// Run in the preview frame after fonts/pagination settle, rather than using text-cell tops.
export function minimumNameInkClearance(selector: string): number {
  const name = document.querySelector(selector);
  const flow = document.querySelector('[data-cv-preview-flow]');
  const context = document.createElement('canvas').getContext('2d');
  if (!name || !flow || !context) throw new Error('Missing name or settled print fragment');
  const clipTop = flow.getBoundingClientRect().top;
  const clearance: number[] = [];
  const walker = document.createTreeWalker(name, NodeFilter.SHOW_TEXT);
  let node;
  while ((node = walker.nextNode())) {
    const style = getComputedStyle(node.parentElement!);
    context.font = `${style.fontStyle} ${style.fontWeight} ${style.fontSize} ${style.fontFamily}`;
    let offset = 0;
    for (const character of node.textContent || '') {
      const range = document.createRange();
      range.setStart(node, offset); range.setEnd(node, offset + character.length);
      offset += character.length;
      if (!character.trim()) continue;
      const rect = range.getClientRects()[0], glyph = context.measureText(character);
      if (!rect) throw new Error('Name glyph has no rendered position');
      clearance.push(rect.top + glyph.fontBoundingBoxAscent - glyph.actualBoundingBoxAscent - clipTop);
    }
  }
  if (!clearance.length) throw new Error('Empty name cannot qualify glyph clearance');
  return Math.min(...clearance);
}