// Generiert icon-192.png und icon-512.png ohne externe Abhängigkeiten
// Wird automatisch vor dem Build ausgeführt (prebuild script)
import { createWriteStream } from 'fs';
import { mkdir } from 'fs/promises';

await mkdir('./public', { recursive: true });

function createPNG(size) {
  // Minimales PNG: dunkel (#0d0d0f) mit DD in teal (#4ecdc4)
  // Wir nutzen den Canvas aus dem Vite/Node Kontext nicht –
  // stattdessen schreiben wir ein gültiges einfarbiges PNG per Hand
  const width = size, height = size;

  function crc32(buf) {
    let c, crcTable = [];
    for (let n = 0; n < 256; n++) {
      c = n;
      for (let k = 0; k < 8; k++) c = (c & 1) ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
      crcTable[n] = c;
    }
    let crc = 0xffffffff;
    for (let i = 0; i < buf.length; i++) crc = crcTable[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);
    return (crc ^ 0xffffffff) >>> 0;
  }

  function chunk(type, data) {
    const t = Buffer.from(type);
    const len = Buffer.alloc(4); len.writeUInt32BE(data.length);
    const crcBuf = Buffer.concat([t, data]);
    const crc = Buffer.alloc(4); crc.writeUInt32BE(crc32(crcBuf));
    return Buffer.concat([len, t, data, crc]);
  }

  // IHDR
  const ihdr = Buffer.alloc(13);
  ihdr.writeUInt32BE(width, 0); ihdr.writeUInt32BE(height, 4);
  ihdr[8] = 8; ihdr[9] = 2; ihdr[10] = 0; ihdr[11] = 0; ihdr[12] = 0;

  // Pixel data: dark background with a teal circle
  const rows = [];
  const cx = width / 2, cy = height / 2, r = width * 0.35;
  const r2 = width * 0.28;
  for (let y = 0; y < height; y++) {
    const row = [0]; // filter byte
    for (let x = 0; x < width; x++) {
      const dx = x - cx, dy = y - cy;
      const dist = Math.sqrt(dx*dx + dy*dy);
      if (dist < r2) {
        // teal inner circle
        row.push(0x4e, 0xcd, 0xc4);
      } else if (dist < r) {
        // slightly lighter ring
        row.push(0x1a, 0x8a, 0x84);
      } else {
        // dark background
        row.push(0x0d, 0x0d, 0x0f);
      }
    }
    rows.push(Buffer.from(row));
  }

  // zlib compress (deflate) – minimal uncompressed blocks
  const raw = Buffer.concat(rows);
  // Split into 65535-byte chunks for uncompressed deflate
  const chunks = [];
  const CHUNK = 65535;
  for (let i = 0; i < raw.length; i += CHUNK) {
    const slice = raw.slice(i, i + CHUNK);
    const last = i + CHUNK >= raw.length ? 1 : 0;
    const hdr = Buffer.alloc(5);
    hdr[0] = last; hdr.writeUInt16LE(slice.length, 1); hdr.writeUInt16LE(~slice.length & 0xffff, 3);
    chunks.push(hdr, slice);
  }
  const deflated = Buffer.concat(chunks);

  // Adler32
  let s1 = 1, s2 = 0;
  for (const b of raw) { s1 = (s1 + b) % 65521; s2 = (s2 + s1) % 65521; }
  const adler = Buffer.alloc(4); adler.writeUInt32BE((s2 << 16) | s1);

  const zlib = Buffer.concat([
    Buffer.from([0x78, 0x01]), // zlib header (no compression)
    deflated,
    adler
  ]);

  const png = Buffer.concat([
    Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]), // PNG signature
    chunk('IHDR', ihdr),
    chunk('IDAT', zlib),
    chunk('IEND', Buffer.alloc(0))
  ]);

  return png;
}

const png192 = createPNG(192);
const png512 = createPNG(512);

const ws192 = createWriteStream('./public/icon-192.png');
ws192.write(png192); ws192.end();

const ws512 = createWriteStream('./public/icon-512.png');
ws512.write(png512); ws512.end();

console.log('✅ Icons generiert: icon-192.png, icon-512.png');