"""Generates the PWA app icons as flat, dependency-free PNGs.

Draws a simple "page with folded corner + text lines" glyph on a solid
brand-blue background, using supersampled coverage for anti-aliasing.
No image libraries required (stdlib struct/zlib only) so this can run
anywhere Python 3 runs.
"""
import struct
import zlib
import os

BRAND_BLUE = (31, 111, 235)
PAGE_WHITE = (255, 255, 255)
FOLD_SHADE = (198, 214, 245)
LINE_BLUE = (99, 150, 235)

SUPERSAMPLE = 4


def mix(c1, c2, t):
    return tuple(round(a + (b - a) * t) for a, b in zip(c1, c2))


def rounded_rect_contains(x, y, left, top, right, bottom, radius):
    if left <= x <= right and top <= y <= bottom:
        cx = min(max(x, left + radius), right - radius)
        cy = min(max(y, top + radius), bottom - radius)
        return (x - cx) ** 2 + (y - cy) ** 2 <= radius * radius
    return False


def line_contains(x, y, cx, cy, half_w, half_h):
    return abs(x - cx) <= half_w and abs(y - cy) <= half_h


def pixel_color(x, y, size):
    # Kept within the maskable-icon "safe zone" (content within a circle of
    # radius 0.4 * size centered on the canvas) so Android's adaptive-icon
    # masks (circle, squircle, rounded square, ...) never clip the glyph.
    left = size * 0.25
    right = size * 0.75
    top = size * 0.20
    bottom = size * 0.80
    radius = size * 0.045
    fold = size * 0.14

    in_page = rounded_rect_contains(x, y, left, top, right, bottom, radius)
    # Cut the top-right corner off diagonally to form a folded-page look.
    if in_page and (x - (right - fold)) > 0 and (top - y) < 0 and (x - (right - fold)) + (y - top) > fold:
        in_page = False

    if in_page:
        # Shadow triangle for the folded flap, just inside the cut edge.
        dx = x - (right - fold)
        dy = y - top
        if dx > 0 and dy >= 0 and dx + dy <= fold and dx + dy >= fold * 0.55:
            return FOLD_SHADE

        page_w = right - left
        line_h = size * 0.028
        line_specs = [
            (0.46, 0.70),
            (0.60, 0.70),
            (0.74, 0.46),
        ]
        for rel_y, rel_w in line_specs:
            cy = top + (bottom - top) * rel_y
            half_h = line_h / 2
            half_w = page_w * rel_w / 2
            cx = left + page_w / 2
            if line_contains(x, y, cx, cy, half_w, half_h):
                return LINE_BLUE
        return PAGE_WHITE

    return BRAND_BLUE


def make_png(path, size):
    raw = bytearray()
    step = 1.0 / SUPERSAMPLE
    for y in range(size):
        raw.append(0)  # filter type 0 for each scanline
        for x in range(size):
            r_acc = g_acc = b_acc = 0
            for sy in range(SUPERSAMPLE):
                for sx in range(SUPERSAMPLE):
                    sample_x = x + (sx + 0.5) * step
                    sample_y = y + (sy + 0.5) * step
                    r, g, b = pixel_color(sample_x, sample_y, size)
                    r_acc += r
                    g_acc += g
                    b_acc += b
            n = SUPERSAMPLE * SUPERSAMPLE
            raw += bytes([round(r_acc / n), round(g_acc / n), round(b_acc / n)])

    compressed = zlib.compress(bytes(raw), 9)

    def chunk(tag, data):
        return struct.pack(">I", len(data)) + tag + data + struct.pack(
            ">I", zlib.crc32(tag + data) & 0xFFFFFFFF
        )

    sig = b"\x89PNG\r\n\x1a\n"
    ihdr = struct.pack(">IIBBBBB", size, size, 8, 2, 0, 0, 0)
    png = sig + chunk(b"IHDR", ihdr) + chunk(b"IDAT", compressed) + chunk(b"IEND", b"")

    os.makedirs(os.path.dirname(path), exist_ok=True)
    with open(path, "wb") as f:
        f.write(png)


if __name__ == "__main__":
    make_png("public/icons/icon-192.png", 192)
    make_png("public/icons/icon-512.png", 512)
    make_png("public/icons/apple-touch-icon.png", 180)
    print("Icons generated")