import torch
import torch.nn as nn
import torch.nn.functional as F
from layer import conv1x1, conv3x3, BasicBlock


class ResidualBlock(nn.Module):
    def __init__(self, in_planes, planes, norm_fn='group', stride=1):
        super(ResidualBlock, self).__init__()
  
        self.conv1 = nn.Conv2d(in_planes, planes, kernel_size=3, padding=1, stride=stride)
        self.conv2 = nn.Conv2d(planes, planes, kernel_size=3, padding=1)
        self.relu = nn.ReLU(inplace=True)

        num_groups = planes // 8

        if norm_fn == 'group':
            self.norm1 = nn.GroupNorm(num_groups=num_groups, num_channels=planes)
            self.norm2 = nn.GroupNorm(num_groups=num_groups, num_channels=planes)
            if not stride == 1:
                self.norm3 = nn.GroupNorm(num_groups=num_groups, num_channels=planes)
        
        elif norm_fn == 'batch':
            self.norm1 = nn.BatchNorm2d(planes)
            self.norm2 = nn.BatchNorm2d(planes)
            if not stride == 1:
                self.norm3 = nn.BatchNorm2d(planes)
        
        elif norm_fn == 'instance':
            self.norm1 = nn.InstanceNorm2d(planes)
            self.norm2 = nn.InstanceNorm2d(planes)
            if not stride == 1:
                self.norm3 = nn.InstanceNorm2d(planes)

        elif norm_fn == 'none':
            self.norm1 = nn.Sequential()
            self.norm2 = nn.Sequential()
            if not stride == 1:
                self.norm3 = nn.Sequential()

        if stride == 1:
            self.downsample = None
        
        else:    
            self.downsample = nn.Sequential(
                nn.Conv2d(in_planes, planes, kernel_size=1, stride=stride), self.norm3)


    def forward(self, x):
        y = x
        y = self.relu(self.norm1(self.conv1(y)))
        y = self.relu(self.norm2(self.conv2(y)))

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

        return self.relu(x+y)



class BottleneckBlock(nn.Module):
    def __init__(self, in_planes, planes, norm_fn='group', stride=1):
        super(BottleneckBlock, self).__init__()
  
        self.conv1 = nn.Conv2d(in_planes, planes//4, kernel_size=1, padding=0)
        self.conv2 = nn.Conv2d(planes//4, planes//4, kernel_size=3, padding=1, stride=stride)
        self.conv3 = nn.Conv2d(planes//4, planes, kernel_size=1, padding=0)
        self.relu = nn.ReLU(inplace=True)

        num_groups = planes // 8

        if norm_fn == 'group':
            self.norm1 = nn.GroupNorm(num_groups=num_groups, num_channels=planes//4)
            self.norm2 = nn.GroupNorm(num_groups=num_groups, num_channels=planes//4)
            self.norm3 = nn.GroupNorm(num_groups=num_groups, num_channels=planes)
            if not stride == 1:
                self.norm4 = nn.GroupNorm(num_groups=num_groups, num_channels=planes)
        
        elif norm_fn == 'batch':
            self.norm1 = nn.BatchNorm2d(planes//4)
            self.norm2 = nn.BatchNorm2d(planes//4)
            self.norm3 = nn.BatchNorm2d(planes)
            if not stride == 1:
                self.norm4 = nn.BatchNorm2d(planes)
        
        elif norm_fn == 'instance':
            self.norm1 = nn.InstanceNorm2d(planes//4)
            self.norm2 = nn.InstanceNorm2d(planes//4)
            self.norm3 = nn.InstanceNorm2d(planes)
            if not stride == 1:
                self.norm4 = nn.InstanceNorm2d(planes)

        elif norm_fn == 'none':
            self.norm1 = nn.Sequential()
            self.norm2 = nn.Sequential()
            self.norm3 = nn.Sequential()
            if not stride == 1:
                self.norm4 = nn.Sequential()

        if stride == 1:
            self.downsample = None
        
        else:    
            self.downsample = nn.Sequential(
                nn.Conv2d(in_planes, planes, kernel_size=1, stride=stride), self.norm4)


    def forward(self, x):
        y = x
        y = self.relu(self.norm1(self.conv1(y)))
        y = self.relu(self.norm2(self.conv2(y)))
        y = self.relu(self.norm3(self.conv3(y)))

