import torch
import numpy as np
import torch.nn as nn
from typing import List
from torch import Tensor
import torch.nn.functional as F
from torchvision.models.resnet import (
    BasicBlock,
    model_urls,
    load_state_dict_from_url,
    conv1x1,
    conv3x3,
)

device = torch.device("cuda")


class CustomResNet(nn.Module):
    def __init__(
        self,
        layers: List[int],
        block=BasicBlock,
        zero_init_residual=False,
        groups=1,
        num_classes=1000,
        width_per_group=64,
        replace_stride_with_dilation=None,
        norm_layer=None,
    ):

        super().__init__()

        if norm_layer is None:
            self._norm_layer = nn.BatchNorm2d

        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 "
                f"or a 3-element tuple, got {replace_stride_with_dilation}"
            )

        self.groups = groups
        self.base_width = width_per_group

        self.conv1 = nn.Conv2d(
            3, self.inplanes, kernel_size=7, stride=2, padding=3, bias=False
        )
        self.bn1 = self._norm_layer(self.inplanes)
        self.relu = nn.ReLU(inplace=True)
        self.maxpool = nn.MaxPool2d(kernel_size=3, stride=(2, 1), padding=1)
        self.layer1 = self._make_layer(block, 64, layers[0])
        self.layer2 = self._make_layer(
            block, 128, layers[1], stride=(2, 1), dilate=replace_stride_with_dilation[0]
        )
        self.layer3 = self._make_layer(
            block, 256, layers[2], stride=(2, 2), dilate=replace_stride_with_dilation[1]
        )
        self.layer4 = self._make_layer(
            block, 512, layers[3], stride=(2, 1), dilate=replace_stride_with_dilation[2]
        )
        self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
        self.fc = nn.Linear(512 * block.expansion, num_classes)

        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, BasicBlock):
                    nn.init.constant_(m.bn2.weight, 0)  # type: ignore[arg-type]

    def _make_layer(
        self,
        block,
        planes,
        blocks,
        stride=1,
        dilate=False,
    ) -> nn.Sequential:
        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: Tensor) -> Tensor:
        # See note [TorchScript super()]
        x = self.conv1(x)
        x = self.bn1(x)
        x = self.relu(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: Tensor) -> Tensor:
        return self._forward_impl(x)


def _resnet(layers: List[int], pretrained=True) -> CustomResNet:
    model = CustomResNet(layers)

    if pretrained:
        model.load_state_dict(load_state_dict_from_url(model_urls["resnet34"]))

    return model


def resnet34(*, pretrained=True) -> CustomResNet:
    """ResNet-34 from `Deep Residual Learning for Image Recognition <https://arxiv.org/pdf/1512.03385.pdf>`__.
    Args:
        weights (:class:`~torchvision.models.ResNet34_Weights`, optional): The
            pretrained weights to use. See
            :class:`~torchvision.models.ResNet34_Weights` below for
            more details, and possible values. By default, no pre-trained
            weights are used.
        progress (bool, optional): If True, displays a progress bar of the
            download to stderr. Default is True.
        **kwargs: parameters passed to the ``torchvision.models.resnet.ResNet``
            base class. Please refer to the `source code
            <https://github.com/pytorch/vision/blob/main/torchvision/models/resnet.py>`_
            for more details about this class.
    .. autoclass:: torchvision.models.ResNet34_Weights
        :members:
    """

    return _resnet([3, 4, 6, 3], pretrained=pretrained)


class ResNetFeatureExtractor(nn.Module):
    """
    Defines Base ResNet-34 feature extractor
    """

    def __init__(self, pretrained=True):
        """
        ---------
        Arguments
        ---------
        pretrained : bool (default=True)
            boolean to indicate whether to use a pretrained resnet model or not
        """
        super().__init__()
        self.output_channels = 512
        self.resnet34 = resnet34(pretrained=pretrained)

    def forward(self, x):
        block1 = self.resnet34.conv1(x)
        block1 = self.resnet34.bn1(block1)
        block1 = self.resnet34.relu(block1)  # [64, H/2, W/2]

        block2 = self.resnet34.maxpool(block1)
        block2 = self.resnet34.layer1(block2)  # [64, H/4, W/4]
        block3 = self.resnet34.layer2(block2)  # [128, H/8, W/8]
        block4 = self.resnet34.layer3(block3)  # [256, H/16, W/16]
        resnet_features = self.resnet34.layer4(block4)  # [512, H/32, W/32]

