# Copyright (c) OpenMMLab. All rights reserved.
import os
import random
import sys
import time
import warnings
from getpass import getuser
from socket import gethostname
from types import ModuleType
from typing import Optional

import numpy as np
import torch

import mmcv


def get_host_info():
    """Get hostname and username.

    Return empty string if exception raised, e.g. ``getpass.getuser()`` will
    lead to error in docker container
    """
    host = ''
    try:
        host = f'{getuser()}@{gethostname()}'
    except Exception as e:
        warnings.warn(f'Host or user not found: {str(e)}')
    finally:
        return host


def get_time_str():
    return time.strftime('%Y%m%d_%H%M%S', time.localtime())


def obj_from_dict(info: dict,
                  parent: Optional[ModuleType] = None,
                  default_args: Optional[dict] = None):
    """Initialize an object from dict.

    The dict must contain the key "type", which indicates the object type, it
    can be either a string or type, such as "list" or ``list``. Remaining
    fields are treated as the arguments for constructing the object.

    Args:
        info (dict): Object types and arguments.
        parent (:class:`module`): Module which may containing expected object
            classes.
        default_args (dict, optional): Default arguments for initializing the
            object.

    Returns:
        any type: Object built from the dict.
    """
    assert isinstance(info, dict) and 'type' in info
    assert isinstance(default_args, dict) or default_args is None
    args = info.copy()
    obj_type = args.pop('type')
    if mmcv.is_str(obj_type):
        if parent is not None:
            obj_type = getattr(parent, obj_type)
        else:
            obj_type = sys.modules[obj_type]
    elif not isinstance(obj_type, type):
        raise TypeError('type must be a str or valid type, but '
                        f'got {type(obj_type)}')
    if default_args is not None:
        for name, value in default_args.items():
            args.setdefault(name, value)
    return obj_type(**args)


def set_random_seed(seed: int,
                    deterministic: bool = False,
                    use_rank_shift: bool = False) -> None:
    """Set random seed.

    Args:
        seed (int): Seed to be used.
        deterministic (bool): Whether to set the deterministic option for
            CUDNN backend, i.e., set `torch.backends.cudnn.deterministic`
            to True and `torch.backends.cudnn.benchmark` to False.
            Default: False.
        rank_shift (bool): Whether to add rank number to the random seed to
            have different random seed in different threads. Default: False.
    """
    if use_rank_shift:
        rank, _ = mmcv.runner.get_dist_info()
        seed += rank
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)
    torch.cuda.manual_seed(seed)
    torch.cuda.manual_seed_all(seed)
    os.environ['PYTHONHASHSEED'] = str(seed)
    if deterministic:
        torch.backends.cudnn.deterministic = True
        torch.backends.cudnn.benchmark = False
