import sys

import pygame

from bullet import Bullet
from alien import Alien
from time import sleep


def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets):
    """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.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets, mouse_x, mouse_y)

        elif event.type == pygame.KEYDOWN:
            # 响应按键按下
            check_keydown_events(event, ai_settings, screen, ship, bullets)

        elif event.type == pygame.KEYUP:
            # 响应按键松开
            check_keyup_events(event, ship)


def check_play_button(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets, mouse_x, mouse_y):
    """在玩家单击Play按钮时开始新游戏"""
    botton_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    # 防止一直点击该区域，一直起作用
    if botton_clicked and not stats.game_active:
        # 重置游戏设置
        ai_settings.initialize_dynamic_settings()
        # 隐藏光标
        pygame.mouse.set_visible(False)
        # 重置游戏统计信息
        stats.reset_stats()
        stats.game_active = True

        # 重置记分牌图像
        sb.prep_score()
        sb.prep_high_score()
        sb.prep_level()
        sb.prep_ships()

        # 清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()

        # 创建一群新的外星人，并让飞船居中
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()


def check_keyup_events(event, ship):
    """响应松开"""
    if event.key == pygame.K_RIGHT:
        # 停止向右移动飞船
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        # 停止向左移动飞船
        ship.moving_left = False


def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """响应按下"""
    if event.key == pygame.K_RIGHT:
        # 向右移动飞船
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        # 向左移动飞船
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        # 按q结束飞船
        sys.exit()


def fire_bullet(ai_settings, screen, ship, bullets):
    """如果还没有到达限制，就发射一颗子弹"""
    # 对子弹数量进行限制
    if len(bullets) < ai_settings.bullets_allowed:
        # 空格用来发射子弹
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)


def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    # 创建一个外星人，并计算一行可容纳多少个外星人
    alien = Alien(ai_settings, screen)
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)
    # 创建第一行外星人
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            # 创建一个外星人并将其加入当前行
            create_alien(ai_settings, screen, aliens, alien_number, row_number)


def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可容纳多少行外星人"""
    available_space_y = (ai_settings.screen_height - (3 * alien_height) - ship_height)
    number_rows = int(available_space_y / (2 * alien_height))
    return number_rows


def get_number_aliens_x(ai_settings, alien_width):
    """计算每行可容纳多少个外星人"""
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x


def create_alien(ai_settings, screen, aliens, alien_number, row_number):
    """创建一个外星人并其放在当前行"""
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)


def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
    # 子弹更新,对编组调用update，会对里面的每个元素调用update()
    # 因为已经写过了Bullet类的update方法，因此会自动调用update()方法
    bullets.update()
    # 删除已经消失不见的子弹
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

    # 检查是否有有子弹击中了外星人
    check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship, aliens, bullets)


def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """响应子弹和外星人的碰撞"""
    # 删除发生碰撞的子弹和外星人
    # 如果是这样，则删除掉相应的子弹和外星人
    # True告诉pygame删除发生碰撞的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)

    if collisions:
        # 当前只要发生碰撞，就加一次
        # 但很有可能，有多次碰撞，并且一次会有多个外星人被消灭掉
        for aliens in collisions.values():
            stats.score += ai_settings.alien_points * len(aliens)

            sb.prep_score()
        # 每次检查碰撞之后，会产生分数，所以在这里检查是否有最高得分产生
        check_high_score(stats, sb)
    # 在检查碰撞之后，需要看场上还有没有外星人，如果没有，就生成新的外星人
    if len(aliens) == 0:
        # 没有外星人了就要删除场上所有的子弹
        bullets.empty()
        # 加快游戏节奏，使速度更快
        ai_settings.increase_speed()
        # 如果整群外星人都被消灭掉了，就提高一个等级
        stats.level += 1
        sb.prep_level()
        # 创建新的外星人群
        create_fleet(ai_settings, screen, ship, aliens)


def update_aliens(ai_settings, stats, sb, screen, ship, aliens, bullets):
    """更新外星人群中所有外星人的位置"""
    check_fleet_edges(ai_settings, aliens)
    # 将会对aliens中的所有精灵调用update函数
    aliens.update()

    # 检测外星人和飞船之间的碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(ai_settings, stats, sb, screen, ship, aliens, bullets)

    # 检查外星人与屏幕底端的碰撞
    check_aliens_bottom(ai_settings, stats, sb, screen, ship, aliens, bullets)


def check_aliens_bottom(ai_settings, stats, sb,  screen, ship, aliens, bullets):
    """检查是否有外星人到达了屏幕底端"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            # 像飞船被撞到一样进行处理
            ship_hit(ai_settings, stats, sb, screen, ship, aliens, bullets)
            break


def ship_hit(ai_settings, stats, sb, screen, ship, aliens, bullets):
    """响应被外星人撞到的飞船"""
    if stats.ships_left > 0:
        # 将ships_left减1
        stats.ships_left -= 1

        # 更新还剩多少飞船
        sb.prep_ships()

        # 清空外星人列表和子弹列表
        aliens.empty()
        bullets.empty()

        # 创建一群新的外星人，并将飞船放到屏幕底部中央
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()

        # 暂停
        sleep(0.5)
    else:
        stats.game_active = False
        # 将鼠标置为可见，方便点击
        pygame.mouse.set_visible(True)


def check_fleet_edges(ai_settings, aliens):
    """有外星人到达边缘时采取相应的措施"""
    for alien in aliens:
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break


def change_fleet_direction(ai_settings, aliens):
    """将整群外星人下移，并改变他们的方向"""
    for alien in aliens:
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1


def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets, play_button):
    """更新屏幕上的图像，并切换到新屏幕"""
    # 每次循环时都重绘屏幕
    screen.fill(ai_settings.bg_color)

    # 在飞船和外星后面重绘所有子弹
    for bullet in bullets.sprites():
        bullet.draw_bullet()

    # 绘制飞船
    ship.blitme()

    # 绘制外星人
    # alien.blitme()
    # 绘制一行外星人
    aliens.draw(screen)

    # 显示得分
    sb.show_score()

    # 如果游戏处于非活动状态，就绘制Play按钮
    if not stats.game_active:
        play_button.draw_button()

    # 让最近绘制的屏幕可见
    pygame.display.flip()


def check_high_score(stats, sb):
    """检查是否诞生了最高得分"""

    if stats.score > stats.high_score:
        stats.high_score = stats.score
        sb.prep_high_score()