import torch
import torch.nn as nn
#from torch.legacy import nn as nnl
import torch.utils.model_zoo as model_zoo

__all__ = ['vggm']

pretrained_settings = {
    'vggm': {
        'imagenet': {
            'url': 'http://data.lip6.fr/cadene/pretrainedmodels/vggm-786f2434.pth',
            'input_space': 'BGR',
            'input_size': [3, 221, 221],
            'input_range': [0, 255],
            'mean': [123.68, 116.779, 103.939],
            'std': [1, 1, 1],
            'num_classes': 1000
        }
    }
}

class SpatialCrossMapLRN(nn.Module):
    def __init__(self, local_size=1, alpha=1.0, beta=0.75, k=1, ACROSS_CHANNELS=True):
        super(SpatialCrossMapLRN, self).__init__()
        self.ACROSS_CHANNELS = ACROSS_CHANNELS
        if ACROSS_CHANNELS:
            self.average=nn.AvgPool3d(kernel_size=(local_size, 1, 1),
                    stride=1,
                    padding=(int((local_size-1.0)/2), 0, 0))
        else:
            self.average=nn.AvgPool2d(kernel_size=local_size,
                    stride=1,
                    padding=int((local_size-1.0)/2))
        self.alpha = alpha
        self.beta = beta
        self.k = k

    def forward(self, x):
        if self.ACROSS_CHANNELS:
            div = x.pow(2).unsqueeze(1)
            div = self.average(div).squeeze(1)
            div = div.mul(self.alpha).add(self.k).pow(self.beta)
        else:
            div = x.pow(2)
            div = self.average(div)
            div = div.mul(self.alpha).add(self.k).pow(self.beta)
        x = x.div(div)
        return x

class LambdaBase(nn.Sequential):
    def __init__(self, fn, *args):
        super(LambdaBase, self).__init__(*args)
        self.lambda_func = fn

    def forward_prepare(self, input):
        output = []
        for module in self._modules.values():
            output.append(module(input))
        return output if output else input

class Lambda(LambdaBase):
    def forward(self, input):
        return self.lambda_func(self.forward_prepare(input))

class VGGM(nn.Module):

    def __init__(self, num_classes=1000):
        super(VGGM, self).__init__()
        self.num_classes = num_classes
        self.features = nn.Sequential(
            nn.Conv2d(3,96,(7, 7),(2, 2)),
            nn.ReLU(),
            SpatialCrossMapLRN(5, 0.0005, 0.75, 2),
            nn.MaxPool2d((3, 3),(2, 2),(0, 0),ceil_mode=True),
            nn.Conv2d(96,256,(5, 5),(2, 2),(1, 1)),
            nn.ReLU(),
            SpatialCrossMapLRN(5, 0.0005, 0.75, 2),
            nn.MaxPool2d((3, 3),(2, 2),(0, 0),ceil_mode=True),
            nn.Conv2d(256,512,(3, 3),(1, 1),(1, 1)),
            nn.ReLU(),
            nn.Conv2d(512,512,(3, 3),(1, 1),(1, 1)),
            nn.ReLU(),
            nn.Conv2d(512,512,(3, 3),(1, 1),(1, 1)),
            nn.ReLU(),
            nn.MaxPool2d((3, 3),(2, 2),(0, 0),ceil_mode=True)
        )
        self.classif = nn.Sequential(
            nn.Linear(18432,4096),
            nn.ReLU(),
            nn.Dropout(0.5),
            nn.Linear(4096,4096),
            nn.ReLU(),
            nn.Dropout(0.5),
            nn.Linear(4096,num_classes)
        )

    def forward(self, x):
        x = self.features(x)
        x = x.view(x.size(0), -1)
        x = self.classif(x)
        return x

def vggm(num_classes=1000, pretrained='imagenet'):
    if pretrained:
        settings = pretrained_settings['vggm'][pretrained]
        assert num_classes == settings['num_classes'], \
            "num_classes should be {}, but is {}".format(settings['num_classes'], num_classes)

        model = VGGM(num_classes=1000)
        model.load_state_dict(model_zoo.load_url(settings['url']))

        model.input_space = settings['input_space']
        model.input_size = settings['input_size']
        model.input_range = settings['input_range']
        model.mean = settings['mean']
        model.std = settings['std']
    else:
        model = VGGM(num_classes=num_classes)
    return model