Adopt the main flow and the entry point
Copied unchanged from the base: screen set-up, key bindings, the animation loop with game_is_on, the eating check, the game-over check, the wait for a click and the quiet exit when the window is closed. main imports food and scoreboard only when it runs, so importing it needs neither turtle nor tkinter. Task: MIL-002#5 Closes #12
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"""! @file
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@brief The main flow of the game: set up the screen, draw the snake and run it.
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The flow follows the lectures "Screen Setup and Creating a Snake Body",
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"Animating the Snake Segments on Screen" and "Controlling the Snake with
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Keypresses", and the day-21 steps in which the snake eats food, the score rises and
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the game ends.
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"""
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import time
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from collections.abc import Callable
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from typing import Protocol
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from snake_game.constants import (
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FOOD_COLLISION_DISTANCE,
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REFRESH_DELAY_SECONDS,
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SCREEN_BACKGROUND_COLOR,
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SCREEN_HEIGHT,
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SCREEN_TITLE,
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SCREEN_WIDTH,
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)
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from snake_game.snake import Snake
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class ScreenLike(Protocol):
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"""! @brief What the helper functions need from the screen.
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A `turtle.Screen` fits this description, and so does a fake in a test.
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"""
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def setup(self, width: float, height: float) -> None:
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"""! @brief Set the size of the window.
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@param width Width in pixels.
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@param height Height in pixels.
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"""
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...
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def bgcolor(self, color: str, /) -> None:
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"""! @brief Set the background colour.
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@param color Name of the colour, for example `black`.
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"""
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...
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def title(self, titlestring: str, /) -> None:
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"""! @brief Set the title of the window.
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@param titlestring The title.
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"""
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...
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def update(self) -> None:
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"""! @brief Draw everything that has changed since the last update."""
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...
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def listen(self) -> None:
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"""! @brief Make the screen receive the key presses."""
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...
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def onkey(self, fun: Callable[[], object], key: str) -> None:
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"""! @brief Call a function when a key is pressed.
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@param fun The function to call.
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@param key Name of the key, for example `Up`.
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"""
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...
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class FoodLike(Protocol):
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"""! @brief What `eat_food_if_close` needs from the food.
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A `Food` fits this description, and so does a fake in a test.
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"""
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def refresh(self) -> None:
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"""! @brief Move the food to a new random place."""
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...
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def position(self) -> tuple[float, float]:
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"""! @brief Tell where the food is.
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@return The x and y coordinates.
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"""
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...
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class ScoreboardLike(Protocol):
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"""! @brief What the eating and game-over checks need from the scoreboard.
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A `Scoreboard` fits this description, and so does a fake in a test.
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"""
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def increase_score(self) -> None:
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"""! @brief Add 1 to the score and write it."""
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...
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def game_over(self) -> None:
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"""! @brief Write the game-over text."""
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...
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def configure_screen(screen: ScreenLike) -> None:
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"""! @brief Give the screen the size, background colour and title of the game.
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@param screen The screen to set up.
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"""
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screen.setup(width=SCREEN_WIDTH, height=SCREEN_HEIGHT)
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screen.bgcolor(SCREEN_BACKGROUND_COLOR)
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screen.title(SCREEN_TITLE)
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def bind_keys(screen: ScreenLike, snake: Snake) -> None:
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"""! @brief Turn the snake with the arrow keys.
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@param screen The screen that receives the key presses.
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@param snake The snake to steer.
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"""
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screen.listen()
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screen.onkey(snake.up, "Up")
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screen.onkey(snake.down, "Down")
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screen.onkey(snake.left, "Left")
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screen.onkey(snake.right, "Right")
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def play_frame(screen: ScreenLike, snake: Snake) -> None:
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"""! @brief Show the snake, wait for `REFRESH_DELAY_SECONDS`, then move it.
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This is one pass of the animation loop. The screen is updated by hand because
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automatic drawing is off, so the whole snake appears at once.
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@param screen The screen to update.
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@param snake The snake to move.
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"""
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screen.update()
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time.sleep(REFRESH_DELAY_SECONDS)
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snake.move()
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def eat_food_if_close(snake: Snake, food: FoodLike, scoreboard: ScoreboardLike) -> None:
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"""! @brief Let the snake eat the food when the head is close enough to it.
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Eating moves the food to a new place, makes the snake one segment longer and
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adds 1 to the score. The head must be closer than `FOOD_COLLISION_DISTANCE`.
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@param snake The snake.
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@param food The food.
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@param scoreboard The scoreboard that shows the score.
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"""
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if snake.head.distance(food.position()) < FOOD_COLLISION_DISTANCE:
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food.refresh()
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snake.extend()
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scoreboard.increase_score()
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def end_game_if_over(snake: Snake, scoreboard: ScoreboardLike) -> bool:
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"""! @brief End the game when the head passes the wall or touches the tail.
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When the game is over the scoreboard writes the game-over text.
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@param snake The snake.
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@param scoreboard The scoreboard that writes the game-over text.
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@return True when the game is over.
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"""
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if snake.hits_wall() or snake.hits_tail():
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scoreboard.game_over()
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return True
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return False
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def main() -> None:
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"""! @brief Open the game window and run the snake until the window is closed.
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Closing the window during the animation loop makes `screen.update()` raise
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`tkinter.TclError` ("invalid command name"), and `turtle` raises
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`turtle.Terminator` in some other calls once its window is gone. Both mean
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"the player closed the window", so the game ends quietly with exit code 0.
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When the snake passes the wall or touches its tail the loop ends, the screen is
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updated so that the game-over text shows, and `screen.exitonclick()` waits for a
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click.
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`turtle` and `tkinter` are imported here and not at the top of the module, and
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so are `food` and `scoreboard`, whose classes inherit from `Turtle`: importing
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this module needs neither a display nor `tkinter`.
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"""
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from tkinter import TclError
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from turtle import Screen, Terminator
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from snake_game.food import Food
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from snake_game.scoreboard import Scoreboard
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screen = Screen()
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configure_screen(screen)
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screen.tracer(0)
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snake = Snake()
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food = Food()
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scoreboard = Scoreboard()
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bind_keys(screen, snake)
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game_is_on = True
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try:
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while game_is_on:
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play_frame(screen, snake)
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eat_food_if_close(snake, food, scoreboard)
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if end_game_if_over(snake, scoreboard):
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game_is_on = False
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screen.update()
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screen.exitonclick()
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except (Terminator, TclError):
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return # the window was closed: there is nothing left to do
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