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

        return self.relu(x+y)

class BasicEncoder(nn.Module):
    def __init__(self, output_dim=128, norm_fn='batch', dropout=0.0):
        super(BasicEncoder, self).__init__()
        self.norm_fn = norm_fn

        if self.norm_fn == 'group':
            self.norm1 = nn.GroupNorm(num_groups=8, num_channels=64)
            
        elif self.norm_fn == 'batch':
            self.norm1 = nn.BatchNorm2d(64)

        elif self.norm_fn == 'instance':
            self.norm1 = nn.InstanceNorm2d(64)

        elif self.norm_fn == 'none':
            self.norm1 = nn.Sequential()

        self.conv1 = nn.Conv2d(3, 64, kernel_size=7, stride=2, padding=3)
        self.relu1 = nn.ReLU(inplace=True)

        self.in_planes = 64
        self.layer1 = self._make_layer(64,  stride=1)
        self.layer2 = self._make_layer(96, stride=2)
        self.layer3 = self._make_layer(128, stride=2)

        # output convolution
        self.conv2 = nn.Conv2d(128, output_dim, kernel_size=1)

        self.dropout = None
        if dropout > 0:
            self.dropout = nn.Dropout2d(p=dropout)

        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.InstanceNorm2d, nn.GroupNorm)):
                if m.weight is not None:
                    nn.init.constant_(m.weight, 1)
                if m.bias is not None:
                    nn.init.constant_(m.bias, 0)

    def _make_layer(self, dim, stride=1):
        layer1 = ResidualBlock(self.in_planes, dim, self.norm_fn, stride=stride)
        layer2 = ResidualBlock(dim, dim, self.norm_fn, stride=1)
        layers = (layer1, layer2)
        
        self.in_planes = dim
        return nn.Sequential(*layers)


    def forward(self, x):

        # if input is list, combine batch dimension
        is_list = isinstance(x, tuple) or isinstance(x, list)
        if is_list:
            batch_dim = x[0].shape[0]
            x = torch.cat(x, dim=0)

        x = self.conv1(x)
        x = self.norm1(x)
        x = self.relu1(x)

        x = self.layer1(x)
        x = self.layer2(x)
        x = self.layer3(x)

        x = self.conv2(x)

        if self.training and self.dropout is not None:
            x = self.dropout(x)

        if is_list:
            x = torch.split(x, [batch_dim, batch_dim], dim=0)

        return x


class SmallEncoder(nn.Module):
    def __init__(self, output_dim=128, norm_fn='batch', dropout=0.0):
        super(SmallEncoder, self).__init__()
        self.norm_fn = norm_fn

        if self.norm_fn == 'group':
            self.norm1 = nn.GroupNorm(num_groups=8, num_channels=32)
            
        elif self.norm_fn == 'batch':
            self.norm1 = nn.BatchNorm2d(32)

        elif self.norm_fn == 'instance':
            self.norm1 = nn.InstanceNorm2d(32)

        elif self.norm_fn == 'none':
            self.norm1 = nn.Sequential()

        self.conv1 = nn.Conv2d(3, 32, kernel_size=7, stride=2, padding=3)
        self.relu1 = nn.ReLU(inplace=True)

        self.in_planes = 32
        self.layer1 = self._make_layer(32,  stride=1)
        self.layer2 = self._make_layer(64, stride=2)
        self.layer3 = self._make_layer(96, stride=2)

        self.dropout = None
        if dropout > 0:
            self.dropout = nn.Dropout2d(p=dropout)
        
        self.conv2 = nn.Conv2d(96, output_dim, kernel_size=1)

        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.InstanceNorm2d, nn.GroupNorm)):
                if m.weight is not None:
                    nn.init.constant_(m.weight, 1)
                if m.bias is not None:
                    nn.init.constant_(m.bias, 0)

    def _make_layer(self, dim, stride=1):
        layer1 = BottleneckBlock(self.in_planes, dim, self.norm_fn, stride=stride)
        layer2 = BottleneckBlock(dim, dim, self.norm_fn, stride=1)
        layers = (layer1, layer2)
    
        self.in_planes = dim
        return nn.Sequential(*layers)


    def forward(self, x):

