from __future__ import annotations

import os
from typing import BinaryIO, Dict, Optional

from .interface import StorageInterface


class LocalStorage(StorageInterface):
    """本地文件存储适配器"""
    
    storage_type = "local"

    def __init__(self, config: dict):
        self.base_path = config.get("base_path")
        if not self.base_path:
            raise ValueError("LocalStorage 需要 base_path 配置")
        os.makedirs(self.base_path, exist_ok=True)

    def _abs_path(self, key: str) -> str:
        """获取文件绝对路径"""
        return os.path.join(self.base_path, key)

    def upload(self, file_stream: BinaryIO, key: str, mime_type: Optional[str] = None) -> Dict:
        """上传文件到本地"""
        # 本地文件存储需要移除前缀
        key = key.lstrip(self.storage_type + ":")
        abs_path = self._abs_path(key)
        os.makedirs(os.path.dirname(abs_path), exist_ok=True)
        
        with open(abs_path, "wb") as f:
            f.write(file_stream.read())
        
        file_size = os.path.getsize(abs_path)
        return {
            "path": abs_path,
            "size": file_size,
        }

    def append_chunk(self, key: str, chunk_stream: BinaryIO, offset: int) -> None:
        """追加写入数据块"""
        abs_path = self._abs_path(key)
        os.makedirs(os.path.dirname(abs_path), exist_ok=True)
        
        mode = "r+b" if os.path.exists(abs_path) else "wb"
        with open(abs_path, mode) as f:
            f.seek(offset)
            f.write(chunk_stream.read())

    def download(self, key: str) -> BinaryIO:
        """下载文件"""
        abs_path = self._abs_path(key)
        if not os.path.exists(abs_path):
            raise FileNotFoundError(f"文件不存在: {key}")
        return open(abs_path, "rb")

    def delete(self, key: str) -> None:
        """删除文件"""
        abs_path = self._abs_path(key)
        if os.path.exists(abs_path):
            os.remove(abs_path)

    def exists(self, key: str) -> bool:
        """检查文件是否存在"""
        abs_path = self._abs_path(key)
        return os.path.exists(abs_path)

    def get_url(self, key: str, expires: int = 3600) -> str:
        """获取文件访问URL（本地存储返回下载路由）"""
        # 本地存储通过后端路由提供下载，无需签名
        return key