import random, pygame, time, sys

# Global Variables
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
WIN_W = 32 * 20
WIN_H = 32 * 20


class Camera(object):
    def __init__(self, total_width, total_height):
        self.state = pygame.Rect(0, 0, total_width, total_height)

    def apply(self, target):
        return target.rect.move(self.state.topleft)

    def update(self, target_rect):
        x = -target_rect.x + WIN_W / 2
        y = -target_rect.y + WIN_H / 2

        # Stop scrolling at left edge
        if x > 0:
            x = 0

        # Stop scrolling at the right edge
        elif x < -(self.state.width - WIN_W):
            x = -(self.state.width - WIN_W)

        # Stop scrolling at top
        if y > 0:
            y = 0

        # Stop scrolling at the bottom
        elif y < -(self.state.height - WIN_H):
            y = -(self.state.height - WIN_H)

        self.state = pygame.Rect(x, y, self.state.width, self.state.height)


class Hero(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.speed = 4
        self.image = pygame.Surface((32, 32)).convert()
        self.rect = self.image.get_rect()
        self.rect.x = 2 * 32
        self.rect.y = 21 * 32

    def collide(self, platform_group, dir):
        for p in platform_group:
            if pygame.sprite.collide_rect(self, p):
                if dir == "up" and self.rect.top < p.rect.bottom:
                    self.rect.top = p.rect.bottom
                elif dir == "down" and self.rect.bottom > p.rect.top:
                    self.rect.bottom = p.rect.top
                elif dir == "left" and self.rect.left < p.rect.right:
                    self.rect.left = p.rect.right
                elif dir == "right" and self.rect.right > p.rect.left:
                    self.rect.right = p.rect.left

    def update(self, platform_group, hero):
        # Movement
        key = pygame.key.get_pressed()

        # Movement and barriers
        if key[pygame.K_w] or key[pygame.K_UP]:
            self.rect.y -= self.speed
            self.collide(platform_group, "up")
        elif key[pygame.K_s] or key[pygame.K_DOWN]:
            self.rect.y += self.speed
            self.collide(platform_group, "down")
        if key[pygame.K_a] or key[pygame.K_LEFT]:
            self.rect.x -= self.speed
            self.collide(platform_group, "left")
        elif key[pygame.K_d] or key[pygame.K_RIGHT]:
            self.rect.x += self.speed
            self.collide(platform_group, "right")


# Function#
class Platform(pygame.sprite.Sprite):
    def __init__(self, x, y, col):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((32, 32))
        self.image.convert()
        self.col = col
        self.rect = pygame.Rect(x, y, 32, 32)


def main():
    # variables
    screen = pygame.display.set_mode((WIN_W, WIN_H), pygame.SRCALPHA)

    hero = Hero()

    map = [
        "PPPPPPPPPPPPPPPPPPPPPPPPPPPP",
        "P                          P",
        "P                          P",
        "P                          P",
        "P        P        P        P",
        "P                          P",
        "P        PPP     PP        P",
        "P                          P",
        "P        PPP     PP        P",
        "P        PPP     PP        P",
        "P                          P",
        "P                          P",
        "P        PP     PPP        P",
        "P        PP     PPP        P",
        "P                          P",
        "P                          P",
        "P        PPP     PP        P",
        "P        PPP     PP        P",
        "P                          P",
        "P        PPP     PP        P",
        "P        PPP     PP        P",
        "P                          P",
        "P                          P",
        "PPPPPPPPPPPPPPPPPPPPPPPPPPPP", ]

    platform_group = pygame.sprite.Group()
    x = y = 0
    for row in map:
        for col in row:
            if col == "P":
                p = Platform(x, y, col)
                platform_group.add(p)
            x += 32
        y += 32
        x = 0

    total_width = len(map[0]) * 32
    total_height = len(map) * 32
    camera = Camera(total_width, total_height)

    play = True
    clock = pygame.time.Clock()
    fps = 60

    while play:
        # Checks if window exit button pressed
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
            elif event.type == pygame.KEYDOWN:
                if event.key == pygame.K_ESCAPE:
                    pygame.quit()
                    sys.exit()

        # Update
        hero.update(platform_group, hero)
        camera.update(hero.rect)


        # Blits
        screen.fill(WHITE)
        screen.blit(hero.image, camera.apply(hero))
        for p in platform_group:
            screen.blit(p.image, camera.apply(p))

        # Limits FPS
        clock.tick(fps)
        # Writes to surface
        pygame.display.flip()


main()