        # if input is list, combine batch dimension
        is_list = isinstance(x, tuple) or isinstance(x, list)
        if is_list:
            batch_dim = x[0].shape[0]
            x = torch.cat(x, dim=0)

        x = self.conv1(x)
        x = self.norm1(x)
        x = self.relu1(x)

        x = self.layer1(x)
        x = self.layer2(x)
        x = self.layer3(x)
        x = self.conv2(x)

        if self.training and self.dropout is not None:
            x = self.dropout(x)

        if is_list:
            x = torch.split(x, [batch_dim, batch_dim], dim=0)

        return x

class ResNetFPN(nn.Module):
    """
    ResNet18, output resolution is 1/8.
    Each block has 2 layers.
    """
    def __init__(self, args, input_dim=3, output_dim=256, ratio=1.0, norm_layer=nn.BatchNorm2d, init_weight=False):
        super().__init__()
        # Config
        block = BasicBlock
        block_dims = args.block_dims
        initial_dim = args.initial_dim
        self.init_weight = init_weight
        self.input_dim = input_dim
        # Class Variable
        self.in_planes = initial_dim
        for i in range(len(block_dims)):
            block_dims[i] = int(block_dims[i] * ratio)
        # Networks
        self.conv1 = nn.Conv2d(input_dim, initial_dim, kernel_size=7, stride=2, padding=3)
        self.bn1 = norm_layer(initial_dim)
        self.relu = nn.ReLU(inplace=True)
        if args.pretrain == 'resnet34':
            n_block = [3, 4, 6]
        elif args.pretrain == 'resnet18':
            n_block = [2, 2, 2]
        else:
            raise NotImplementedError       
        self.layer1 = self._make_layer(block, block_dims[0], stride=1, norm_layer=norm_layer, num=n_block[0])  # 1/2
        self.layer2 = self._make_layer(block, block_dims[1], stride=2, norm_layer=norm_layer, num=n_block[1])  # 1/4
        self.layer3 = self._make_layer(block, block_dims[2], stride=2, norm_layer=norm_layer, num=n_block[2])  # 1/8
        self.final_conv = conv1x1(block_dims[2], output_dim)
        self._init_weights(args)

    def _init_weights(self, args):

        for m in self.modules():
            if isinstance(m, nn.Conv2d):
                nn.init.kaiming_normal_(m.weight, mode='fan_out', nonlinearity='relu')
                if m.bias is not None:
                    nn.init.constant_(m.bias, 0)
            elif isinstance(m, (nn.BatchNorm2d, nn.InstanceNorm2d, nn.GroupNorm)):
                if m.weight is not None:
                    nn.init.constant_(m.weight, 1)
                if m.bias is not None:
                    nn.init.constant_(m.bias, 0)

        if self.init_weight:
            from torchvision.models import resnet18, ResNet18_Weights, resnet34, ResNet34_Weights
            if args.pretrain == 'resnet18':
                pretrained_dict = resnet18(weights=ResNet18_Weights.IMAGENET1K_V1).state_dict()
            else:
                pretrained_dict = resnet34(weights=ResNet34_Weights.IMAGENET1K_V1).state_dict()
            model_dict = self.state_dict()
            pretrained_dict = {k: v for k, v in pretrained_dict.items() if k in model_dict}
            if self.input_dim == 6:
                for k, v in pretrained_dict.items():
                    if k == 'conv1.weight':
                        pretrained_dict[k] = torch.cat((v, v), dim=1)
            model_dict.update(pretrained_dict)
            self.load_state_dict(model_dict, strict=False)
        

    def _make_layer(self, block, dim, stride=1, norm_layer=nn.BatchNorm2d, num=2):
        layers = []
        layers.append(block(self.in_planes, dim, stride=stride, norm_layer=norm_layer))
        for i in range(num - 1):
            layers.append(block(dim, dim, stride=1, norm_layer=norm_layer))
        self.in_planes = dim
        return nn.Sequential(*layers)

    def forward(self, x):
        # ResNet Backbone
        x = self.relu(self.bn1(self.conv1(x)))
        for i in range(len(self.layer1)):
            x = self.layer1[i](x)
        for i in range(len(self.layer2)):
            x = self.layer2[i](x)
        for i in range(len(self.layer3)):
            x = self.layer3[i](x)
        # Output
        output = self.final_conv(x)
        return output