# Copyright (c) Facebook, Inc. and its affiliates.
# All rights reserved.
#
# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.

import logging
import math
import torch.nn as nn
import pdb


logger = logging.getLogger(__name__)

def conv3x3(in_planes, out_planes, stride=1):
    return nn.Conv2d(in_planes, out_planes, kernel_size=3, stride=stride,
                     padding=1, bias=False)


def downsample_basic_block( inplanes, outplanes, stride ):
    return  nn.Sequential(
                nn.Conv2d(inplanes, outplanes, kernel_size=1, stride=stride, bias=False),
                nn.BatchNorm2d(outplanes),
            )

def downsample_basic_block_v2( inplanes, outplanes, stride ):
    return  nn.Sequential(
                nn.AvgPool2d(kernel_size=stride, stride=stride, ceil_mode=True, count_include_pad=False),
                nn.Conv2d(inplanes, outplanes, kernel_size=1, stride=1, bias=False),
                nn.BatchNorm2d(outplanes),
            )



class BasicBlock(nn.Module):
    expansion = 1

    def __init__(self, inplanes, planes, stride=1, downsample=None, relu_type = 'relu' ):
        super(BasicBlock, self).__init__()

        assert relu_type in ['relu','prelu']

        self.conv1 = conv3x3(inplanes, planes, stride)
        self.bn1 = nn.BatchNorm2d(planes)

        if relu_type == 'relu':
            self.relu1 = nn.ReLU(inplace=True)
            self.relu2 = nn.ReLU(inplace=True)
        elif relu_type == 'prelu':
            self.relu1 = nn.PReLU(num_parameters=planes)
            self.relu2 = nn.PReLU(num_parameters=planes)
        else:
            raise Exception('relu type not implemented')

        self.conv2 = conv3x3(planes, planes)
        self.bn2 = nn.BatchNorm2d(planes)
        
        self.downsample = downsample
        self.stride = stride

    def forward(self, x):
        residual = x
        out = self.conv1(x)
        out = self.bn1(out)
        out = self.relu1(out)
        out = self.conv2(out)
        out = self.bn2(out)
        if self.downsample is not None:
            residual = self.downsample(x)

        out += residual
        out = self.relu2(out)

        return out


class ResNet(nn.Module):

    def __init__(self, block, layers, num_classes=1000, relu_type = 'relu', gamma_zero = False, avg_pool_downsample = False):
        self.inplanes = 64
        self.relu_type = relu_type
        self.gamma_zero = gamma_zero
        self.downsample_block = downsample_basic_block_v2 if avg_pool_downsample else downsample_basic_block

        super(ResNet, self).__init__()
        self.layer1 = self._make_layer(block, 64, layers[0])
        self.layer2 = self._make_layer(block, 128, layers[1], stride=2)
        self.layer3 = self._make_layer(block, 256, layers[2], stride=2)
        self.layer4 = self._make_layer(block, 512, layers[3], stride=2)
        self.avgpool = nn.AdaptiveAvgPool2d(1)

        for m in self.modules():
            if isinstance(m, nn.Conv2d):
                n = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
                m.weight.data.normal_(0, math.sqrt(2. / n))
            elif isinstance(m, nn.BatchNorm2d):
                m.weight.data.fill_(1)
                m.bias.data.zero_()

        if self.gamma_zero:
            for m in self.modules():
                if isinstance(m, BasicBlock ):
                    m.bn2.weight.data.zero_()

    def _make_layer(self, block, planes, blocks, stride=1):


        downsample = None
        if stride != 1 or self.inplanes != planes * block.expansion:
            downsample = self.downsample_block( inplanes = self.inplanes, 
                                                 outplanes = planes * block.expansion, 
                                                 stride = stride )

        layers = []
        layers.append(block(self.inplanes, planes, stride, downsample, relu_type = self.relu_type))
        self.inplanes = planes * block.expansion
        for i in range(1, blocks):
            layers.append(block(self.inplanes, planes, relu_type = self.relu_type))

        return nn.Sequential(*layers)

    def forward(self, x):
        x = self.layer1(x)
        x = self.layer2(x)
        x = self.layer3(x)
        x = self.layer4(x)
        x = self.avgpool(x)
        x = x.view(x.size(0), -1)
        return x

class ResEncoder(nn.Module):
    def __init__(self, relu_type, weights):
        super(ResEncoder, self).__init__()
        self.frontend_nout = 64
        self.backend_out = 512
        frontend_relu = nn.PReLU(num_parameters=self.frontend_nout) if relu_type == 'prelu' else nn.ReLU()
        self.frontend3D = nn.Sequential(
            nn.Conv3d(1, self.frontend_nout, kernel_size=(5, 7, 7), stride=(1, 2, 2), padding=(2, 3, 3), bias=False),
            nn.BatchNorm3d(self.frontend_nout),
            frontend_relu,
            nn.MaxPool3d( kernel_size=(1, 3, 3), stride=(1, 2, 2), padding=(0, 1, 1)))
        self.trunk = ResNet(BasicBlock, [2, 2, 2, 2], relu_type=relu_type)
        if weights is not None:
            logger.info(f"Load {weights} for resnet")
            std = torch.load(weights, map_location=torch.device('cpu'))['model_state_dict']
            frontend_std, trunk_std = OrderedDict(), OrderedDict()
            for key, val in std.items():
                new_key = '.'.join(key.split('.')[1:])
                if 'frontend3D' in key:
                    frontend_std[new_key] = val
                if 'trunk' in key:
                    trunk_std[new_key] = val
            self.frontend3D.load_state_dict(frontend_std)
            self.trunk.load_state_dict(trunk_std)

    def forward(self, x):
        B, C, T, H, W = x.size()
        x = self.frontend3D(x)
        Tnew = x.shape[2]
        x = self.threeD_to_2D_tensor(x)
        x = self.trunk(x)
        x = x.view(B, Tnew, x.size(1))
        x = x.transpose(1, 2).contiguous()
        return x

    def threeD_to_2D_tensor(self, x):
        n_batch, n_channels, s_time, sx, sy = x.shape
        x = x.transpose(1, 2).contiguous()
        return x.reshape(n_batch*s_time, n_channels, sx, sy)