Function parsePngCardBytes

apps/webuiapps/src/lib/cardExtractor.ts:155–210

(buffer: ArrayBuffer)

// ── PNG parsing ────────────────────────────────────────────────────

function parsePngCardBytes(buffer: ArrayBuffer): Record<string, unknown> {
  const view = new DataView(buffer);
  const bytes = new Uint8Array(buffer);

  // Verify PNG signature
  if (bytes[0] !== 0x89 || bytes[1] !== 0x50 || bytes[2] !== 0x4e || bytes[3] !== 0x47) {
    throw new Error('Not a valid PNG file');
  }

  const chunks: Record<string, string> = {};
  let offset = 8; // Skip PNG signature

  while (offset < buffer.byteLength) {
    if (offset + 8 > buffer.byteLength) break;

    const length = view.getUint32(offset);
    const chunkType = String.fromCharCode(
      bytes[offset + 4],
      bytes[offset + 5],
      bytes[offset + 6],
      bytes[offset + 7],
    );
    offset += 8;

    if (offset + length + 4 > buffer.byteLength) break;

    if (chunkType === 'tEXt') {
      const data = bytes.slice(offset, offset + length);
      const nullIdx = data.indexOf(0);
      if (nullIdx !== -1) {
        const keyword = new TextDecoder('latin1').decode(data.slice(0, nullIdx));
        const text = new TextDecoder('latin1').decode(data.slice(nullIdx + 1));
        chunks[keyword] = text;
      }
    }

    offset += length + 4; // data + CRC

    if (chunkType === 'IEND') break;
  }

  // Prefer ccv3 over chara
  const raw = chunks['ccv3'] || chunks['chara'];
  if (!raw) {
    throw new Error('No character data found in PNG');
  }

  // Decode base64 → binary string → UTF-8
  const binaryStr = atob(raw);
  const decoded = new Uint8Array(binaryStr.length);
  for (let i = 0; i < binaryStr.length; i++) {
    decoded[i] = binaryStr.charCodeAt(i);
  }
  const jsonStr = new TextDecoder('utf-8').decode(decoded);
  return JSON.parse(jsonStr);
}

// ── CharX (ZIP) parsing ────────────────────────────────────────────