"""
The functions in this module are used for comparing two LabColor objects
using various Delta E formulas.
"""

import numpy

from colormath import color_diff_matrix


def _get_lab_color1_vector(color):
    """
    Converts an LabColor into a NumPy vector.

    :param LabColor color:
    :rtype: numpy.ndarray
    """
    if not color.__class__.__name__ == 'LabColor':
        raise ValueError(
            "Delta E functions can only be used with two LabColor objects.")
    return numpy.array([color.lab_l, color.lab_a, color.lab_b])


def _get_lab_color2_matrix(color):
    """
    Converts an LabColor into a NumPy matrix.

    :param LabColor color:
    :rtype: numpy.ndarray
    """
    if not color.__class__.__name__ == 'LabColor':
        raise ValueError(
            "Delta E functions can only be used with two LabColor objects.")
    return numpy.array([(color.lab_l, color.lab_a, color.lab_b)])


# noinspection PyPep8Naming
def delta_e_cie1976(color1, color2):
    """
    Calculates the Delta E (CIE1976) of two colors.
    """
    color1_vector = _get_lab_color1_vector(color1)
    color2_matrix = _get_lab_color2_matrix(color2)
    delta_e = color_diff_matrix.delta_e_cie1976(color1_vector, color2_matrix)[0]
    return numpy.asscalar(delta_e)


# noinspection PyPep8Naming
def delta_e_cie1994(color1, color2, K_L=1, K_C=1, K_H=1, K_1=0.045, K_2=0.015):
    """
    Calculates the Delta E (CIE1994) of two colors.
    
    K_l:
      0.045 graphic arts
      0.048 textiles
    K_2:
      0.015 graphic arts
      0.014 textiles
    K_L:
      1 default
      2 textiles
    """
    color1_vector = _get_lab_color1_vector(color1)
    color2_matrix = _get_lab_color2_matrix(color2)
    delta_e = color_diff_matrix.delta_e_cie1994(
        color1_vector, color2_matrix, K_L=K_L, K_C=K_C, K_H=K_H, K_1=K_1, K_2=K_2)[0]
    return numpy.asscalar(delta_e)


# noinspection PyPep8Naming
def delta_e_cie2000(color1, color2, Kl=1, Kc=1, Kh=1):
    """
    Calculates the Delta E (CIE2000) of two colors.
    """
    color1_vector = _get_lab_color1_vector(color1)
    color2_matrix = _get_lab_color2_matrix(color2)
    delta_e = color_diff_matrix.delta_e_cie2000(
        color1_vector, color2_matrix, Kl=Kl, Kc=Kc, Kh=Kh)[0]
    return numpy.asscalar(delta_e)


# noinspection PyPep8Naming
def delta_e_cmc(color1, color2, pl=2, pc=1):
    """
    Calculates the Delta E (CMC) of two colors.
    
    CMC values
      Acceptability: pl=2, pc=1
      Perceptability: pl=1, pc=1
    """
    color1_vector = _get_lab_color1_vector(color1)
    color2_matrix = _get_lab_color2_matrix(color2)
    delta_e = color_diff_matrix.delta_e_cmc(
        color1_vector, color2_matrix, pl=pl, pc=pc)[0]
    return numpy.asscalar(delta_e)
