"""Gera os 11 quadros (46x45, RGBA) da explosao do missil do Stellar Highway.

Substitui a "Missile Explosion Animation" do nyknck (sem licenca). Desenho proprio, determinístico
(PRNG com semente fixa, sem Pillow: o PNG e escrito com zlib), dedicado ao dominio publico (CC0).

  python3 -I explosion.py <pasta-de-saida>
"""
import math, os, random, struct, sys, zlib

W, H, N = 46, 45, 11
CX, CY = 22.5, 22.0

# (limite de distancia normalizada, cor) do centro para fora
PALETTE = [(0.30, (255, 248, 214)), (0.55, (255, 214, 64)), (0.78, (255, 140, 24)), (1.01, (214, 58, 24))]
SMOKE = (74, 62, 70)


def png(path, px):
    raw = b''.join(b'\x00' + bytes(v for p in px[y * W:(y + 1) * W] for v in p) for y in range(H))
    def chunk(t, d):
        c = struct.pack('>I', len(d)) + t + d
        return c + struct.pack('>I', zlib.crc32(t + d) & 0xffffffff)
    data = b'\x89PNG\r\n\x1a\n' + chunk(b'IHDR', struct.pack('>IIBBBBB', W, H, 8, 6, 0, 0, 0)) \
        + chunk(b'IDAT', zlib.compress(raw, 9)) + chunk(b'IEND', b'')
    open(path, 'wb').write(data)


def frame(t):
    rng = random.Random(1000 + t)
    # raio do clarao: cresce rapido ate o quadro 5, depois encolhe; fumaca e fagulhas ate o fim
    grow = min(t, 5) / 5.0
    fire_r = 4 + 17 * math.sin(grow * math.pi / 2) if t <= 5 else 21 - (t - 5) * 3.2
    fire_r = max(fire_r, 0)
    lobes = [rng.uniform(0.75, 1.15) for _ in range(12)]
    smoke_a = 0 if t < 3 else min(1.0, (t - 2) / 3.0) * (1.0 if t < 8 else (11 - t) / 3.0)
    smoke_r = 8 + t * 1.6
    sparks = [(rng.uniform(0, 2 * math.pi), rng.uniform(0.5, 1.0)) for _ in range(10)]
    px = [(0, 0, 0, 0)] * (W * H)
    for y in range(H):
        for x in range(W):
            dx, dy = x + 0.5 - CX, y + 0.5 - CY
            d = math.hypot(dx, dy)
            ang = math.atan2(dy, dx)
            lobe = lobes[int((ang + math.pi) / (2 * math.pi) * 12) % 12]
            col = None
            if fire_r > 0:
                edge = fire_r * lobe
                if d < edge:
                    nd = d / edge + (0.12 if t > 5 else 0.0) * (t - 5) * 0.4
                    for lim, c in PALETTE:
                        if nd < lim:
                            col = c + (255,)
                            break
                    if col is None:
                        col = PALETTE[-1][1] + (255,)
            if col is None and smoke_a > 0 and d < smoke_r * lobe and (x + y + t) % 2 == 0:
                col = SMOKE + (int(200 * smoke_a),)
            px[y * W + x] = col or (0, 0, 0, 0)
    # fagulhas: pontos que se afastam do centro
    for a, s in sparks:
        r = (4 + t * 2.0) * s * 1.6
        if t >= 1 and r < 22:
            sx, sy = int(CX + math.cos(a) * r), int(CY + math.sin(a) * r)
            if 0 <= sx < W - 1 and 0 <= sy < H - 1 and t < 10:
                px[sy * W + sx] = (255, 226, 120, 255)
                if t < 7:
                    px[sy * W + sx + 1] = (255, 160, 40, 255)
    return px


out = sys.argv[1]
os.makedirs(out, exist_ok=True)
for i in range(N):
    png(os.path.join(out, f'{i}.png'), frame(i))