# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved

# Implementation adapted from OFA - https://github.com/mit-han-lab/once-for-all

import torch
import torch.nn as nn
import copy

multiply_adds = 1


def count_convNd(m, _, y):
    cin = m.in_channels

    kernel_ops = m.weight.size()[2] * m.weight.size()[3]
    ops_per_element = kernel_ops
    output_elements = y.nelement()

    # cout x oW x oH
    total_ops = cin * output_elements * ops_per_element // m.groups
    m.total_ops = torch.Tensor([int(total_ops)])


def count_linear(m, _, __):
    total_ops = m.in_features * m.out_features

    m.total_ops = torch.Tensor([int(total_ops)])


register_hooks = {
    nn.Conv1d: count_convNd,
    nn.Conv2d: count_convNd,
    nn.Conv3d: count_convNd,
    ######################################
    nn.Linear: count_linear,
    ######################################
    nn.Dropout: None,
    nn.Dropout2d: None,
    nn.Dropout3d: None,
    nn.BatchNorm2d: None,
}


def profile(model, input_size=(1, 3, 224, 224), custom_ops=None):
    handler_collection = []
    custom_ops = {} if custom_ops is None else custom_ops

    def add_hooks(m_):
        if len(list(m_.children())) > 0:
            return

        m_.register_buffer('total_ops', torch.zeros(1))
        m_.register_buffer('total_params', torch.zeros(1))

        for p in m_.parameters():
            m_.total_params += torch.Tensor([p.numel()])

        m_type = type(m_)
        fn = None

        if m_type in custom_ops:
            fn = custom_ops[m_type]
        elif m_type in register_hooks:
            fn = register_hooks[m_type]
        else:
            # print("Not implemented for ", m_)
            pass

        if fn is not None:
            # print("Register FLOP counter for module %s" % str(m_))
            _handler = m_.register_forward_hook(fn)
            handler_collection.append(_handler)

    original_device = model.parameters().__next__().device
    training = model.training

    model.eval()
    model.apply(add_hooks)

    x = torch.zeros(input_size).to(original_device)
    with torch.no_grad():
        model(x)

    total_ops = 0
    total_params = 0
    for m in model.modules():
        if len(list(m.children())) > 0:  # skip for non-leaf module
            continue
        total_ops += m.total_ops
        total_params += m.total_params

    total_ops = total_ops.item()
    total_params = total_params.item()

    model.train(training)
    model.to(original_device)

    for handler in handler_collection:
        handler.remove()

    return total_ops, total_params


def count_net_flops_and_params(net, data_shape=(1, 3, 224, 224)):
    if isinstance(net, nn.DataParallel):
        net = net.module

    net = copy.deepcopy(net)
    flop, nparams = profile(net, data_shape)
    return flop /1e6, nparams /1e6


