const fs = require('fs');
const path = require('path');
const zlib = require('zlib');

function crc32(buf) {
  let c = ~0;
  const table = 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;
  });
  for (let i = 0; i < buf.length; i++) {
    c = table[(c ^ buf[i]) & 0xff] ^ (c >>> 1);
  }
  return ~(c >>> 0) >>> 0;
}

function pngChunk(type, data) {
  const typeBuf = Buffer.from(type, 'ascii');
  const buf = Buffer.concat([typeBuf, data]);
  const crc = crc32(buf);
  const len = Buffer.allocUnsafe(4);
  len.writeUInt32BE(data.length, 0);
  const crcBuf = Buffer.allocUnsafe(4);
  crcBuf.writeUInt32BE(crc, 0);
  return Buffer.concat([len, buf, crcBuf]);
}

function createSolidPng(size, r, g, b) {
  const header = Buffer.from([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);

  const ihdr = Buffer.allocUnsafe(13);
  ihdr.writeUInt32BE(size, 0);  // width
  ihdr.writeUInt32BE(size, 4);  // height
  ihdr[8] = 8;   // bit depth
  ihdr[9] = 2;   // color type (RGB)
  ihdr[10] = 0;  // compression
  ihdr[11] = 0;  // filter method
  ihdr[12] = 0;  // interlace

  const row = Buffer.allocUnsafe(1 + size * 3);
  row[0] = 0; // filter byte
  for (let x = 0; x < size; x++) {
    row[1 + x * 3] = r;
    row[1 + x * 3 + 1] = g;
    row[1 + x * 3 + 2] = b;
  }
  const rawData = Buffer.concat(Array.from({ length: size }, () => row));
  const idat = zlib.deflateSync(rawData, { level: 9 });

  return Buffer.concat([header, pngChunk('IHDR', ihdr), pngChunk('IDAT', idat), pngChunk('IEND', Buffer.alloc(0))]);
}

const dir = path.join(__dirname, 'public', 'icons');
fs.mkdirSync(dir, { recursive: true });

const sizes = [16, 48, 128];
const colors = { 16: [59, 130, 246], 48: [59, 130, 246], 128: [59, 130, 246] };

for (const size of sizes) {
  const [r, g, b] = colors[size];
  const png = createSolidPng(size, r, g, b);
  fs.writeFileSync(path.join(dir, `icon${size}.png`), png);
  console.log(`Generated icon${size}.png`);
}