"""Tab Shooter — Icon Generator (pure stdlib).

Erzeugt icons/icon16.png, icon48.png, icon128.png direkt über zlib+struct.
Keine externen Abhängigkeiten (PIL nicht nötig).
"""
import os
import struct
import zlib

OUT_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)), "icons")


def write_png(path, width, height, rgba_pixels):
    """rgba_pixels: bytearray mit width*height*4 Bytes (RGBA)."""
    def chunk(tag, data):
        c = tag + data
        crc = struct.pack(">I", zlib.crc32(c) & 0xFFFFFFFF)
        return struct.pack(">I", len(data)) + c + crc

    header = b"\x89PNG\r\n\x1a\n"
    ihdr = struct.pack(">IIBBBBB", width, height, 8, 6, 0, 0, 0)  # 8-bit, RGBA
    # Filter byte 0 am Anfang jeder Zeile
    raw = bytearray()
    stride = width * 4
    for y in range(height):
        raw.append(0)
        raw.extend(rgba_pixels[y * stride:(y + 1) * stride])
    idat = zlib.compress(bytes(raw), 9)
    png = header + chunk(b"IHDR", ihdr) + chunk(b"IDAT", idat) + chunk(b"IEND", b""  )
    with open(path, "wb") as f:
        f.write(png)


def lerp(a, b, t):
    return int(a + (b - a) * t)


def lerp_color(c1, c2, t):
    return tuple(lerp(c1[i], c2[i], t) for i in range(3))


def render_icon(size):
    """Zeichnet ein Raumschiff mit Cyan->Magenta Verlauf auf dunklem Grund."""
    bg_top = (10, 6, 30)
    bg_bot = (30, 8, 50)
    cyan = (0, 240, 255)
    magenta = (255, 0, 229)
    yellow = (255, 170, 0)

    px = bytearray(size * size * 4)
    cx = (size - 1) / 2.0
    nose_y = size * 0.18
    base_y = size * 0.80
    half_w = size * 0.34

    def set_pixel(x, y, r, g, b, a=255):
        if 0 <= x < size and 0 <= y < size:
            i = (y * size + x) * 4
            # alpha-blend over existing
            if px[i + 3] == 0:
                px[i:i + 4] = bytes([r, g, b, a])
            else:
                ia = a / 255.0
                px[i]     = int(r * ia + px[i]     * (1 - ia))
                px[i + 1] = int(g * ia + px[i + 1] * (1 - ia))
                px[i + 2] = int(b * ia + px[i + 2] * (1 - ia))
                px[i + 3] = min(255, px[i + 3] + a)

    for y in range(size):
        for x in range(size):
            # Hintergrund-Verlauf (radial-ish)
            t = y / max(1, size - 1)
            r, g, b = lerp_color(bg_top, bg_bot, t)
            # Sterne
            if (x * 7 + y * 13) % 37 == 0 and size >= 48:
                r, g, b = 220, 220, 255
            set_pixel(x, y, r, g, b, 255)

    # Raumschiff: für jede Zeile y berechne ship-x-Bereich
    for y in range(size):
        # relative position im Schiff (0 = nose, 1 = base)
        if y < nose_y or y > base_y:
            continue
        t = (y - nose_y) / max(1, (base_y - nose_y))
        # Schiffsbreite wächst zur Basis
        w = half_w * (0.15 + 0.85 * t)
        # Schiff-Verlauf cyan->magenta
        cr, cg, cb = lerp_color(cyan, magenta, t)
        for x in range(size):
            if abs(x - cx) <= w:
                # leichte Randabdunklung
                edge = abs(x - cx) / max(1, w)
                shade = 1.0 - edge * 0.3
                set_pixel(x, y, int(cr * shade), int(cg * shade), int(cb * shade), 255)
        # Triebwerk-Glühen an der Basis
        if t > 0.9:
            for x in range(size):
                if abs(x - cx) < w * 0.5:
                    set_pixel(x, y, *yellow, 255)

    # Cockpit (kleiner Magenta-Kreis nahe der Spitze)
    cockpit_cy = int(nose_y + (base_y - nose_y) * 0.35)
    cockpit_r = max(1, size // 12)
    for y in range(size):
        for x in range(size):
            dx = x - cx
            dy = y - cockpit_cy
            if dx * dx + dy * dy <= cockpit_r * cockpit_r:
                set_pixel(x, y, *magenta, 255)

    return px


def main():
    os.makedirs(OUT_DIR, exist_ok=True)
    for s in (16, 48, 128):
        pixels = render_icon(s)
        path = os.path.join(OUT_DIR, f"icon{s}.png")
        write_png(path, s, s, pixels)
        print(f"Wrote {path}")


if __name__ == "__main__":
    main()