from collections import OrderedDict
from importlib import import_module
import os
import random
import re
import warnings
from typing import Union, Any

import numpy as np
import torch
from torch import distributed as dist
import torch.nn as nn
from torch.nn.parallel import DataParallel, DistributedDataParallel

from .dist_util import get_dist_info

MODULE_WRAPPERS = [DataParallel, DistributedDataParallel]


MODEL_ABBR_MAP = {
    's': 'small',
    'b': 'base',
    'l': 'large',
    'h': 'huge'
}


def infer_dataset_by_path(model_path: str) -> Union[str, Any]:
    model = os.path.basename(model_path)
    p = r'-([a-zA-Z0-9_]+)\.[pth, onnx, engine]'
    m = re.search(p, model)
    if not m:
        raise ValueError('Could not infer the dataset from ckpt name, specify it')
    return m.group(1)


def dyn_model_import(dataset: str, model: str):
    config_name = f'configs.ViTPose_{dataset}'
    imp = import_module(config_name)
    model = f'model_{MODEL_ABBR_MAP[model]}'
    return getattr(imp, model)


def init_random_seed(seed=None, device='cuda'):
    """Initialize random seed.

    If the seed is not set, the seed will be automatically randomized,
    and then broadcast to all processes to prevent some potential bugs.

    Args:
        seed (int, Optional): The seed. Default to None.
        device (str): The device where the seed will be put on.
            Default to 'cuda'.

    Returns:
        int: Seed to be used.
    """
    if seed is not None:
        return seed

    # Make sure all ranks share the same random seed to prevent
    # some potential bugs. Please refer to
    # https://github.com/open-mmlab/mmdetection/issues/6339
    rank, world_size = get_dist_info()
    seed = np.random.randint(2**31)
    if world_size == 1:
        return seed

    if rank == 0:
        random_num = torch.tensor(seed, dtype=torch.int32, device=device)
    else:
        random_num = torch.tensor(0, dtype=torch.int32, device=device)
    dist.broadcast(random_num, src=0)
    return random_num.item()


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, _ = 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


def is_module_wrapper(module: nn.Module) -> bool:
    """ Check if module wrrapper exists recursively """
    def is_module_in_wrapper(module, module_wrapper):
        module_wrappers = tuple(module_wrapper.module_dict.values())
        if isinstance(module, module_wrappers):
            return True
        for child in module_wrapper.children.values():
            if is_module_in_wrapper(module, child):
                return True
    return is_module_in_wrapper(module, MODULE_WRAPPERS)


def load_state_dict(module, state_dict, strict=False, logger=None):
    """Load state_dict to a module.

    This method is modified from :meth:`torch.nn.Module.load_state_dict`.
    Default value for ``strict`` is set to ``False`` and the message for
    param mismatch will be shown even if strict is False.

    Args:
        module (Module): Module that receives the state_dict.
        state_dict (OrderedDict): Weights.
        strict (bool): whether to strictly enforce that the keys
            in :attr:`state_dict` match the keys returned by this module's
            :meth:`~torch.nn.Module.state_dict` function. Default: ``False``.
        logger (:obj:`logging.Logger`, optional): Logger to log the error
            message. If not specified, print function will be used.
    """
    unexpected_keys = []
    all_missing_keys = []
    err_msg = []

    metadata = getattr(state_dict, '_metadata', None)
    state_dict = state_dict.copy()
    if metadata is not None:
        state_dict._metadata = metadata

    # use _load_from_state_dict to enable checkpoint version control
    def load(module, prefix=''):
        # recursively check parallel module in case that the model has a
        # complicated structure, e.g., nn.Module(nn.Module(DDP))
        if is_module_wrapper(module):
            module = module.module
        local_metadata = {} if metadata is None else metadata.get(
            prefix[:-1], {})
        module._load_from_state_dict(state_dict, prefix, local_metadata, True,
                                     all_missing_keys, unexpected_keys,
                                     err_msg)
        for name, child in module._modules.items():
            if child is not None:
                load(child, prefix + name + '.')

