"""
Author(s):
Abdelrahman Abdelhamed (a.abdelhamed@samsung.com)

Copyright (c) 2022 Samsung Electronics Co., Ltd.

Licensed under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) License, (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at https://creativecommons.org/licenses/by-nc/4.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and limitations under the License.
For conditions of distribution and use, see the accompanying LICENSE.md file.


Utility function for working with correlated color temperatures.
"""

import numpy as np
import sys


def dot(x, y):
    return np.sum(x * y, axis=-1)


def norm(x):
    return np.sqrt(dot(x, x))


def raw_rgb_to_cct(raw_rgb, xyz2cam1, xyz2cam2):
    """Convert raw-RGB triplet to corresponding correlated color temperature (CCT)"""
    # pxyz = [.5, 1, .5]
    pxyz = [.3, .3, .3]
    # cct = xyz2cct(pxyz)
    loss = 1e10
    k = 1
    cct = 6500  # default
    while loss > 1e-4:
        cct = xyz2cct(pxyz)
        xyz = raw_rgb_to_xyz(raw_rgb, cct, xyz2cam1, xyz2cam2)
        loss = norm(xyz - pxyz)
        # loss = ang_err(xyz, pxyz)
        pxyz = xyz
        k = k + 1
    return cct


def raw_rgb_to_xyz(raw_rgb, temp, xyz2cam1, xyz2cam2):
    # TODO: what if temperature > 6500?
    # RawRgbToXyz Convert raw-RGB triplet to corresponding XYZ
    cct1 = 6500  # D65, DNG code = 21
    cct2 = 2500  # A, DNG code = 17
    cct1inv = 1 / cct1
    cct2inv = 1 / cct2
    tempinv = 1 / temp
    g = (tempinv - cct2inv) / (cct1inv - cct2inv)
    h = 1 - g
    # if g < 0:
    #     g = 0
    # if h < 0:
    #     h = 0
    # if h > 1:
    #     h = 1
    xyz2cam = g * xyz2cam1 + h * xyz2cam2
    xyz = np.matmul(np.linalg.inv(xyz2cam), np.transpose(raw_rgb))

    # xyz = xyz / xyz(2)
    # xyz_ = [xyz(1) / sum(xyz), xyz(2) / sum(xyz), 1]
    # xyz = xyz_

    return xyz


# /* LERP(a,b,c) = linear interpolation macro, is 'a' when c == 0.0 and 'b' when c == 1.0 */
def lerp(a, b, c):
    return (b - a) * c + a


def xyz2cct(xyz):

    rt = [  # /* reciprocal temperature (K) */
        sys.float_info.min, 10.0e-6, 20.0e-6, 30.0e-6, 40.0e-6, 50.0e-6,
        60.0e-6, 70.0e-6, 80.0e-6, 90.0e-6, 100.0e-6, 125.0e-6,
        150.0e-6, 175.0e-6, 200.0e-6, 225.0e-6, 250.0e-6, 275.0e-6,
        300.0e-6, 325.0e-6, 350.0e-6, 375.0e-6, 400.0e-6, 425.0e-6,
        450.0e-6, 475.0e-6, 500.0e-6, 525.0e-6, 550.0e-6, 575.0e-6,
        600.0e-6
    ]

    uvt = [
        [0.18006, 0.26352, -0.24341],
        [0.18066, 0.26589, -0.25479],
        [0.18133, 0.26846, -0.26876],
        [0.18208, 0.27119, -0.28539],
        [0.18293, 0.27407, -0.30470],
        [0.18388, 0.27709, -0.32675],
        [0.18494, 0.28021, -0.35156],
        [0.18611, 0.28342, -0.37915],
        [0.18740, 0.28668, -0.40955],
        [0.18880, 0.28997, -0.44278],
        [0.19032, 0.29326, -0.47888],
        [0.19462, 0.30141, -0.58204],
        [0.19962, 0.30921, -0.70471],
        [0.20525, 0.31647, -0.84901],
        [0.21142, 0.32312, -1.0182],
        [0.21807, 0.32909, -1.2168],
        [0.22511, 0.33439, -1.4512],
        [0.23247, 0.33904, -1.7298],
        [0.24010, 0.34308, -2.0637],
        [0.24792, 0.34655, -2.4681],
        # /* Note: 0.24792 is a corrected value for the error found in W&S as 0.24702 */
        [0.25591, 0.34951, -2.9641],
        [0.26400, 0.35200, -3.5814],
        [0.27218, 0.35407, -4.3633],
        [0.28039, 0.35577, -5.3762],
        [0.28863, 0.35714, -6.7262],
        [0.29685, 0.35823, -8.5955],
        [0.30505, 0.35907, -11.324],
        [0.31320, 0.35968, -15.628],
        [0.32129, 0.36011, -23.325],
        [0.32931, 0.36038, -40.770],
        [0.33724, 0.36051, -116.45]
    ]

    # us = 0
    # vs = 0
    # p = 0
    di = 0
    # dm = 0
    i = 0
    if (xyz[0] < 1.0e-20) and (xyz[1] < 1.0e-20) and (xyz[2] < 1.0e-20):
        return -1  # /* protect against possible divide-by-zero failure */
    us = (4.0 * xyz[0]) / (xyz[0] + 15.0 * xyz[1] + 3.0 * xyz[2])
    vs = (6.0 * xyz[1]) / (xyz[0] + 15.0 * xyz[1] + 3.0 * xyz[2])
    dm = 0.0
    for i in range(31):
        di = (vs - uvt[i][1]) - uvt[i][2] * (us - uvt[i][0])
        if (i > 0) and (((di < 0.0) and (dm >= 0.0)) or ((di >= 0.0) and (dm < 0.0))):
            break  # /* found lines bounding (us, vs) : i-1 and i */
        dm = di

    if i == 31:
        # /* bad XYZ input, color temp would be less than minimum of 1666.7 degrees, or too far towards blue */
        return -1
    di = di / np.sqrt(1.0 + uvt[i][2] * uvt[i][2])
    dm = dm / np.sqrt(1.0 + uvt[i - 1][2] * uvt[i - 1][2])
    p = dm / (dm - di)  # /* p = interpolation parameter, 0.0 : i-1, 1.0 : i */
    p = 1.0 / (lerp(rt[i - 1], rt[i], p))
    cct = p
    return cct  # /* success */


def interpolate_cst(xyz2cam1, xyz2cam2, temp):
    # RawRgbToXyz Convert raw-RGB triplet to corresponding XYZ
    cct1 = 6500  # D65, DNG code = 21
    cct2 = 2500  # A, DNG code = 17
    cct1inv = 1 / cct1
    cct2inv = 1 / cct2
    tempinv = 1 / temp
    g = (tempinv - cct2inv) / (cct1inv - cct2inv)
    h = 1 - g
    if g < 0:
        g = 0
    if h < 0:
        h = 0
    if h > 1:
        h = 1
    xyz2cam = g * xyz2cam1 + h * xyz2cam2
    return xyz2cam