        # [B, 512, H/32, W/32]
        return resnet_features


#########################################
### STN - Spatial Transformer Network ###
#########################################
class TPS_SpatialTransformerNetwork(nn.Module):
    """Rectification Network of RARE, namely TPS based STN"""

    def __init__(self, num_fiducial_points, I_size, I_r_size, I_channel_num=1):
        """Based on RARE TPS
        input:
            batch_I: Batch Input Image [batch_size x I_channel_num x I_height x I_width]
            I_size : (height, width) of the input image I
            I_r_size : (height, width) of the rectified image I_r
            I_channel_num : the number of channels of the input image I
        output:
            batch_I_r: rectified image [batch_size x I_channel_num x I_r_height x I_r_width]
        """
        super(TPS_SpatialTransformerNetwork, self).__init__()
        self.num_fiducial_points = num_fiducial_points
        self.I_size = I_size
        self.I_r_size = I_r_size  # = (I_r_height, I_r_width)
        self.I_channel_num = I_channel_num
        self.LocalizationNetwork = LocalizationNetwork(
            self.num_fiducial_points, self.I_channel_num
        )
        self.GridGenerator = GridGenerator(self.num_fiducial_points, self.I_r_size)

    def forward(self, batch_I):
        batch_C_prime = self.LocalizationNetwork(batch_I)  # batch_size x K x 2
        build_P_prime = self.GridGenerator.build_P_prime(
            batch_C_prime
        )  # batch_size x n (= I_r_width x I_r_height) x 2
        build_P_prime_reshape = build_P_prime.reshape(
            [build_P_prime.size(0), self.I_r_size[0], self.I_r_size[1], 2]
        )

        if torch.__version__ > "1.2.0":
            batch_I_r = F.grid_sample(
                batch_I,
                build_P_prime_reshape,
                padding_mode="border",
                align_corners=True,
            )
        else:
            batch_I_r = F.grid_sample(
                batch_I, build_P_prime_reshape, padding_mode="border"
            )

        return batch_I_r


class LocalizationNetwork(nn.Module):
    """Localization Network of RARE, which predicts C' (K x 2) from I (I_width x I_height)"""

    def __init__(self, num_fiducial_points, I_channel_num):
        super(LocalizationNetwork, self).__init__()
        self.num_fiducial_points = num_fiducial_points
        self.I_channel_num = I_channel_num
        self.conv = nn.Sequential(
            nn.Conv2d(
                in_channels=self.I_channel_num,
                out_channels=64,
                kernel_size=3,
                stride=1,
                padding=1,
                bias=False,
            ),
            nn.BatchNorm2d(64),
            nn.ReLU(True),
            nn.MaxPool2d(2, 2),  # batch_size x 64 x I_height/2 x I_width/2
            nn.Conv2d(64, 128, 3, 1, 1, bias=False),
            nn.BatchNorm2d(128),
            nn.ReLU(True),
            nn.MaxPool2d(2, 2),  # batch_size x 128 x I_height/4 x I_width/4
            nn.Conv2d(128, 256, 3, 1, 1, bias=False),
            nn.BatchNorm2d(256),
            nn.ReLU(True),
            nn.MaxPool2d(2, 2),  # batch_size x 256 x I_height/8 x I_width/8
            nn.Conv2d(256, 512, 3, 1, 1, bias=False),
            nn.BatchNorm2d(512),
            nn.ReLU(True),
            nn.AdaptiveAvgPool2d(1),  # batch_size x 512
        )

        self.localization_fc1 = nn.Sequential(nn.Linear(512, 256), nn.ReLU(True))
        self.localization_fc2 = nn.Linear(256, self.num_fiducial_points * 2)

