# -*- coding: utf-8 -*-
"""
Created on Tue Jul 06 2020

Resnet(from pytorch master) + polarpadding(from Iselin) -> Unet with polar
we can only resnet 50 use.......

@author: Shunsuke Yoshizawa
"""

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


def conv3x3(in_planes, out_planes, stride=1, groups=1, dilation=1):
    """3x3 convolution with padding"""
    return nn.Conv2d(in_planes, out_planes, kernel_size=3, stride=stride,
                     padding=0, groups=groups, bias=False, dilation=dilation)  # dilation changed to 0


def conv1x1(in_planes, out_planes, stride=1):
    """1x1 convolution"""
    return nn.Conv2d(in_planes, out_planes, kernel_size=1, stride=stride, bias=False)


class PolarPadding(torch.nn.Module):

    def __init__(self, padding):
        super().__init__()

        self.padding = padding

    def forward(self, x):
        if self.padding > 0:
            x = F.pad(x, (self.padding, self.padding, 0, 0), "constant", 0)

            top = x[..., 0: self.padding, :]
            bottom = x[..., x.shape[-2] - self.padding: x.shape[-2], :]

            x = torch.cat((bottom, x, top), dim=-2)

        return x


class BasicBlock(nn.Module):
    expansion = 1

    def __init__(self, inplanes, planes, stride=1, downsample=None, groups=1,
                 base_width=64, dilation=1, norm_layer=None):
        super(BasicBlock, self).__init__()
        if norm_layer is None:
            norm_layer = nn.BatchNorm2d
        if groups != 1 or base_width != 64:
            raise ValueError('BasicBlock only supports groups=1 and base_width=64')
        if dilation > 1:
            raise NotImplementedError("Dilation > 1 not supported in BasicBlock")
        # Both self.conv1 and self.downsample layers downsample the input when stride != 1

        self.polar1 = PolarPadding(1)  # change
        self.conv1 = conv3x3(inplanes, planes, stride)
        self.bn1 = norm_layer(planes)
        self.relu = nn.ReLU(inplace=True)
        self.polar1 = PolarPadding(1)
        self.conv2 = conv3x3(planes, planes)
        self.bn2 = norm_layer(planes)
        self.downsample = downsample
        self.stride = stride

    def forward(self, x):
        identity = x

        out = self.polar1(x)
        out = self.conv1(out)
        out = self.bn1(out)
        out = self.relu(out)

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

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

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

        return out


class Bottleneck(nn.Module):
    # Bottleneck in torchvision places the stride for downsampling at 3x3 convolution(self.conv2)
    # while original implementation places the stride at the first 1x1 convolution(self.conv1)
    # according to "Deep residual learning for image recognition"https://arxiv.org/abs/1512.03385.
    # This variant is also known as ResNet V1.5 and improves accuracy according to
    # https://ngc.nvidia.com/catalog/model-scripts/nvidia:resnet_50_v1_5_for_pytorch.

    expansion = 2

    def __init__(self, inplanes, planes, stride=1, downsample=None, groups=1,
                 base_width=64, dilation=1, norm_layer=None):
        super(Bottleneck, self).__init__()
        if norm_layer is None:
            norm_layer = nn.BatchNorm2d
        width = int(planes * (base_width / 64.)) * groups
        # Both self.conv2 and self.downsample layers downsample the input when stride != 1
        self.conv1 = conv1x1(inplanes, width)
        self.bn1 = norm_layer(width)
        self.polar1 = PolarPadding(dilation)
        self.conv2 = conv3x3(width, width, stride, groups)
        self.bn2 = norm_layer(width)
        self.conv3 = conv1x1(width, planes * self.expansion)
        self.bn3 = norm_layer(planes * self.expansion)
        self.relu = nn.ReLU(inplace=True)
        self.downsample = downsample
        self.stride = stride

    def forward(self, x):
        identity = x

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

        out = self.polar1(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:
            identity = self.downsample(x)

