#!/usr/bin/env python3
# -*- coding: utf-8 -*-


def edge_intersection(x1: int, y1: int, x2: int, y2: int, x3: int, y3: int, x4: int, y4: int) -> list:
    """Intersection point of two line segments in 2 dimensions

    params:
    ----------
    x1, y1, x2, y2 -> coordinates of line a, p1 ->(x1, y1), p2 ->(x2, y2), 

    x3, y3, x4, y4 -> coordinates of line b, p3 ->(x3, y3), p4 ->(x4, y4)

    Return:
    ----------
    list
        A list contains x and y coordinates of the intersection point,
        but return an empty list if no intersection point.

    """
    # None of lines' length could be 0.
    if ((x1 == x2 and y1 == y2) or (x3 == x4 and y3 == y4)):
        return []

    # The denominators for the equations for ua and ub are the same.
    den = ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))

    # Lines are parallel when denominator equals to 0,
    # No intersection point
    if den == 0:
        return []

    # Avoid the divide overflow
    ua = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / (den + 1e-16)
    ub = ((x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)) / (den + 1e-16)

    # if ua and ub lie between 0 and 1.
    # Whichever one lies within that range then the corresponding line segment contains the intersection point.
    # If both lie within the range of 0 to 1 then the intersection point is within both line segments.
    if (ua < 0 or ua > 1 or ub < 0 or ub > 1):
        return []

    # Return a list with the x and y coordinates of the intersection
    x = x1 + ua * (x2 - x1)
    y = y1 + ua * (y2 - y1)
    return [x, y]


if __name__ == "__main__":
    line_a = [494, 117, 1051, 123]
    line_b = [1011, 133, 1011, 74]
    intersection_point = edge_intersection(*line_a, *line_b)
    print(intersection_point)