        # Init fc2 in LocalizationNetwork
        self.localization_fc2.weight.data.fill_(0)
        """ see RARE paper Fig. 6 (a) """
        ctrl_pts_x = np.linspace(-1.0, 1.0, int(num_fiducial_points / 2))
        ctrl_pts_y_top = np.linspace(0.0, -1.0, num=int(num_fiducial_points / 2))
        ctrl_pts_y_bottom = np.linspace(1.0, 0.0, num=int(num_fiducial_points / 2))
        ctrl_pts_top = np.stack([ctrl_pts_x, ctrl_pts_y_top], axis=1)
        ctrl_pts_bottom = np.stack([ctrl_pts_x, ctrl_pts_y_bottom], axis=1)
        initial_bias = np.concatenate([ctrl_pts_top, ctrl_pts_bottom], axis=0)
        self.localization_fc2.bias.data = (
            torch.from_numpy(initial_bias).float().view(-1)
        )

    def forward(self, batch_I):
        """
        input:     batch_I : Batch Input Image [batch_size x I_channel_num x I_height x I_width]
        output:    batch_C_prime : Predicted coordinates of fiducial points for input batch [batch_size x F x 2]
        """
        batch_size = batch_I.size(0)
        features = self.conv(batch_I).view(batch_size, -1)
        batch_C_prime = self.localization_fc2(self.localization_fc1(features)).view(
            batch_size, self.num_fiducial_points, 2
        )
        return batch_C_prime


class GridGenerator(nn.Module):
    """Grid Generator of RARE, which produces P_prime by multipling T with P"""

    def __init__(self, num_fiducial_points, I_r_size):
        """Generate P_hat and inv_delta_C for later"""
        super(GridGenerator, self).__init__()
        self.eps = 1e-6
        self.I_r_height, self.I_r_width = I_r_size
        self.num_fiducial_points = num_fiducial_points
        self.C = self._build_C(self.num_fiducial_points)  # F x 2
        self.P = self._build_P(self.I_r_width, self.I_r_height)
        ## for multi-gpu, you need register buffer
        self.register_buffer(
            "inv_delta_C",
            torch.tensor(
                self._build_inv_delta_C(self.num_fiducial_points, self.C)
            ).float(),
        )  # F+3 x F+3
        self.register_buffer(
            "P_hat",
            torch.tensor(
                self._build_P_hat(self.num_fiducial_points, self.C, self.P)
            ).float(),
        )  # n x F+3
        ## for fine-tuning with different image width, you may use below instead of self.register_buffer
        # self.inv_delta_C = torch.tensor(self._build_inv_delta_C(self.num_fiducial_points, self.C)).float().cuda()  # F+3 x F+3
        # self.P_hat = torch.tensor(self._build_P_hat(self.num_fiducial_points, self.C, self.P)).float().cuda()  # n x F+3

    def _build_C(self, F):
        """Return coordinates of fiducial points in I_r; C"""
        ctrl_pts_x = np.linspace(-1.0, 1.0, int(F / 2))
        ctrl_pts_y_top = -1 * np.ones(int(F / 2))
        ctrl_pts_y_bottom = np.ones(int(F / 2))
        ctrl_pts_top = np.stack([ctrl_pts_x, ctrl_pts_y_top], axis=1)
        ctrl_pts_bottom = np.stack([ctrl_pts_x, ctrl_pts_y_bottom], axis=1)
        C = np.concatenate([ctrl_pts_top, ctrl_pts_bottom], axis=0)
        return C  # F x 2

    def _build_inv_delta_C(self, F, C):
        """Return inv_delta_C which is needed to calculate T"""
        hat_C = np.zeros((F, F), dtype=float)  # F x F
        for i in range(0, F):
            for j in range(i, F):
                r = np.linalg.norm(C[i] - C[j])
                hat_C[i, j] = r
                hat_C[j, i] = r
        np.fill_diagonal(hat_C, 1)
        hat_C = (hat_C**2) * np.log(hat_C)
        # print(C.shape, hat_C.shape)
        delta_C = np.concatenate(  # F+3 x F+3
            [
                np.concatenate([np.ones((F, 1)), C, hat_C], axis=1),  # F x F+3
                np.concatenate([np.zeros((2, 3)), np.transpose(C)], axis=1),  # 2 x F+3
                np.concatenate([np.zeros((1, 3)), np.ones((1, F))], axis=1),  # 1 x F+3
            ],
            axis=0,
        )
        inv_delta_C = np.linalg.inv(delta_C)
        return inv_delta_C  # F+3 x F+3

