# ------------------------------------------------------------------------------
# Copyright (c) Microsoft
# Licensed under the MIT License.
# Written by Bin Xiao (Bin.Xiao@microsoft.com)
# ------------------------------------------------------------------------------

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import math

import numpy as np
import cv2

from utils.transforms import transform_preds


def get_max_preds(batch_heatmaps):
    '''
    get predictions from score maps
    heatmaps: numpy.ndarray([batch_size, num_joints, height, width])
    '''
    assert isinstance(batch_heatmaps, np.ndarray), \
        'batch_heatmaps should be numpy.ndarray'
    assert batch_heatmaps.ndim == 4, 'batch_images should be 4-ndim'

    batch_size = batch_heatmaps.shape[0]
    num_joints = batch_heatmaps.shape[1]
    width = batch_heatmaps.shape[3]
    heatmaps_reshaped = batch_heatmaps.reshape((batch_size, num_joints, -1))
    idx = np.argmax(heatmaps_reshaped, 2) ## B x 17
    maxvals = np.amax(heatmaps_reshaped, 2) ## B x 17

    maxvals = maxvals.reshape((batch_size, num_joints, 1)) ## B x 17 x 1
    idx = idx.reshape((batch_size, num_joints, 1)) ## B x 17 x 1

    preds = np.tile(idx, (1, 1, 2)).astype(np.float32) ## B x 17 x 2, like repeat in pytorch

    preds[:, :, 0] = (preds[:, :, 0]) % width
    preds[:, :, 1] = np.floor((preds[:, :, 1]) / width)

    pred_mask = np.tile(np.greater(maxvals, 0.0), (1, 1, 2))
    pred_mask = pred_mask.astype(np.float32)

    preds *= pred_mask
    return preds, maxvals


# def get_final_preds(config, batch_heatmaps, center, scale, use_dark=True):
def get_final_preds(config, batch_heatmaps, center, scale, use_dark=False):

    if use_dark is True:
        print('using dark')
        return get_final_preds_dark(config, batch_heatmaps, center, scale)


    coords, maxvals = get_max_preds(batch_heatmaps)

    heatmap_height = batch_heatmaps.shape[2]
    heatmap_width = batch_heatmaps.shape[3]

    # post-processing
    if config.TEST.POST_PROCESS:
        for n in range(coords.shape[0]):
            for p in range(coords.shape[1]):
                hm = batch_heatmaps[n][p]
                px = int(math.floor(coords[n][p][0] + 0.5))
                py = int(math.floor(coords[n][p][1] + 0.5))
                if 1 < px < heatmap_width-1 and 1 < py < heatmap_height-1:
                    diff = np.array(
                        [
                            hm[py][px+1] - hm[py][px-1],
                            hm[py+1][px]-hm[py-1][px]
                        ]
                    )
                    coords[n][p] += np.sign(diff) * .25

    preds = coords.copy()

    # Transform back
    for i in range(coords.shape[0]):
        preds[i] = transform_preds(
            coords[i], center[i], scale[i], [heatmap_width, heatmap_height]
        )

    return preds, maxvals

# --------------------------------------------------
def taylor(hm, coord):
    heatmap_height = hm.shape[0]
    heatmap_width = hm.shape[1]
    px = int(coord[0])
    py = int(coord[1])
    if 1 < px < heatmap_width-2 and 1 < py < heatmap_height-2:
        dx  = 0.5 * (hm[py][px+1] - hm[py][px-1])
        dy  = 0.5 * (hm[py+1][px] - hm[py-1][px])
        dxx = 0.25 * (hm[py][px+2] - 2 * hm[py][px] + hm[py][px-2])
        dxy = 0.25 * (hm[py+1][px+1] - hm[py-1][px+1] - hm[py+1][px-1] \
            + hm[py-1][px-1])
        dyy = 0.25 * (hm[py+2*1][px] - 2 * hm[py][px] + hm[py-2*1][px])
        derivative = np.matrix([[dx],[dy]])
        hessian = np.matrix([[dxx,dxy],[dxy,dyy]])
        if dxx * dyy - dxy ** 2 != 0:
            hessianinv = hessian.I
            offset = -hessianinv * derivative
            offset = np.squeeze(np.array(offset.T), axis=0)
            coord += offset
    return coord


### https://github.com/ilovepose/DarkPose/blob/master/lib/core/inference.py
def gaussian_blur(hm, kernel=11):
    border = (kernel - 1) // 2
    batch_size = hm.shape[0]
    num_joints = hm.shape[1]
    height = hm.shape[2]
    width = hm.shape[3]
    for i in range(batch_size):
        for j in range(num_joints):
            origin_max = np.max(hm[i,j])
            dr = np.zeros((height + 2 * border, width + 2 * border))
            dr[border: -border, border: -border] = hm[i,j].copy()
            dr = cv2.GaussianBlur(dr, (kernel, kernel), 0)
            hm[i,j] = dr[border: -border, border: -border].copy()
            hm[i,j] *= origin_max / np.max(hm[i,j])
    return hm


# ----------------------------------------
def get_final_preds_dark(config, hm, center, scale):
    coords, maxvals = get_max_preds(hm)
    heatmap_height = hm.shape[2]
    heatmap_width = hm.shape[3]

    # post-processing
    hm = gaussian_blur(hm, 11)
    hm = np.maximum(hm, 1e-10)
    hm = np.log(hm)
    for n in range(coords.shape[0]):
        for p in range(coords.shape[1]):
            coords[n,p] = taylor(hm[n][p], coords[n][p])

    preds = coords.copy()

    # Transform back
    for i in range(coords.shape[0]):
        preds[i] = transform_preds(
            coords[i], center[i], scale[i], [heatmap_width, heatmap_height]
        )

    return preds, maxvals

