// Writes public/icon-192.png and icon-512.png (teal square with two white waves) with no dependencies.
import { deflateSync } from 'node:zlib';
import { writeFileSync } from 'node:fs';
import { fileURLToPath } from 'node:url';

const crcTable = Array.from({ length: 256 }, (_, n) => {
  let c = n;
  for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
  return c >>> 0;
});
const crc = (b) => {
  let c = 0xffffffff;
  for (const x of b) c = crcTable[(c ^ x) & 255] ^ (c >>> 8);
  return (c ^ 0xffffffff) >>> 0;
};
const chunk = (type, data) => {
  const len = Buffer.alloc(4); len.writeUInt32BE(data.length);
  const td = Buffer.concat([Buffer.from(type), data]);
  const c = Buffer.alloc(4); c.writeUInt32BE(crc(td));
  return Buffer.concat([len, td, c]);
};

function png(size) {
  const raw = Buffer.alloc((size * 4 + 1) * size);
  for (let y = 0; y < size; y++) {
    raw[y * (size * 4 + 1)] = 0;
    for (let x = 0; x < size; x++) {
      const u = x / size, v = y / size; // 0..1
      const wave = (off) => 0.5 + off + 0.06 * Math.sin((u - 0.19) * Math.PI * 6);
      const body = v > wave(0.0) + 0.06 && v < 0.85 && u > 0.19 && u < 0.81; // lower filled wave
      const line = Math.abs(v - wave(-0.1)) < 0.03 && u > 0.19 && u < 0.81;
      const i = y * (size * 4 + 1) + 1 + x * 4;
      const on = body || line;
      raw[i] = on ? 255 : 0x1f; raw[i + 1] = on ? 255 : 0x5c; raw[i + 2] = on ? 255 : 0x5c; raw[i + 3] = 255;
    }
  }
  const ihdr = Buffer.alloc(13);
  ihdr.writeUInt32BE(size, 0); ihdr.writeUInt32BE(size, 4); ihdr[8] = 8; ihdr[9] = 6;
  return Buffer.concat([Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]), chunk('IHDR', ihdr), chunk('IDAT', deflateSync(raw)), chunk('IEND', Buffer.alloc(0))]);
}

for (const s of [192, 512]) writeFileSync(fileURLToPath(new URL(`../public/icon-${s}.png`, import.meta.url)), png(s));
console.log('icons written');