import os

from distutils.version import LooseVersion
import pkg_resources
from mlagents.torch_utils import cpu_utils
from mlagents.trainers.settings import TorchSettings
from mlagents_envs.logging_util import get_logger


logger = get_logger(__name__)


def assert_torch_installed():
    # Check that torch version 1.6.0 or later has been installed. If not, refer
    # user to the PyTorch webpage for install instructions.
    torch_pkg = None
    try:
        torch_pkg = pkg_resources.get_distribution("torch")
    except pkg_resources.DistributionNotFound:
        pass
    assert torch_pkg is not None and LooseVersion(torch_pkg.version) >= LooseVersion(
        "1.6.0"
    ), (
        "A compatible version of PyTorch was not installed. Please visit the PyTorch homepage "
        + "(https://pytorch.org/get-started/locally/) and follow the instructions to install. "
        + "Version 1.6.0 and later are supported."
    )


assert_torch_installed()

# This should be the only place that we import torch directly.
# Everywhere else is caught by the banned-modules setting for flake8
import torch  # noqa I201


torch.set_num_threads(cpu_utils.get_num_threads_to_use())
os.environ["KMP_BLOCKTIME"] = "0"


_device = torch.device("cpu")


def set_torch_config(torch_settings: TorchSettings) -> None:
    global _device

    if torch_settings.device is None:
        device_str = "cuda" if torch.cuda.is_available() else "cpu"
    else:
        device_str = torch_settings.device

    _device = torch.device(device_str)

    if _device.type == "cuda":
        torch.set_default_tensor_type(torch.cuda.FloatTensor)
    else:
        torch.set_default_tensor_type(torch.FloatTensor)
    logger.debug(f"default Torch device: {_device}")


# Initialize to default settings
set_torch_config(TorchSettings(device=None))

nn = torch.nn


def default_device():
    return _device