particles.py

"""
简单粒子特效系统
"""
import random
import math
import pygame


class Particle:
    """单个粒子"""

    SHAPES = ["circle", "square", "star"]

    x: float
    y: float
    color: tuple[int, int, int]
    vx: float
    vy: float
    life: float
    max_life: float
    size: int
    shape: str

    def __init__(self, x: float, y: float, color: tuple[int, int, int],
                 speed: float, life: float, shape: str | None = None) -> None:
        self.x = x
        self.y = y
        self.color = color
        angle = random.uniform(0, math.pi * 2)
        self.vx = math.cos(angle) * speed * random.uniform(0.5, 1.5)
        self.vy = math.sin(angle) * speed * random.uniform(0.5, 1.5)
        self.life = life
        self.max_life = life
        self.size = random.randint(2, 5)
        self.shape = shape if shape else random.choice(self.SHAPES)

    @property
    def alive(self) -> bool:
        return self.life > 0

    @property
    def alpha(self) -> int:
        return int(255 * (self.life / self.max_life))

    def update(self, dt: float) -> None:
        self.x += self.vx * dt
        self.y += self.vy * dt
        self.life -= dt

    def draw(self, screen: pygame.Surface) -> None:
        c = self.color
        a = self.alpha
        if a < 0:
            return
        color = (c[0], c[1], c[2], a)

        if self.shape == "circle":
            surf = pygame.Surface((self.size * 2, self.size * 2), pygame.SRCALPHA)
            pygame.draw.circle(surf, color, (self.size, self.size), self.size)
            screen.blit(surf, (int(self.x - self.size), int(self.y - self.size)))

        elif self.shape == "square":
            surf = pygame.Surface((self.size * 2, self.size * 2), pygame.SRCALPHA)
            half = self.size
            rect = (half - self.size // 2, half - self.size // 2, self.size, self.size)
            pygame.draw.rect(surf, color, rect)
            screen.blit(surf, (int(self.x - self.size), int(self.y - self.size)))

        elif self.shape == "star":
            surf = pygame.Surface((self.size * 2, self.size * 2), pygame.SRCALPHA)
            cx = cy = self.size
            r = self.size
            points = []
            for i in range(8):
                angle = i * math.pi / 4
                dist = r if i % 2 == 0 else r * 0.4
                points.append((cx + math.cos(angle) * dist,
                              cy + math.sin(angle) * dist))
            if len(points) >= 3:
                pygame.draw.polygon(surf, color, points)
            screen.blit(surf, (int(self.x - self.size), int(self.y - self.size)))


class ParticleSystem:
    """管理所有活跃粒子"""

    particles: list[Particle]

    def __init__(self) -> None:
        self.particles = []

    def burst(self, x: float, y: float, color: tuple[int, int, int],
              count: int, speed: float) -> None:
        """在 (x, y) 爆发 count 个粒子，随机混合形状（Item 15）"""
        for _ in range(count):
            life = random.uniform(0.3, 0.8)
            shape = random.choice(["circle", "square", "star"])
            self.particles.append(Particle(x, y, color, speed, life, shape=shape))

    def update(self, dt: float) -> None:
        # alive-list 重建：避免 O(n) 的 list.remove()
        alive = []
        for p in self.particles:
            p.update(dt)
            if p.alive:
                alive.append(p)
        self.particles = alive

    def draw(self, screen: pygame.Surface) -> None:
        for p in self.particles:
            p.draw(screen)

    @property
    def is_empty(self) -> bool:
        return len(self.particles) == 0