import os
from pathlib import Path
from datetime import datetime, timezone


class LocalFileClient:
    """本地文件系统存储客户端"""

    def __init__(self, base_dir: str):
        self._base_dir = Path(base_dir).resolve()
        self._base_dir.mkdir(parents=True, exist_ok=True)

    def _resolve_path(self, key: str) -> Path:
        """将 key 转换为文件系统路径，确保不会逃出 base_dir"""
        path = (self._base_dir / key).resolve()
        if not path.is_relative_to(self._base_dir):
            raise ValueError(f"Path traversal attempt: {key}")
        return path

    def list_objects(self, prefix: str) -> list[dict]:
        """列出指定前缀下的所有对象（文件和目录）"""
        prefix_path = self._base_dir / prefix if prefix else self._base_dir

        if not prefix_path.exists():
            return []

        result = []
        try:
            for entry in prefix_path.iterdir():
                rel_path = entry.relative_to(self._base_dir)
                key = str(rel_path).replace(os.sep, "/")

                if entry.is_dir():
                    result.append({
                        "key": key + "/",
                        "size": None,
                        "is_dir": True,
                        "modifiedAt": None,
                    })
                else:
                    stat = entry.stat()
                    result.append({
                        "key": key,
                        "size": stat.st_size,
                        "is_dir": False,
                        "modifiedAt": datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc).isoformat(),
                    })
        except (PermissionError, OSError):
            pass

        return result

    def get_object(self, key: str) -> bytes:
        path = self._resolve_path(key)
        if not path.exists() or not path.is_file():
            raise FileNotFoundError(key)
        return path.read_bytes()

    def put_object(self, key: str, data: bytes, content_type: str) -> None:
        path = self._resolve_path(key)
        path.parent.mkdir(parents=True, exist_ok=True)
        path.write_bytes(data)

    def delete_object(self, key: str) -> None:
        path = self._resolve_path(key)
        if not path.exists():
            raise FileNotFoundError(key)
        path.unlink()
        # 清理空目录（逐层向上）
        parent = path.parent
        while parent != self._base_dir:
            if not any(parent.iterdir()):
                parent.rmdir()
                parent = parent.parent
            else:
                break