import torch
import torch.nn as nn
import math
import torch.utils.model_zoo as model_zoo

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 Normalize(nn.Module):
    def __init__(self, power=2):
        super(Normalize, self).__init__()
        self.power = power

    def forward(self, x):
        norm = x.pow(self.power).sum(1, keepdim=True).pow(1.0 / self.power)
        out = x.div(norm)
        return out


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 = nn.BatchNorm2d(planes)
        self.relu = nn.ReLU(inplace=True)
        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.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 = nn.BatchNorm2d(planes)
        self.conv2 = nn.Conv2d(
            planes, planes, kernel_size=3, stride=stride, padding=1, bias=False
        )
        self.bn2 = nn.BatchNorm2d(planes)
        self.conv3 = nn.Conv2d(planes, planes * 4, kernel_size=1, bias=False)
        self.bn3 = nn.BatchNorm2d(planes * 4)
        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 Interpolate(nn.Module):
    def __init__(self, size, mode):
        super(Interpolate, self).__init__()
        self.interp = nn.functional.interpolate
        self.size = size
        self.mode = mode

    def forward(self, x):
        x = self.interp(x, size=self.size, mode=self.mode, align_corners=False)
        return x


class ResNet(nn.Module):
    def __init__(self, block, layers, low_dim=128, in_channel=3, width=1, pool_size=7):

        self.inplanes = 64
        super(ResNet, self).__init__()
        self.conv1 = nn.Conv2d(
            in_channel, 64, kernel_size=7, stride=2, padding=3, bias=False
        )
        self.bn1 = nn.BatchNorm2d(64)
        self.relu = nn.ReLU(inplace=True)
        self.base = int(64 * width)

        self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
        self.layer1 = self._make_layer(block, self.base, layers[0])
        self.layer2 = self._make_layer(block, self.base * 2, layers[1], stride=2)
        self.layer3 = self._make_layer(block, self.base * 4, layers[2], stride=2)
        self.layer4 = self._make_layer(block, self.base * 8, layers[3], stride=2)
        self.avgpool = nn.AvgPool2d(pool_size, stride=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(2.0 / n))
            elif isinstance(m, nn.BatchNorm2d):
                m.weight.data.fill_(1)
                m.bias.data.zero_()

    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),
            )

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

        return nn.Sequential(*layers)

    def forward(self, x):

        x1 = self.conv1(x)
        x2 = self.bn1(x1)
        x3 = self.relu(x2)
        x4 = self.maxpool(x3)
        x5 = self.layer1(x4)
        x6 = self.layer2(x5)
        x7 = self.layer3(x6)
        x8 = self.layer4(x7)
        x9 = self.avgpool(x8)
        x10 = x9.view(x9.size(0), -1)

        output = {
            "f1": x1,
            "f2": x2,
            "f3": x3,
            "f4": x4,
            "f5": x5,
            "f6": x6,
            "f7": x7,
            "f8": x8,
            "f9": x9,
            "f10": x10,
        }

        return output


def resnet18(pretrained=False, **kwargs):
    """Constructs a ResNet-18 model.
    Args:
        pretrained (bool): If True, returns a model pre-trained on ImageNet
    """
    model = ResNet(BasicBlock, [2, 2, 2, 2], **kwargs)
    
    return model