    def _build_P(self, I_r_width, I_r_height):
        I_r_grid_x = (
            np.arange(-I_r_width, I_r_width, 2) + 1.0
        ) / I_r_width  # self.I_r_width
        I_r_grid_y = (
            np.arange(-I_r_height, I_r_height, 2) + 1.0
        ) / I_r_height  # self.I_r_height
        P = np.stack(  # self.I_r_width x self.I_r_height x 2
            np.meshgrid(I_r_grid_x, I_r_grid_y), axis=2
        )
        return P.reshape([-1, 2])  # n (= self.I_r_width x self.I_r_height) x 2

    def _build_P_hat(self, F, C, P):
        n = P.shape[0]  # n (= self.I_r_width x self.I_r_height)
        P_tile = np.tile(
            np.expand_dims(P, axis=1), (1, F, 1)
        )  # n x 2 -> n x 1 x 2 -> n x F x 2
        C_tile = np.expand_dims(C, axis=0)  # 1 x F x 2
        P_diff = P_tile - C_tile  # n x F x 2
        rbf_norm = np.linalg.norm(P_diff, ord=2, axis=2, keepdims=False)  # n x F
        rbf = np.multiply(np.square(rbf_norm), np.log(rbf_norm + self.eps))  # n x F
        P_hat = np.concatenate([np.ones((n, 1)), P, rbf], axis=1)
        return P_hat  # n x F+3

    def build_P_prime(self, batch_C_prime):
        """Generate Grid from batch_C_prime [batch_size x F x 2]"""
        batch_size = batch_C_prime.size(0)
        batch_inv_delta_C = self.inv_delta_C.repeat(batch_size, 1, 1)
        batch_P_hat = self.P_hat.repeat(batch_size, 1, 1)
        batch_C_prime_with_zeros = torch.cat(
            (batch_C_prime, torch.zeros(batch_size, 3, 2).float().to(device)), dim=1
        )  # batch_size x F+3 x 2
        batch_T = torch.bmm(
            batch_inv_delta_C, batch_C_prime_with_zeros
        )  # batch_size x F+3 x 2
        batch_P_prime = torch.bmm(batch_P_hat, batch_T)  # batch_size x n x 2
        return batch_P_prime  # batch_size x n x 2


"""
########################################
######## Pyramid Pooling Block #########
########################################
class PyramidPool(nn.Module):
    def __init__(self, pool_kernel_size, in_channels, out_channels):
        super().__init__()
        self.pool_kernel_size = pool_kernel_size
        self.avg_pool_block = nn.Sequential(
            nn.AvgPool2d((1, self.pool_kernel_size), stride=(1, self.pool_kernel_size)),
            nn.Conv2d(in_channels, out_channels, kernel_size=1, stride=1, padding="same", bias=False),
            nn.BatchNorm2d(out_channels),
            nn.ELU(inplace=True),
        )

        for m in self.modules():
            if isinstance(m, nn.Conv2d):
                nn.init.xavier_normal_(m.weight)
            elif isinstance(m, (nn.BatchNorm2d, nn.GroupNorm)):
                nn.init.constant_(m.weight, 1)
                nn.init.constant_(m.bias, 0)

    def forward(self, x):
        _, _, in_height, in_width = x.size()
        x = self.avg_pool_block(x)
        x = F.interpolate(x, size=(in_height, in_width), mode="bilinear")
        return x


class PyramidPoolBlock(nn.Module):
    def __init__(self, pyramid_pool_kernel_sizes=[4, 8, 16, 32], num_channels=512):
        super().__init__()
        pp_out_channels = 256
        self.pyramid_pool_layers = nn.ModuleList([PyramidPool(pool_kernel_size=k, in_channels=num_channels, out_channels=pp_out_channels) for k in pyramid_pool_kernel_sizes])
        self.final_layer = nn.Sequential(
            nn.Conv2d((num_channels + (pp_out_channels * len(self.pyramid_pool_layers))), num_channels, (1, 5), stride=1, padding="same"),
            nn.BatchNorm2d(num_channels),
            nn.ELU(inplace=True),
            nn.Dropout(p=0.1),
        )

    def forward(self, input):
        pp_outputs = []
        for pp_layer in self.pyramid_pool_layers:
            pp_output = pp_layer(input)
            pp_outputs.append(pp_output)
        pp_outputs.append(input)
        x = torch.cat(pp_outputs, dim=1)
        x = self.final_layer(x)
        return x
"""