# -*- coding: utf-8 -*-

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# holder of all proprietary rights on this computer program.
# You can only use this computer program if you have closed
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# program from someone who is authorized to grant you that right.
# Any use of the computer program without a valid license is prohibited and
# liable to prosecution.
#
# Copyright©2019 Max-Planck-Gesellschaft zur Förderung
# der Wissenschaften e.V. (MPG). acting on behalf of its Max Planck Institute
# for Intelligent Systems. All rights reserved.
#
# Contact: ps-license@tuebingen.mpg.de

import functools

import torch
import torch.nn as nn
import torch.nn.functional as F
from torch.autograd import grad
from torch.nn import init


def gradient(inputs, outputs):
    d_points = torch.ones_like(outputs, requires_grad=False, device=outputs.device)
    points_grad = grad(
        outputs=outputs,
        inputs=inputs,
        grad_outputs=d_points,
        create_graph=True,
        retain_graph=True,
        only_inputs=True,
        allow_unused=True,
    )[0]
    return points_grad


# def conv3x3(in_planes, out_planes, strd=1, padding=1, bias=False):
#     "3x3 convolution with padding"
#     return nn.Conv2d(in_planes, out_planes, kernel_size=3,
#                      stride=strd, padding=padding, bias=bias)


def conv3x3(in_planes, out_planes, kernel=3, strd=1, dilation=1, padding=1, bias=False):
    "3x3 convolution with padding"
    return nn.Conv2d(
        in_planes,
        out_planes,
        kernel_size=kernel,
        dilation=dilation,
        stride=strd,
        padding=padding,
        bias=bias,
    )


def conv1x1(in_planes, out_planes, stride=1):
    """1x1 convolution"""
    return nn.Conv2d(in_planes, out_planes, kernel_size=1, stride=stride, bias=False)


def init_weights(net, init_type="normal", init_gain=0.02):
    """Initialize network weights.

    Parameters:
        net (network)   -- network to be initialized
        init_type (str) -- the name of an initialization method: normal | xavier | kaiming | orthogonal
        init_gain (float)    -- scaling factor for normal, xavier and orthogonal.

    We use 'normal' in the original pix2pix and CycleGAN paper. But xavier and kaiming might
    work better for some applications. Feel free to try yourself.
    """
    def init_func(m):    # define the initialization function
        classname = m.__class__.__name__
        if hasattr(m,
                   "weight") and (classname.find("Conv") != -1 or classname.find("Linear") != -1):
            if init_type == "normal":
                init.normal_(m.weight.data, 0.0, init_gain)
            elif init_type == "xavier":
                init.xavier_normal_(m.weight.data, gain=init_gain)
            elif init_type == "kaiming":
                init.kaiming_normal_(m.weight.data, a=0, mode="fan_in")
            elif init_type == "orthogonal":
                init.orthogonal_(m.weight.data, gain=init_gain)
            else:
                raise NotImplementedError(
                    "initialization method [%s] is not implemented" % init_type
                )
            if hasattr(m, "bias") and m.bias is not None:
                init.constant_(m.bias.data, 0.0)
        elif (
            classname.find("BatchNorm2d") != -1
        ):    # BatchNorm Layer's weight is not a matrix; only normal distribution applies.
            init.normal_(m.weight.data, 1.0, init_gain)
            init.constant_(m.bias.data, 0.0)

    # print('initialize network with %s' % init_type)
    net.apply(init_func)    # apply the initialization function <init_func>


def init_net(net, init_type="xavier", init_gain=0.02, gpu_ids=[]):
    """Initialize a network: 1. register CPU/GPU device (with multi-GPU support); 2. initialize the network weights
    Parameters:
        net (network)      -- the network to be initialized
        init_type (str)    -- the name of an initialization method: normal | xavier | kaiming | orthogonal
        gain (float)       -- scaling factor for normal, xavier and orthogonal.
        gpu_ids (int list) -- which GPUs the network runs on: e.g., 0,1,2

    Return an initialized network.
    """
    if len(gpu_ids) > 0:
        assert torch.cuda.is_available()
        net = torch.nn.DataParallel(net)    # multi-GPUs
    init_weights(net, init_type, init_gain=init_gain)
    return net


def imageSpaceRotation(xy, rot):
    """
    args:
        xy: (B, 2, N) input
        rot: (B, 2) x,y axis rotation angles

    rotation center will be always image center (other rotation center can be represented by additional z translation)
    """
    disp = rot.unsqueeze(2).sin().expand_as(xy)
    return (disp * xy).sum(dim=1)


def cal_gradient_penalty(
    netD, real_data, fake_data, device, type="mixed", constant=1.0, lambda_gp=10.0
):
    """Calculate the gradient penalty loss, used in WGAN-GP paper https://arxiv.org/abs/1704.00028

