import os


_DEFAULT_ENDPOINT = "https://os.zhdk.cloud.switch.ch"


def make_fs(storage: str):
    """Return an S3FileSystem for storage='s3', or None for local."""
    if storage != "s3":
        return None
    import s3fs

    return s3fs.S3FileSystem(
        key=os.environ["S3_ACCESS_KEY"],
        secret=os.environ["S3_SECRET_ACCESS_KEY"],
        client_kwargs={
            "endpoint_url": os.environ.get("S3_ENDPOINT_URL", _DEFAULT_ENDPOINT)
        },
    )


def fsjoin(base, *parts: str) -> str:
    """Join path segments with forward slashes (works for both local and S3)."""
    return "/".join([str(base).rstrip("/"), *[str(p).strip("/") for p in parts if p]])


def fsstem(path) -> str:
    """Filename stem (no extension) for local Path or S3 string."""
    name = str(path).replace("\\", "/").split("/")[-1]
    return name.rsplit(".", 1)[0] if "." in name else name


def fsname(path) -> str:
    """Filename component (with extension) for local Path or S3 string."""
    return str(path).replace("\\", "/").split("/")[-1]