""" Modified from offical repo and mmlab's repo of HRNet
MIT License
Copyright (c) 2019 Microsoft
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
"""

import torch
import torch.nn as nn
from torch.utils.model_zoo import load_url as load_state_dict_from_url

BatchNorm2d = nn.BatchNorm2d

BN_MOMENTUM = 0.1

__all__ = ['HighResolutionNet', 'HighResolutionModule',
           'hrnetv2_w18', 'hrnetv2_w32', 'hrnetv2_w40', 'hrnetv2_w48']

model_urls = {
    "hrnetv2_w18": "https://download.openmmlab.com/pretrain/third_party/hrnetv2_w18-00eb2006.pth",
    "hrnetv2_w32": "https://download.openmmlab.com/pretrain/third_party/hrnetv2_w32-dc9eeb4f.pth",
    "hrnetv2_w40": "https://download.openmmlab.com/pretrain/third_party/hrnetv2_w40-ed0b031c.pth",
    "hrnetv2_w48": "https://download.openmmlab.com/pretrain/third_party/hrnetv2_w48-d2186c55.pth",
}
model_extra = dict(
    hrnetv2_w18=dict(
        stage1=dict(
            num_modules=1,
            num_branches=1,
            block='BOTTLENECK',
            num_blocks=(4,),
            num_channels=(64,),
            fuse_method='SUM'),
        stage2=dict(
            num_modules=1,
            num_branches=2,
            block='BASIC',
            num_blocks=(4, 4),
            num_channels=(18, 36),
            fuse_method='SUM'),
        stage3=dict(
            num_modules=4,
            num_branches=3,
            block='BASIC',
            num_blocks=(4, 4, 4),
            num_channels=(18, 36, 72),
            fuse_method='SUM'),
        stage4=dict(
            num_modules=3,
            num_branches=4,
            block='BASIC',
            num_blocks=(4, 4, 4, 4),
            num_channels=(18, 36, 72, 144),
            fuse_method='SUM')),
    hrnetv2_w32=dict(
        stage1=dict(
            num_modules=1,
            num_branches=1,
            block='BOTTLENECK',
            num_blocks=(4,),
            num_channels=(64,),
            fuse_method='SUM'),
        stage2=dict(
            num_modules=1,
            num_branches=2,
            block='BASIC',
            num_blocks=(4, 4),
            num_channels=(32, 64),
            fuse_method='SUM'),
        stage3=dict(
            num_modules=4,
            num_branches=3,
            block='BASIC',
            num_blocks=(4, 4, 4),
            num_channels=(32, 64, 128),
            fuse_method='SUM'),
        stage4=dict(
            num_modules=3,
            num_branches=4,
            block='BASIC',
            num_blocks=(4, 4, 4, 4),
            num_channels=(32, 64, 128, 256),
            fuse_method='SUM')),
    hrnetv2_w40=dict(
        stage1=dict(
            num_modules=1,
            num_branches=1,
            block='BOTTLENECK',
            num_blocks=(4,),
            num_channels=(64,),
            fuse_method='SUM'),
        stage2=dict(
            num_modules=1,
            num_branches=2,
            block='BASIC',
            num_blocks=(4, 4),
            num_channels=(40, 80),
            fuse_method='SUM'),
        stage3=dict(
            num_modules=4,
            num_branches=3,
            block='BASIC',
            num_blocks=(4, 4, 4),
            num_channels=(40, 80, 160),
            fuse_method='SUM'),
        stage4=dict(
            num_modules=3,
            num_branches=4,
            block='BASIC',
            num_blocks=(4, 4, 4, 4),
            num_channels=(40, 80, 160, 320),
            fuse_method='SUM')),
    hrnetv2_w48=dict(
        stage1=dict(
            num_modules=1,
            num_branches=1,
            block='BOTTLENECK',
            num_blocks=(4,),
            num_channels=(64,),
            fuse_method='SUM'),
        stage2=dict(
            num_modules=1,
            num_branches=2,
            block='BASIC',
            num_blocks=(4, 4),
            num_channels=(48, 96),
            fuse_method='SUM'),
        stage3=dict(
            num_modules=4,
            num_branches=3,
            block='BASIC',
            num_blocks=(4, 4, 4),
            num_channels=(48, 96, 192),
            fuse_method='SUM'),
        stage4=dict(
            num_modules=3,
            num_branches=4,
            block='BASIC',
            num_blocks=(4, 4, 4, 4),
            num_channels=(48, 96, 192, 384),
            fuse_method='SUM'))
)


