from torch.nn import (
    Linear,
    Conv2d,
    BatchNorm1d,
    BatchNorm2d,
    PReLU,
    ReLU,
    Sigmoid,
    Dropout,
    MaxPool2d,
    AdaptiveAvgPool2d,
    Sequential,
    Module,
    Parameter,
)
import torch
from collections import namedtuple
import math

##################################  Original Arcface Model #############################################################


class Flatten(Module):
    def forward(self, input):
        return input.view(input.size(0), -1)


def l2_norm(input, axis=1):
    norm = torch.norm(input, 2, axis, True)
    output = torch.div(input, norm)
    return output


class SEModule(Module):
    def __init__(self, channels, reduction):
        super(SEModule, self).__init__()
        self.avg_pool = AdaptiveAvgPool2d(1)
        self.fc1 = Conv2d(
            channels, channels // reduction, kernel_size=1, padding=0, bias=False
        )
        self.relu = ReLU(inplace=True)
        self.fc2 = Conv2d(
            channels // reduction, channels, kernel_size=1, padding=0, bias=False
        )
        self.sigmoid = Sigmoid()

    def forward(self, x):
        module_input = x
        x = self.avg_pool(x)
        x = self.fc1(x)
        x = self.relu(x)
        x = self.fc2(x)
        x = self.sigmoid(x)
        return module_input * x


class bottleneck_IR(Module):
    def __init__(self, in_channel, depth, stride):
        super(bottleneck_IR, self).__init__()
        if in_channel == depth:
            self.shortcut_layer = MaxPool2d(1, stride)
        else:
            self.shortcut_layer = Sequential(
                Conv2d(in_channel, depth, (1, 1), stride, bias=False),
                BatchNorm2d(depth),
            )
        self.res_layer = Sequential(
            BatchNorm2d(in_channel),
            Conv2d(in_channel, depth, (3, 3), (1, 1), 1, bias=False),
            PReLU(depth),
            Conv2d(depth, depth, (3, 3), stride, 1, bias=False),
            BatchNorm2d(depth),
        )

    def forward(self, x):
        shortcut = self.shortcut_layer(x)
        res = self.res_layer(x)
        return res + shortcut


class bottleneck_IR_SE(Module):
    def __init__(self, in_channel, depth, stride):
        super(bottleneck_IR_SE, self).__init__()
        if in_channel == depth:
            self.shortcut_layer = MaxPool2d(1, stride)
        else:
            self.shortcut_layer = Sequential(
                Conv2d(in_channel, depth, (1, 1), stride, bias=False),
                BatchNorm2d(depth),
            )
        self.res_layer = Sequential(
            BatchNorm2d(in_channel),
            Conv2d(in_channel, depth, (3, 3), (1, 1), 1, bias=False),
            PReLU(depth),
            Conv2d(depth, depth, (3, 3), stride, 1, bias=False),
            BatchNorm2d(depth),
            SEModule(depth, 16),
        )

    def forward(self, x):
        shortcut = self.shortcut_layer(x)
        res = self.res_layer(x)
        return res + shortcut


class Bottleneck(namedtuple("Block", ["in_channel", "depth", "stride"])):
    """A named tuple describing a ResNet block."""


def get_block(in_channel, depth, num_units, stride=2):
    return [Bottleneck(in_channel, depth, stride)] + [
        Bottleneck(depth, depth, 1) for i in range(num_units - 1)
    ]


def get_blocks(num_layers):
    if num_layers == 50:
        blocks = [
            get_block(in_channel=64, depth=64, num_units=3),
            get_block(in_channel=64, depth=128, num_units=4),
            get_block(in_channel=128, depth=256, num_units=14),
            get_block(in_channel=256, depth=512, num_units=3),
        ]
    elif num_layers == 100:
        blocks = [
            get_block(in_channel=64, depth=64, num_units=3),
            get_block(in_channel=64, depth=128, num_units=13),
            get_block(in_channel=128, depth=256, num_units=30),
            get_block(in_channel=256, depth=512, num_units=3),
        ]
    elif num_layers == 152:
        blocks = [
            get_block(in_channel=64, depth=64, num_units=3),
            get_block(in_channel=64, depth=128, num_units=8),
            get_block(in_channel=128, depth=256, num_units=36),
            get_block(in_channel=256, depth=512, num_units=3),
        ]
    return blocks


