import random

grid_x_count = 20
grid_y_count = 15

def move_food():
    global food_position

    possible_food_positions = []

    for food_x in range(grid_x_count):
        for food_y in range(grid_y_count):
            possible = True

            for segment in snake_segments:
                if food_x == segment['x'] and food_y == segment['y']:
                    possible = False

            if possible:
                possible_food_positions.append({'x': food_x, 'y': food_y})

    food_position = random.choice(possible_food_positions)

def reset():
    global timer
    global direction_queue
    global snake_segments

    timer = 0
    direction_queue = ['right']
    snake_segments = [
        {'x': 2, 'y': 0},
        {'x': 1, 'y': 0},
        {'x': 0, 'y': 0},
    ]
    move_food()

reset()

def update(dt):
    global timer
    global food_position

    timer += dt
    if timer >= 0.15:
        timer = 0

        if len(direction_queue) > 1:
            direction_queue.pop(0)

        next_x_position = snake_segments[0]['x']
        next_y_position = snake_segments[0]['y']

        if direction_queue[0] == 'right':
            next_x_position += 1
            if next_x_position >= grid_x_count:
                next_x_position = 0

        elif direction_queue[0] == 'left':
            next_x_position -= 1
            if next_x_position < 0:
                next_x_position = grid_x_count - 1

        elif direction_queue[0] == 'down':
            next_y_position += 1
            if next_y_position >= grid_y_count:
                next_y_position = 0

        elif direction_queue[0] == 'up':
            next_y_position -= 1
            if next_y_position < 0:
                next_y_position = grid_y_count - 1

        can_move = True

        for segment in snake_segments[:-1]:
            if (next_x_position == segment['x']
            and next_y_position == segment['y']):
                can_move = False

        if can_move:
            snake_segments.insert(0, {'x': next_x_position, 'y': next_y_position})

            if (snake_segments[0]['x'] == food_position['x']
            and snake_segments[0]['y'] == food_position['y']):
                move_food()
            else:
                snake_segments.pop()
        else:
            reset()

def on_key_down(key):
    if (key == keys.RIGHT
    and direction_queue[-1] != 'right'
    and direction_queue[-1] != 'left'):
        direction_queue.append('right')

    elif (key == keys.LEFT
    and direction_queue[-1] != 'left'
    and direction_queue[-1] != 'right'):
        direction_queue.append('left')

    elif (key == keys.DOWN
    and direction_queue[-1] != 'down'
    and direction_queue[-1] != 'up'):
        direction_queue.append('down')

    elif (key == keys.UP
    and direction_queue[-1] != 'up'
    and direction_queue[-1] != 'down'):
        direction_queue.append('up')

def draw():
    screen.fill((0, 0, 0))

    cell_size = 15

    screen.draw.filled_rect(
        Rect(
            0, 0,
            grid_x_count * cell_size, grid_y_count * cell_size
        ),
        color=(70, 70, 70)
    )

    def draw_cell(x, y, color):
        screen.draw.filled_rect(
            Rect(
                x * cell_size, y * cell_size,
                cell_size - 1, cell_size - 1
            ),
            color=color
        )

    for segment in snake_segments:
        draw_cell(segment['x'], segment['y'], color=(165, 255, 81))

    draw_cell(food_position['x'], food_position['y'], (255, 76, 76))