import pygame as pg

from random import randint

import sys

from pygame.locals import *



FPS = 6  # 画面帧数，代表蛇的移动速率

window_width = 600

window_height = 500

cellsize = 20

cell_width = int(window_width / cellsize)

cell_height = int(window_height / cellsize)

BGcolor = (0, 0, 0)

BLUE = (0, 0, 255)

RED = (255, 0, 0)

apple_color = (255, 0, 0)

snake_color = (0, 150, 0)

GREEN = (0, 255, 0)

WHITE = (255, 255, 255)

DARKGRAY = (40, 40, 40)



UP = "up"

DOWN = "down"

LEFT = "left"

RIGHT = "right"

HEAD = 0





def main():  # 有函数

    global FPSclock, window, BASICFONT

    pg.init()

    FPSclock = pg.time.Clock()

    window = pg.display.set_mode((window_width, window_height))

    BASICFONT = pg.font.Font("freesansbold.ttf", 18)

    pg.display.set_caption("贪吃蛇")

    showStartScreen()

    while True:

        runGame()

        showGameOverScreen()





def runGame():  # 运行游戏函数

    startx = randint(5, cell_width - 6)

    starty = randint(5, cell_height - 6)

    snakeCoords = [{"x": startx, "y": starty}, {"x": startx - 1, "y": starty}, {"x": startx - 2, "y": starty}]

    direction = RIGHT

    apple = getRandomLocation()

    while True:

        for event in pg.event.get():

            if event.type == QUIT:

                terminate()

            elif event.type == KEYDOWN:

                if event.key == K_LEFT and direction != RIGHT:

                    direction = LEFT

                elif event.key == K_RIGHT and direction != LEFT:

                    direction = RIGHT

                elif event.key == K_UP and direction != DOWN:

                    direction = UP

                elif event.key == K_DOWN and direction != UP:

                    direction = DOWN

                elif event.key == K_ESCAPE:

                    terminate()

        if snakeCoords[HEAD]["x"] == -1 or snakeCoords[HEAD]["x"] == cell_width or snakeCoords[HEAD]["y"] == -1 or \

                snakeCoords[HEAD]["y"] == cell_height:

            return

        for snakeBody in snakeCoords[1:]:

            if snakeBody["x"] == snakeCoords[HEAD]["x"] and snakeBody["y"] == snakeCoords[HEAD]["y"]:

                return

            if snakeCoords[HEAD]["x"] == apple["x"] and snakeCoords[HEAD]["y"] == apple["y"]:

                apple = getRandomLocation()

            else:

                del snakeCoords[-1]

            if direction == UP:

                newHead = {"x": snakeCoords[HEAD]["x"], "y": snakeCoords[HEAD]["y"] - 1}

            elif direction == DOWN:

                newHead = {"x": snakeCoords[HEAD]["x"], "y": snakeCoords[HEAD]["y"] + 1}

            elif direction == LEFT:

                newHead = {"x": snakeCoords[HEAD]["x"] - 1, "y": snakeCoords[HEAD]["y"]}

            elif direction == RIGHT:

                newHead = {"x": snakeCoords[HEAD]["x"] + 1, "y": snakeCoords[HEAD]["y"]}



            snakeCoords.insert(0, newHead)

            window.fill(BGcolor)

            drawGrid()

            drawSnake(snakeCoords)

            drawApple(apple)



            drawScore(len(snakeCoords) - 3)



            pg.display.update()

            FPSclock.tick(FPS)





def drawPressKeyMsg():  # 游戏开始提示信息

    pressKeySurf = BASICFONT.render("press a key to play", True, BLUE)

    pressKeyRect = pressKeySurf.get_rect()

    pressKeyRect.topleft = (window_width - 200, window_height - 30)

    window.blit(pressKeySurf, pressKeyRect)





def checkForKeyPress():  # 检查是否触发按键

    if len(pg.event.get(QUIT)) > 0:

        terminate()

    keyUpEvents = pg.event.get(KEYUP)

    if len(keyUpEvents) == 0:

        return None

    if keyUpEvents[0].key == K_ESCAPE:

        terminate()

    return keyUpEvents[0].key





def showStartScreen():  # 开始画面

    window.fill(BGcolor)

    titleFont = pg.font.Font("freesansbold.ttf", 100)

    titleSurf = titleFont.render("snake!", True, RED)

    titleRect = titleSurf.get_rect()

    titleRect.center = (window_width / 2, window_height / 2)

    window.blit(titleSurf, titleRect)

    drawPressKeyMsg()

    pg.display.update()

    while True:

        if checkForKeyPress():

            pg.event.get()

            return





def terminate():  # 退出

    pg.quit()

    sys.exit()





def getRandomLocation():  # 出现位置

    return {"x": randint(0, cell_width - 1), "y": randint(0, cell_height - 1)}





def showGameOverScreen():  # 游戏结束

    gameOverFont = pg.font.Font("freesansbold.tff", 150)

    gameSurf = gameOverFont.render("Game", True, WHITE)

    overSurf = gameOverFont.render("over", True, WHITE)

    gameRect = gameSurf.get_rect()

    overRect = overSurf.get_rect()

    gameRect.midtop = (window_width / 2, 10)

    overRect.midtop = (window_width / 2, gameRect.height10 + 25)

    window.blit(gameSurf, gameRect)

    window.blit(overSurf, overRect)



    drawPressKeyMsg()

    pg.display.update()

    pg.time.wait(500)

    checkForKeyPress()

    while True:

        if checkForKeyPress():

            pg.event.get()

            return





def drawScore(score):  # 显示分数

    scoreSurf = BASICFONT.render("Score:%s" % (score), True, WHITE)

    scoreRect = scoreSurf.get_rect()

    scoreRect.topleft = (window_width - 120, 10)

    window.blit(scoreSurf, scoreRect)





def drawSnake(snakeCoords):  # 画蛇

    for coord in snakeCoords:

        x = coord["x"] * cellsize

        y = coord["y"] * cellsize

        snakeSegmentRect = pg.Rect(x, y, cellsize, cellsize)

        pg.draw.rect(window, snake_color, snakeSegmentRect)

        snakeInnerSegmentRect = pg.Rect(x + 4, y + 4, cellsize - 8, cellsize - 8)

        pg.draw.rect(window, GREEN, snakeInnerSegmentRect)





def drawApple(coord):

    x = coord["x"] * cellsize

    y = coord["y"] * cellsize

    appleRect = pg.Rect(x, y, cellsize, cellsize)

    pg.draw.rect(window, apple_color, appleRect)





def drawGrid():  # 画方格

    for x in range(0, window_width, cellsize):

        pg.draw.line(window, DARKGRAY, (x, 0), (x, window_height))

    for y in range(0, window_height, cellsize):

        pg.draw.line(window, DARKGRAY, (0, y), (window_width, y))





if __name__ == "__main__":

    main()