class Backbone(Module):
    def __init__(self, num_layers, drop_ratio, mode="ir"):
        super(Backbone, self).__init__()
        assert num_layers in [50, 100, 152], "num_layers should be 50,100, or 152"
        assert mode in ["ir", "ir_se"], "mode should be ir or ir_se"
        blocks = get_blocks(num_layers)
        if mode == "ir":
            unit_module = bottleneck_IR
        elif mode == "ir_se":
            unit_module = bottleneck_IR_SE
        self.input_layer = Sequential(
            Conv2d(3, 64, (3, 3), 1, 1, bias=False), BatchNorm2d(64), PReLU(64)
        )
        self.output_layer = Sequential(
            BatchNorm2d(512),
            Dropout(drop_ratio),
            Flatten(),
            Linear(512 * 7 * 7, 512),
            BatchNorm1d(512),
        )
        modules = []
        for block in blocks:
            for bottleneck in block:
                modules.append(
                    unit_module(
                        bottleneck.in_channel, bottleneck.depth, bottleneck.stride
                    )
                )
        self.body = Sequential(*modules)

    def forward(self, x):
        x = self.input_layer(x)
        x = self.body(x)
        x = self.output_layer(x)
        return l2_norm(x)


##################################  MobileFaceNet #############################################################


class Conv_block(Module):
    def __init__(
        self, in_c, out_c, kernel=(1, 1), stride=(1, 1), padding=(0, 0), groups=1
    ):
        super(Conv_block, self).__init__()
        self.conv = Conv2d(
            in_c,
            out_channels=out_c,
            kernel_size=kernel,
            groups=groups,
            stride=stride,
            padding=padding,
            bias=False,
        )
        self.bn = BatchNorm2d(out_c)
        self.prelu = PReLU(out_c)

    def forward(self, x):
        x = self.conv(x)
        x = self.bn(x)
        x = self.prelu(x)
        return x


class Linear_block(Module):
    def __init__(
        self, in_c, out_c, kernel=(1, 1), stride=(1, 1), padding=(0, 0), groups=1
    ):
        super(Linear_block, self).__init__()
        self.conv = Conv2d(
            in_c,
            out_channels=out_c,
            kernel_size=kernel,
            groups=groups,
            stride=stride,
            padding=padding,
            bias=False,
        )
        self.bn = BatchNorm2d(out_c)

    def forward(self, x):
        x = self.conv(x)
        x = self.bn(x)
        return x


class Depth_Wise(Module):
    def __init__(
        self,
        in_c,
        out_c,
        residual=False,
        kernel=(3, 3),
        stride=(2, 2),
        padding=(1, 1),
        groups=1,
    ):
        super(Depth_Wise, self).__init__()
        self.conv = Conv_block(
            in_c, out_c=groups, kernel=(1, 1), padding=(0, 0), stride=(1, 1)
        )
        self.conv_dw = Conv_block(
            groups, groups, groups=groups, kernel=kernel, padding=padding, stride=stride
        )
        self.project = Linear_block(
            groups, out_c, kernel=(1, 1), padding=(0, 0), stride=(1, 1)
        )
        self.residual = residual

    def forward(self, x):
        if self.residual:
            short_cut = x
        x = self.conv(x)
        x = self.conv_dw(x)
        x = self.project(x)
        if self.residual:
            output = short_cut + x
        else:
            output = x
        return output


class Residual(Module):
    def __init__(
        self, c, num_block, groups, kernel=(3, 3), stride=(1, 1), padding=(1, 1)
    ):
        super(Residual, self).__init__()
        modules = []
        for _ in range(num_block):
            modules.append(
                Depth_Wise(
                    c,
                    c,
                    residual=True,
                    kernel=kernel,
                    padding=padding,
                    stride=stride,
                    groups=groups,
                )
            )
        self.model = Sequential(*modules)

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


class MobileFaceNet(Module):
    def __init__(self, embedding_size):
        super(MobileFaceNet, self).__init__()
        self.conv1 = Conv_block(3, 64, kernel=(3, 3), stride=(2, 2), padding=(1, 1))
        self.conv2_dw = Conv_block(
            64, 64, kernel=(3, 3), stride=(1, 1), padding=(1, 1), groups=64
        )
        self.conv_23 = Depth_Wise(
            64, 64, kernel=(3, 3), stride=(2, 2), padding=(1, 1), groups=128
        )
        self.conv_3 = Residual(
            64, num_block=4, groups=128, kernel=(3, 3), stride=(1, 1), padding=(1, 1)
        )
        self.conv_34 = Depth_Wise(
            64, 128, kernel=(3, 3), stride=(2, 2), padding=(1, 1), groups=256
        )
        self.conv_4 = Residual(
            128, num_block=6, groups=256, kernel=(3, 3), stride=(1, 1), padding=(1, 1)
        )
        self.conv_45 = Depth_Wise(
            128, 128, kernel=(3, 3), stride=(2, 2), padding=(1, 1), groups=512
        )
        self.conv_5 = Residual(
            128, num_block=2, groups=256, kernel=(3, 3), stride=(1, 1), padding=(1, 1)
        )
        self.conv_6_sep = Conv_block(
            128, 512, kernel=(1, 1), stride=(1, 1), padding=(0, 0)
        )
        self.conv_6_dw = Linear_block(
            512, 512, groups=512, kernel=(7, 7), stride=(1, 1), padding=(0, 0)
        )
        self.conv_6_flatten = Flatten()
        self.linear = Linear(512, embedding_size, bias=False)
        self.bn = BatchNorm1d(embedding_size)

