// Pure JS PNG Generator for QR codes
// Write a minimal valid PNG with no external dependencies
const fs = require('fs');
const zlib = require('zlib');

function crc32(buf) {
  let crc = 0xFFFFFFFF;
  const table = new Uint32Array(256);
  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;
  }
  for (let i = 0; i < buf.length; i++) crc = table[(crc ^ buf[i]) & 0xFF] ^ (crc >>> 8);
  return (crc ^ 0xFFFFFFFF) >>> 0;
}

function makeChunk(type, data) {
  const typeB = Buffer.from(type);
  const lenB = Buffer.alloc(4);
  lenB.writeUInt32BE(data.length);
  const crcB = Buffer.alloc(4);
  crcB.writeUInt32BE(crc32(Buffer.concat([typeB, data])));
  return Buffer.concat([lenB, typeB, data, crcB]);
}

function createPNG(matrix) {
  const size = matrix.length;
  const scale = 10;
  const outSize = size * scale;
  
  // Raw image data: filter byte (0) + RGB pixels per row
  const raw = Buffer.alloc((1 + size * 3) * outSize);
  for (let y = 0; y < outSize; y++) {
    const rowOffset = y * (1 + outSize * 3);
    raw[rowOffset] = 0; // filter type: none
    const moduleY = Math.floor(y / scale);
    for (let x = 0; x < outSize; x++) {
      const moduleX = Math.floor(x / scale);
      const pixel = matrix[moduleY][moduleX] ? 0 : 255;
      const offset = rowOffset + 1 + x * 3;
      raw[offset] = pixel;     // R
      raw[offset + 1] = pixel; // G
      raw[offset + 2] = pixel; // B
    }
  }
  
  const compressed = zlib.deflateSync(raw);
  
  // PNG signature
  const signature = Buffer.from([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);
  
  // IHDR chunk
  const ihdr = Buffer.alloc(13);
  ihdr.writeUInt32BE(outSize, 0);  // width
  ihdr.writeUInt32BE(outSize, 4);  // height
  ihdr[8] = 8;  // bit depth
  ihdr[9] = 2;  // color type (RGB)
  ihdr[10] = 0; // compression
  ihdr[11] = 0; // filter
  ihdr[12] = 0; // interlace
  
  const ihdrChunk = makeChunk('IHDR', ihdr);
  const idatChunk = makeChunk('IDAT', compressed);
  const iendChunk = makeChunk('IEND', Buffer.alloc(0));
  
  return Buffer.concat([signature, ihdrChunk, idatChunk, iendChunk]);
}

// Matrix from our QR generator (21x21 for "TEST")
const matrix = [
  [1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,1,1],
  [1,0,0,0,0,0,1,0,1,0,1,0,1,0,1,0,0,0,0,0,1],
  [1,0,1,1,1,0,1,0,1,1,0,1,0,1,0,1,1,1,0,0,1],
  [1,0,1,1,1,0,1,0,0,1,1,0,1,0,1,0,1,1,1,0,1],
  [1,0,1,1,1,0,1,0,1,0,1,0,0,1,0,1,1,1,0,0,1],
  [1,0,0,0,0,0,1,0,1,1,0,1,1,1,1,1,0,0,0,0,1],
  [1,1,1,1,1,1,1,0,0,0,0,0,1,0,1,1,1,1,1,1,1],
  [0,0,0,0,0,0,0,0,1,0,1,0,1,0,0,0,0,0,0,0,0],
  [1,0,1,0,1,0,1,0,0,0,1,1,0,1,0,1,0,1,1,0,1],
  [0,1,0,1,0,1,0,1,1,0,0,1,0,1,0,1,1,0,0,1,0],
  [0,0,1,0,0,1,0,1,0,1,0,1,0,1,0,0,1,0,0,0,0],
  [1,1,0,1,0,0,1,0,1,0,1,0,1,0,1,1,0,1,1,1,1],
  [0,0,0,1,1,1,0,1,0,1,0,1,0,1,1,0,1,1,0,0,0],
  [1,1,1,0,0,0,1,0,0,0,1,0,0,1,0,1,1,0,1,1,0],
  [1,0,1,1,1,0,1,0,1,1,0,1,0,1,0,0,0,0,0,1,0],
  [1,0,0,0,0,0,1,0,0,1,1,0,1,0,1,1,1,0,1,0,1],
  [1,1,1,1,1,1,1,0,1,0,1,0,1,1,0,1,0,1,0,0,1],
  [0,0,0,0,0,0,0,0,1,0,1,1,0,1,0,1,1,0,1,1,0],
  [1,1,1,1,1,1,1,0,0,1,0,1,0,0,0,1,1,0,0,0,0],
  [1,0,0,0,0,0,1,0,1,0,1,0,1,0,1,1,0,1,1,1,1],
  [1,1,1,1,1,1,1,0,1,0,1,1,0,0,1,0,0,0,0,0,0],
];

const png = createPNG(matrix);
fs.writeFileSync('/home/node/.openclaw/workspace/assets/qr-test.png', png);
console.log('PNG written:', png.length, 'bytes');