    load(module)
    load = None  # break load->load reference cycle

    # ignore "num_batches_tracked" of BN layers
    missing_keys = [
        key for key in all_missing_keys if 'num_batches_tracked' not in key
    ]

    if unexpected_keys:
        err_msg.append('unexpected key in source '
                       f'state_dict: {", ".join(unexpected_keys)}\n')
    if missing_keys:
        err_msg.append(
            f'missing keys in source state_dict: {", ".join(missing_keys)}\n')

    rank, _ = get_dist_info()
    if len(err_msg) > 0 and rank == 0:
        err_msg.insert(
            0, 'The model and loaded state dict do not match exactly\n')
        err_msg = '\n'.join(err_msg)
        if strict:
            raise RuntimeError(err_msg)
        elif logger is not None:
            logger.warning(err_msg)
        else:
            print(err_msg)


def load_checkpoint(model,
                    filename,
                    map_location='cpu',
                    strict=False,
                    logger=None):
    """Load checkpoint from a file or URI.

    Args:
        model (Module): Module to load checkpoint.
        filename (str): Accept local filepath, URL, ``torchvision://xxx``,
            ``open-mmlab://xxx``.
        map_location (str): Same as :func:`torch.load`.
        strict (bool): Whether to allow different params for the model and
            checkpoint.
        logger (:mod:`logging.Logger` or None): The logger for error message.

    Returns:
        dict or OrderedDict: The loaded checkpoint.
    """
    checkpoint = torch.load(filename, map_location=map_location, weights_only=True)
    # OrderedDict is a subclass of dict
    if not isinstance(checkpoint, dict):
        raise RuntimeError(
            f'No state_dict found in checkpoint file {filename}')
    # get state_dict from checkpoint
    if 'state_dict' in checkpoint:
        state_dict_tmp = checkpoint['state_dict']
    else:
        state_dict_tmp = checkpoint

    state_dict = OrderedDict()
    # strip prefix of state_dict
    for k, v in state_dict_tmp.items():
        if k.startswith('module.backbone.'):
            state_dict[k[16:]] = v
        elif k.startswith('module.'):
            state_dict[k[7:]] = v
        elif k.startswith('backbone.'):
            state_dict[k[9:]] = v
        else:
            state_dict[k] = v
    # load state_dict
    load_state_dict(model, state_dict, strict, logger)
    return checkpoint


def resize(input,
           size=None,
           scale_factor=None,
           mode='nearest',
           align_corners=None,
           warning=True):
    if warning:
        if size is not None and align_corners:
            input_h, input_w = int(input.shape[0]), int(input.shape[1])
            output_h, output_w = int(size[0]), int(size[1])
            if output_h > input_h or output_w > output_h:
                if ((output_h > 1 and output_w > 1 and input_h > 1
                     and input_w > 1) and (output_h - 1) % (input_h - 1)
                        and (output_w - 1) % (input_w - 1)):
                    warnings.warn(
                        f'When align_corners={align_corners}, '
                        'the output would more aligned if '
                        f'input size {(input_h, input_w)} is `x+1` and '
                        f'out size {(output_h, output_w)} is `nx+1`')

def constant_init(module: nn.Module, val: float, bias: float = 0) -> None:
    if hasattr(module, 'weight') and module.weight is not None:
        nn.init.constant_(module.weight, val)
    if hasattr(module, 'bias') and module.bias is not None:
        nn.init.constant_(module.bias, bias)


def normal_init(module: nn.Module,
                mean: float = 0,
                std: float = 1,
                bias: float = 0) -> None:
    if hasattr(module, 'weight') and module.weight is not None:
        nn.init.normal_(module.weight, mean, std)
    if hasattr(module, 'bias') and module.bias is not None:
        nn.init.constant_(module.bias, bias)
