"""Moon orbital simulation demo.

This module defines :class:`Moon` which subclasses :class:`game.Game` and
uses :func:`compute.rot_2D` and :func:`compute.matmul` to animate a moon
orbiting the Earth.

The original repository contained a fully functional example, but the
``moon.py`` file was overwritten by another module during a previous
edit.  The following implementation restores the expected behaviour.
"""

from __future__ import annotations

import pygame

from compute import rot_2D, matmul
from game import Game


EARTH_RADIUS = 30
MOON_RADIUS = 10
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
BLUE = (0, 0, 255)


class Moon(Game):

    def __init__(self, title: str = "Moon", fps: int = 60, size: Tuple[int, int] = (640, 400)) -> None:
        super().__init__(title, fps, size)
        # Earth centre – centre of the window
        self.center: Tuple[int, int] = (size[0] // 2, size[1] // 2)
        # Fixed orbit offset from the centre
        self.offset: Tuple[float, float] = (150.0, 0.0)
        # Angular speed (radians per frame)
        self.delta_theta: float = 0.01
        self.theta: float = 0.0
        self.rot_moon: list[list[float]] = rot_2D(self.theta)
        # Initial moon position
        self.position_moon = (
            self.center[0] + self.offset[0],
            self.center[1] + self.offset[1],
        )

    def update_game(self) -> bool:
        # Advance the angle and recompute the rotation matrix
        self.theta += self.delta_theta
        self.rot_moon = rot_2D(self.theta)
        # Rotate the fixed offset vector
        point = [[self.offset[0]], [self.offset[1]]]
        result = matmul(self.rot_moon, point)
        # Translate back to screen coordinates
        self.position_moon = (
            self.center[0] + result[0][0],
            self.center[1] + result[1][0],
        )
        return True

    def draw_game(self) -> None:
        self.screen.fill(BLACK)
        pygame.draw.circle(self.screen, BLUE, self.center, EARTH_RADIUS)
        pygame.draw.circle(
            self.screen,
            WHITE,
            (int(self.position_moon[0]), int(self.position_moon[1])),
            MOON_RADIUS,
        )


if __name__ == "__main__":
    moon = Moon()
    moon.run()