# ------------------------------------------------------------------------------
# The implementation is adopted from CenterNet,
# made publicly available under the MIT License at https://github.com/xingyizhou/CenterNet.git
# ------------------------------------------------------------------------------

import os

import torch
import torch.nn as nn
import torch.nn.functional as F

BN_MOMENTUM = 0.1


class BasicBlock(nn.Module):
    expansion = 1

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

    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(residual)

        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 = nn.BatchNorm2d(planes, momentum=BN_MOMENTUM)
        self.conv2 = nn.Conv2d(
            planes,
            planes,
            kernel_size=3,
            stride=stride,
            padding=1,
            bias=False)
        self.bn2 = nn.BatchNorm2d(planes, momentum=BN_MOMENTUM)
        self.conv3 = nn.Conv2d(
            planes, planes * self.expansion, kernel_size=1, bias=False)
        self.bn3 = nn.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 PoseResNet(nn.Module):

    def __init__(self, block, layers, head_conv=64, **kwargs):
        self.inplanes = 64
        self.deconv_with_bias = False
        self.heads = {'hm': 1, 'cls': 4, 'ftype': 11, 'wh': 8, 'reg': 2}

        super(PoseResNet, self).__init__()
        self.conv1 = nn.Conv2d(
            3, 64, kernel_size=7, stride=2, padding=3, bias=False)
        self.bn1 = nn.BatchNorm2d(64, momentum=BN_MOMENTUM)
        self.relu = nn.ReLU(inplace=True)
        self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
        self.layer1 = self._make_layer(block, 64, layers[0], stride=2)
        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, 256, layers[3], stride=2)

        self.adaption3 = nn.Conv2d(
            256, 256, kernel_size=1, stride=1, padding=0, bias=False)
        self.adaption2 = nn.Conv2d(
            128, 256, kernel_size=1, stride=1, padding=0, bias=False)
        self.adaption1 = nn.Conv2d(
            64, 256, kernel_size=1, stride=1, padding=0, bias=False)
        self.adaption0 = nn.Conv2d(
            64, 256, kernel_size=1, stride=1, padding=0, bias=False)

        self.adaptionU1 = nn.Conv2d(
            256, 256, kernel_size=1, stride=1, padding=0, bias=False)

        self.deconv_layers1 = self._make_deconv_layer(
            1,
            [256],
            [4],
        )
        self.deconv_layers2 = self._make_deconv_layer(
            1,
            [256],
            [4],
        )
        self.deconv_layers3 = self._make_deconv_layer(
            1,
            [256],
            [4],
        )
        self.deconv_layers4 = self._make_deconv_layer(
            1,
            [256],
            [4],
        )

        for head in sorted(self.heads):
            num_output = self.heads[head]
            if head_conv > 0:
                inchannel = 256
                fc = nn.Sequential(
                    nn.Conv2d(
                        inchannel,
                        head_conv,
                        kernel_size=3,
                        padding=1,
                        bias=True), nn.ReLU(inplace=True),
                    nn.Conv2d(
                        head_conv,
                        num_output,
                        kernel_size=1,
                        stride=1,
                        padding=0))
            else:
                inchannel = 256
                fc = nn.Conv2d(
                    in_channels=inchannel,
                    out_channels=num_output,
                    kernel_size=1,
                    stride=1,
                    padding=0)
            self.__setattr__(head, fc)

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

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

        return nn.Sequential(*layers)

    def _get_deconv_cfg(self, deconv_kernel, index):
        if deconv_kernel == 4:
            padding = 1
            output_padding = 0
        elif deconv_kernel == 3:
            padding = 1
            output_padding = 1
        elif deconv_kernel == 2:
            padding = 0
            output_padding = 0
        elif deconv_kernel == 7:
            padding = 3
            output_padding = 0

        return deconv_kernel, padding, output_padding

    def _make_deconv_layer(self, num_layers, num_filters, num_kernels):
        assert num_layers == len(num_filters), \
            'ERROR: num_deconv_layers is different len(num_deconv_filters)'
        assert num_layers == len(num_kernels), \
            'ERROR: num_deconv_layers is different len(num_deconv_filters)'

        layers = []
        for i in range(num_layers):
            kernel, padding, output_padding = \
                self._get_deconv_cfg(num_kernels[i], i)

            planes = num_filters[i]
            layers.append(
                nn.ConvTranspose2d(
                    in_channels=self.inplanes,
                    out_channels=planes,
                    kernel_size=kernel,
                    stride=2,
                    padding=padding,
                    output_padding=output_padding,
                    bias=self.deconv_with_bias))
            layers.append(nn.BatchNorm2d(planes, momentum=BN_MOMENTUM))
            layers.append(nn.ReLU(inplace=True))
            self.inplanes = planes

        return nn.Sequential(*layers)

    def forward(self, x):
        x = self.conv1(x)
        x = self.bn1(x)
        x = self.relu(x)
        x0 = self.maxpool(x)
        x1 = self.layer1(x0)
        x2 = self.layer2(x1)
        x3 = self.layer3(x2)
        x4 = self.layer4(x3)

        x3_ = self.deconv_layers1(x4)
        x3_ = self.adaption3(x3) + x3_

        x2_ = self.deconv_layers2(x3_)
        x2_ = self.adaption2(x2) + x2_

        x1_ = self.deconv_layers3(x2_)
        x1_ = self.adaption1(x1) + x1_

        x0_ = self.deconv_layers4(x1_) + self.adaption0(x0)
        x0_ = self.adaptionU1(x0_)

        ret = {}

        for head in self.heads:
            ret[head] = self.__getattr__(head)(x0_)
        return [ret]


resnet_spec = {
    18: (BasicBlock, [2, 2, 2, 2]),
    34: (BasicBlock, [3, 4, 6, 3]),
    50: (Bottleneck, [3, 4, 6, 3]),
    101: (Bottleneck, [3, 4, 23, 3]),
    152: (Bottleneck, [3, 8, 36, 3])
}


def LicensePlateDet(num_layers=18):
    block_class, layers = resnet_spec[num_layers]
    model = PoseResNet(block_class, layers)
    return model
