"""Vector utility."""
from typing import Optional

import numpy as np

__author__ = "Sergey Vartanov"
__email__ = "me@enzet.ru"

from shapely.geometry import LineString


def compute_angle(vector: np.ndarray) -> float:
    """
    For the given vector compute an angle between it and (1, 0) vector.

    The result is in [0, 2π].
    """
    if vector[0] == 0.0:
        if vector[1] > 0.0:
            return np.pi / 2.0
        return np.pi + np.pi / 2.0
    if vector[0] < 0.0:
        return np.arctan(vector[1] / vector[0]) + np.pi
    if vector[1] < 0.0:
        return np.arctan(vector[1] / vector[0]) + 2.0 * np.pi
    return np.arctan(vector[1] / vector[0])


def turn_by_angle(vector: np.ndarray, angle: float) -> np.ndarray:
    """Turn vector by an angle."""
    return np.array(
        (
            vector[0] * np.cos(angle) - vector[1] * np.sin(angle),
            vector[0] * np.sin(angle) + vector[1] * np.cos(angle),
        )
    )


def norm(vector: np.ndarray) -> np.ndarray:
    """Compute vector with the same direction and length 1."""
    return vector / np.linalg.norm(vector)


class Polyline:
    """List of connected points."""

    def __init__(self, points: list[np.ndarray]) -> None:
        self.points: list[np.ndarray] = points

    def get_path(self, parallel_offset: float = 0.0) -> str:
        """Construct SVG path commands."""
        points: list[np.ndarray]

        if np.allclose(parallel_offset, 0.0):
            points = self.points
        else:
            try:
                points = (
                    LineString(self.points)
                    .parallel_offset(parallel_offset)
                    .coords
                    if parallel_offset
                    else self.points
                )
            except (ValueError, NotImplementedError):
                points = self.points

        return (
            "M "
            + " L ".join(f"{point[0]},{point[1]}" for point in points)
            + (" Z" if np.allclose(points[0], points[-1]) else "")
        )

    def shorten(self, index: int, length: float) -> None:
        """Make shorten part specified with index."""
        index_2: int = 1 if index == 0 else -2
        diff: np.ndarray = self.points[index_2] - self.points[index]
        self.points[index] = (
            self.points[index] + diff / np.linalg.norm(diff) * length
        )


class Line:
    """Infinity line: Ax + By + C = 0."""

    def __init__(self, start: np.ndarray, end: np.ndarray) -> None:
        # if start.near(end):
        #     util.error("cannot create line by one point")
        self.a: float = start[1] - end[1]
        self.b: float = end[0] - start[0]
        self.c: float = start[0] * end[1] - end[0] * start[1]

    def parallel_shift(self, shift: np.ndarray) -> None:
        """
        Shift current vector according with shift.

        :param shift: shift vector
        """
        self.c -= self.a * shift[0] + self.b * shift[1]

    def is_parallel(self, other: "Line") -> bool:
        """If lines are parallel or equal."""
        return np.allclose(other.a * self.b - self.a * other.b, 0.0)

    def get_intersection_point(self, other: "Line") -> np.ndarray:
        """Get point of intersection current line with other."""
        if other.a * self.b - self.a * other.b == 0.0:
            return np.array((0.0, 0.0))

        x: float = -(self.b * other.c - other.b * self.c) / (
            other.a * self.b - self.a * other.b
        )
        y: float = -(self.a * other.c - other.a * self.c) / (
            other.b * self.a - self.b * other.a
        )
        return np.array((x, y))

    def __repr__(self) -> str:
        return f"{self.a} * x + {self.b} * y + {self.c} == 0"


class Segment:
    """Closed line segment."""

    def __init__(self, point_1: np.ndarray, point_2: np.ndarray) -> None:
        self.point_1: np.ndarray = point_1
        self.point_2: np.ndarray = point_2

        self.y = ((self.point_1 + self.point_2) / 2.0)[1]

        difference: np.ndarray = point_2 - point_1
        vector: np.ndarray = difference / np.linalg.norm(difference)
        if vector[0] > 0:
            vector = -vector
        self.angle: float = (
            np.arccos(np.dot(vector, np.array((0.0, 1.0)))) / np.pi
        )

    def __repr__(self) -> str:
        """Get simple string representation."""
        return f"{self.point_1} -- {self.point_2}"

    def __lt__(self, other: "Segment") -> bool:
        """Compare central y coordinates of segments."""
        return self.y < other.y

    def intersection(self, other: "Segment") -> Optional[list[float]]:
        """
        Find and intersection point between two segments.

        :return: `None` if segments don't intersect, [x, y] coordinates of
            the resulting point otherwise.
        """
        divisor: float = (self.point_1[0] - self.point_2[0]) * (
            other.point_1[1] - other.point_2[1]
        ) - (self.point_1[1] - self.point_2[1]) * (
            other.point_1[0] - other.point_2[0]
        )
        if not divisor:
            return None

        t: float = (
            (self.point_1[0] - other.point_1[0])
            * (other.point_1[1] - other.point_2[1])
            - (self.point_1[1] - other.point_1[1])
            * (other.point_1[0] - other.point_2[0])
        ) / divisor

        u: float = (
            (self.point_1[0] - other.point_1[0])
            * (self.point_1[1] - self.point_2[1])
            - (self.point_1[1] - other.point_1[1])
            * (self.point_1[0] - self.point_2[0])
        ) / divisor

        if 0 <= t <= 1 and 0 <= u <= 1:
            return [
                self.point_1[0] + t * (self.point_2[0] - self.point_1[0]),
                self.point_1[1] + t * (self.point_2[1] - self.point_1[1]),
            ]
        else:
            return None