from typing import Optional
from smolagents import tool

@tool
def download_file_from_url(url: str, filename: Optional[str] = None) -> str:
    """
    Downloads a file from the given URL to a temporary local location.

    The file is saved in the system's temporary directory. The filename is either passed as argument or
    inferred from the URL's path; if it cannot be determined, a generic name is used.

    Args:
        url: The URL of the file to download (str).
        filename: Optional filename, will generate one based on URL if not provided

    Returns:
        The full local file path (str) of the downloaded file if successful,
        or an error message string detailing the failure.
    """

    import requests, tempfile, os
    from urllib.parse import urlparse

    try:
        if not filename:
            filename = os.path.basename(urlparse(url).path) or "downloaded_file"
        filepath = os.path.join(tempfile.gettempdir(), filename)

        response = requests.get(url, stream=True)
        response.raise_for_status()

        with open(filepath, "wb") as f:
            for chunk in response.iter_content(chunk_size=8192):
                f.write(chunk)

        return filepath
    except Exception as e:
        return f"Download error: {e}"