# -*- coding: utf-8 -*-

import importlib

import torch
import torch.distributed as dist



def get_obj_from_str(string, reload=False):
    module, cls = string.rsplit(".", 1)
    if reload:
        module_imp = importlib.import_module(module)
        importlib.reload(module_imp)
    return getattr(importlib.import_module(module, package=None), cls)


def get_obj_from_config(config):
    if "target" not in config:
        raise KeyError("Expected key `target` to instantiate.")

    return get_obj_from_str(config["target"])


def instantiate_from_config(config, **kwargs):
    if "target" not in config:
        raise KeyError("Expected key `target` to instantiate.")

    cls = get_obj_from_str(config["target"])

    params = config.get("params", dict())
    # params.update(kwargs)
    # instance = cls(**params)
    kwargs.update(params)
    instance = cls(**kwargs)

    return instance


def is_dist_avail_and_initialized():
    if not dist.is_available():
        return False
    if not dist.is_initialized():
        return False
    return True


def get_rank():
    if not is_dist_avail_and_initialized():
        return 0
    return dist.get_rank()


def get_world_size():
    if not is_dist_avail_and_initialized():
        return 1
    return dist.get_world_size()


def all_gather_batch(tensors):
    """
    Performs all_gather operation on the provided tensors.
    """
    # Queue the gathered tensors
    world_size = get_world_size()
    # There is no need for reduction in the single-proc case
    if world_size == 1:
        return tensors
    tensor_list = []
    output_tensor = []
    for tensor in tensors:
        tensor_all = [torch.ones_like(tensor) for _ in range(world_size)]
        dist.all_gather(
            tensor_all,
            tensor,
            async_op=False  # performance opt
        )

        tensor_list.append(tensor_all)

    for tensor_all in tensor_list:
        output_tensor.append(torch.cat(tensor_all, dim=0))
    return output_tensor