"""备份执行抽象基类：MySQL / Directory 都实现此接口。"""
from abc import ABC, abstractmethod
from dataclasses import dataclass
from typing import AsyncIterator, Optional


@dataclass
class BackupMetadata:
    """备份产物的元信息。"""

    suggested_filename: str  # e.g. "db-20260622-030000.sql.gz" 或 "logs-20260622.tar.gz"
    content_type: str = "application/octet-stream"
    extra: Optional[dict] = None


class BaseBackup(ABC):
    """所有数据源类型实现此接口。

    方法职责：
      - metadata(): 计算建议文件名等
      - produce(): 以异步字节流形式产出备份内容
    """

    def __init__(self, source_config: dict, job_name: str):
        self.source_config = source_config
        self.job_name = job_name

    @abstractmethod
    def metadata(self) -> BackupMetadata: ...

    @abstractmethod
    async def produce(self) -> AsyncIterator[bytes]:
        """异步产出备份字节流。"""
        # 子类应使用 async with + async generator
        ...
        yield b""  # pragma: no cover