import os
import sys
import pygame
from PIL import Image, ImageDraw
from pathlib import Path

print(f"python executable: {sys.executable}")

### CONSTANTS ###

# Convention: use capital letters for constants (= variables you leave unchanged)

# Windows
WIN_HEIGHT = 800
WIN_WIDTH = 500

# Define colors
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)
BG_COLOR = WHITE

# Framerate
FPS = 30
TIME_DELAY = int(1000 / FPS)

# Game Constants
SPEED = 12

### FUNCTIONS ###

### CLASSES ###
class Player(pygame.sprite.Sprite):
    def __init__(self, img_path, xy_center, v, mass):
        super().__init__() # call __init__ of parent class (i.e. of pygame.sprite.Sprite)

        # ASSIGN CLASS ATTRIBUTES
        if not os.path.exists(img_path):
            raise Exception("THE FOLLOWING FILE DOES NOT EXIST: {0}".format(img_path))
        self.image = pygame.image.load(str(img_path)) # load image
        self.rect = self.image.get_rect() # create rectangle containing ball image
        self.rect.center = (int(xy_center[0]),int(xy_center[1])) # set center coords of ball
        self.mask = pygame.mask.from_surface(self.image) # creates a mask, used for collision detection (see manual about pygame.sprite.collide_mask())
        self.mass = mass # give sprite a mass -> realistic collisions

    def update(self):
        # in each step, this method is called
        if self.rect.left <= 0: self.rect.left = 0
        elif self.rect.right >= WIN_WIDTH: self.rect.right = WIN_WIDTH
        if self.rect.top <= 0: self.rect.top = 0
        elif self.rect.bottom >= WIN_HEIGHT: self.rect.bottom = WIN_HEIGHT


    def collide(self,ball):
        pass

class Ball(pygame.sprite.Sprite):
    """
    Class for balls, derive from pygame's sprite class
    -> makes your life easier since you can use e.g. the collision detection of the sprite class
    """
    def __init__(self, img_path, xy_center, v, mass):
        super().__init__() # call __init__ of parent class (i.e. of pygame.sprite.Sprite)
        
        # ASSIGN CLASS ATTRIBUTES
        if not os.path.exists(img_path): # check if folder of image exists
            raise Exception("THE FOLLOWING FILE DOES NOT EXIST: {0}".format(img_path))
        self.image = pygame.image.load(str(img_path)) # load image
        self.rect = self.image.get_rect() # create rectangle containing ball image
        self.rect.center = (int(xy_center[0]),int(xy_center[1])) # set center coords of ball
        self.mask = pygame.mask.from_surface(self.image) # creates a mask, used for collision detection (see manual about pygame.sprite.collide_mask())
        self.mass = mass # is relevant for realistic collisions

    def update(self):
        """
        - update function gets executed in every step
        - determines motion of ball
        """
        pass


    def collide(self,ball):
        """
        ball self collides with other ball, given as argument
        this method updates velocities of BOTH balls
        """
        pass

class Game:
    """
    Main GAME class
    """
    def __init__(self):
        pygame.init()
        pygame.font.init()
        self.time_delay = TIME_DELAY
        self.screen = pygame.display.set_mode((WIN_WIDTH, WIN_HEIGHT)) # create screen which will display everything
        self.win = pygame.display.set_mode((WIN_WIDTH, WIN_HEIGHT))
        pygame.display.set_caption("Bouncing Balls") # Game title

    def quit(self):
        pygame.quit()
        sys.exit(0)

    def play(self):
        # CREATE PLAYER
        player = Player(os.path.join("data","ball_r=100_col=0_255_0.png"),[150,550],[0,0],1)

        # CREATE GAME GROUPS
        Balls = pygame.sprite.Group()

        # CREATE OBJECTS AND ASSIGN TO GROUPS
        balls_list = [
                        Ball(os.path.join("data","ball_r=100_col=0_0_255.png"),[100,200],[0,0],1),
                        Ball(os.path.join("data","ball_r=100_col=0_0_255.png"),[200,400],[0,0],1)
            ]
        Balls.add(balls_list)

        # GAME PERMANENT LOOP
        while True:
            pygame.time.delay(TIME_DELAY)

            # KEY EVENTS
            for event in pygame.event.get():
                # Exit app if click quit button
                if event.type == pygame.QUIT:
                    self.quit()
            
            # Naviation of player
            keys = pygame.key.get_pressed()
            if keys[pygame.K_UP]:
                player.rect.top -= SPEED
            # and so on ...


            # COLLISION DETECTION
            # see manual for all types of collisions: https://www.pygame.org/docs/ref/sprite.html#pygame.sprite.spritecollide
            # TODO: check for collisions between any two balls. If there is any, call the collision() method of the Ball class.
            for ball in balls_list:
                pass

            # UPDATE
            Balls.update()
            player.update()

            # DRAW
            self.screen.fill(BG_COLOR)  # draw empty screen

            Balls.draw(self.screen)
            self.screen.blit(player.image, player.rect)

            pygame.display.update()

        pygame.quit()

if __name__ == "__main__":
    Game().play()