"""
Ported to pytorch thanks to [tstandley](https://github.com/tstandley/Xception-PyTorch)

@author: tstandley
Adapted by cadene

Creates an Xception Model as defined in:

Francois Chollet
Xception: Deep Learning with Depthwise Separable Convolutions
https://arxiv.org/pdf/1610.02357.pdf

This weights ported from the Keras implementation. Achieves the following performance on the validation set:

Loss:0.9173 Prec@1:78.892 Prec@5:94.292

REMEMBER to set your image size to 3x299x299 for both test and validation

normalize = transforms.Normalize(mean=[0.5, 0.5, 0.5],
                                  std=[0.5, 0.5, 0.5])

The resize parameter of the validation transform should be 333, and make sure to center crop at 299x299
"""
from __future__ import print_function, division, absolute_import
import math
import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.utils.model_zoo as model_zoo
from torch.nn import init

__all__ = ['xception']

pretrained_config = {
    'xception': {
        'imagenet': {
            'url': 'http://data.lip6.fr/cadene/pretrainedmodels/xception-43020ad28.pth',
            'input_space': 'RGB',
            'input_size': [3, 299, 299],
            'input_range': [0, 1],
            'mean': [0.5, 0.5, 0.5],
            'std': [0.5, 0.5, 0.5],
            'num_classes': 1000,
            'scale': 0.8975
        # The resize parameter of the validation transform should be 333, and make sure to center crop at 299x299
        }
    }
}


class SeparableConv2d(nn.Module):
    def __init__(self, in_channels, out_channels, kernel_size=1, stride=1, padding=0, dilation=1, bias=False):
        super(SeparableConv2d, self).__init__()

        self.conv1 = nn.Conv2d(
            in_channels, in_channels, kernel_size, stride, padding, dilation, groups=in_channels, bias=bias)
        self.pointwise = nn.Conv2d(in_channels, out_channels, 1, 1, 0, 1, 1, bias=bias)

    def forward(self, x):
        x = self.conv1(x)
        x = self.pointwise(x)
        return x


class Block(nn.Module):
    def __init__(self, in_filters, out_filters, reps, strides=1, start_with_relu=True, grow_first=True):
        super(Block, self).__init__()

        if out_filters != in_filters or strides != 1:
            self.skip = nn.Conv2d(in_filters, out_filters, 1, stride=strides, bias=False)
            self.skipbn = nn.BatchNorm2d(out_filters)
        else:
            self.skip = None

        self.relu = nn.ReLU(inplace=True)
        rep = []

        filters = in_filters
        if grow_first:
            rep.append(self.relu)
            rep.append(SeparableConv2d(in_filters, out_filters, 3, stride=1, padding=1, bias=False))
            rep.append(nn.BatchNorm2d(out_filters))
            filters = out_filters

        for i in range(reps - 1):
            rep.append(self.relu)
            rep.append(SeparableConv2d(filters, filters, 3, stride=1, padding=1, bias=False))
            rep.append(nn.BatchNorm2d(filters))

        if not grow_first:
            rep.append(self.relu)
            rep.append(SeparableConv2d(in_filters, out_filters, 3, stride=1, padding=1, bias=False))
            rep.append(nn.BatchNorm2d(out_filters))

        if not start_with_relu:
            rep = rep[1:]
        else:
            rep[0] = nn.ReLU(inplace=False)

        if strides != 1:
            rep.append(nn.MaxPool2d(3, strides, 1))
        self.rep = nn.Sequential(*rep)

    def forward(self, inp):
        x = self.rep(inp)

        if self.skip is not None:
            skip = self.skip(inp)
            skip = self.skipbn(skip)
        else:
            skip = inp

        x += skip
        return x


class Xception(nn.Module):
    """
    Xception optimized for the ImageNet dataset, as specified in
    https://arxiv.org/pdf/1610.02357.pdf
    """

    def __init__(self, num_classes=1000):
        """ Constructor
        Args:
            num_classes: number of classes
        """
        super(Xception, self).__init__()
        self.num_classes = num_classes