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


def kaiming_init(module,
                 a=0,
                 mode='fan_out',
                 nonlinearity='relu',
                 bias=0,
                 distribution='normal'):
    assert distribution in ['uniform', 'normal']
    if distribution == 'uniform':
        nn.init.kaiming_uniform_(
            module.weight, a=a, mode=mode, nonlinearity=nonlinearity)
    else:
        nn.init.kaiming_normal_(
            module.weight, a=a, mode=mode, nonlinearity=nonlinearity)
    if hasattr(module, 'bias') and module.bias is not None:
        nn.init.constant_(module.bias, bias)


def conv3x3(in_planes, out_planes, stride=1):
    """3x3 convolution with padding"""
    return nn.Conv2d(in_planes, out_planes, kernel_size=3, stride=stride,
                     padding=1, bias=False)


class BasicBlock(nn.Module):
    expansion = 1

    def __init__(self, inplanes, planes, stride=1, downsample=None):
        super(BasicBlock, self).__init__()
        self.conv1 = conv3x3(inplanes, planes, stride)
        self.bn1 = BatchNorm2d(planes, momentum=BN_MOMENTUM)
        self.relu = nn.ReLU(inplace=True)
        self.conv2 = conv3x3(planes, planes)
        self.bn2 = BatchNorm2d(planes, momentum=BN_MOMENTUM)
        self.downsample = downsample
        self.stride = stride

    def forward(self, x):
        residual = x

        out = self.conv1(x)
        out = self.bn1(out)
        out = self.relu(out)

        out = self.conv2(out)
        out = self.bn2(out)

        if self.downsample is not None:
            residual = self.downsample(x)

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

        return out


class Bottleneck(nn.Module):
    expansion = 4

    def __init__(self, inplanes, planes, stride=1, downsample=None):
        super(Bottleneck, self).__init__()
        self.conv1 = nn.Conv2d(inplanes, planes, kernel_size=1, bias=False)
        self.bn1 = BatchNorm2d(planes, momentum=BN_MOMENTUM)
        self.conv2 = nn.Conv2d(planes, planes, kernel_size=3, stride=stride,
                               padding=1, bias=False)
        self.bn2 = BatchNorm2d(planes, momentum=BN_MOMENTUM)
        self.conv3 = nn.Conv2d(planes, planes * self.expansion, kernel_size=1,
                               bias=False)
        self.bn3 = BatchNorm2d(planes * self.expansion,
                               momentum=BN_MOMENTUM)
        self.relu = nn.ReLU(inplace=True)
        self.downsample = downsample
        self.stride = stride

    def forward(self, x):
        residual = x

        out = self.conv1(x)
        out = self.bn1(out)
        out = self.relu(out)

        out = self.conv2(out)
        out = self.bn2(out)
        out = self.relu(out)

        out = self.conv3(out)
        out = self.bn3(out)

        if self.downsample is not None:
            residual = self.downsample(x)

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

        return out


class HighResolutionModule(nn.Module):
    def __init__(self, num_branches, blocks, num_blocks, num_inchannels,
                 num_channels, fuse_method, multi_scale_output=True):
        super(HighResolutionModule, self).__init__()
        self._check_branches(
            num_branches, blocks, num_blocks, num_inchannels, num_channels)

        self.num_inchannels = num_inchannels
        self.fuse_method = fuse_method
        self.num_branches = num_branches

        self.multi_scale_output = multi_scale_output

        self.branches = self._make_branches(
            num_branches, blocks, num_blocks, num_channels)
        self.fuse_layers = self._make_fuse_layers()
        self.relu = nn.ReLU(False)

    def _check_branches(self, num_branches, blocks, num_blocks,
                        num_inchannels, num_channels):
        if num_branches != len(num_blocks):
            error_msg = 'NUM_BRANCHES({}) <> NUM_BLOCKS({})'.format(
                num_branches, len(num_blocks))
            raise ValueError(error_msg)

        if num_branches != len(num_channels):
            error_msg = 'NUM_BRANCHES({}) <> NUM_CHANNELS({})'.format(
                num_branches, len(num_channels))
            raise ValueError(error_msg)

        if num_branches != len(num_inchannels):
            error_msg = 'NUM_BRANCHES({}) <> NUM_INCHANNELS({})'.format(
                num_branches, len(num_inchannels))
            raise ValueError(error_msg)

