# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
# All rights reserved.
#
# SPDX-License-Identifier: BSD-3-Clause

"""Sub-module that defines the host-server where assets and resources are stored.

By default, we use the Isaac Sim Nucleus Server for hosting assets and resources. This makes
distribution of the assets easier and makes the repository smaller in size code-wise.

For more information, please check information on `Omniverse Nucleus`_.

.. _Omniverse Nucleus: https://docs.omniverse.nvidia.com/nucleus/latest/overview/overview.html
"""

import asyncio
import io
import logging
import os
import tempfile
import time
from typing import Literal

import carb
import omni.client

# import logger
logger = logging.getLogger(__name__)

NUCLEUS_ASSET_ROOT_DIR = carb.settings.get_settings().get("/persistent/isaac/asset_root/cloud")
"""Path to the root directory on the Nucleus Server."""

NVIDIA_NUCLEUS_DIR = f"{NUCLEUS_ASSET_ROOT_DIR}/NVIDIA"
"""Path to the root directory on the NVIDIA Nucleus Server."""

ISAAC_NUCLEUS_DIR = f"{NUCLEUS_ASSET_ROOT_DIR}/Isaac"
"""Path to the ``Isaac`` directory on the NVIDIA Nucleus Server."""

ISAACLAB_NUCLEUS_DIR = f"{ISAAC_NUCLEUS_DIR}/IsaacLab"
"""Path to the ``Isaac/IsaacLab`` directory on the NVIDIA Nucleus Server."""


def check_file_path(path: str) -> Literal[0, 1, 2]:
    """Checks if a file exists on the Nucleus Server or locally.

    Args:
        path: The path to the file.

    Returns:
        The status of the file. Possible values are listed below.

        * :obj:`0` if the file does not exist
        * :obj:`1` if the file exists locally
        * :obj:`2` if the file exists on the Nucleus Server
    """
    if os.path.isfile(path):
        return 1
    # we need to convert backslash to forward slash on Windows for omni.client API
    elif omni.client.stat(path.replace(os.sep, "/"))[0] == omni.client.Result.OK:
        return 2
    else:
        return 0


def retrieve_file_path(path: str, download_dir: str | None = None, force_download: bool = True) -> str:
    """Retrieves the path to a file on the Nucleus Server or locally.

    If the file exists locally, then the absolute path to the file is returned.
    If the file exists on the Nucleus Server, then the file is downloaded to the local machine
    and the absolute path to the file is returned.

    Args:
        path: The path to the file.
        download_dir: The directory where the file should be downloaded. Defaults to None, in which
            case the file is downloaded to the system's temporary directory.
        force_download: Whether to force download the file from the Nucleus Server. This will overwrite
            the local file if it exists. Defaults to True.

    Returns:
        The path to the file on the local machine.

    Raises:
        FileNotFoundError: When the file not found locally or on Nucleus Server.
        RuntimeError: When the file cannot be copied from the Nucleus Server to the local machine. This
            can happen when the file already exists locally and :attr:`force_download` is set to False.
    """
    # check file status
    file_status = check_file_path(path)
    if file_status == 1:
        return os.path.abspath(path)
    elif file_status == 2:
        # resolve download directory
        if download_dir is None:
            download_dir = tempfile.gettempdir()
        else:
            download_dir = os.path.abspath(download_dir)
        # create download directory if it does not exist
        if not os.path.exists(download_dir):
            os.makedirs(download_dir)
        # download file in temp directory using os
        file_name = os.path.basename(omni.client.break_url(path.replace(os.sep, "/")).path)
        target_path = os.path.join(download_dir, file_name)
        # check if file already exists locally
        if not os.path.isfile(target_path) or force_download:
            # copy file to local machine
            result = omni.client.copy(path.replace(os.sep, "/"), target_path, omni.client.CopyBehavior.OVERWRITE)
            if result != omni.client.Result.OK and force_download:
                raise RuntimeError(f"Unable to copy file: '{path}'. Is the Nucleus Server running?")
        return os.path.abspath(target_path)
    else:
        raise FileNotFoundError(f"Unable to find the file: {path}")


def read_file(path: str) -> io.BytesIO:
    """Reads a file from the Nucleus Server or locally.

    Args:
        path: The path to the file.

    Raises:
        FileNotFoundError: When the file not found locally or on Nucleus Server.

    Returns:
        The content of the file.
    """
    # check file status
    file_status = check_file_path(path)
    if file_status == 1:
        with open(path, "rb") as f:
            return io.BytesIO(f.read())
    elif file_status == 2:
        file_content = omni.client.read_file(path.replace(os.sep, "/"))[2]
        return io.BytesIO(memoryview(file_content).tobytes())
    else:
        raise FileNotFoundError(f"Unable to find the file: {path}")


"""
Nucleus Connection.
"""


def check_usd_path_with_timeout(usd_path: str, timeout: float = 300, log_interval: float = 30) -> bool:
    """Checks whether the given USD file path is available on the NVIDIA Nucleus server.

    This function synchronously runs an asynchronous USD path availability check,
    logging progress periodically until it completes. The file is available on the server
    if the HTTP status code is 200. Otherwise, the file is not available on the server.

    This is useful for checking server responsiveness before attempting to load a remote
    asset. It will block execution until the check completes or times out.

    Args:
        usd_path: The remote USD file path to check.
        timeout: Maximum time (in seconds) to wait for the server check.
        log_interval: Interval (in seconds) at which progress is logged.

    Returns:
        Whether the given USD path is available on the server.
    """
    start_time = time.time()
    loop = asyncio.get_event_loop()

    coroutine = _is_usd_path_available(usd_path, timeout)
    task = asyncio.ensure_future(coroutine)

    next_log_time = start_time + log_interval

    first_log = True
    while not task.done():
        now = time.time()
        if now >= next_log_time:
            elapsed = int(now - start_time)
            if first_log:
                logger.warning(f"Checking server availability for USD path: {usd_path} (timeout: {timeout}s)")
                first_log = False
            logger.warning(f"Waiting for server response... ({elapsed}s elapsed)")
            next_log_time += log_interval
        loop.run_until_complete(asyncio.sleep(0.1))  # Yield to allow async work

    return task.result()


"""
Helper functions.
"""


async def _is_usd_path_available(usd_path: str, timeout: float) -> bool:
    """Checks whether the given USD path is available on the Omniverse Nucleus server.

    This function is a asynchronous routine to check the availability of the given USD path on
    the Omniverse Nucleus server. It will return True if the USD path is available on the server,
    False otherwise.

    Args:
        usd_path: The remote or local USD file path to check.
        timeout: Timeout in seconds for the async stat call.

    Returns:
        Whether the given USD path is available on the server.
    """
    try:
        result, _ = await asyncio.wait_for(omni.client.stat_async(usd_path), timeout=timeout)
        return result == omni.client.Result.OK
    except asyncio.TimeoutError:
        logger.warning(f"Timed out after {timeout}s while checking for USD: {usd_path}")
        return False
    except Exception as ex:
        logger.warning(f"Exception during USD file check: {type(ex).__name__}: {ex}")
        return False
