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

import numpy as np
import torch
import torch.nn as nn
from torch.autograd import Variable

def EntropyLoss(input_):
    mask = input_.ge(0.000001)
    mask_out = torch.masked_select(input_, mask)
    entropy = -(torch.sum(mask_out * torch.log(mask_out)))
    return entropy / float(input_.size(0))

def guassian_kernel(source, target, kernel_mul=2.0, kernel_num=5, fix_sigma=None):
    n_samples = int(source.size()[0])+int(target.size()[0])
    total = torch.cat([source, target], dim=0)
    total0 = total.unsqueeze(0).expand(int(total.size(0)), int(total.size(0)), int(total.size(1)))
    total1 = total.unsqueeze(1).expand(int(total.size(0)), int(total.size(0)), int(total.size(1)))
    L2_distance = ((total0-total1)**2).sum(2)
    if fix_sigma:
        bandwidth = fix_sigma
    else:
        bandwidth = torch.sum(L2_distance.data) / (n_samples**2-n_samples)
    bandwidth /= kernel_mul ** (kernel_num // 2)
    bandwidth_list = [bandwidth * (kernel_mul**i) for i in range(kernel_num)]
    kernel_val = [torch.exp(-L2_distance / bandwidth_temp) for bandwidth_temp in bandwidth_list]
    return sum(kernel_val)


def CON(source, target, kernel_mul=2.0, kernel_num=5, fix_sigma=None):
    batch_size_source = int(source.size()[0])
    batch_size_target = int(target.size()[0])
    kernels = guassian_kernel(source, target,
        kernel_mul=kernel_mul, kernel_num=kernel_num, fix_sigma=fix_sigma)
    loss = 0
    for i in range(batch_size_source):
        s1, s2 = i, (i+1)%batch_size_source
        t1, t2 = s1+batch_size_target, s2+batch_size_target
        loss += kernels[s1, s2] + kernels[t1, t2]
        loss -= kernels[s1, t2] + kernels[s2, t1]
    return loss / float(batch_size_source+batch_size_target)

def PROB(source, target,prob, kernel_mul=2.0, kernel_num=5, fix_sigma=None):
    batch_size_source = int(source.size()[0])
    batch_size_target = int(target.size()[0])
    kernels = guassian_kernel(source, target,
        kernel_mul=kernel_mul, kernel_num=kernel_num, fix_sigma=fix_sigma)
    loss = 0
    for i in range(batch_size_source):
        s1, s2 = i, (i+1)%batch_size_source
        t1, t2 = s1+batch_size_target, s2+batch_size_target
        loss += kernels[s1, s2] + kernels[t1, t2]
        loss -= kernels[s1, t2] + kernels[s2, t1]
    return loss / float(batch_size_source+prob)

def DRCN(source_list, target_list, kernel_muls=[2.0, 2.0], kernel_nums=[5, 1], fix_sigma_list=[None, 1.68]):
    batch_size = int(source_list[0].size()[0])
    layer_num = len(source_list)
    joint_kernels = None

    for i in range(layer_num):

        fix_sigma=fix_sigma_list[i]

        source = source_list[i]
        target = target_list[i]
        kernel_mul = kernel_muls[i]
        kernel_num = kernel_nums[i]
        kernels = guassian_kernel(source, target,
            kernel_mul=kernel_mul, kernel_num=kernel_num, fix_sigma=fix_sigma)
        if joint_kernels is not None:
            joint_kernels = joint_kernels * kernels
        else:
            joint_kernels = kernels
    
    loss = 0
    for i in range(batch_size):
        s1, s2 = i, (i+1)%batch_size
        t1, t2 = s1+batch_size, s2+batch_size
        loss += joint_kernels[s1, s2] + joint_kernels[t1, t2]
        loss -= joint_kernels[s1, t2] + joint_kernels[s2, t1]
    return loss / float(batch_size)


loss_dict = { "DRCN":DRCN,"CON":CON,"PROB":PROB}