    def _make_one_branch(self, branch_index, block, num_blocks, num_channels,
                         stride=1):
        downsample = None
        if stride != 1 or \
                self.num_inchannels[branch_index] != num_channels[branch_index] * block.expansion:
            downsample = nn.Sequential(
                nn.Conv2d(self.num_inchannels[branch_index],
                          num_channels[branch_index] * block.expansion,
                          kernel_size=1, stride=stride, bias=False),
                BatchNorm2d(num_channels[branch_index] * block.expansion,
                            momentum=BN_MOMENTUM),
            )

        layers = []
        layers.append(block(self.num_inchannels[branch_index],
                            num_channels[branch_index], stride, downsample))
        self.num_inchannels[branch_index] = \
            num_channels[branch_index] * block.expansion
        for i in range(1, num_blocks[branch_index]):
            layers.append(block(self.num_inchannels[branch_index],
                                num_channels[branch_index]))

        return nn.Sequential(*layers)

    def _make_branches(self, num_branches, block, num_blocks, num_channels):
        branches = []

        for i in range(num_branches):
            branches.append(
                self._make_one_branch(i, block, num_blocks, num_channels))

        return nn.ModuleList(branches)

    def _make_fuse_layers(self):
        if self.num_branches == 1:
            return None

        num_branches = self.num_branches
        num_inchannels = self.num_inchannels
        fuse_layers = []
        for i in range(num_branches if self.multi_scale_output else 1):
            fuse_layer = []
            for j in range(num_branches):
                if j > i:
                    fuse_layer.append(nn.Sequential(
                        nn.Conv2d(num_inchannels[j],
                                  num_inchannels[i],
                                  1,
                                  1,
                                  0,
                                  bias=False),
                        BatchNorm2d(num_inchannels[i], momentum=BN_MOMENTUM),
                        nn.Upsample(scale_factor=2 ** (j - i), mode='nearest')))
                elif j == i:
                    fuse_layer.append(None)
                else:
                    conv3x3s = []
                    for k in range(i - j):
                        if k == i - j - 1:
                            num_outchannels_conv3x3 = num_inchannels[i]
                            conv3x3s.append(nn.Sequential(
                                nn.Conv2d(num_inchannels[j],
                                          num_outchannels_conv3x3,
                                          3, 2, 1, bias=False),
                                BatchNorm2d(num_outchannels_conv3x3, momentum=BN_MOMENTUM)))
                        else:
                            num_outchannels_conv3x3 = num_inchannels[j]
                            conv3x3s.append(nn.Sequential(
                                nn.Conv2d(num_inchannels[j],
                                          num_outchannels_conv3x3,
                                          3, 2, 1, bias=False),
                                BatchNorm2d(num_outchannels_conv3x3,
                                            momentum=BN_MOMENTUM),
                                nn.ReLU(False)))
                    fuse_layer.append(nn.Sequential(*conv3x3s))
            fuse_layers.append(nn.ModuleList(fuse_layer))

        return nn.ModuleList(fuse_layers)

    def get_num_inchannels(self):
        return self.num_inchannels

    def forward(self, x):
        if self.num_branches == 1:
            return [self.branches[0](x[0])]

        for i in range(self.num_branches):
            x[i] = self.branches[i](x[i])

        x_fuse = []
        for i in range(len(self.fuse_layers)):
            if i == 0:
                y = x[0]
            else:
                y = self.fuse_layers[i][0](x[0])
            for j in range(1, self.num_branches):
                if i == j:
                    y = y + x[j]
                else:
                    y = y + self.fuse_layers[i][j](x[j])
            x_fuse.append(self.relu(y))

        return x_fuse


blocks_dict = {
    'BASIC': BasicBlock,
    'BOTTLENECK': Bottleneck
}


class HighResolutionNet(nn.Module):

    def __init__(self,
                 extra,
                 norm_eval=True,
                 zero_init_residual=False,
                 frozen_stages=-1):
        super(HighResolutionNet, self).__init__()
        self.norm_eval = norm_eval
        self.frozen_stages = frozen_stages
        self.zero_init_residual = zero_init_residual
        # for
        self.extra = extra
        # stem network
        # stem net
        self.conv1 = nn.Conv2d(3, 64, kernel_size=3, stride=2, padding=1,
                               bias=False)
        self.bn1 = BatchNorm2d(64, momentum=BN_MOMENTUM)
        self.conv2 = nn.Conv2d(64, 64, kernel_size=3, stride=2, padding=1,
                               bias=False)
        self.bn2 = BatchNorm2d(64, momentum=BN_MOMENTUM)
        self.relu = nn.ReLU(inplace=True)