    def forward(self, x):
        out = self.conv1(x)

        out = self.conv2_dw(out)

        out = self.conv_23(out)

        out = self.conv_3(out)

        out = self.conv_34(out)

        out = self.conv_4(out)

        out = self.conv_45(out)

        out = self.conv_5(out)

        out = self.conv_6_sep(out)

        out = self.conv_6_dw(out)

        out = self.conv_6_flatten(out)

        out = self.linear(out)

        out = self.bn(out)
        return l2_norm(out)


##################################  Arcface head #############################################################


class Arcface(Module):
    # implementation of additive margin softmax loss in https://arxiv.org/abs/1801.05599
    def __init__(self, embedding_size=512, classnum=51332, s=64.0, m=0.5):
        super(Arcface, self).__init__()
        self.classnum = classnum
        self.kernel = Parameter(torch.Tensor(embedding_size, classnum))
        # initial kernel
        self.kernel.data.uniform_(-1, 1).renorm_(2, 1, 1e-5).mul_(1e5)
        self.m = m  # the margin value, default is 0.5
        self.s = s  # scalar value default is 64, see normface https://arxiv.org/abs/1704.06369
        self.cos_m = math.cos(m)
        self.sin_m = math.sin(m)
        self.mm = self.sin_m * m  # issue 1
        self.threshold = math.cos(math.pi - m)

    def forward(self, embbedings, label):
        # weights norm
        nB = len(embbedings)
        kernel_norm = l2_norm(self.kernel, axis=0)
        # cos(theta+m)
        cos_theta = torch.mm(embbedings, kernel_norm)
        #         output = torch.mm(embbedings,kernel_norm)
        cos_theta = cos_theta.clamp(-1, 1)  # for numerical stability
        cos_theta_2 = torch.pow(cos_theta, 2)
        sin_theta_2 = 1 - cos_theta_2
        sin_theta = torch.sqrt(sin_theta_2)
        cos_theta_m = cos_theta * self.cos_m - sin_theta * self.sin_m
        # this condition controls the theta+m should in range [0, pi]
        #      0<=theta+m<=pi
        #     -m<=theta<=pi-m
        cond_v = cos_theta - self.threshold
        cond_mask = cond_v <= 0
        keep_val = cos_theta - self.mm  # when theta not in [0,pi], use cosface instead
        cos_theta_m[cond_mask] = keep_val[cond_mask]
        output = (
            cos_theta * 1.0
        )  # a little bit hacky way to prevent in_place operation on cos_theta
        idx_ = torch.arange(0, nB, dtype=torch.long)
        output[idx_, label] = cos_theta_m[idx_, label]
        output *= (
            self.s
        )  # scale up in order to make softmax work, first introduced in normface
        return output


##################################  Cosface head #############################################################


class Am_softmax(Module):
    # implementation of additive margin softmax loss in https://arxiv.org/abs/1801.05599
    def __init__(self, embedding_size=512, classnum=51332):
        super(Am_softmax, self).__init__()
        self.classnum = classnum
        self.kernel = Parameter(torch.Tensor(embedding_size, classnum))
        # initial kernel
        self.kernel.data.uniform_(-1, 1).renorm_(2, 1, 1e-5).mul_(1e5)
        self.m = 0.35  # additive margin recommended by the paper
        self.s = 30.0  # see normface https://arxiv.org/abs/1704.06369

    def forward(self, embbedings, label):
        kernel_norm = l2_norm(self.kernel, axis=0)
        cos_theta = torch.mm(embbedings, kernel_norm)
        cos_theta = cos_theta.clamp(-1, 1)  # for numerical stability
        phi = cos_theta - self.m
        label = label.view(-1, 1)  # size=(B,1)
        index = cos_theta.data * 0.0  # size=(B,Classnum)
        index.scatter_(1, label.data.view(-1, 1), 1)
        index = index.byte()
        output = cos_theta * 1.0
        output[index] = phi[index]  # only change the correct predicted output
        output *= (
            self.s
        )  # scale up in order to make softmax work, first introduced in normface
        return output