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


# Support: ['IR_50', 'IR_101', 'IR_152', 'IR_SE_50', 'IR_SE_101', 'IR_SE_152']
class FaceNet(nn.Module):
    def __init__(self, num_classes=1000, vis=False):
        super(FaceNet, self).__init__()
        self.vis = vis
        self.feature = IR_50_pre((112, 112))
        self.feat_dim = 512
        self.num_classes = num_classes
        self.fc_layer = nn.Sequential(
            nn.Linear(self.feat_dim, self.num_classes), nn.Softmax(dim=1)
        )

    def forward(self, x):
        if self.vis:
            out = []
            for module in self.feature.input_layer.children():
                x = module(x)
                out.append(torch.flatten(x, 1))
            for module in self.feature.body.children():
                x = module(x)
                out.append(torch.flatten(x, 1))
            for module in self.feature.output_layer.children():
                x = module(x)
                out.append(torch.flatten(x, 1))

            x = x.contiguous().view(x.size(0), -1)
            for module in self.fc_layer:
                x = module(x)
                out.append(torch.flatten(x, 1))
            return out

        feat = self.feature(x)
        feat = feat.view(feat.size(0), -1)
        out = self.fc_layer(feat)
        __, iden = torch.max(out, dim=1)
        # iden = iden.view(-1, 1)
        return feat, out, iden


class FaceNet152(nn.Module):
    def __init__(self, num_classes=1000, vis=False):
        super(FaceNet152, self).__init__()
        self.vis = vis
        self.feature = IR_152((112, 112))
        self.feat_dim = 512 * 7 * 7
        self.num_classes = num_classes
        self.fc_layer = nn.Sequential(
            nn.Linear(self.feat_dim, self.num_classes), nn.Softmax(dim=1)
        )

    def forward(self, x):
        if self.vis:
            out = []
            for module in self.feature.input_layer.children():
                x = module(x)
                out.append(torch.flatten(x, 1))
            for module in self.feature.body.children():
                x = module(x)
                out.append(torch.flatten(x, 1))
            for module in self.feature.output_layer.children():
                x = module(x)
                out.append(torch.flatten(x, 1))

            x = x.contiguous().view(x.size(0), -1)
            for module in self.fc_layer:
                x = module(x)
                out.append(torch.flatten(x, 1))
            return out

        feat = self.feature(x)
        feat = feat.view(feat.size(0), -1)
        out = self.fc_layer(feat)
        __, iden = torch.max(out, dim=1)
        # iden = iden.view(-1, 1)
        return feat, out, iden


class FaceNet64(nn.Module):
    def __init__(self, num_classes=1000):
        super(FaceNet64, self).__init__()
        self.feature = IR_50((64, 64))
        self.feat_dim = 512
        self.num_classes = num_classes
        self.output_layer = nn.Sequential(
            nn.BatchNorm2d(512),
            nn.Dropout(),
            Flatten(),
            nn.Linear(512 * 4 * 4, 512),
            nn.BatchNorm1d(512),
        )

        self.fc_layer = nn.Sequential(
            nn.Linear(self.feat_dim, self.num_classes), nn.Softmax(dim=1)
        )

    def forward(self, x):
        feat = self.feature(x)
        feat = self.output_layer(feat)
        feat = feat.view(feat.size(0), -1)
        out = self.fc_layer(feat)
        __, iden = torch.max(out, dim=1)
        iden = iden.view(-1, 1)
        return feat, out, iden


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
        )

        nn.init.xavier_uniform_(self.fc1.weight.data)

        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, input_size, num_layers, mode='ir'):
        super(Backbone, self).__init__()
        assert input_size[0] in [
            64,
            112,
            224,
        ], "input_size should be [112, 112] or [224, 224]"
        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)
        )

        if input_size[0] == 64:
            self.output_layer = Sequential(
                BatchNorm2d(512),
                Dropout(),
                Flatten(),
                Linear(512 * 4 * 4, 512),
                BatchNorm1d(512),
            )
        if input_size[0] == 112:
            self.output_layer = Sequential(
                BatchNorm2d(512),
                Dropout(),
                Flatten(),
                Linear(512 * 7 * 7, 512),
                BatchNorm1d(512),
            )
        else:
            self.output_layer = Sequential(
                BatchNorm2d(512),
                Dropout(),
                Flatten(),
                Linear(512 * 14 * 14, 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)

        self._initialize_weights()

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

        return x

    def _initialize_weights(self):
        for m in self.modules():
            if isinstance(m, nn.Conv2d):
                nn.init.xavier_uniform_(m.weight.data)
                if m.bias is not None:
                    m.bias.data.zero_()
            elif isinstance(m, nn.BatchNorm2d):
                m.weight.data.fill_(1)
                m.bias.data.zero_()
            elif isinstance(m, nn.BatchNorm1d):
                m.weight.data.fill_(1)
                m.bias.data.zero_()
            elif isinstance(m, nn.Linear):
                nn.init.xavier_uniform_(m.weight.data)
                if m.bias is not None:
                    m.bias.data.zero_()


class Backbone2(Module):
    def __init__(self, input_size, num_layers, mode='ir'):
        super(Backbone2, self).__init__()
        assert input_size[0] in [
            64,
            112,
            224,
        ], "input_size should be [112, 112] or [224, 224]"
        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)
        )

        if input_size[0] == 64:
            self.output_layer = Sequential(
                BatchNorm2d(512),
                Dropout(),
                Flatten(),
                Linear(512 * 4 * 4, 512),
                BatchNorm1d(512),
            )
        if input_size[0] == 112:
            self.output_layer = Sequential(
                BatchNorm2d(512),
                Dropout(),
                Flatten(),
                Linear(512 * 7 * 7, 512),
                BatchNorm1d(512),
            )
        else:
            self.output_layer = Sequential(
                BatchNorm2d(512),
                Dropout(),
                Flatten(),
                Linear(512 * 14 * 14, 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)

        self._initialize_weights()

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

        return x

    def _initialize_weights(self):
        for m in self.modules():
            if isinstance(m, nn.Conv2d):
                nn.init.xavier_uniform_(m.weight.data)
                if m.bias is not None:
                    m.bias.data.zero_()
            elif isinstance(m, nn.BatchNorm2d):
                m.weight.data.fill_(1)
                m.bias.data.zero_()
            elif isinstance(m, nn.BatchNorm1d):
                m.weight.data.fill_(1)
                m.bias.data.zero_()
            elif isinstance(m, nn.Linear):
                nn.init.xavier_uniform_(m.weight.data)
                if m.bias is not None:
                    m.bias.data.zero_()


def IR_50(input_size):
    """Constructs a ir-50 model."""
    model = Backbone(input_size, 50, 'ir')

    return model


def IR_50_pre(input_size):
    """Constructs a ir-50 model."""
    model = Backbone2(input_size, 50, 'ir')

    return model


def IR_101(input_size):
    """Constructs a ir-101 model."""
    model = Backbone(input_size, 100, 'ir')

    return model


def IR_152(input_size):
    """Constructs a ir-152 model."""
    model = Backbone(input_size, 152, 'ir')

    return model


def IR_SE_50(input_size):
    """Constructs a ir_se-50 model."""
    model = Backbone(input_size, 50, 'ir_se')

    return model


def IR_SE_101(input_size):
    """Constructs a ir_se-101 model."""
    model = Backbone(input_size, 100, 'ir_se')

    return model


def IR_SE_152(input_size):
    """Constructs a ir_se-152 model."""
    model = Backbone(input_size, 152, 'ir_se')

    return model
