import pygame
import math

class Knob:
    
    def __init__(self, screen):
        self.screen = screen
        self.radius = screen.get_width()/20
        self.fill_color = (255,0,255)
        self.position = (screen.get_width()/2, screen.get_height()/2)
        self.value = 0.1

    def set_value(self, value):
        self.value = value

    def get_pointer_position(self):
        x = self.radius * math.cos((self.value * 2 + 0.5) * math.pi) + self.position[0]
        y = self.radius * math.sin((self.value * 2 + 0.5) * math.pi) + self.position[1]
        return(x, y)

    def display(self):
        pygame.draw.circle(self.screen, self.fill_color, self.position, self.radius)
        pygame.draw.line(self.screen, "black", self.position, self.get_pointer_position(), 3)