        # stage 1
        self.stage1_cfg = self.extra['stage1']
        num_channels = self.stage1_cfg['num_channels'][0]
        block_type = self.stage1_cfg['block']
        num_blocks = self.stage1_cfg['num_blocks'][0]

        block = blocks_dict[block_type]
        stage1_out_channels = num_channels * block.expansion
        self.layer1 = self._make_layer(block, 64, num_channels, num_blocks)

        # stage 2
        self.stage2_cfg = self.extra['stage2']
        num_channels = self.stage2_cfg['num_channels']
        block_type = self.stage2_cfg['block']

        block = blocks_dict[block_type]
        num_channels = [num_channels[i] * block.expansion for i in range(len(num_channels))]
        self.transition1 = self._make_transition_layer([stage1_out_channels], num_channels)
        # num_modules, num_branches, num_blocks, num_channels, block, fuse_method, num_inchannels
        self.stage2, pre_stage_channels = self._make_stage(self.stage2_cfg, num_channels)

        # stage 3
        self.stage3_cfg = self.extra['stage3']
        num_channels = self.stage3_cfg['num_channels']
        block_type = self.stage3_cfg['block']

        block = blocks_dict[block_type]
        num_channels = [num_channels[i] * block.expansion for i in range(len(num_channels))]
        self.transition2 = self._make_transition_layer(pre_stage_channels, num_channels)
        self.stage3, pre_stage_channels = self._make_stage(self.stage3_cfg, num_channels)

        # stage 4
        self.stage4_cfg = self.extra['stage4']
        num_channels = self.stage4_cfg['num_channels']
        block_type = self.stage4_cfg['block']

        block = blocks_dict[block_type]
        num_channels = [num_channels[i] * block.expansion for i in range(len(num_channels))]
        self.transition3 = self._make_transition_layer(pre_stage_channels, num_channels)
        self.stage4, pre_stage_channels = self._make_stage(self.stage4_cfg, num_channels)

        self._frozen_stages()

    def _make_transition_layer(
            self, num_channels_pre_layer, num_channels_cur_layer):
        num_branches_cur = len(num_channels_cur_layer)
        num_branches_pre = len(num_channels_pre_layer)

        transition_layers = []
        for i in range(num_branches_cur):
            if i < num_branches_pre:
                if num_channels_cur_layer[i] != num_channels_pre_layer[i]:
                    transition_layers.append(nn.Sequential(
                        nn.Conv2d(num_channels_pre_layer[i],
                                  num_channels_cur_layer[i],
                                  3,
                                  1,
                                  1,
                                  bias=False),
                        BatchNorm2d(
                            num_channels_cur_layer[i], momentum=BN_MOMENTUM),
                        nn.ReLU(inplace=True)))
                else:
                    transition_layers.append(None)
            else:
                conv3x3s = []
                for j in range(i + 1 - num_branches_pre):
                    inchannels = num_channels_pre_layer[-1]
                    outchannels = num_channels_cur_layer[i] \
                        if j == i - num_branches_pre else inchannels
                    conv3x3s.append(nn.Sequential(
                        nn.Conv2d(
                            inchannels, outchannels, 3, 2, 1, bias=False),
                        BatchNorm2d(outchannels, momentum=BN_MOMENTUM),
                        nn.ReLU(inplace=True)))
                transition_layers.append(nn.Sequential(*conv3x3s))

        return nn.ModuleList(transition_layers)

    def _make_layer(self, block, inplanes, planes, blocks, stride=1):
        downsample = None
        if stride != 1 or inplanes != planes * block.expansion:
            downsample = nn.Sequential(
                nn.Conv2d(inplanes, planes * block.expansion,
                          kernel_size=1, stride=stride, bias=False),
                BatchNorm2d(planes * block.expansion, momentum=BN_MOMENTUM),
            )

