#! /usr/bin/env python
# Time-stamp: <2021-11-16 13:53:46 christophe@pallier.org>

"""Draws the Ebbinghaus-Titchener illusion.

See https://en.wikipedia.org/wiki/Ebbinghaus_illusion

"""

import pygame  # see www.pygame.org
import numpy as np

BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
GRAY = (127, 127, 127)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)


def Ebbinghaus(surface, n, d, r1, r2, col1, col2, x, y):
        """ Draws a circle surrounded by outer ones.

        Args:
            surface: pygame surface to display the stimulus on
            n: number of peripheral, outer circles
            d: distance between the center of inner circle and peripheral ones
            r1: radius of inner circle
            r2: radius of outer circles
            col1: color of the inner circle
            col2: color of the outer circles
            x, y: coordinates of the center of the figure on the screen
        Returns:
            None
            the stimulus is drawn on the surface

        """

        # draw inner circle
        pygame.draw.circle(surface, col1, (x, y), r1, 0)
        # draw peripheral circles
        for i in range(n):
                angle = (2 * 3.1415 * i) / n
                x1 = x + int(d * np.cos(angle))
                y1 = y + int(d * np.sin(angle))
                pygame.draw.circle(surface, col2, (x1, y1), r2, 0)


def main():
        W, H = 700, 500  # graphic window size

        pygame.init()
        screen = pygame.display.set_mode((W, H), pygame.DOUBLEBUF)
        screen.fill(WHITE)

        big_circles_size, upper_limit = 35, 35
        small_circles_size, lower_limit = 15, 15
        time_between_refresh = 200  # ms
        delta = -1

        done = False
        while not done:
                screen.fill(WHITE)
                Ebbinghaus(screen, 8, 100, 25, big_circles_size,
                           BLACK, BLACK, W//2 + 150, H//2)

                Ebbinghaus(screen, 8, 100, 25, small_circles_size,
                           BLACK, BLACK, W//2 - 150, H//2)

                pygame.display.flip()

                if big_circles_size == upper_limit:
                        delta = -1
                if big_circles_size == lower_limit:
                        delta = +1

                big_circles_size += delta
                small_circles_size -= delta

                pygame.time.wait(time_between_refresh)
                for event in pygame.event.get():
                        if event.type == pygame.QUIT:
                                done = True


if __name__ == '__main__':
        main()