"""
@author: Jun Wang 
@date: 20201019
@contact: jun21wangustc@gmail.com
"""
# based on:
# https://github.com/TreB1eN/InsightFace_Pytorch/blob/master/model.py

from torch.nn import Linear, Conv2d, BatchNorm1d, BatchNorm2d, PReLU, Sequential, Module
import torch

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 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, out_h, out_w):
        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=(out_h, out_w), 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)
