game_functions.py

import sys
from time import sleep

import pygame

from bullet import Bullet
from alien import Alien

def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """Respond to keypresses."""
    if event.key == pygame.K_RIGHT:
         ship.moving_right = True
    elif event.key == pygame.K_LEFT:
         ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        sys.exit()

def fire_bullet(ai_settings, screen, ship, bullets):        
    # Create a new bullet and add it to the bullets group.
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)

def check_keyup_events(event, ship):
    """Respond to keyreleases."""
    if event.key == pygame.K_RIGHT:
         ship.moving_right = False
    elif event.key == pygame.K_LEFT:
         ship.moving_left = False


def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets):
    """Respond to keypresses and mouse events."""
    for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
            elif event.type == pygame.KEYDOWN:
                check_keydown_events(event, ai_settings, screen, ship, bullets)

            elif event.type == pygame.KEYUP:
                check_keyup_events(event, ship)
            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)
                
def check_play_button(ai_settings, screen, stats, sb, play_button, ship, aliens, bullets, mouse_x, mouse_y):
    """ Start a new game when the player clicks Play"""
    button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    if button_clicked and not stats.game_active:
        #Reset the game settings
        ai_settings.initialize_dynamic_settings()

        #Hide mouse cursor
        pygame.mouse.set_visible(False)
        #Reset the game stats
        stats.reset_stats()
        stats.game_active = True

        #Reset the scoreboard images
        sb.prep_score()
        sb.prep_high_score()
        sb.prep_level()
        sb.prep_ships()

        #Empty the list of aliens and bullets
        aliens.empty()
        bullets.empty()

        #Create a new fleet and center the ship
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()

def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets, play_button):
    """Update images on the screen and flip to the new screen."""
    #Redraw the screen during each pass through the loop.
    screen.fill(ai_settings.bg_color)
    #Redraw all bullets behind ship and aliens.
    for bullet in bullets.sprites():
        bullet.draw_bullet()

    ship.blitme()
    aliens.draw(screen)

    #Draw the score info
    sb.show_score()

    #Draw the play button if the game is inactive
    if not stats.game_active:
        play_button.draw_button()
    #Make the most recently drawn screen visible.
    pygame.display.flip()

def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """Update position of bullets and get rid of old bullets."""
    #Update bullet positions.
    bullets.update()
    #Get rid of bullets that have disappeared.
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

    check_bullet_alien_collision(ai_settings, screen, stats, sb, ship, aliens, bullets)
    
def check_bullet_alien_collision(ai_settings, screen, stats, sb, ship, aliens, bullets):
    #Check for any bullets that have hit aliens.
    # If so, get rid of the bullet and the alien.
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)

    if collisions:
        for aliens in collisions.values():
            stats.score += ai_settings.alien_points * len(aliens)
            sb.prep_score()
        check_high_score(stats, sb)

    if len(aliens) == 0:
        #Destroy existing bullets, speed up game and create new fleet.
        #If the entire fleet is destroyed, start a new level
        bullets.empty()
        ai_settings.increase_speed()

        #Increase level.
        stats.level += 1
        sb.prep_level()

        create_fleet(ai_settings, screen, ship, aliens)

    
def create_fleet(ai_settings, screen,ship, aliens):
    """Create a full fleet of aliens"""
    #Create an alien and find the number of aliens in a row.
    #Spacing between each alien is equal to one alien width.
    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)
    #Create the first row of aliens.
    for row_number in range(number_rows):
    #Create an alien and place it in the row.
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number, row_number)
        

def get_number_aliens_x(ai_settings, alien_width):
    """Determine the number of aliens that fir in a row."""
    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):
    """Create an alien and place it in the row"""
    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 get_number_rows(ai_settings, ship_height, alien_height):
    """Determine the number of rows of aliens that fit on the screen."""
    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 check_fleet_edges(ai_settings, aliens):
    """Respond appropriately if any aliens have reached an edge."""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break

def change_fleet_direction(ai_settings, aliens):
    """Drop the entire fleet and change the fleet's direction."""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1

def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """Respond to ship being hit by alien."""
    if stats.ships_left > 0:
        #Decrement ships_left.
        stats.ships_left -= 1

        #Update scoreboard
        sb.prep_ships()
    
    else: 
        stats.game_active = False
        pygame.mouse.set_visible(True)

    #Empty the list of aliens and bullets.
    aliens.empty()
    bullets.empty()

    #Create a new fleet and center the ship.
    create_fleet(ai_settings, screen, ship, aliens)
    ship.center_ship()

    #Pause
    sleep(0.5)

def check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """Check if any aliens have reached the bottom of the screen"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            #Treat this the same as if the ship got hit
            ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
            break

def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """Check if the fleet is at an edge, and then update the positions of all aliens in the fleet"""
    check_fleet_edges(ai_settings, aliens)
    aliens.update()

    #Look for alien-ship collisions.
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)

    #Look for aliens hitting the bottom of the screen
    check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets)

def check_high_score(stats, sb):
    """Check to see if there's a new high score."""
    if stats.score > stats.high_score:
        stats.high_score = stats.score
        sb.prep_high_score()