import qrcode from 'qrcode-generator';

export interface QrShape {
  /** Width/height in modules (no quiet zone; renderers add margin). */
  size: number;
  /** SVG path in module units: draw it in a `0 0 size size` viewBox. */
  path: string;
}

/** Dark/light grid for `text`. Medium error correction survives a scratched or dim screen. */
export function qrMatrix(text: string): boolean[][] {
  const qr = qrcode(0, 'M'); // 0 = smallest version that fits
  qr.addData(text);
  qr.make();
  const n = qr.getModuleCount();
  return Array.from({ length: n }, (_, row) => Array.from({ length: n }, (_, col) => qr.isDark(row, col)));
}

/** One SVG path for the whole code, merging horizontal runs so it stays small to render. */
export function qrShape(text: string): QrShape {
  const matrix = qrMatrix(text);
  let path = '';
  matrix.forEach((cells, y) => {
    let x = 0;
    while (x < cells.length) {
      if (!cells[x]) {
        x++;
        continue;
      }
      const start = x;
      while (x < cells.length && cells[x]) x++;
      path += `M${start} ${y}h${x - start}v1h${start - x}z`;
    }
  });
  return { size: matrix.length, path };
}