import sys
import pygame
from settings import Settings
from ship import Ship
from bullet import Bullet
from alien import Alien

class AlienInvasion:
    """管理游戏资源和行为的类"""
    def __init__(self):
        pygame.init()
        self.settings = Settings()
        self.screen = pygame.display.set_mode((self.settings.screen_width, self.settings.screen_height))
        pygame.display.set_caption("Alien Invasion")
        self.ship = Ship(self)
        self.bullets = pygame.sprite.Group()
        self.bullets_num = 0
        self.aliens = pygame.sprite.Group()
        self._create_fleet()

    def run_game(self):
        """开始游戏的主循环"""
        while True:
            self._check_events()
            self.ship.update()
            self._update_bullet()
            self._update_screen()


    def _check_events(self):
        """响应按键和鼠标事件"""
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
            elif event.type == pygame.KEYDOWN:
                # 按下按键
                self._check_keydown_events(event)
            elif event.type == pygame.KEYUP:
                # 松开按键
                self._check_keyup_events(event)

    def _check_keydown_events(self, event):
        """响应按键"""
        if event.key == pygame.K_RIGHT:
            self.ship.moving_right = True
        elif event.key == pygame.K_LEFT:
            self.ship.moving_left = True
        elif event.key == pygame.K_UP:
            self.ship.moving_up = True
        elif event.key == pygame.K_DOWN:
            self.ship.moving_down = True
        elif event.key == pygame.K_q:
            sys.exit() # 中文输入法下无法正常退出
        elif event.key == pygame.K_SPACE:
            self._fire_bullet()

    def _check_keyup_events(self, event):
        """响应松开"""
        if event.key == pygame.K_RIGHT:
            self.ship.moving_right = False
        elif event.key == pygame.K_LEFT:
            self.ship.moving_left = False
        elif event.key == pygame.K_UP:
            self.ship.moving_up = False
        elif event.key == pygame.K_DOWN:
            self.ship.moving_down = False

    def _fire_bullet(self):
        """创建一颗子弹，并将其加入编组bullets中"""
        new_bullet = Bullet(self)
        self.bullets.add(new_bullet)

    def _update_bullet(self):
        """更新子弹的位置并删除消失的子弹"""
        # 自动开火
        self.bullets_num += 1
        if self.bullets_num % self.settings.bullet_time == 0:
            self._fire_bullet()
        # 更新子弹的位置
        self.bullets.update()
        for bullet in self.bullets.copy():
            if bullet.rect.bottom <= 0:
                self.bullets.remove(bullet)
        # 显示当前屏幕内的子弹数目
        # print(len(self.bullets))

    def _update_screen(self):
        # 每次循环都重绘屏幕
        self.screen.fill(self.settings.bg_color)
        # 重绘飞船
        self.ship.blitme()
        # 绘制子弹
        for bullet in self.bullets.sprites():
            bullet.draw_bullet()
        #绘制外星人
        self.aliens.draw(self.screen)
        # 让最近绘制的屏幕可见
        pygame.display.flip()

    def _create_fleet(self):
        """创建外星人群"""
        # 创建一个外星人
        alien = Alien(self)
        self.aliens.add(alien)

if __name__ == '__main__':
    # 创建游戏实例并运行游戏
    ai = AlienInvasion()
    ai.run_game()