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

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

function crc32(buf) {
  const table = [];
  for (let i = 0; i < 256; i++) {
    let c = i;
    for (let k = 0; k < 8; k++) {
      c = (c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1);
    }
    table[i] = c;
  }
  let crc = -1;
  for (const byte of buf) {
    crc = table[(crc ^ byte) & 0xFF] ^ (crc >>> 8);
  }
  return (crc ^ -1) >>> 0;
}

function makeChunk(typeStr, data) {
  const typeBuf = Buffer.from(typeStr, 'ascii');
  const c = crc32(Buffer.concat([typeBuf, data]));
  const crcBuf = Buffer.alloc(4);
  crcBuf.writeUInt32BE(c, 0);
  const lenBuf = Buffer.alloc(4);
  lenBuf.writeUInt32BE(data.length, 0);
  return Buffer.concat([lenBuf, typeBuf, data, crcBuf]);
}

function makePng(size, r, g, b) {
  const sig = Buffer.from([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);
  const ihdrData = Buffer.alloc(13);
  ihdrData.writeUInt32BE(size, 0);
  ihdrData.writeUInt32BE(size, 4);
  ihdrData.writeUInt8(8, 8);
  ihdrData.writeUInt8(2, 9);
  ihdrData.writeUInt8(0, 10);
  ihdrData.writeUInt8(0, 11);
  ihdrData.writeUInt8(0, 12);

  const rawData = [];
  for (let y = 0; y < size; y++) {
    rawData.push(0);
    for (let x = 0; x < size; x++) {
      rawData.push(r, g, b);
    }
  }
  const imageData = zlib.deflateSync(Buffer.from(rawData));

  const ihdr = makeChunk('IHDR', ihdrData);
  const idat = makeChunk('IDAT', imageData);
  const iend = makeChunk('IEND', Buffer.alloc(0));

  return Buffer.concat([sig, ihdr, idat, iend]);
}

const r = 15, g = 52, b = 96;
fs.writeFileSync(path.join(iconsDir, 'icon16.png'), makePng(16, r, g, b));
fs.writeFileSync(path.join(iconsDir, 'icon48.png'), makePng(48, r, g, b));
fs.writeFileSync(path.join(iconsDir, 'icon128.png'), makePng(128, r, g, b));
console.log('Icons created');