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


        return out


class ResNet(nn.Module):

    def __init__(self, block, layers, num_classes=5, zero_init_residual=False,
                 groups=1, width_per_group=64, replace_stride_with_dilation=None,
                 norm_layer=None):
        super(ResNet, self).__init__()
        if norm_layer is None:
            norm_layer = nn.BatchNorm2d
        self._norm_layer = norm_layer

        self.inplanes = 64
        self.dilation = 1
        if replace_stride_with_dilation is None:
            # each element in the tuple indicates if we should replace
            # the 2x2 stride with a dilated convolution instead
            replace_stride_with_dilation = [False, False, False]
        if len(replace_stride_with_dilation) != 3:
            raise ValueError("replace_stride_with_dilation should be None "
                             "or a 3-element tuple, got {}".format(replace_stride_with_dilation))
        self.groups = groups
        self.base_width = width_per_group
        self.polar1 = PolarPadding(padding=3)
        self.conv1 = nn.Conv2d(3, self.inplanes, kernel_size=7, stride=2,
                               bias=False)
        self.bn1 = norm_layer(self.inplanes)
        self.relu = nn.ReLU(inplace=True)
        self.polar2 = PolarPadding(1)
        self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2)
        self.layer1 = self._make_layer(block, 64, layers[0])
        self.layer2 = self._make_layer(block, 128, layers[1], stride=2,
                                       dilate=replace_stride_with_dilation[0])
        self.layer3 = self._make_layer(block, 256, layers[2], stride=2,
                                       dilate=replace_stride_with_dilation[1])
        self.layer4 = self._make_layer(block, 512, layers[3], stride=2,
                                       dilate=replace_stride_with_dilation[2])

        for m in self.modules():
            if isinstance(m, nn.Conv2d):
                nn.init.kaiming_normal_(m.weight, mode='fan_out', nonlinearity='relu')
            elif isinstance(m, (nn.BatchNorm2d, nn.GroupNorm)):
                nn.init.constant_(m.weight, 1)
                nn.init.constant_(m.bias, 0)

        # Zero-initialize the last BN in each residual branch,
        # so that the residual branch starts with zeros, and each residual block behaves like an identity.
        # This improves the model by 0.2~0.3% according to https://arxiv.org/abs/1706.02677
        if zero_init_residual:
            for m in self.modules():
                if isinstance(m, Bottleneck):
                    nn.init.constant_(m.bn3.weight, 0)
                elif isinstance(m, BasicBlock):
                    nn.init.constant_(m.bn2.weight, 0)

    def _make_layer(self, block, planes, blocks, stride=1, dilate=False):
        norm_layer = self._norm_layer
        downsample = None
        previous_dilation = self.dilation
        if dilate:
            self.dilation *= stride
            stride = 1
        if stride != 1 or self.inplanes != planes * block.expansion:
            downsample = nn.Sequential(
                conv1x1(self.inplanes, planes * block.expansion, stride),
                norm_layer(planes * block.expansion),
            )

        layers = []
        layers.append(block(self.inplanes, planes, stride, downsample, self.groups,
                            self.base_width, previous_dilation, norm_layer))
        self.inplanes = planes * block.expansion
        for _ in range(1, blocks):
            layers.append(block(self.inplanes, planes, groups=self.groups,
                                base_width=self.base_width, dilation=self.dilation,
                                norm_layer=norm_layer))

        return nn.Sequential(*layers)

    def _forward_impl(self, x):
        # See note [TorchScript super()]
        pool1 = x
        x = self.polar1(x)

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

        x = self.polar2(x)
        x = self.maxpool(x)

        x = self.layer1(x)

        x = self.layer2(x)

        x = self.layer3(x)

        x = self.layer4(x)

        return x

    def forward(self, x):
        return self._forward_impl(x)


import torch
import torch.nn as nn


class ConvBlock(nn.Module):
    """
    Helper module that consists of a Conv -> BN -> ReLU
    """

    def __init__(self, in_channels, out_channels, padding=1, kernel_size=3, stride=1, with_nonlinearity=True):
        super().__init__()
        if padding > 0:
            self.pad = PolarPadding(padding=padding)
            padding = 0
        self.conv = nn.Conv2d(in_channels, out_channels, padding=padding, kernel_size=kernel_size, stride=stride)
        self.bn = nn.BatchNorm2d(out_channels)
        self.relu = nn.ReLU()
        self.with_nonlinearity = with_nonlinearity

    def forward(self, x):
        x = self.pad(x)
        x = self.conv(x)
        x = self.bn(x)
        if self.with_nonlinearity:
            x = self.relu(x)
        return x


