###############################################################################
#
# Adapted from https://github.com/lrjconan/GRAN/ which in turn is adapted from https://github.com/JiaxuanYou/graph-generation
#
###############################################################################
import pyemd
import numpy as np
import concurrent.futures
from functools import partial
from scipy.linalg import toeplitz


def emd(x, y, distance_scaling=1.0):
    support_size = max(len(x), len(y))
    d_mat = toeplitz(range(support_size)).astype(float)
    distance_mat = d_mat / distance_scaling

    # convert histogram values x and y to float, and make them equal len
    x = x.astype(float)
    y = y.astype(float)
    if len(x) < len(y):
        x = np.hstack((x, [0.0] * (support_size - len(x))))
    elif len(y) < len(x):
        y = np.hstack((y, [0.0] * (support_size - len(y))))

    emd = pyemd.emd(x, y, distance_mat)
    return emd



def l2(x, y):
    dist = np.linalg.norm(x - y, 2)
    return dist


def emd(x, y, sigma=1.0, distance_scaling=1.0):
    ''' EMD
        Args:
            x, y: 1D pmf of two distributions with the same support
            sigma: standard deviation
    '''
    support_size = max(len(x), len(y))
    d_mat = toeplitz(range(support_size)).astype(float)
    distance_mat = d_mat / distance_scaling

    # convert histogram values x and y to float, and make them equal len
    x = x.astype(float)
    y = y.astype(float)
    if len(x) < len(y):
        x = np.hstack((x, [0.0] * (support_size - len(x))))
    elif len(y) < len(x):
        y = np.hstack((y, [0.0] * (support_size - len(y))))

    return np.abs(pyemd.emd(x, y, distance_mat))


def gaussian_emd(x, y, sigma=1.0, distance_scaling=1.0):
    ''' Gaussian kernel with squared distance in exponential term replaced by EMD
        Args:
            x, y: 1D pmf of two distributions with the same support
            sigma: standard deviation
    '''
    support_size = max(len(x), len(y))
    d_mat = toeplitz(range(support_size)).astype(float)
    distance_mat = d_mat / distance_scaling

    # convert histogram values x and y to float, and make them equal len
    x = x.astype(float)
    y = y.astype(float)
    if len(x) < len(y):
        x = np.hstack((x, [0.0] * (support_size - len(x))))
    elif len(y) < len(x):
        y = np.hstack((y, [0.0] * (support_size - len(y))))

    emd = pyemd.emd(x, y, distance_mat)
    return np.exp(-emd * emd / (2 * sigma * sigma))


def gaussian(x, y, sigma=1.0):
    support_size = max(len(x), len(y))
    # convert histogram values x and y to float, and make them equal len
    x = x.astype(float)
    y = y.astype(float)
    if len(x) < len(y):
        x = np.hstack((x, [0.0] * (support_size - len(x))))
    elif len(y) < len(x):
        y = np.hstack((y, [0.0] * (support_size - len(y))))

    dist = np.linalg.norm(x - y, 2)
    return np.exp(-dist * dist / (2 * sigma * sigma))


def gaussian_tv(x, y, sigma=1.0):  
    support_size = max(len(x), len(y))
    # convert histogram values x and y to float, and make them equal len
    x = x.astype(float)
    y = y.astype(float)
    if len(x) < len(y):
        x = np.hstack((x, [0.0] * (support_size - len(x))))
    elif len(y) < len(x):
        y = np.hstack((y, [0.0] * (support_size - len(y))))

    dist = np.abs(x - y).sum() / 2.0
    return np.exp(-dist * dist / (2 * sigma * sigma))


def kernel_parallel_unpacked(x, samples2, kernel):
    d = 0
    for s2 in samples2:
        d += kernel(x, s2)
    return d


def kernel_parallel_worker(t):
    return kernel_parallel_unpacked(*t)


def disc(samples1, samples2, kernel, is_parallel=True, *args, **kwargs):
    ''' Discrepancy between 2 samples '''
    d = 0

    if not is_parallel:
        for s1 in samples1:
            for s2 in samples2:
                d += kernel(s1, s2, *args, **kwargs)
    else:
        with concurrent.futures.ThreadPoolExecutor() as executor:
            for dist in executor.map(kernel_parallel_worker, [
                    (s1, samples2, partial(kernel, *args, **kwargs)) for s1 in samples1
            ]):
                d += dist
    if len(samples1) * len(samples2) > 0:
        d /= len(samples1) * len(samples2)
    else:
        d = 1e+6
    return d


def compute_mmd(samples1, samples2, kernel, is_hist=True, *args, **kwargs):
    ''' MMD between two samples '''
    # normalize histograms into pmf
    if is_hist:
        samples1 = [s1 / (np.sum(s1) + 1e-6) for s1 in samples1]
        samples2 = [s2 / (np.sum(s2) + 1e-6) for s2 in samples2]
    return disc(samples1, samples1, kernel, *args, **kwargs) + disc(samples2, samples2, kernel, *args, **kwargs) - \
                2 * disc(samples1, samples2, kernel, *args, **kwargs)


def compute_emd(samples1, samples2, kernel, is_hist=True, *args, **kwargs):
    ''' EMD between average of two samples '''
    # normalize histograms into pmf
    if is_hist:
        samples1 = [np.mean(samples1)]
        samples2 = [np.mean(samples2)]
    return disc(samples1, samples2, kernel, *args,
                            **kwargs), [samples1[0], samples2[0]]