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

        return nn.Sequential(*layers)

    def _frozen_stages(self):
        # frozen stage  1 or stem networks
        if self.frozen_stages >= 0:
            for m in [self.conv1, self.bn1, self.conv2, self.bn2]:
                for param in m.parameters():
                    param.requires_grad = False
        if self.frozen_stages == 1:
            for param in self.layer1.parameters():
                param.requires_grad = False

    def _make_stage(self, layer_config, num_inchannels,
                    multi_scale_output=True):
        num_modules = layer_config['num_modules']
        num_branches = layer_config['num_branches']
        num_blocks = layer_config['num_blocks']
        num_channels = layer_config['num_channels']
        block = blocks_dict[layer_config['block']]
        fuse_method = layer_config['fuse_method']

        modules = []
        for i in range(num_modules):
            # multi_scale_output is only used last module
            if not multi_scale_output and i == num_modules - 1:
                reset_multi_scale_output = False
            else:
                reset_multi_scale_output = True

            modules.append(
                HighResolutionModule(num_branches,
                                     block,
                                     num_blocks,
                                     num_inchannels,
                                     num_channels,
                                     fuse_method,
                                     reset_multi_scale_output)
            )
            num_inchannels = modules[-1].get_num_inchannels()

        return nn.Sequential(*modules), num_inchannels

    def forward(self, x):
        # h, w = x.size(2), x.size(3)
        x = self.conv1(x)
        x = self.bn1(x)
        x = self.relu(x)
        x = self.conv2(x)
        x = self.bn2(x)
        x = self.relu(x)
        x = self.layer1(x)

        x_list = []
        for i in range(self.stage2_cfg['num_branches']):
            if self.transition1[i] is not None:
                x_list.append(self.transition1[i](x))
            else:
                x_list.append(x)
        y_list = self.stage2(x_list)

        x_list = []
        for i in range(self.stage3_cfg['num_branches']):
            if self.transition2[i] is not None:
                x_list.append(self.transition2[i](y_list[-1]))
            else:
                x_list.append(y_list[i])
        y_list = self.stage3(x_list)

        x_list = []
        for i in range(self.stage4_cfg['num_branches']):
            if self.transition3[i] is not None:
                x_list.append(self.transition3[i](y_list[-1]))
            else:
                x_list.append(y_list[i])
        y_list = self.stage4(x_list)

        return y_list

    def train(self, mode=True):
        super(HighResolutionNet, self).train(mode)
        if mode and self.norm_eval:
            for m in self.modules():
                # trick: eval have effect on BatchNorm only
                if isinstance(m, nn.BatchNorm2d):
                    m.eval()


def hrnetv2_w18(pretrained=False, weight_path=None, norm_eval=False, frozen_stages=-1):
    model = HighResolutionNet(model_extra['hrnetv2_w18'], norm_eval, zero_init_residual=False,
                              frozen_stages=frozen_stages)
    if pretrained:
        if weight_path is not None:
            state_dict = torch.load(weight_path, map_location=torch.device("cpu"))
        else:
            state_dict = load_state_dict_from_url(model_urls['hrnetv2_w18'],
                                                  progress=True)
        model.load_state_dict(state_dict, strict=False)
    return model


def hrnetv2_w32(pretrained=False, weight_path=None, norm_eval=False, frozen_stages=-1):
    model = HighResolutionNet(model_extra['hrnetv2_w32'], norm_eval, zero_init_residual=False,
                              frozen_stages=frozen_stages)
    if pretrained:
        if weight_path is not None:
            state_dict = torch.load(weight_path, map_location=torch.device("cpu"))
        else:
            state_dict = load_state_dict_from_url(model_urls['hrnetv2_w32'],
                                                  progress=True)
        model.load_state_dict(state_dict, strict=False)
    return model


def hrnetv2_w40(pretrained=False, weight_path=None, norm_eval=False, frozen_stages=-1):
    model = HighResolutionNet(model_extra['hrnetv2_w40'], norm_eval, zero_init_residual=False,
                              frozen_stages=frozen_stages)
    if pretrained:
        if weight_path is not None:
            state_dict = torch.load(weight_path, map_location=torch.device("cpu"))
        else:
            state_dict = load_state_dict_from_url(model_urls['hrnetv2_w40'],
                                                  progress=True)
        model.load_state_dict(state_dict, strict=False)
    return model


def hrnetv2_w48(pretrained=False, weight_path=None, norm_eval=False, frozen_stages=-1):
    model = HighResolutionNet(model_extra['hrnetv2_w48'], norm_eval, zero_init_residual=False,
                              frozen_stages=frozen_stages)
    if pretrained:
        if weight_path is not None:
            state_dict = torch.load(weight_path, map_location=torch.device("cpu"))
        else:
            raise FileNotFoundError('there is not pretrained model for HRNet-w48')
            state_dict = load_state_dict_from_url(model_urls['hrnetv2_w48'],
                                                  progress=True)
        model.load_state_dict(state_dict, strict=False)
    return model
