from geometry.point import Point
from geometry.vector import Vector
from geometry.validation import expect_type
from simulation.drawing import centered_circle
from turtle import begin_fill, end_fill, fillcolor

class Ball:
    def __init__(self, position, velocity=None, mass=1, radius=20, color="black"):
        expect_type(position, Point)
        self.position = position
        self.velocity = velocity or Vector()
        expect_type(self.velocity, Vector)
        self.acceleration = Vector()
        self.radius = radius
        self.mass = mass
        self.color = color

    def update(self):
        """Update the ball's position and velocity at this moment. 
        
        """
        self.velocity += self.acceleration
        self.position += self.velocity
        self.acceleration = Vector()

    def collided_with(self, other_ball):
        """Checks whether this ball collided with another ball.
        """
        return (self.position - other_ball.position).mag() <= self.radius + other_ball.radius

    def draw(self):
        "Draws a colored ball."
        fillcolor(self.color)
        begin_fill()
        centered_circle(self.radius)
        end_fill()