# coding: utf-8
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"""This module contains utils class for axes management.
"""

__authors__ = ["H. Payno", ]
__license__ = "MIT"
__date__ = "18/05/2020"


import numpy


def lines_intersection(line1_pt1, line1_pt2, line2_pt1, line2_pt2):
    """
    line segment intersection using vectors (Computer Graphics by F.S. Hill)

    :param tuple line1_pt1:
    :param tuple line1_pt2:
    :param tuple line2_pt1:
    :param tuple line2_pt2:
    :return: Union[None,numpy.array]
    """
    dir_line1 = line1_pt2[0] - line1_pt1[0], line1_pt2[1] - line1_pt1[1]
    dir_line2 = line2_pt2[0] - line2_pt1[0], line2_pt2[1] - line2_pt1[1]
    dp = line1_pt1 - line2_pt1

    def perp(a):
        b = numpy.empty_like(a)
        b[0] = -a[1]
        b[1] = a[0]
        return b

    dap = perp(dir_line1)
    denom = numpy.dot(dap, dir_line2)
    num = numpy.dot(dap, dp)
    if denom == 0:
        return None
    return (
        (num / denom.astype(float)) * dir_line2[0] + line2_pt1[0],
        (num / denom.astype(float)) * dir_line2[1] + line2_pt1[1])


def segments_intersection(seg1_start_pt, seg1_end_pt, seg2_start_pt,
                          seg2_end_pt):
    """
    Compute intersection between two segments

    :param seg1_start_pt:
    :param seg1_end_pt:
    :param seg2_start_pt:
    :param seg2_end_pt:
    :return: numpy.array if an intersection exists, else None
    :rtype: Union[None,numpy.array]
    """
    intersection = lines_intersection(line1_pt1=seg1_start_pt,
                                      line1_pt2=seg1_end_pt,
                                      line2_pt1=seg2_start_pt,
                                      line2_pt2=seg2_end_pt)
    if intersection is not None:
        max_x_seg1 = max(seg1_start_pt[0], seg1_end_pt[0])
        max_x_seg2 = max(seg2_start_pt[0], seg2_end_pt[0])
        max_y_seg1 = max(seg1_start_pt[1], seg1_end_pt[1])
        max_y_seg2 = max(seg2_start_pt[1], seg2_end_pt[1])

        min_x_seg1 = min(seg1_start_pt[0], seg1_end_pt[0])
        min_x_seg2 = min(seg2_start_pt[0], seg2_end_pt[0])
        min_y_seg1 = min(seg1_start_pt[1], seg1_end_pt[1])
        min_y_seg2 = min(seg2_start_pt[1], seg2_end_pt[1])

        min_tmp_x = max(min_x_seg1, min_x_seg2)
        max_tmp_x = min(max_x_seg1, max_x_seg2)
        min_tmp_y = max(min_y_seg1, min_y_seg2)
        max_tmp_y = min(max_y_seg1, max_y_seg2)
        if (min_tmp_x <= intersection[0] <= max_tmp_x and
                min_tmp_y <= intersection[1] <= max_tmp_y):
            return intersection
        else:
            return None