class Bridge(nn.Module):
    """
    This is the middle layer of the UNet which just consists of some
    """

    def __init__(self, in_channels, out_channels):
        super().__init__()
        self.bridge = nn.Sequential(
            ConvBlock(in_channels, out_channels),
            ConvBlock(out_channels, out_channels)
        )

    def forward(self, x):
        return self.bridge(x)


class UpBlockForUNetWithResNet50(nn.Module):
    """
    Up block that encapsulates one up-sampling step which consists of Upsample -> ConvBlock -> ConvBlock
    """

    def __init__(self, in_channels, out_channels, up_conv_in_channels=None, up_conv_out_channels=None,
                 upsampling_method="conv_transpose"):
        super().__init__()

        if up_conv_in_channels == None:
            up_conv_in_channels = in_channels
        if up_conv_out_channels == None:
            up_conv_out_channels = out_channels

        if upsampling_method == "conv_transpose":
            self.upsample = nn.ConvTranspose2d(up_conv_in_channels, up_conv_out_channels, kernel_size=2, stride=2)
        elif upsampling_method == "bilinear":
            self.upsample = nn.Sequential(
                nn.Upsample(mode='bilinear', scale_factor=2),
                nn.Conv2d(in_channels, out_channels, kernel_size=1, stride=1)
            )
        self.conv_block_1 = ConvBlock(in_channels, out_channels)
        self.conv_block_2 = ConvBlock(out_channels, out_channels)

    def forward(self, up_x, down_x):
        """
        :param up_x: this is the output from the previous up block
        :param down_x: this is the output from the down block
        :return: upsampled feature map
        """
        x = self.upsample(up_x)
        if x.size(3) != down_x.size(3):

            x = torch.cat([x[:, :, :, 1:], down_x], 1)
        else:
            x = torch.cat([x, down_x], 1)
        x = self.conv_block_1(x)
        x = self.conv_block_2(x)
        return x


class UNetWithPolarResnet50Encoder_half(nn.Module):
    DEPTH = 6

    def __init__(self, n_classes=5):
        super().__init__()
        resnet = ResNet(Bottleneck, [3, 4, 6, 3], num_classes=5)
        down_blocks = []
        up_blocks = []
        self.input_block = nn.Sequential(*list(resnet.children()))[:4]
        self.input_pool = nn.Sequential(*list(resnet.children())[4:6])
        for bottleneck in list(resnet.children()):
            if isinstance(bottleneck, nn.Sequential):
                down_blocks.append(bottleneck)
        self.down_blocks = nn.ModuleList(down_blocks)
        self.bridge = Bridge(1024, 1024)
        up_blocks.append(UpBlockForUNetWithResNet50(1024, 512))
        up_blocks.append(UpBlockForUNetWithResNet50(512, 256))
        up_blocks.append(UpBlockForUNetWithResNet50(256, 128))
        up_blocks.append(UpBlockForUNetWithResNet50(in_channels=64 + 64, out_channels=64,
                                                    up_conv_in_channels=128, up_conv_out_channels=64))
        up_blocks.append(UpBlockForUNetWithResNet50(in_channels=32 + 3, out_channels=32,
                                                    up_conv_in_channels=64, up_conv_out_channels=32))

        self.up_blocks = nn.ModuleList(up_blocks)

        self.out = nn.Conv2d(32, n_classes, kernel_size=1, stride=1)

    def forward(self, x, with_output_feature_map=False):
        pre_pools = dict()
        pre_pools[f"layer_0"] = x
        x = self.input_block(x)
        pre_pools[f"layer_1"] = x
        x = self.input_pool(x)

        for i, block in enumerate(self.down_blocks, 2):
            x = block(x)
            if i == (UNetWithPolarResnet50Encoder_half.DEPTH - 1):
                continue
            pre_pools[f"layer_{i}"] = x

        x = self.bridge(x)


        for i, block in enumerate(self.up_blocks, 1):
            key = f"layer_{UNetWithPolarResnet50Encoder_half.DEPTH - 1 - i}"
            x = block(x, pre_pools[key])
        output_feature_map = x
        x = self.out(x)
        del pre_pools
        if with_output_feature_map:
            return x, output_feature_map
        else:
            return x