        self.conv1 = nn.Conv2d(3, 32, 3, 2, 0, bias=False)
        self.bn1 = nn.BatchNorm2d(32)
        self.relu = nn.ReLU(inplace=True)

        self.conv2 = nn.Conv2d(32, 64, 3, bias=False)
        self.bn2 = nn.BatchNorm2d(64)
        # do relu here

        self.block1 = Block(64, 128, 2, 2, start_with_relu=False, grow_first=True)
        self.block2 = Block(128, 256, 2, 2, start_with_relu=True, grow_first=True)
        self.block3 = Block(256, 728, 2, 2, start_with_relu=True, grow_first=True)

        self.block4 = Block(728, 728, 3, 1, start_with_relu=True, grow_first=True)
        self.block5 = Block(728, 728, 3, 1, start_with_relu=True, grow_first=True)
        self.block6 = Block(728, 728, 3, 1, start_with_relu=True, grow_first=True)
        self.block7 = Block(728, 728, 3, 1, start_with_relu=True, grow_first=True)

        self.block8 = Block(728, 728, 3, 1, start_with_relu=True, grow_first=True)
        self.block9 = Block(728, 728, 3, 1, start_with_relu=True, grow_first=True)
        self.block10 = Block(728, 728, 3, 1, start_with_relu=True, grow_first=True)
        self.block11 = Block(728, 728, 3, 1, start_with_relu=True, grow_first=True)

        self.block12 = Block(728, 1024, 2, 2, start_with_relu=True, grow_first=False)

        self.conv3 = SeparableConv2d(1024, 1536, 3, 1, 1)
        self.bn3 = nn.BatchNorm2d(1536)

        # do relu here
        self.conv4 = SeparableConv2d(1536, 2048, 3, 1, 1)
        self.bn4 = nn.BatchNorm2d(2048)

        self.fc = nn.Linear(2048, num_classes)

        # #------- init weights --------
        # for m in self.modules():
        #     if isinstance(m, nn.Conv2d):
        #         n = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
        #         m.weight.data.normal_(0, math.sqrt(2. / n))
        #     elif isinstance(m, nn.BatchNorm2d):
        #         m.weight.data.fill_(1)
        #         m.bias.data.zero_()
        # #-----------------------------

    def forward_features(self, input):
        x = self.conv1(input)
        x = self.bn1(x)
        x = self.relu(x)

        x = self.conv2(x)
        x = self.bn2(x)
        x = self.relu(x)

        x = self.block1(x)
        x = self.block2(x)
        x = self.block3(x)
        x = self.block4(x)
        x = self.block5(x)
        x = self.block6(x)
        x = self.block7(x)
        x = self.block8(x)
        x = self.block9(x)
        x = self.block10(x)
        x = self.block11(x)
        x = self.block12(x)

        x = self.conv3(x)
        x = self.bn3(x)
        x = self.relu(x)

        x = self.conv4(x)
        x = self.bn4(x)
        return x

    def logits(self, features):
        x = self.relu(features)

        x = F.adaptive_avg_pool2d(x, (1, 1))
        x = x.view(x.size(0), -1)
        x = self.last_linear(x)
        return x

    def forward(self, input):
        x = self.forward_features(input)
        x = self.logits(x)
        return x


def xception(num_classes=1000, pretrained='imagenet'):
    model = Xception(num_classes=num_classes)
    if pretrained:
        config = pretrained_config['xception'][pretrained]
        assert num_classes == config['num_classes'], \
            "num_classes should be {}, but is {}".format(config['num_classes'], num_classes)

        model = Xception(num_classes=num_classes)
        model.load_state_dict(model_zoo.load_url(config['url']))

        model.input_space = config['input_space']
        model.input_size = config['input_size']
        model.input_range = config['input_range']
        model.mean = config['mean']
        model.std = config['std']

    # TODO: ugly
    model.last_linear = model.fc
    del model.fc
    return model