    Arguments:
        netD (network)              -- discriminator network
        real_data (tensor array)    -- real images
        fake_data (tensor array)    -- generated images from the generator
        device (str)                -- GPU / CPU: from torch.device('cuda:{}'.format(self.gpu_ids[0])) if self.gpu_ids else torch.device('cpu')
        type (str)                  -- if we mix real and fake data or not [real | fake | mixed].
        constant (float)            -- the constant used in formula ( | |gradient||_2 - constant)^2
        lambda_gp (float)           -- weight for this loss

    Returns the gradient penalty loss
    """
    if lambda_gp > 0.0:
        # either use real images, fake images, or a linear interpolation of two.
        if type == "real":
            interpolatesv = real_data
        elif type == "fake":
            interpolatesv = fake_data
        elif type == "mixed":
            alpha = torch.rand(real_data.shape[0], 1)
            alpha = (
                alpha.expand(real_data.shape[0],
                             real_data.nelement() //
                             real_data.shape[0]).contiguous().view(*real_data.shape)
            )
            alpha = alpha.to(device)
            interpolatesv = alpha * real_data + ((1 - alpha) * fake_data)
        else:
            raise NotImplementedError("{} not implemented".format(type))
        interpolatesv.requires_grad_(True)
        disc_interpolates = netD(interpolatesv)
        gradients = torch.autograd.grad(
            outputs=disc_interpolates,
            inputs=interpolatesv,
            grad_outputs=torch.ones(disc_interpolates.size()).to(device),
            create_graph=True,
            retain_graph=True,
            only_inputs=True,
        )
        gradients = gradients[0].view(real_data.size(0), -1)    # flat the data
        gradient_penalty = (((gradients + 1e-16).norm(2, dim=1) - constant)**
                            2).mean() * lambda_gp    # added eps
        return gradient_penalty, gradients
    else:
        return 0.0, None


def get_norm_layer(norm_type="instance"):
    """Return a normalization layer
    Parameters:
        norm_type (str) -- the name of the normalization layer: batch | instance | none
    For BatchNorm, we use learnable affine parameters and track running statistics (mean/stddev).
    For InstanceNorm, we do not use learnable affine parameters. We do not track running statistics.
    """
    if norm_type == "batch":
        norm_layer = functools.partial(nn.BatchNorm2d, affine=True, track_running_stats=True)
    elif norm_type == "instance":
        norm_layer = functools.partial(nn.InstanceNorm2d, affine=False, track_running_stats=False)
    elif norm_type == "group":
        norm_layer = functools.partial(nn.GroupNorm, 32)
    elif norm_type == "none":
        norm_layer = None
    else:
        raise NotImplementedError("normalization layer [%s] is not found" % norm_type)
    return norm_layer


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


class ConvBlock(nn.Module):
    def __init__(self, in_planes, out_planes, opt):
        super(ConvBlock, self).__init__()
        [k, s, d, p] = opt.conv3x3
        self.conv1 = conv3x3(in_planes, int(out_planes / 2), k, s, d, p)
        self.conv2 = conv3x3(int(out_planes / 2), int(out_planes / 4), k, s, d, p)
        self.conv3 = conv3x3(int(out_planes / 4), int(out_planes / 4), k, s, d, p)

        if opt.norm == "batch":
            self.bn1 = nn.BatchNorm2d(in_planes)
            self.bn2 = nn.BatchNorm2d(int(out_planes / 2))
            self.bn3 = nn.BatchNorm2d(int(out_planes / 4))
            self.bn4 = nn.BatchNorm2d(in_planes)
        elif opt.norm == "group":
            self.bn1 = nn.GroupNorm(32, in_planes)
            self.bn2 = nn.GroupNorm(32, int(out_planes / 2))
            self.bn3 = nn.GroupNorm(32, int(out_planes / 4))
            self.bn4 = nn.GroupNorm(32, in_planes)

        if in_planes != out_planes:
            self.downsample = nn.Sequential(
                self.bn4,
                nn.ReLU(True),
                nn.Conv2d(in_planes, out_planes, kernel_size=1, stride=1, bias=False),
            )
        else:
            self.downsample = None

    def forward(self, x):
        residual = x

        out1 = self.bn1(x)
        out1 = F.relu(out1, True)
        out1 = self.conv1(out1)

        out2 = self.bn2(out1)
        out2 = F.relu(out2, True)
        out2 = self.conv2(out2)

        out3 = self.bn3(out2)
        out3 = F.relu(out3, True)
        out3 = self.conv3(out3)

        out3 = torch.cat((out1, out2, out3), 1)

        if self.downsample is not None:
            residual = self.downsample(residual)

        out3 += residual

        return out3