
                conf = UserConfig.get_by_key(db=db, username=username, key=key)
                if conf:
                    if value:
                        conf.value = copy.deepcopy(value)
                    else:
                        db.delete(conf)
                else:
                    db.add(
                        UserConfig(
                            username=username,
                            key=key,
                            value=copy.deepcopy(value),
                        )
                    )

            self._execute_sync_write(write)
            # 既有运行时语义会保留刚写入的假值，即使其数据库记录被删除。
            self.__set_config_cache(username=username, key=key, value=value)

    def get(self, username: str, key: Optional[Union[str, UserConfigKey]] = None) -> Any:
        """
        获取用户配置
        """
        with self._snapshot_lock:
            self._require_loaded()
            if not username:
                return copy.deepcopy(self.__USERCONF)
            if isinstance(key, UserConfigKey):
                key = key.value
            if not key:
                return copy.deepcopy(self.__get_config_caches(username=username))
            return copy.deepcopy(self.__get_config_cache(username=username, key=key))

    def __set_config_cache(self, username: str, key: str, value: Any):
        """
        设置配置缓存
        """
        if not username or not key:
            return
        with self._snapshot_lock:
            user_cache = self.__USERCONF.setdefault(username, {})
            user_cache[key] = copy.deepcopy(value)

    def __get_config_caches(self, username: str) -> Optional[Dict[str, Any]]:
        """
        获取配置缓存
        """
        if not username or not self.__USERCONF:
            return None
        return self.__USERCONF.get(username)

    def __get_config_cache(self, username: str, key: str) -> Any:
        """
        获取配置缓存
        """
        if not username or not key or not self.__USERCONF:
            return None
        user_cache = self.__get_config_caches(username)
        if not user_cache:
            return None
        return user_cache.get(key)