# Copyright The PyTorch Lightning team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""General utilities"""
import importlib
import platform
from distutils.version import LooseVersion
from enum import Enum
from typing import Union

import numpy
import torch

from pytorch_lightning.utilities.apply_func import move_data_to_device
from pytorch_lightning.utilities.distributed import AllGatherGrad, rank_zero_info, rank_zero_only, rank_zero_warn
from pytorch_lightning.utilities.parsing import AttributeDict, flatten_dict, is_picklable
from pytorch_lightning.utilities.xla_device_utils import XLA_AVAILABLE, XLADeviceUtils


def _module_available(module_path: str) -> bool:
    """Testing if given module is avalaible in your env

    >>> _module_available('os')
    True
    >>> _module_available('bla.bla')
    False
    """
    # todo: find a better way than try / except
    try:
        mods = module_path.split('.')
        assert mods, 'nothing given to test'
        # it has to be tested as per partets
        for i in range(len(mods)):
            module_path = '.'.join(mods[:i + 1])
            if importlib.util.find_spec(module_path) is None:
                return False
        return True
    except AttributeError:
        return False


APEX_AVAILABLE = _module_available("apex.amp")
NATIVE_AMP_AVAILABLE = _module_available("torch.cuda.amp") and hasattr(torch.cuda.amp, "autocast")
OMEGACONF_AVAILABLE = _module_available("omegaconf")
HYDRA_AVAILABLE = _module_available("hydra")
HOROVOD_AVAILABLE = _module_available("horovod.torch")
BOLTS_AVAILABLE = _module_available("pl_bolts")

TPU_AVAILABLE = XLADeviceUtils.tpu_device_exists()
FAIRSCALE_AVAILABLE = platform.system() != 'Windows' and _module_available('fairscale.nn.data_parallel')
RPC_AVAILABLE = platform.system() != 'Windows' and _module_available('torch.distributed.rpc')
GROUP_AVAILABLE = platform.system() != 'Windows' and _module_available('torch.distributed.group')
FAIRSCALE_PIPE_AVAILABLE = FAIRSCALE_AVAILABLE and LooseVersion(torch.__version__) == LooseVersion("1.6.0")
BOLTS_AVAILABLE = _module_available('pl_bolts')

FLOAT16_EPSILON = numpy.finfo(numpy.float16).eps
FLOAT32_EPSILON = numpy.finfo(numpy.float32).eps
FLOAT64_EPSILON = numpy.finfo(numpy.float64).eps


class LightningEnum(str, Enum):
    """ Type of any enumerator with allowed comparison to string invariant to cases. """

    @classmethod
    def from_str(cls, value: str) -> 'LightningEnum':
        statuses = [status for status in dir(cls) if not status.startswith('_')]
        for st in statuses:
            if st.lower() == value.lower():
                return getattr(cls, st)
        return None

    def __eq__(self, other: Union[str, Enum]) -> bool:
        other = other.value if isinstance(other, Enum) else str(other)
        return self.value.lower() == other.lower()


class AMPType(LightningEnum):
    """Type of Automatic Mixed Precission used for training.

    >>> # you can math the type with string
    >>> AMPType.APEX == 'apex'
    True
    """
    APEX = 'apex'
    NATIVE = 'native'


class DistributedType(LightningEnum):
    """ Define type of ditributed computing.

    >>> # you can math the type with string
    >>> DistributedType.DDP == 'ddp'
    True
    >>> # which is case invariant
    >>> DistributedType.DDP2 == 'DDP2'
    True
    """
    DP = 'dp'
    DDP = 'ddp'
    DDP2 = 'ddp2'
    DDP_SPAWN = 'ddp_spawn'
    HOROVOD = 'horovod'


class DeviceType(LightningEnum):
    """ Define Device type byt its nature - acceleatrors.

    >>> DeviceType.CPU == DeviceType.from_str('cpu')
    True
    >>> # you can math the type with string
    >>> DeviceType.GPU == 'GPU'
    True
    >>> # which is case invariant
    >>> DeviceType.TPU == 'tpu'
    True
    """
    CPU = 'CPU'
    GPU = 'GPU'
    TPU = 'TPU'